Review Article
Sports Medicine 9 (6): 380-389, 1990 0112-1642/0006-0380/$05.00/0 © ADIS Press Limited
All rights reserved. SPORT2 285
Benefits of Exercise for the Treatment of Depression Egil W. Martinsen Department of Psychiatry, Central Hospital of Sogn og Fjordane, F0rde, Norway
Contents
Summary ..................................................................................................................................380 I. Classification of Depression .............. ................................................... ....... ............ ........... 38I 2. Physical Activity Level ....................................................................................................... 381 3. Physical Fitness ............................................................................................. ...................... 382 4. Exercise Intervention ...................... ....................................................................................382 5. Aerobic vs Nonaerobic Exercise ............................... ............... .................... ....................... 384 6. Discussion of Exercise Intervention Studies .....................................................................384 7. Adherence ................................................................,............................................................ 385 8. Exercise Adherence and Mental Health ............................................................................ 385 9. Evaluation ................................................................................................. ...........................386 10. Possible Mechanisms ......................... ......... ............................................... .........................386 II . Practical Management ................................................... .......... ............... .............. ............... 387 12. Practical Complications ............................. ......................................................................... 387 13. Implications for Psychiatric Treatment .............................................. ............................... 387 14. Implications for Future Research ...................................................................................... 387 15. Conclusion ............................................................................................. .............................. 388
Summary
In general, depressed patients are physically sedentary. They have reduced physical work capacity but normal pulmonary function compared with the general population. This indicates that the reduced fitness level is caused by physical inactivity and is a strong argument for integrating physical fitness training into comprehensive treatment programmes for depression. Exercise is associated with an antidepressive effect in patients with mild to moderate forms of nonbipolar depressive disorders. An increase in aerobic fitness does not seem to be essential for the antidepressive effect, because similar results are obtained with nonaerobic forms of exercise. More than half of the patients continue with regular exercise I year after termination of the training programmes. Patients who continue to exercise tend to have lower depression scores than the sedentary ones. Patients appreciate physical exercise, and rank exercise to be the most important element in comprehensive treatment programmes. Exercise seems to be a promising new approach in the treatment of nonbipolar depressive disorders of mild to moderate severity.
Exercise in the Treatment of Depression
Depression is a major health problem. The most common forms of treatment have been medication and various forms of psychotherapy. However, psychotherapy can never meet the needs of this common disorder, while medication may have unpleasant side effects, and the established treatment methods are not always effective. There is therefore a great need for effective low cost or self-administered strategies, with minimal dangerous side effects, which may be used alone or as adjuncts to the traditional forms of treatment. Physical exercise has been put forward as one such method. There has been a growing interest in the psychological effects associated with regular exercise during the last 20 years, and an increasing number of publications on this topic [for an overview of the beneficial and detrimental effects of exercise on mental health, see the article by Raglin (1990) in this issue] have emerged. Depression is the mental disorder most commonly studied, and aerobic exercise has been the most commonly used form of exercise intervention. The early studies often Consisted of small samples with poor methodology (Weinstein & Meyers 1983). In the last years, however, studies with quasiexperimental or experimental design have started to emerge. During the last 7 years my colleagues and I have performed a series of clinical investigations, where we have addressed aspects of physical exercise intervention in patients with unipolar depressive disorders. A search of the English language literature in the databases Medline and Dialog Information Services from 1980 to 1988 with the keywords 'depression', 'exercise' and 'aerobic' was performed. Studies on patients with clinical depression from bibliographies of other articles and papers presented at professional meetings were also included. The purpose of this paper is to review this literature, including these personal studies on central aspects of physical fitness and exercise intervention in clinically depressed patients. The paper focusses on physical activity level and physical fitness level prior to treatment. The exercise intervention studies in clinically depressed patients are reviewed, including studies comparing aerobic and nonaerobic forms of exercise. The adherence
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rate to exercise and patients' evaluation of exercise compared with other forms of treatment are addressed. Finally, the various hypotheses of mechanisms mediating the antidepressive effects of exercise are discussed in light of the present knowledge, and some aspects of the practical management of exercising depressed patients are mentioned; the implications ofthese findings for treatment and future research will also be addressed.
1. Classification of Depression The most precise diagnoses of depressive disorders are obtained by the use of criteria-based diagnostic systems. Examples of such are 'Research Diagnostic Criteria' [ROC] (Spitzer et al. 1978) and 'Diagnostic and Statistical Manual of Mental Disorders' (DSM-III) [American Psychiatric Association 1980]. The disorders which are classified as unipolar depressive disorders in the DSM-III are major depression, dysthymic disorder and depressive disorders not otherwise specified. Various self-report instruments have been developed to assess the severity of depression. The Beck Depression Inventory (BDI) [Beck et al. 1961] is one such instrument which is often used. In some studies patients are classified as clinically depressed when they have a score above the normal range on self-report instruments. This is an easy way of obtaining diagnoses, but it is less reliable than the use of diagnostic systems.
2. Physical Activity Level Depressed patients seem to engage in significantly fewer leisure activities than non psychiatric controls (Eisemann 1985), but no previous study has specifically addressed exercise habits of depressed patients. We registered physical activity level prior to admission in 235 patients, with mean age 39 years, with nonpsychotic mental disorders, most commonly unipolar depression (Martinsen et al. 1989b,c). All patients in our studies were hospitalised at the Modum Bads Nervesanatorium. This is a psychiatric clinic, specialising in inpatient treatment of patients with severe neuroses and per-
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sonality disorders. Prior to admission 23% of the patients exercised regularly. A previous national survey using the same questionnaires found that about 50% of the adult Norwegian population of the same age and with the same sex distribution performed regular exercise (Aare & Brekke 1983). This indicates that depressed patients may be physically sedentary compared with the general population.
3. Physical Fitness The most common measure of physical fitness is the physical work capacity (PWC), which usually is defined as the maximum oxygen consumption. PWC can be calculated indirectly from submaximal tests or measured directly from maximal tests. Maximal tests are most accurate if the test subjects are able to work near exhaustion (Astrand & Rodahl 1985). We have found only I study assessing the physical fitness level in depressed patients. Morgan (1969) studied 17 male patients admitted to a mental health centre. The level of depression was assessed with Zung's Self-Rating Depression Scale (Zung et al. 1965), PWC was calculated from a submaximal bicycle ergometer test. The study showed that the depressed patients had significantly lower PWC values than the nondepressed patients. In a sample of 90 inpatients, meeting the DSMIII-R criteria (American Psychiatric Association 1987) for anxiety and/or unipolar depressive disorders (Martinsen et al. 1989a), major depression and dysthymic disorder were the most common diagnoses. Shortly after admission bicycle ergometer tests were performed. PWC was calculated indirectly from submaximal tests and measured directly from maximal tests, and the results were compared with predicted normal values (Astrand 1960). We found that PWC was dramatically reduced with indirect calculations as well as direct measurements. With direct measurement the mean PWC values were 83% of predicted. We also studied lung function in these patients. No such study has previously been reported. Simple spirometry was performed with a dry spiro-
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meter. Forced vital capacity (FVC) was measured, forced expiratory volume in 1 second (FEV,) was calculated, and the values were compared with predicted normal values (Vitalograph 1980). We found that both FVC and FEV, values were slightly larger than predicted normal values: 103% and 109%, respectively. The PWC is strongly dependent upon the habitual physical activity level, while this only has minimal influence upon lung function. The finding of reduced PWC and normal pulmonary function strongly indicates that the low values of PWC are due to physical inactivity. This is consistent with the studies of exercise habits, showing that most patients were sedentary when seeking treatment. None of these studies, however, tells us anything about causal relationships. Do sedentary and less fit subjects become depressed because they are sedentary, or do depressed patients become sedentary and less fit because they are depressed? These questions are left for future research to answer.
4. Exercise Intervention Physical exercise may be divided into the following forms (American College of Sports Medicine 1980): (a) training of aerobic capacity and endurance (aerobic exercise); and (b) training of muscular strength and endurance, and flexibility, coordination and relaxation (nonaerobic exercise). Most exercise intervention studies had used aerobic exercise, most commonly jogging or running. Opinions diverged whether the psychological benefits of physical fitness training were restricted to aerobic exercise, or if the same could be achieved with other forms (Simons et al. 1985). In the following the literature on exercise intervention studies on clinically depressed patients with at least quasiexperimental design are reviewed. Ten studies were found. Two were quasiexperiments with multiple baseline designs, where the subjects served as their own controls. Eight were experimental studies, where patients were randomly assigned to different treatment conditions. In 2 experiments aerobic and nonaerobic forms of exercise were compared.
Exercise in the Treatment of Depression
Doyne et al. (1983) used a multiple baseline design in a study of 4 women with major depression according to the ROC criteria. The level of depression was assessed by 2 self-report measures, Depression Adjective Checklist (DACL) [Lubin 1965] and the BDl. Reductions in depression scores were significantly greater during the aerobic exercise period (4 weekly sessions of ergometer bicycling for 6 weeks) compared with the attention placebo baseline period. Sime (1987) used a similar design on a sample of 15 moderately depressed subjects. No formal diagnoses were given and the level of depression was assessed by the BDI. Multiple measures of depression were obtained over several weeks' screening and a 2-week placebo exercise period prior to the 10-week aerobic training programme, consisting of 4 weekly sessions. Depression scores did not change significantly during the screening and placebo periods, but dropped significantly towards the end of the exercise period. The first experimental exercise intervention study on clinically depressed subjects was performed by Greist et al. (1979), who studied 28 outpatients, meeting the ROC criteria for minor depression. The level of depression was assessed by a self-report measure, Symptom Checklist-90 (SCL90) depression subscale (Derogatis et al. 1973). Patients were randomly assigned either to running (1 hour 3 to 4 times per week) or to 1 of 2 kinds of individual psychotherapy (1 session per week) for 12 weeks. The study showed that there were no statistically significant differences among the groups; significant reductions in depression scores were obtained in all groups. However, the study had methodological shortcomings, as the number of subjects was small, and the randomisation principle was not strictly adhered to. Rueter et al. (1982) studied 18 depressed outpatients with elevated BDI scores without formal diagnoses. They were randomly assigned to either counselling therapy (1 session per week), or to counselling and running (20 minutes supervised running 3 times per week). No significant reductions in depression scores occurred in the counselling group, while the running and counselling
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group achieved reductions in depression scores which were significant and significantly larger than in the counselling group. McCann & Holmes (1984) studied 43 depressed women with elevated BDI scores with no formal diagnosis. They were randomly assigned to either aerobic exercise (1 hour twice per week), relaxation training (20 minutes 4 times per week) or a waiting list control condition. In all groups depression was reduced after 12 weeks, but the reductions in the aerobic group were significantly larger than in the 2 other groups. Klein et al. (1985) studied 74 outpatients meeting the ROC criteria for major or minor depression. The patients were randomly assigned to either aerobic exercise (running/walking 1 hour twice per week), meditation-relaxation (2 hours once per week) or group psychotherapy (2 hours per week) for 12 weeks. In each treatment group there were significant decreases in depression scores (SCL-90) after 12 weeks, but there were no significant differences among the groups. At 9 months follow-up the study indicated a better outcome for the exercise and meditation groups. Freemont and Craighead (1987) investigated 49 individuals with elevated BDI scores without formal diagnoses. They were randomly assigned to either aerobic exercise (three 20-minute sessions per week), cognitive therapy (I session per week) and a combination of the two. The depression scores dropped significantly during the study in each treatment group, and this effect was maintained at 2 months' follow-up. There were no significant differences among the groups. In a personal experiment (Martinsen 1987a; Martinsen et al. 1985) 49 inpatients meeting the DSM-III criteria for major depression were hospitalised and attended 1 or 2 sessions of individual psychotherapy per week, in addition to occupational and milieu therapy. The patients were randomly assigned either to a control group, receiving this standard treatment, or a training group, where 3 weekly sessions of occupational therapy were substituted by aerobic exercise for 1 hour. Nine in the training group and 14 in the control group received tricyclic antidepressant medication. The
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level of depression was assessed by the BDI and the Comprehensive Psychopathological Rating Scale (CPRS) depression subscale (Asberg et al. 1978), which is a therapist rating. After 6 to 9 weeks there was a statistically significant increase in PWC in the training group, while the control group was unchanged in this variable. Both groups had achieved significant reductions in depression scores, but the reductions in the training group were significantly greater than in the control group. Patients who were on tricyclic antidepressants had similar reductions in depression scores to those who did not use medication.
5. Aerobic vs Nonaerobic Exercise To assess the importance of the aerobic element of training, one has to compare aerobic and nonaerobic forms of exercise in the treatment of depression. Two studies have addressed this. Doyne et al. (1987) compared the effects of aerobic and nonaerobic exercise in the treatment of 41 patients meeting the RDC criteria for major or minor depression. Subjects exercised 4 times per week for 8 weeks. Subjects in the aerobic group walked or ran around an indoor track, while those in the nonaerobic group went through a standard lO-station programme on a Universal Exercise Machine. The level of depression was assessed by the BDI, the DACL and the Hamilton Rating Scale for Depression (HRSD) [Hamilton 1960]. This randomised study showed that both forms of exercise were significantly better than a waiting list control condition. The difference between the exercise groups was not statistically significant. The findings were remarkably consistent across measures. There was a nonsignificant trend on some measures favouring nonaerobic exercise. As no measurable fitness effects were achieved in the aerobic group, however, the importance of the aerobic element could not be specifically addressed. In a later study (Martinsen et al. I 989b) aerobic and nonaerobic forms of exercise in the treatment of patients meeting the DSM-III-R criteria (American Psychiatric Association 1987) for unipolar depressive disorders were compared. 99 hospitalised
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patients of both sexes were randomly assigned to aerobic (walking/running) or nonaerobic (training of muscular strength and endurance, flexibility, coordination and relaxation) of exercise 1 hour 3 times per week for 8 weeks. In contrast to Doyne et al. (1987) the aerobic element was successfully manipulated. In the aerobic group there was a significant increase in aerobic capacity, while the nonaerobic group was unchanged on this variable. The difference in treatment outcome between the 2 forms of exercise was not statistically significant, and there was no observable tendency in favour of either of the two. In each group 14 patients used tricyclic antidepressants during the study. Those who were taking tricyclic antidepressants had a somewhat larger reduction in depression scores than those who did not use medication, but the difference was not statistically significant (Martinsen et al. 1989b).
6. Discussion 0/ Exercise Intervention Studies The most important methodological criteria for such studies are a design of either an experiment or a quasiexperiment, the use of stringent diagnostic criteria, the employment of standardised instruments for assessing the level of depression, ideally both self-report and therapist ratings, and inclusion of an adequate number of subjects. All the reviewed studies at least had a quasiexperimental design, and 6 of 10 used stringent diagnostic criteria. In all studies the level of depression was assessed with standardised instruments, but only 3 used therapist ratings in addition to selfreport. Four studies consisted of small samples, and in one study the randomisation procedures were not strictly adhered to. In spite of the fact that the number of studies are few, and that many have methodological shortcomings, it is striking that the results in all studies point in the same direction. Aerobic exercise is more effective than no treatment, and not significantly different from other forms of treatment, including various forms of psychotherapy. This indicates that aerobic exercise is associated with an
Exercise in the Treatment of Depression
antidepressive effect in patients with mild to moderate forms of depression. The studies comparing aerobic and nonaerobic forms of exercise strongly suggest that increase in physical fitness level is not a necessary precondition for the antidepressive effect. Reductions in depression scores may be achieved by various forms of exercise, not only the aerobic form. Interaction of exercise and other forms of treatment is another important aspect. In one study the combination of exercise and counselling was found to be more effective than counselling alone (Rueter et al. 1982). We found a significant increase in therapeutic effect when exercise was added to a general hospital treatment programme (Martinsen et al. 1985). The combination of exercise and cognitive therapy, however, was not significantly better than either of the 2 used alone (Freemont & Craighead 1987). Thus, the results are divergent, indicating a need for more studies. The interaction of exercise and medication is of particular interest, as the use of tricyclic antidepressants is the best established treatment method for depression. This has been addressed in 2 studies: while 1 study showed no better outcome in patients who were on tricyclic antidepressants (Martinsen 1987a), in the second study there was a nonsignificant trend towards better outcome for those who used medication in addition to exercise (Martinsen et al. 1989b). Thus, there may be an additional effect in combining the two, but it does not seem to be large. Only patients with mild to moderate forms of unipolar depressive disorders were studied. No study has addressed the value of exercise intervention in patients with melancholia or psychotic depression, or in the treatment of bipolar disorders. However, clinical experience from the US (Greist 1987) and from Norwegian hospitals (Martinsen 1987b) indicates that the value of exercise intervention in these disorders is of limited value. Thus, the results are restricted to the mild to moderate forms of unipolar depressive illness, which are the most common forms.
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7. Adherence Depressive disorders have a great tendency for relapse. The value of self-administered strategies like exercise is therefore highly dependent on the degree to which the patients continue with the activity after the termination of the training programmes. One to 2 hours aerobic exercise per week is necessary to maintain aerobic capacity in trained individuals (Pollock 1978). Adherence rates to exercise programmes ranging from II to 89% have been reported in other populations, with a mean of 50% (Dishman 1987). Five of the 8 outpatient studies reported adherence rates at termination of the programme, ranging from 92% (Freemont & Craighead 1987) to 56% (Klein et al. 1985). In our hospital studies we found aherence rates between 97% (Martinsen et al. 1989c) and 86% (Martinsen et al. 1985). Three studies reported adherence rates at 4 to 12 months follow-up, ranging from 37% (Klein et al. 1985) to 79% (Freemont & Craighead 1987). Our inpatients studies showed that 53% (Martinsen et al. 1989c) and 54% (Martinsen & Medhus 1989) of patients who had participated in exercise programmes at the hospital still exercised regularly I year after discharge, and most of these exercised aerobically at least 2 hours per week. In studies comparing aerobic and nonaerobic training conditions there was a nonsignificant tendency for lower adherence rates in aerobic than in nonaerobic training programmes; 60% vs 71 % (Doyne et al. 1987), and 84 vs 98% (Martinsen et al. 1989a). Adherence rates in psychiatric populations do not seem to differ much from those in other populations. More than half of the patients continued with regular exercise I year after termination of the training programmes. Thus, physical exercise programmes seem to have a lasting effect on exercise habits in a large proportion of depressed patients.
8. Exercise Adherence and Mental Health Previous studies found diverging results regarding the correlation between mental health and exercise adherence 1 year after termination of the
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training programmes. Sime (1987) found a clear tendency; subjects who continued with regular exercise maintained low depression scores, while those who dropped out tended to relapse. Klein et al. (1985), however, found no such tendency. In 2 studies patients who had taken part in hospital exercise programmes for 6 to 9 weeks were investigated. 132 patients in total were studied I year after discharge. Patients who continued with regular exercise had lower symptom scores than the sedentary ones. We found diverging results regarding strength of the correlation between exercise adherence and depression scores. In I study (Martinsen et al. 1989c) this correlation was strong and highly statistically significant (r = -0.45, p < 0.01), while in the other (Martinsen & Medhus 1989) the correlation was weak and not statistically significant (r = -0.20, p > 0.05). Thus, those who continue with regular exercise tend to have lower depression scores than the sedentary ones, but the strength of the correlation between exercise adherence ann depression scores is unclear.
9. Evaluation A common attitude among psychiatric health workers has been that patients do not like to take part in strenuous physical exercise programmes (Kathol 1984). There is no empirical evidence, however, to support this assumption. A simple way to test this is simply to ask patients about what they think has helped them. This approach has been useful in the evaluation of other forms of treatment (Llewelyn 1988). We asked patients to rank the usefulness of exercise as compared with other forms of treatment (Martinsen et al. 1989c; Martinsen & Medhus 1989). Both studies showed that patients evaluated physical fitness training as the most important element in the comprehensive treatment programmes. It was ranked above traditional forms of therapy; psychotherapy, milieu therapy and medication. Although these results of course do not prove that physical exercise is more effective than other forms of therapy, they do show
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that patients appreciate physical fitness training as part of comprehensive treatment programmes.
10. Possible Mechanisms The mechanisms mediating the beneficial effects of exercise on mental status are unknown, but various hypotheses have been put forward. Several biological changes accompany exercise, and some of these have been forwarded as explanations for the antidepressive effects. The most important of these are discussed. One explanation has been the temporary increase in body temperature, which accompanies intensive exercise, the so-called 'pyrogen hypothesis' (Morgan 1984). It has been demonstrated that plasma catecholamine concentrations at a constant exercise intensity are lower following endurance exercise training (Cousineau et al. 1977). Lymphocyte i3-receptor activity also is reduced as a result of aerobic endurance training (Gordon et al. 1983). An increase in circulating i3-endorphin concentrations appears to occur with endurance exercise (Carr et al. 1981; Howlett et al. 1984). An increase in the concentrations of monoamines in the brain also have been postulated to accompany aerobic exercise (Ransford 1982). It is important to note that empirical evidence linking these biological phenomena to depression is lacking. As explanations of the antidepressive effects associated with exercise they must be considered as hypotheses. Based on the limited data available, if the psychological benefits of exercise have a biological basis, then it is sustained aerobic exercise that most likely will provide the necessary stimulus (Haskell 1987). Our findings that the same psychological gains were found to accompany nonaerobic as well as aerobic exercise are indirect arguments against the biological hypotheses. This opens up the field for psychological mechanisms, like mastering (White 1959), self-efficacy (Bandura 1977) and distraction (Bahrke & Morgan 1978).
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Exercise in the Treatment of Depression
11. Practical Management Several components in the depressive syndrome may make it difficult to exercise. Fatigue, lassitude, low self-esteem and psychomotor retardation are common symptoms. For those receiving tricyclic antidepressant agents, side effects like dryness of mouth, drowsiness and increased heart rate may cause additional problems. Because of these factors many patients will need encouragement and support when starting to exercise. It is important that the intensity of exercise is no higher than what the patients can master, because most patients are unfit. When these factors are taken into account, we have found that it is possible to help a large proportion of depressed patients start with regular exercise.
reasonably well adapted to medication, intensive exercise can start. If this rule is followed, physically healthy people who require psychotropic medication may safely exercise (Martinsen 1987a).
13. Implications for Psychiatric Treatment
During the last 10 years more than 200 patients aged 17 to 60 years involved in the research at our hospital have taken part in systematic physical training programmes. Most of these have performed aerobic exercise, most commonly brisk
The present studies show that depressed patients are on the average more sedentary and less physically fit than the general population, and that a substantial increase in physical fitness is obtained by regular physical training programmes. Patients appreciate physical training as an important activity, and more than 50% continue with regular exercise I year after termination of the treatment programmes. These findings are important arguments for integrating physical fitness training into comprehensive treatment programmes for depression. The psychological effects are best documented for nonbipolar, nonpsychotic depressive disorders, and for these disorders physical exercise may be considered as a supplement or an alternative to traditional forms of therapy. Most studies have used aerobic exercise pro-
walks or jogging. We have had no serious compli-
grammes. Recent studies, however, strongly indi-
cations associated with the training. When previously sedentary patients start with exercise, some will experience overuse injuries. These are minor and self-limiting, and the treatment simple. Reduced level of exercise eventually combined with anti-inflammatory drugs for some days is almost always successful. The patients involved in this research have undergone careful medical screening. Patients with a history of cardiovascular disease, or those suspected of having such a disease, have not taken part in the exercise programmes until they have been cleared by a cardiologist. A number of patients have received tricyclic antidepressant agents as part of their treatment. Among the side effects of these drugs are effects on the cardiovascular system. Our policy has been that the intensity of exercise should be low while the doses of medication are increasing. When one has reached steady-state level, and the circulation is
cate that an increase in aerobic fitness is not a necessary condition for the antidepressive benefits. This has implications for practical training. For the psychological gains, the important point seems to be the participation in exercise itself, not the acquisition of a fitness effect. This leaves important freedom for instructors and patients; they can choose activities which suit for the individual, and do not need to focus the aerobic element of training.
12. Practical Complications
14. Implications for Future Research Although all published studies on clinically depressed patients indicate that exercise is associated with an antidepressive effect, the studies are few, and most of them have methodological shortcomings. More well designed studies are needed. An important aspect would be to compare physical exercise with established treatment methods.
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Some studies have compared exercise with psychotherapy and counselling, finding no statistically significant differences among the various methods (Freemont & Craighead 1987; Greist et al. 1979; Klein et al. 1985). This opens up interesting perspectives, and should be followed by new well-controlled studies. Clinical experience indicates that the individual differences in the therapeutic response to exercise are great. For some patients exercise seems to be very useful, while in others the psychological benefits are minimal. The identification of patients responding especially well to exercise might be an important topic for future research. In one study (Martinsen et al. 1989c) 2 factors which predicted long term treatment response were identified. Those who had received no previous psychiatric treatment and those with previous adult experience with exercise and sports were doing well at follow-up. The first factor is unspecific. The second factor, however, is more interesting, as it may be exercisespecific. This is a new finding, which needs to be replicated in studies to come. The identification of the effective elements within exercise is another topic of interest. One study focussed upon objective measures of physical work capacity, finding that increases in physical fitness were not essential for the antidepressive effects (Martinsen et al. 1989b). What the effective elements of exercise intervention are is still unknown. Candidates for this are the patients' subjective experience of altered fitness state, rather than the objective fitness level. Other factors may be changes in self-concept, body image, experiences of mastering and group cohesiveness. The identification of potentially effective elements is important. A more precise knowledge about this will make it possible to emphasise these factors in the practical training, and thereby enhance the therapeutic effects.
15. Conclusion Depressed patients in general are physically sedentary. On average they have reduced physical work capacity, but normal pulmonary function,
compared with the general population. This indicates that the reduced fitness level is caused by physical inactivity, and is a strong argument for integrating physical fitness training into comprehensive treatment programmes for depression. Exercise is associated with an antidepressive effect in patients with mild to moderate forms of unipolar depression. No studies on patients with melancholic, psychotic or bipolar depressive disorders have been published, but clinical experience indicates that exercise intervention is of limited value in the treatment of these disorders. Most studies have used aerobic forms of exercise, but increases in aerobic fitness do not seem to be essential for the antidepressive effects as similar results are obtained with nonaerobic forms of exercise. More than half of the patients continue with regular exercise 1 year after termination of the training programmes, and patients who continue to exercise tend to have lower depression scores than the sedentary ones. Patients appreciate physical exercise, and rank exercise to be the most important element in comprehensive treatment programmes for depression. Exercise seems to be a promising new approach in the treatment of nonbipolar depressive disorders of mild to moderate severity.
Acknowledgements These studies have been supported by The Norwegian Council for Science and the Humanities (NAVF) [Grant no 13.39.66-186], The Research Institute at the Modum Bads Nervesantorium, Ciba-Geigy Pharma A/S, Maja and Jonn Nilsen's Legacy, Josef and Haldis Andresen's Legacy, and the Sogn og Fjordane County. Research Director Svein Friis, MD, has made valuable comments on this paper.
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Aaaro LE, Brekke T. Physical activity among adult Norwegians. Journal of the Norwegian Medical Association 103: 402-409, 1983 Asberg M, Perris C, Schalling D, Sed vall G. The CPRS - development and applications of a psychiatric rating scale. Acta Psychiatrica Scandinavica 271 (Suppl.): 1-27, 1978 Astrand I. Aerobic work capacity in men and women with special reference to age. Acta Physiologica Scandinavica 169 (Suppl.) 1960 Astrand PO, Rodahl K. Textbook in work physiology, McGrawHill, New York, 1985 Bahrke MS, Morgan WP. Anxiety reduction following exercise and meditation. Cognitive Therapy and Research 4: 323-333, 1978 Bandura A. Self-efficacy: toward a unifying theory of behavioural change. Psychological Review 84: 191-215, 1977 Beck AT, Ward CH, Mendelsohn M, Mock J, Erbaugh H. An inventory for measuring depression. Archives of General Psychiatry 4: 561-571, 1961 Carr DB. Bullen BA, Skrinar GS, Arnold MA, Rosenblatt M, et al. Physical conditioning facilitates the exercise-induced secretion of beta-endorphin and beta-lipoprotein in women. New England Journal of Medicine 305: 560-563, 1981 Cousineau D, Ferguson RJ, de Champlain J, Gauthier P, Cote P, et al. Cathecolamines in cornary sinus during exercise in man before and after training. Journal of Applied Physiology 43: 801-806, 1977 Derogatis LR, Lipman RS, Covi L. An outpatient rating scale preliminary report. Psychopharmacological Bulletin 9: 13-28, 1973 Dishman R. Exercise adherence and habitual physical activity. In Morgan & Goldston (Eds) Exercise and mental health, Hemisphere Publishing, Washington, 1987 Doyne EJ, Chambless DL, Beutler LE. Aerobic exercise as a treatment for depression in women. Behavioural Therapy 14: 434440, 1983 Doyne EJ, Ossip-Klein DJ, Bowman ED, Osborn KM, McDougall-Wilson IB, et at. Running versus weight-lifting in the treatment of depression. Journal of Consulting and Clinical Psychology 55: 748-754, 1987 Eisemann M. Leisure activities in depressed patients. Acta Psychiatrica Scandinavica 71: 495-498, 1985 Freemont J, Craighead LW. Aerobic exercise and cognitive therapy in the treatment of dysphoric moods. Cognitive Therapy and Research 2: 241-251, 1987 Gordon E, Savin W, Haskell WL, Bristow M. {3-adrenergic receptor response to exercise training in the presence of {3-1 selective and non-selective blockade. Circulation 68: 148, 1983 Greist JH, Klein MH, Eischens RR, Faris J, Gurman AS, et al. Running as a treatment for depression. Comprehensive Psychiatry 20: 41-54, 1979 Greist JH. Exercise intervention with depressed outpatients. In Morgan & Goldston (Eds) Exercise and mental health, Hemisphere Publishing, Washington 1987 Hamilton M. A rating scale for depression. Journal of Neurological and Neurosurgical Psychiatry 23: 56-61, 1960 Haskell WL. Developing an activity plan for improving health. In Morgan & Goldston (Eds) Exercise and mental health, Hemisphere Publishing, Washington, 1987 Howlett TA, Tomlin S, NgahtTong L, Rees LH, Bulen BA, et al. Release of beta endorphin and met-enkephalin during exercise in normal women. British Medical Journal 288: 1950-1952, 1984 Kathol RE. Running. American Journal of Psychiatry 141: 16351636, 1984 Klein MH, Greist JH, Gurman AS, Neimeyer RA, Lesser DP, et al. A comparative outcome study of group psychotherapy vs exercise treatments for depression. International Journal of Mental Health 13: 148-177, 1985
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Llewelyn SP. Psychological therapy as viewed by therapists and clients. British Journal of Clinical Psychology 27: 223-237, 1988 Lubin B. Adjective checklist for measurement of depression. Archives of General Psychiatry 12: 47-62, 1965 Martinsen EW. Exercise and medication in the psychiatric patient. In Morgan & Goldston (Eds) Exercise and mental health. Hemisphere Publishing, Washington, 1987a Martinsen EW. The role of aerobic exercise in the treatment of depression. Stress Medicine 3: 93-100, 1987b Martinsen EW, HotTart A, Solberg 0. Comparing aerobic and nonaerobic forms of exercise in the treatment of clinical depression: a randomized trial. Comprehensive Psychiatry 30: 324-331, 1989b Martinsen EW, Medhus A. Exercise adherence and patients' evaluation of exercise in a comprehensive treatment programme for depression. Nordic Journal of Psychiatry 43: 521-529, 1989 Martinsen EW, Medhus A, Sandvik L. EtTects of aerobic exercise on depression: controlled study. British Medical Journal 291: 109, 1985 Martinsen EW, Sandvik L, Kolbjf1Jrnsrud 08. Aerobic exercise in the treatment of non psychotic mental disorders: an exploratory study. Nordic Journal of Psychiatry 43: 411-415, 1989c Martinsen EW, Strand J, Paulsson G, Kaggestad J. Physical fitness level in patients with anxiety and depressive disorders. International Journal of Sports Medicine 10: 58-61, 1989a McCann IL, Holmes DS. Influence of aerobic exercise on depression. Journal of Personality and Social Psychology 46: 11421147, 1984 Morgan WP. A pilot investigation of physical working capacity in depressed and nondepressed psychiatric males. Research Quarterly 4: 859-861, 1969 Morgan WP. Physical activity and mental health. In Eckhert & Montoye (Eds) Exercise and health, Human Kinetics Publishers, Champaign IL, 1984 Polloch ML. How much exercise is enough? Physician and Sportsmedicine 6: 50-54, 1978 Raglin JS. Exercise and mental health: beneficial and detrimental etTects. Sports Medicine 9: 323-329, 1990 Ransford CPo A role for amines in the antidepressant etTect of exercise. Medicine and Science in Sports and Exercise 14: 110, 1982 Rueter M, Mutrie N, Harris D. Running as an adjunct to counselling in the treatment of depression. Unpublished manuscript, The Pennsylvania State University, 1982 Sime WE. Exercise in the treatment and prevention of depression. In Morgan & Goldston (Eds) Exercise and mental health, Hemisphere Publishing, Washington, 1987 Simons AD, McGowan CR, Epstein LH, Kupfer OJ, Robertson R. Exercise as treatment for depression: an update. Clinical Psychological Review 5: 288-301, 1985 Spitzer RL, Endicott J, Robins E. Research diagnostic criteria. Archives of General Psychiatry 35: 773-782, 1978 Vitalograph Ltd. Tables for normal values oflung function, Morton Press, Buckingham, 1980 Weinstein WS, Meyers AW. Running as treatment for depression: is it worth it? Journal of Sports Psychology 5: 288-30 I, 1983 White R W. Motivation reconsidered: the concept of competence. Psychological Review 66: 297-333, 1959 Zung WWK, Richards CB, Short MJ. Self-rating depression scale in an outpatient clinic. Archives of General Psychiatry 13: 508515, 1965
Authors' address: Dr Egi/ W. Martinsen. Medical Director, Department of Psychiatry, Central Hospital of Sogn og Fjordane, N-6800 Ff1Jrde, Norway.
Sports Medicine 9 (6): 380-389, 1990 0112-1642/0006-0380/$05.00/0 © ADIS Press Limited
All rights reserved. SPORT2 285
Benefits of Exercise for the Treatment of Depression Egil W. Martinsen Department of Psychiatry, Central Hospital of Sogn og Fjordane, F0rde, Norway
Contents
Summary ..................................................................................................................................380 I. Classification of Depression .............. ................................................... ....... ............ ........... 38I 2. Physical Activity Level ....................................................................................................... 381 3. Physical Fitness ............................................................................................. ...................... 382 4. Exercise Intervention ...................... ....................................................................................382 5. Aerobic vs Nonaerobic Exercise ............................... ............... .................... ....................... 384 6. Discussion of Exercise Intervention Studies .....................................................................384 7. Adherence ................................................................,............................................................ 385 8. Exercise Adherence and Mental Health ............................................................................ 385 9. Evaluation ................................................................................................. ...........................386 10. Possible Mechanisms ......................... ......... ............................................... .........................386 II . Practical Management ................................................... .......... ............... .............. ............... 387 12. Practical Complications ............................. ......................................................................... 387 13. Implications for Psychiatric Treatment .............................................. ............................... 387 14. Implications for Future Research ...................................................................................... 387 15. Conclusion ............................................................................................. .............................. 388
Summary
In general, depressed patients are physically sedentary. They have reduced physical work capacity but normal pulmonary function compared with the general population. This indicates that the reduced fitness level is caused by physical inactivity and is a strong argument for integrating physical fitness training into comprehensive treatment programmes for depression. Exercise is associated with an antidepressive effect in patients with mild to moderate forms of nonbipolar depressive disorders. An increase in aerobic fitness does not seem to be essential for the antidepressive effect, because similar results are obtained with nonaerobic forms of exercise. More than half of the patients continue with regular exercise I year after termination of the training programmes. Patients who continue to exercise tend to have lower depression scores than the sedentary ones. Patients appreciate physical exercise, and rank exercise to be the most important element in comprehensive treatment programmes. Exercise seems to be a promising new approach in the treatment of nonbipolar depressive disorders of mild to moderate severity.
Exercise in the Treatment of Depression
Depression is a major health problem. The most common forms of treatment have been medication and various forms of psychotherapy. However, psychotherapy can never meet the needs of this common disorder, while medication may have unpleasant side effects, and the established treatment methods are not always effective. There is therefore a great need for effective low cost or self-administered strategies, with minimal dangerous side effects, which may be used alone or as adjuncts to the traditional forms of treatment. Physical exercise has been put forward as one such method. There has been a growing interest in the psychological effects associated with regular exercise during the last 20 years, and an increasing number of publications on this topic [for an overview of the beneficial and detrimental effects of exercise on mental health, see the article by Raglin (1990) in this issue] have emerged. Depression is the mental disorder most commonly studied, and aerobic exercise has been the most commonly used form of exercise intervention. The early studies often Consisted of small samples with poor methodology (Weinstein & Meyers 1983). In the last years, however, studies with quasiexperimental or experimental design have started to emerge. During the last 7 years my colleagues and I have performed a series of clinical investigations, where we have addressed aspects of physical exercise intervention in patients with unipolar depressive disorders. A search of the English language literature in the databases Medline and Dialog Information Services from 1980 to 1988 with the keywords 'depression', 'exercise' and 'aerobic' was performed. Studies on patients with clinical depression from bibliographies of other articles and papers presented at professional meetings were also included. The purpose of this paper is to review this literature, including these personal studies on central aspects of physical fitness and exercise intervention in clinically depressed patients. The paper focusses on physical activity level and physical fitness level prior to treatment. The exercise intervention studies in clinically depressed patients are reviewed, including studies comparing aerobic and nonaerobic forms of exercise. The adherence
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rate to exercise and patients' evaluation of exercise compared with other forms of treatment are addressed. Finally, the various hypotheses of mechanisms mediating the antidepressive effects of exercise are discussed in light of the present knowledge, and some aspects of the practical management of exercising depressed patients are mentioned; the implications ofthese findings for treatment and future research will also be addressed.
1. Classification of Depression The most precise diagnoses of depressive disorders are obtained by the use of criteria-based diagnostic systems. Examples of such are 'Research Diagnostic Criteria' [ROC] (Spitzer et al. 1978) and 'Diagnostic and Statistical Manual of Mental Disorders' (DSM-III) [American Psychiatric Association 1980]. The disorders which are classified as unipolar depressive disorders in the DSM-III are major depression, dysthymic disorder and depressive disorders not otherwise specified. Various self-report instruments have been developed to assess the severity of depression. The Beck Depression Inventory (BDI) [Beck et al. 1961] is one such instrument which is often used. In some studies patients are classified as clinically depressed when they have a score above the normal range on self-report instruments. This is an easy way of obtaining diagnoses, but it is less reliable than the use of diagnostic systems.
2. Physical Activity Level Depressed patients seem to engage in significantly fewer leisure activities than non psychiatric controls (Eisemann 1985), but no previous study has specifically addressed exercise habits of depressed patients. We registered physical activity level prior to admission in 235 patients, with mean age 39 years, with nonpsychotic mental disorders, most commonly unipolar depression (Martinsen et al. 1989b,c). All patients in our studies were hospitalised at the Modum Bads Nervesanatorium. This is a psychiatric clinic, specialising in inpatient treatment of patients with severe neuroses and per-
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sonality disorders. Prior to admission 23% of the patients exercised regularly. A previous national survey using the same questionnaires found that about 50% of the adult Norwegian population of the same age and with the same sex distribution performed regular exercise (Aare & Brekke 1983). This indicates that depressed patients may be physically sedentary compared with the general population.
3. Physical Fitness The most common measure of physical fitness is the physical work capacity (PWC), which usually is defined as the maximum oxygen consumption. PWC can be calculated indirectly from submaximal tests or measured directly from maximal tests. Maximal tests are most accurate if the test subjects are able to work near exhaustion (Astrand & Rodahl 1985). We have found only I study assessing the physical fitness level in depressed patients. Morgan (1969) studied 17 male patients admitted to a mental health centre. The level of depression was assessed with Zung's Self-Rating Depression Scale (Zung et al. 1965), PWC was calculated from a submaximal bicycle ergometer test. The study showed that the depressed patients had significantly lower PWC values than the nondepressed patients. In a sample of 90 inpatients, meeting the DSMIII-R criteria (American Psychiatric Association 1987) for anxiety and/or unipolar depressive disorders (Martinsen et al. 1989a), major depression and dysthymic disorder were the most common diagnoses. Shortly after admission bicycle ergometer tests were performed. PWC was calculated indirectly from submaximal tests and measured directly from maximal tests, and the results were compared with predicted normal values (Astrand 1960). We found that PWC was dramatically reduced with indirect calculations as well as direct measurements. With direct measurement the mean PWC values were 83% of predicted. We also studied lung function in these patients. No such study has previously been reported. Simple spirometry was performed with a dry spiro-
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meter. Forced vital capacity (FVC) was measured, forced expiratory volume in 1 second (FEV,) was calculated, and the values were compared with predicted normal values (Vitalograph 1980). We found that both FVC and FEV, values were slightly larger than predicted normal values: 103% and 109%, respectively. The PWC is strongly dependent upon the habitual physical activity level, while this only has minimal influence upon lung function. The finding of reduced PWC and normal pulmonary function strongly indicates that the low values of PWC are due to physical inactivity. This is consistent with the studies of exercise habits, showing that most patients were sedentary when seeking treatment. None of these studies, however, tells us anything about causal relationships. Do sedentary and less fit subjects become depressed because they are sedentary, or do depressed patients become sedentary and less fit because they are depressed? These questions are left for future research to answer.
4. Exercise Intervention Physical exercise may be divided into the following forms (American College of Sports Medicine 1980): (a) training of aerobic capacity and endurance (aerobic exercise); and (b) training of muscular strength and endurance, and flexibility, coordination and relaxation (nonaerobic exercise). Most exercise intervention studies had used aerobic exercise, most commonly jogging or running. Opinions diverged whether the psychological benefits of physical fitness training were restricted to aerobic exercise, or if the same could be achieved with other forms (Simons et al. 1985). In the following the literature on exercise intervention studies on clinically depressed patients with at least quasiexperimental design are reviewed. Ten studies were found. Two were quasiexperiments with multiple baseline designs, where the subjects served as their own controls. Eight were experimental studies, where patients were randomly assigned to different treatment conditions. In 2 experiments aerobic and nonaerobic forms of exercise were compared.
Exercise in the Treatment of Depression
Doyne et al. (1983) used a multiple baseline design in a study of 4 women with major depression according to the ROC criteria. The level of depression was assessed by 2 self-report measures, Depression Adjective Checklist (DACL) [Lubin 1965] and the BDl. Reductions in depression scores were significantly greater during the aerobic exercise period (4 weekly sessions of ergometer bicycling for 6 weeks) compared with the attention placebo baseline period. Sime (1987) used a similar design on a sample of 15 moderately depressed subjects. No formal diagnoses were given and the level of depression was assessed by the BDI. Multiple measures of depression were obtained over several weeks' screening and a 2-week placebo exercise period prior to the 10-week aerobic training programme, consisting of 4 weekly sessions. Depression scores did not change significantly during the screening and placebo periods, but dropped significantly towards the end of the exercise period. The first experimental exercise intervention study on clinically depressed subjects was performed by Greist et al. (1979), who studied 28 outpatients, meeting the ROC criteria for minor depression. The level of depression was assessed by a self-report measure, Symptom Checklist-90 (SCL90) depression subscale (Derogatis et al. 1973). Patients were randomly assigned either to running (1 hour 3 to 4 times per week) or to 1 of 2 kinds of individual psychotherapy (1 session per week) for 12 weeks. The study showed that there were no statistically significant differences among the groups; significant reductions in depression scores were obtained in all groups. However, the study had methodological shortcomings, as the number of subjects was small, and the randomisation principle was not strictly adhered to. Rueter et al. (1982) studied 18 depressed outpatients with elevated BDI scores without formal diagnoses. They were randomly assigned to either counselling therapy (1 session per week), or to counselling and running (20 minutes supervised running 3 times per week). No significant reductions in depression scores occurred in the counselling group, while the running and counselling
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group achieved reductions in depression scores which were significant and significantly larger than in the counselling group. McCann & Holmes (1984) studied 43 depressed women with elevated BDI scores with no formal diagnosis. They were randomly assigned to either aerobic exercise (1 hour twice per week), relaxation training (20 minutes 4 times per week) or a waiting list control condition. In all groups depression was reduced after 12 weeks, but the reductions in the aerobic group were significantly larger than in the 2 other groups. Klein et al. (1985) studied 74 outpatients meeting the ROC criteria for major or minor depression. The patients were randomly assigned to either aerobic exercise (running/walking 1 hour twice per week), meditation-relaxation (2 hours once per week) or group psychotherapy (2 hours per week) for 12 weeks. In each treatment group there were significant decreases in depression scores (SCL-90) after 12 weeks, but there were no significant differences among the groups. At 9 months follow-up the study indicated a better outcome for the exercise and meditation groups. Freemont and Craighead (1987) investigated 49 individuals with elevated BDI scores without formal diagnoses. They were randomly assigned to either aerobic exercise (three 20-minute sessions per week), cognitive therapy (I session per week) and a combination of the two. The depression scores dropped significantly during the study in each treatment group, and this effect was maintained at 2 months' follow-up. There were no significant differences among the groups. In a personal experiment (Martinsen 1987a; Martinsen et al. 1985) 49 inpatients meeting the DSM-III criteria for major depression were hospitalised and attended 1 or 2 sessions of individual psychotherapy per week, in addition to occupational and milieu therapy. The patients were randomly assigned either to a control group, receiving this standard treatment, or a training group, where 3 weekly sessions of occupational therapy were substituted by aerobic exercise for 1 hour. Nine in the training group and 14 in the control group received tricyclic antidepressant medication. The
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level of depression was assessed by the BDI and the Comprehensive Psychopathological Rating Scale (CPRS) depression subscale (Asberg et al. 1978), which is a therapist rating. After 6 to 9 weeks there was a statistically significant increase in PWC in the training group, while the control group was unchanged in this variable. Both groups had achieved significant reductions in depression scores, but the reductions in the training group were significantly greater than in the control group. Patients who were on tricyclic antidepressants had similar reductions in depression scores to those who did not use medication.
5. Aerobic vs Nonaerobic Exercise To assess the importance of the aerobic element of training, one has to compare aerobic and nonaerobic forms of exercise in the treatment of depression. Two studies have addressed this. Doyne et al. (1987) compared the effects of aerobic and nonaerobic exercise in the treatment of 41 patients meeting the RDC criteria for major or minor depression. Subjects exercised 4 times per week for 8 weeks. Subjects in the aerobic group walked or ran around an indoor track, while those in the nonaerobic group went through a standard lO-station programme on a Universal Exercise Machine. The level of depression was assessed by the BDI, the DACL and the Hamilton Rating Scale for Depression (HRSD) [Hamilton 1960]. This randomised study showed that both forms of exercise were significantly better than a waiting list control condition. The difference between the exercise groups was not statistically significant. The findings were remarkably consistent across measures. There was a nonsignificant trend on some measures favouring nonaerobic exercise. As no measurable fitness effects were achieved in the aerobic group, however, the importance of the aerobic element could not be specifically addressed. In a later study (Martinsen et al. I 989b) aerobic and nonaerobic forms of exercise in the treatment of patients meeting the DSM-III-R criteria (American Psychiatric Association 1987) for unipolar depressive disorders were compared. 99 hospitalised
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patients of both sexes were randomly assigned to aerobic (walking/running) or nonaerobic (training of muscular strength and endurance, flexibility, coordination and relaxation) of exercise 1 hour 3 times per week for 8 weeks. In contrast to Doyne et al. (1987) the aerobic element was successfully manipulated. In the aerobic group there was a significant increase in aerobic capacity, while the nonaerobic group was unchanged on this variable. The difference in treatment outcome between the 2 forms of exercise was not statistically significant, and there was no observable tendency in favour of either of the two. In each group 14 patients used tricyclic antidepressants during the study. Those who were taking tricyclic antidepressants had a somewhat larger reduction in depression scores than those who did not use medication, but the difference was not statistically significant (Martinsen et al. 1989b).
6. Discussion 0/ Exercise Intervention Studies The most important methodological criteria for such studies are a design of either an experiment or a quasiexperiment, the use of stringent diagnostic criteria, the employment of standardised instruments for assessing the level of depression, ideally both self-report and therapist ratings, and inclusion of an adequate number of subjects. All the reviewed studies at least had a quasiexperimental design, and 6 of 10 used stringent diagnostic criteria. In all studies the level of depression was assessed with standardised instruments, but only 3 used therapist ratings in addition to selfreport. Four studies consisted of small samples, and in one study the randomisation procedures were not strictly adhered to. In spite of the fact that the number of studies are few, and that many have methodological shortcomings, it is striking that the results in all studies point in the same direction. Aerobic exercise is more effective than no treatment, and not significantly different from other forms of treatment, including various forms of psychotherapy. This indicates that aerobic exercise is associated with an
Exercise in the Treatment of Depression
antidepressive effect in patients with mild to moderate forms of depression. The studies comparing aerobic and nonaerobic forms of exercise strongly suggest that increase in physical fitness level is not a necessary precondition for the antidepressive effect. Reductions in depression scores may be achieved by various forms of exercise, not only the aerobic form. Interaction of exercise and other forms of treatment is another important aspect. In one study the combination of exercise and counselling was found to be more effective than counselling alone (Rueter et al. 1982). We found a significant increase in therapeutic effect when exercise was added to a general hospital treatment programme (Martinsen et al. 1985). The combination of exercise and cognitive therapy, however, was not significantly better than either of the 2 used alone (Freemont & Craighead 1987). Thus, the results are divergent, indicating a need for more studies. The interaction of exercise and medication is of particular interest, as the use of tricyclic antidepressants is the best established treatment method for depression. This has been addressed in 2 studies: while 1 study showed no better outcome in patients who were on tricyclic antidepressants (Martinsen 1987a), in the second study there was a nonsignificant trend towards better outcome for those who used medication in addition to exercise (Martinsen et al. 1989b). Thus, there may be an additional effect in combining the two, but it does not seem to be large. Only patients with mild to moderate forms of unipolar depressive disorders were studied. No study has addressed the value of exercise intervention in patients with melancholia or psychotic depression, or in the treatment of bipolar disorders. However, clinical experience from the US (Greist 1987) and from Norwegian hospitals (Martinsen 1987b) indicates that the value of exercise intervention in these disorders is of limited value. Thus, the results are restricted to the mild to moderate forms of unipolar depressive illness, which are the most common forms.
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7. Adherence Depressive disorders have a great tendency for relapse. The value of self-administered strategies like exercise is therefore highly dependent on the degree to which the patients continue with the activity after the termination of the training programmes. One to 2 hours aerobic exercise per week is necessary to maintain aerobic capacity in trained individuals (Pollock 1978). Adherence rates to exercise programmes ranging from II to 89% have been reported in other populations, with a mean of 50% (Dishman 1987). Five of the 8 outpatient studies reported adherence rates at termination of the programme, ranging from 92% (Freemont & Craighead 1987) to 56% (Klein et al. 1985). In our hospital studies we found aherence rates between 97% (Martinsen et al. 1989c) and 86% (Martinsen et al. 1985). Three studies reported adherence rates at 4 to 12 months follow-up, ranging from 37% (Klein et al. 1985) to 79% (Freemont & Craighead 1987). Our inpatients studies showed that 53% (Martinsen et al. 1989c) and 54% (Martinsen & Medhus 1989) of patients who had participated in exercise programmes at the hospital still exercised regularly I year after discharge, and most of these exercised aerobically at least 2 hours per week. In studies comparing aerobic and nonaerobic training conditions there was a nonsignificant tendency for lower adherence rates in aerobic than in nonaerobic training programmes; 60% vs 71 % (Doyne et al. 1987), and 84 vs 98% (Martinsen et al. 1989a). Adherence rates in psychiatric populations do not seem to differ much from those in other populations. More than half of the patients continued with regular exercise I year after termination of the training programmes. Thus, physical exercise programmes seem to have a lasting effect on exercise habits in a large proportion of depressed patients.
8. Exercise Adherence and Mental Health Previous studies found diverging results regarding the correlation between mental health and exercise adherence 1 year after termination of the
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training programmes. Sime (1987) found a clear tendency; subjects who continued with regular exercise maintained low depression scores, while those who dropped out tended to relapse. Klein et al. (1985), however, found no such tendency. In 2 studies patients who had taken part in hospital exercise programmes for 6 to 9 weeks were investigated. 132 patients in total were studied I year after discharge. Patients who continued with regular exercise had lower symptom scores than the sedentary ones. We found diverging results regarding strength of the correlation between exercise adherence and depression scores. In I study (Martinsen et al. 1989c) this correlation was strong and highly statistically significant (r = -0.45, p < 0.01), while in the other (Martinsen & Medhus 1989) the correlation was weak and not statistically significant (r = -0.20, p > 0.05). Thus, those who continue with regular exercise tend to have lower depression scores than the sedentary ones, but the strength of the correlation between exercise adherence ann depression scores is unclear.
9. Evaluation A common attitude among psychiatric health workers has been that patients do not like to take part in strenuous physical exercise programmes (Kathol 1984). There is no empirical evidence, however, to support this assumption. A simple way to test this is simply to ask patients about what they think has helped them. This approach has been useful in the evaluation of other forms of treatment (Llewelyn 1988). We asked patients to rank the usefulness of exercise as compared with other forms of treatment (Martinsen et al. 1989c; Martinsen & Medhus 1989). Both studies showed that patients evaluated physical fitness training as the most important element in the comprehensive treatment programmes. It was ranked above traditional forms of therapy; psychotherapy, milieu therapy and medication. Although these results of course do not prove that physical exercise is more effective than other forms of therapy, they do show
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that patients appreciate physical fitness training as part of comprehensive treatment programmes.
10. Possible Mechanisms The mechanisms mediating the beneficial effects of exercise on mental status are unknown, but various hypotheses have been put forward. Several biological changes accompany exercise, and some of these have been forwarded as explanations for the antidepressive effects. The most important of these are discussed. One explanation has been the temporary increase in body temperature, which accompanies intensive exercise, the so-called 'pyrogen hypothesis' (Morgan 1984). It has been demonstrated that plasma catecholamine concentrations at a constant exercise intensity are lower following endurance exercise training (Cousineau et al. 1977). Lymphocyte i3-receptor activity also is reduced as a result of aerobic endurance training (Gordon et al. 1983). An increase in circulating i3-endorphin concentrations appears to occur with endurance exercise (Carr et al. 1981; Howlett et al. 1984). An increase in the concentrations of monoamines in the brain also have been postulated to accompany aerobic exercise (Ransford 1982). It is important to note that empirical evidence linking these biological phenomena to depression is lacking. As explanations of the antidepressive effects associated with exercise they must be considered as hypotheses. Based on the limited data available, if the psychological benefits of exercise have a biological basis, then it is sustained aerobic exercise that most likely will provide the necessary stimulus (Haskell 1987). Our findings that the same psychological gains were found to accompany nonaerobic as well as aerobic exercise are indirect arguments against the biological hypotheses. This opens up the field for psychological mechanisms, like mastering (White 1959), self-efficacy (Bandura 1977) and distraction (Bahrke & Morgan 1978).
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Exercise in the Treatment of Depression
11. Practical Management Several components in the depressive syndrome may make it difficult to exercise. Fatigue, lassitude, low self-esteem and psychomotor retardation are common symptoms. For those receiving tricyclic antidepressant agents, side effects like dryness of mouth, drowsiness and increased heart rate may cause additional problems. Because of these factors many patients will need encouragement and support when starting to exercise. It is important that the intensity of exercise is no higher than what the patients can master, because most patients are unfit. When these factors are taken into account, we have found that it is possible to help a large proportion of depressed patients start with regular exercise.
reasonably well adapted to medication, intensive exercise can start. If this rule is followed, physically healthy people who require psychotropic medication may safely exercise (Martinsen 1987a).
13. Implications for Psychiatric Treatment
During the last 10 years more than 200 patients aged 17 to 60 years involved in the research at our hospital have taken part in systematic physical training programmes. Most of these have performed aerobic exercise, most commonly brisk
The present studies show that depressed patients are on the average more sedentary and less physically fit than the general population, and that a substantial increase in physical fitness is obtained by regular physical training programmes. Patients appreciate physical training as an important activity, and more than 50% continue with regular exercise I year after termination of the treatment programmes. These findings are important arguments for integrating physical fitness training into comprehensive treatment programmes for depression. The psychological effects are best documented for nonbipolar, nonpsychotic depressive disorders, and for these disorders physical exercise may be considered as a supplement or an alternative to traditional forms of therapy. Most studies have used aerobic exercise pro-
walks or jogging. We have had no serious compli-
grammes. Recent studies, however, strongly indi-
cations associated with the training. When previously sedentary patients start with exercise, some will experience overuse injuries. These are minor and self-limiting, and the treatment simple. Reduced level of exercise eventually combined with anti-inflammatory drugs for some days is almost always successful. The patients involved in this research have undergone careful medical screening. Patients with a history of cardiovascular disease, or those suspected of having such a disease, have not taken part in the exercise programmes until they have been cleared by a cardiologist. A number of patients have received tricyclic antidepressant agents as part of their treatment. Among the side effects of these drugs are effects on the cardiovascular system. Our policy has been that the intensity of exercise should be low while the doses of medication are increasing. When one has reached steady-state level, and the circulation is
cate that an increase in aerobic fitness is not a necessary condition for the antidepressive benefits. This has implications for practical training. For the psychological gains, the important point seems to be the participation in exercise itself, not the acquisition of a fitness effect. This leaves important freedom for instructors and patients; they can choose activities which suit for the individual, and do not need to focus the aerobic element of training.
12. Practical Complications
14. Implications for Future Research Although all published studies on clinically depressed patients indicate that exercise is associated with an antidepressive effect, the studies are few, and most of them have methodological shortcomings. More well designed studies are needed. An important aspect would be to compare physical exercise with established treatment methods.
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Some studies have compared exercise with psychotherapy and counselling, finding no statistically significant differences among the various methods (Freemont & Craighead 1987; Greist et al. 1979; Klein et al. 1985). This opens up interesting perspectives, and should be followed by new well-controlled studies. Clinical experience indicates that the individual differences in the therapeutic response to exercise are great. For some patients exercise seems to be very useful, while in others the psychological benefits are minimal. The identification of patients responding especially well to exercise might be an important topic for future research. In one study (Martinsen et al. 1989c) 2 factors which predicted long term treatment response were identified. Those who had received no previous psychiatric treatment and those with previous adult experience with exercise and sports were doing well at follow-up. The first factor is unspecific. The second factor, however, is more interesting, as it may be exercisespecific. This is a new finding, which needs to be replicated in studies to come. The identification of the effective elements within exercise is another topic of interest. One study focussed upon objective measures of physical work capacity, finding that increases in physical fitness were not essential for the antidepressive effects (Martinsen et al. 1989b). What the effective elements of exercise intervention are is still unknown. Candidates for this are the patients' subjective experience of altered fitness state, rather than the objective fitness level. Other factors may be changes in self-concept, body image, experiences of mastering and group cohesiveness. The identification of potentially effective elements is important. A more precise knowledge about this will make it possible to emphasise these factors in the practical training, and thereby enhance the therapeutic effects.
15. Conclusion Depressed patients in general are physically sedentary. On average they have reduced physical work capacity, but normal pulmonary function,
compared with the general population. This indicates that the reduced fitness level is caused by physical inactivity, and is a strong argument for integrating physical fitness training into comprehensive treatment programmes for depression. Exercise is associated with an antidepressive effect in patients with mild to moderate forms of unipolar depression. No studies on patients with melancholic, psychotic or bipolar depressive disorders have been published, but clinical experience indicates that exercise intervention is of limited value in the treatment of these disorders. Most studies have used aerobic forms of exercise, but increases in aerobic fitness do not seem to be essential for the antidepressive effects as similar results are obtained with nonaerobic forms of exercise. More than half of the patients continue with regular exercise 1 year after termination of the training programmes, and patients who continue to exercise tend to have lower depression scores than the sedentary ones. Patients appreciate physical exercise, and rank exercise to be the most important element in comprehensive treatment programmes for depression. Exercise seems to be a promising new approach in the treatment of nonbipolar depressive disorders of mild to moderate severity.
Acknowledgements These studies have been supported by The Norwegian Council for Science and the Humanities (NAVF) [Grant no 13.39.66-186], The Research Institute at the Modum Bads Nervesantorium, Ciba-Geigy Pharma A/S, Maja and Jonn Nilsen's Legacy, Josef and Haldis Andresen's Legacy, and the Sogn og Fjordane County. Research Director Svein Friis, MD, has made valuable comments on this paper.
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Authors' address: Dr Egi/ W. Martinsen. Medical Director, Department of Psychiatry, Central Hospital of Sogn og Fjordane, N-6800 Ff1Jrde, Norway.
