Impact of Expectations on the Effects of Exercise on Psychological Distress Björg Helgadóttir, MSc; Örjan Ekblom PhD; Yvonne Forsell PhD, MD Objective: To evaluate the influence of expectations on effectiveness of exercise in reducing psychological distress. Method: Data came from a Swedish longitudinal population-based study consisting of 4631 people aged 20-64 years. Psychological distress was measured with the Major Depressive Inventory. Expectations (positive expectations or indifference) towards exercise were combined with exercise (regular exercise: yes or no). Results: Indifferent non-exercisers had increased risk of psychological distress. Regular exer-

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sychological distress and mental health issues are prominent public health problems in the world today and depression is one of the most common mental health disorders. The lifetime prevalence of major depression in Europe has been found to be 12.8%1 and a Danish study showed that the prevalence is increasing.2 Many people with depression do not seek help from professionals instead they try to cope by using selfhelp strategies.3,4 One of the most popular self-help strategies for depression is exercise5 and it has the advantage of being potentially cost-effective, with few side-effects. Physical Exercise and Depression Research has been conducted on the beneficial effects of physical exercise on depressive symptoms. Longitudinal studies have shown that regular exercise can be a protective against developing depression.6-8 Exercise can also be used as a treatment and this has been explored in numerous clinical trials and subsequent systematic reviews and meta-analyses on the subject. Several metaanalyses have shown that exercise can reduce Björg Helgadóttir, PhD student, Karolinska Institutet, Department of Public Health Sciences, Stockholm, Sweden. Örjan Ekblom Senior lecturer, The Swedish School of Sport and Health Sciences, Stockholm, Sweden. Yvonne Forsell, Professor, Karolinska Institutet, Department of Public Health Sciences, Stockholm, Sweden. Correspondence Ms Helgadóttir; [email protected]

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cisers who were indifferent towards exercise as a self-help method were less likely to be psychologically distressed compared to exercisers with positive expectations. Conclusion: The results encourage systematic use of exercise in prevention and rehabilitation of persons suffering from psychological distress. People’s personal expectations might not be needed for treatment effect. Key words: exercise, expectations, placebo effects, cohort-study, depression Am J Health Behav. 2014;38(5):650-656 DOI: http://dx.doi.org/10.5993/AJHB.38.5.2

depressive symptoms, though the effect size differed.9-11 A Cochrane review compared the effects of exercise on depression with 3 other alternatives: no treatment, cognitive therapy and anti-depressants. The results showed that exercise had an advantage over no treatment and similar effect as cognitive therapy and anti-depressants. The findings also indicated that the effects of exercise may fade after the treatment ends.12 Results from another meta-analysis were consistent with this, as the authors concluded that there were only some short-term benefits of physical exercise on clinical depression. However, the authors suggest that this might be due to lack of adherence in long-term trials which might make it difficult to detect the effects.13 There have been some suggestions on possible mechanisms for the beneficial effects of exercise on depression, both somatic and psychological. Somatic pathways include adult-neurogenesis,14 improvements in the sleep cycle, changes in serotonin function,15,16 modifications in endorphin or monoamine levels and lower levels of cortisol.17 Psychological pathways consist of changes in increased self-efficacy, sense of mastery, interruption of negative thoughts, modification of action tendencies and social contact.11,15,18 Placebo Effects Stewart-Williams and Podd define placebo effects as “a genuine psychological or physiological effect, in human or another animal, which is attributable to receiving a substance or undergoing a

Helgadóttir et al procedure, but is not due to the inherent powers of that substance or procedure.”19 However, placebo effects need not be exclusive to substances or procedures that have no inherent powers. A controversial article by Kirsch and Sapirstein stated that large proportions of the effects of antidepressants are due to placebo effects.20 Hence, the placebo effect may be working on top of the effect derived from the real effects of the treatments.19 There are 2 main schools of thought when it comes to explaining placebo effects: classical conditioning and expectation theory. Classical conditioning holds that people (and animals) can be conditioned to learn to react to a stimuli (in this case placebo) in a certain way (ie, by getting better in response to the stimuli) because they have been conditioned to connect treatment with health benefits. Expectation theory maintains that placebos have an effect because people expect it to have an effect. Stewart-Williams and Podd19 attempted to unify these theories, suggesting that at least in some cases, conditioning is mediated by conscious expectations. As previously explained, exercise can reduce depressive symptoms but it is possible that some of that effect comes from placebo effects. Desharnsais et al21 conducted a randomized controlled trial where all participants received the same aerobic training but the experimental group was told that their training was meant to improve psychological well-being. The experimental group showed significantly bigger improvements in self-esteem compared with the control group. Another more recent study of psychological benefits associated with running showed that at least part of these improvements might have been the result of either conditioning or expectations.22 The effects of exercise could work through conditioning in a way that people who previously have experienced mental relief from exercising meaning that they unconsciously connect exercise with relief. This may add to a biological effect. Or, this effect could be mediated by expectations, with those that expect to get relief from exercising improving more than those that do not expect it, in other words, those who do not consciously seek exercise as a way to treat mental anguish.

pation rate 65.3%). Only those who responded to the first questionnaire were invited to participate at T2 and only those who participated at T2 could participate at T3.23,24 Psychological Distress As a proxy for psychological distress, depressive symptoms were measured using a Swedish translation of the Major Depression Inventory (MDI).25 This scale has been shown to have good validity, both in clinic-based and population-based settings.25,26 The MDI scale consists of 10 questions with response options on a 6-point Likert item, ranging from never (0 points) to all the time (5 points). The questions were summed to a Likert scale ranging from 0-50. MDI scores were calculated for T2 and T3, with the T3 scores used as a categorical outcome and the T2 scores used as a continuous confounder in the analysis. MDI scores were split into 5 categories (see Hjarsbech et al27), with the last category (MDI ≥ 20) representing the cut-off point for major depression in a population based sample.26

Aim The aim of this study was to study if the association between physical exercise and psychological distress was affected by expectations.

Exercise And Expectations Respondents were asked at T2 if they exercised regularly, meaning 2-3 times a week (response options were yes or no). Similar simple, single itemquestions have previously been shown to be valid measures for categorizing people into exercisers and non-exercisers.28,29 The participants also were asked what they do to feel better when they do not feel good, eg, because of personal problems or difficulties (also at T2). They could choose multiple options from a long list of self-help activities. This list derived from interviews conducted with a subsample of participants from T1.30 Exercise was one of the self-help activities on the list. Respondents that chose exercise were defined as having positive expectations towards exercise as a means to relieve psychological distress. Those that chose other methods were defined as being indifferent towards exercise as a means to relieve psychological distress. There was also a group of people who chose the option “never feel bad.” These were excluded from the analysis to eliminate any ambiguity about the variable’s definition. These 2 questions were then combined into 4 categories: positive expectations and exercise, positive expectations and no exercise, indifference and exercise, and finally, indifference and no exercise.

METHODS The data derived from the Swedish PART study (for more information see Hällström et al23). The study population included 19,742 persons aged 20-64 years residing in Stockholm County during the years 1998-2000. Questionnaires were mailed to the participants in 3 separate waves: T1 = 19982000 (participation rate: 52.9%); T2 = 2001-2003 (participation rate: 82.5%); and T3 = 2010 (partici-

Confounders Sex and age were obtained from registers. Age had a non-linear relationship with depressive symptoms, and was therefore used as a categorical variable. As previously described, the MDI score at T2 was used as a continuous confounder because the MDI score at T2 had a linear distribution with the categorized version of the MDI score at T3. Education (obtained from registers) in 3 catego-

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Impact of Expectations on the Effects of Exercise on Psychological Distress

Table 1 Characteristics of the Study Population Divided into Participants and Non-Participants, Differences Tested with χ2 Tests (Data Were Collected in Stockholm, Sweden from 1998 to 2010) Participantsa N Age* (mean)

Non-participantsb %

N

(46.41±0.17)

% (43.20±0.21)

20-30 years old

662

13.2

665

19.1

31-40 years old

1129

22.5

1014

29.1

41-50 years old

1074

21.4

691

19.8

51-60 years old

1466

29.2

739

21.2

61-70 years old

690

13.7

378

10.8

Men

2033

40.5

1564

44.9

Women

2988

59.5

1923

55.1

Primary ≤ 9 years

523

10.6

436

12.8

Secondary 9-12 years

2058

41.5

1562

45.8

University ≥ 12 years

2375

47.9

1415

Sex*

Education*

BMI (mean)

(24.75±4.13)

Underweight (BMI < 18.5)

41.5 (24.62±4.12)

60

1.27

65

1.97

Normal weight (BMI = 18.5-25)

2784

58.70

1939

58.90

Overweight (BMI = 25-30)

1494

31.50

1003

30.47

Obese (BMI ≥ 30)

405

8.54

285

8.66

No somatic disease

3803

79.91

2646

79.92

One or more somatic diseases

956

20.09

665

20.08

Positive expectations & exercise

2131

44.8

1361

41.1

Positive expectations & no exercise

698

14.7

490

14.8

Indifference & exercise

534

11.2

333

10.1

Indifference & no exercise

1396

29.3

1127

34.0

Somatic disease

Exercise**

p < .01, **p < .001

*

Note. Sex and education collected at T1, other variables collected at T2 a Participated at both T2 and T3 b Participated at T2

ries (primary ≤ 9 years, secondary 10-12 years and university ≥ 12 years) was considered a confounder along with body mass index (BMI) in its continuous form. Finally, presence of a somatic disorder was obtained from a list of 11 common chronic somatic disorders listed in the questionnaire, such as cardiovascular disorders and neurological dis-

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orders. Only those treated by a physician was taken into consideration. This variable was then dichotomized into yes/no. Statistical Analysis Non-participation analysis was performed using independent t-tests for continuous variables and

Helgadóttir et al χ2 tests for categorical variables. Participants were those that participated at both T2 and T3 while nonparticipants were those that dropped out between waves, ie, participated at T2 but not T3. The main analyses were performed using multinomial logistic regression since the MDI scale was positively skewed and leptokurtic rendering all methods inappropriate where linearity of the outcome variable is required. As taking the log of the MDI did not correct this problem multinomial logistic regression was the optimal way of analyzing the data. Multinomial logistic regression is similar to logistic regression except the outcome variable can have multiple categories instead of just 2. This allows comparison between those that are free from psychological distress (defined as MDI=0-4) to groups with varying degrees of severity (MDI=5-9, 10-14, 14-15,16-20 and ≥ 21). The potential confounders were checked for inclusion in the model by adding them one at a time into the model for the association between exercise/expectations and psychological distress. Those that changed the point estimates 10% or more were included in the final model. Age, sex, previous depressive symptoms, education and BMI fulfilled this criteria; somatic disease (yes/no) did not. All analyses were performed with SAS version 9.3 and the α-level for all significance tests was set at p < .05. RESULTS Table 1 provides a description of the study sample. Non-participants were more often men, younger, and with less education. The distribution across the expectations/exercise variable was unequal for non-participants compared with participants; non-participants were less likely to be in the category of positive expectations and exercise, but had higher percentages in the indifference and no exercise category compared to participants at both T2 and T3. A bigger proportion of non-participants were depressed (MDI ≥ 20) at T2 (10.91%) than those that participated at both T2 and T3 (7.9%). Of those that participated at both T2 and T3, 6.3% were depressed at T3. The distribution of characteristics across categories for the expectation/exercise variable (not shown in table) revealed that the distributions of sex and age were similar but it was notable that the indifference and no exercise category had a larger proportion of depressed people (MDI score ≥ 20). The opposite was seen in the category of positive expectations and exercise, which had a bigger proportion of non-depressed. Multinomial Logistic Regression Model Table 2 shows the results from the multinomial logistic regression with lowest MDI score (MDI = 0-4) as reference group. Persons that were indifferent towards exercise that exercised had lower MDI scores at the follow-up than the reference group of people with positive expectations who exercise in those with 5-9 points on the MDI scale. This incli-

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nation was also present for the groups MDI = 1014 and MDI≥20 though not statistically significant. Those that were indifferent, did not exercise had a higher risk of having an MDI score ≥ 15 at the follow-up. No significant differences were found between those that had positive expectations and did not exercise and persons who had positive expectations and exercised. The likelihood ratio test revealed that the variable of exercise in combination with expectation had an overall statistically significant association with the MDI variable in (p < .001). DISCUSSION Our results showed that persons that were neither regular exercisers nor had expectations that exercise will work as a self-help method for psychological distress had an increased risk of increased psychological distress at follow-up. These results are in line with those of previous cohort studies that found a link between regular exercise and lower risk of depression.6,7 Another interesting finding was that there was no difference between regular exercisers and non-exercisers when both had positive expectations towards exercise. This could be due to the effect being too small to detect as all the odds ratios pointed in the same direction, or that using exercise only as a response to psychological distress when it arises is enough to keep psychological distress at bay. The results also suggested that those who exercised without expectations tended to be less psychologically distressed at follow-up than those who exercised with positive expectations. These results might be interpreted to mean that having positive expectations towards exercise as a means to relieve psychological distress can be harmful. However other explanations seem more likely. De Moor et al31 investigated the causal relationship between regular exercise and depressive symptoms and found that the association could be explained by genetic factors. They concluded that the same genetic factors that lead people to exercise might also be protective against depression. Another possibility is that those who exercise with an indifferent attitude exercise in a different manner than those who expect exercise to relieve psychological distress. Results from randomized controlled trials suggest that exercise parameters, ie, intensity, frequency and duration, may change the effect size of exercise treatment on depression.9,32 Our exercise question did not capture these details but this could be explored in future studies. Yet another alternative explanation is that those with positive expectations towards exercise as a self-help strategy became disappointed if it did not work immediately and as a result stop exercising altogether during the follow-up period leading to worsening of psychological distress. Strengths and Limitations Among the strengths of this study were its size

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Impact of Expectations on the Effects of Exercise on Psychological Distress

Table 2 Multinomial Logistic Regression Model with Expectations Combined with Exercise as Independent Variable and Psychological Distress (MDI Score at T3) as the Dependant Variable Using MDI = 0-4 as a Reference Group, N = 4631(Data Were Collected in Stockholm, Sweden from 1998 to 2010)

Positive expectations & exercise

MDI = 5-9 (N = 1098)

MDI = 10-14 (N = 331)

MDI = 15-19 (N = 201)

MDI ≥ 20 (N = 300)

OR (95% CI)

OR (95% CI)

OR (95% CI)

OR (95% CI)

1

1

1

1

Positive expectations & no exercise

1.03 (0.83-1.28)

1.05 (0.73-1.51)

1.16 (0.73-1.86)

1.13 (0.75-1.71)

Indifference & exercise

0.77 (0.60-0.99)

0.75 (0.48-1.16)

1.20 (0.73-1.98)

0.66 (0.39-1.12)

Indifference & no exercise

1.03 (0.87-1.23)

1.28 (0.97-1.70)

1.46 (1.02-2.10)

1.49 (1.09-2.05)

Note. Adjusted for sex, age, education, MDI score at T2 and BMI MDI = 0-4 (N = 2701)

and the longitudinal design. Depressive symptoms were measured using the MDI, which has been reported to have good sensitivity and specificity25 and acceptable internal and external validity for patients with different levels of depression severity.33 However psychological distress is not interchangeable with depressive symptoms. Using depressive symptoms as a proxy for psychological distress is a limitation as it might not capture everything that is contained in the concept of psychological distress such as anxiety symptoms. However, depression is one of the most prominent mental disorders1 and shares many of its symptoms with anxiety disorders and at least half of those that experience major depression also experience an anxiety disorder.34 Our belief is, therefore, that this had only a marginal impact on the results. The response rate could be a possible limitation. Extensive non-response analyses were done after the first and second wave of the PART study using available official registers.24,35 Participation was found to be related to being female, older, higher income and education, being born in the Nordic countries, and having no psychiatric diagnosis in the hospital discharge register or in the early retirement register. The associations among age, sex, income, country of origin, and in-patient hospital care due to psychiatric diagnosis were calculated for participants and non-participants separately. The odds ratios (ORs) for these associations were similar for participants and non-participants.24,35 It is, therefore, likely that the results from the present study are only underestimating the relationships between the outcome and the exposure. Another potential limitation is the use of selfreport data which are associated with many complications,36 such as social desirability bias. This

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could affect the measurement of exercise in the present study as social norms have been shown to be predictive of intention to exercise.37 The exercise question used in this study asked about current regular exercise and the prevalence of regular exercise among the participants in this study was 56%. A previous self-report study on regular exercise among Swedes found a prevalence of 65% among women and 66% among men.38 This number is higher than what we found, perhaps due to differences in methods. The previous study used a dose definition (at least 30 minutes a day), which would identify those that, for example, walk to work but do not consider themselves to be regular exercisers. We chose to exclude the group that answered “never feel bad” on the self-help activities question as they made the definitions of the expectation group more difficult. This group was 4.9% of the sample (N = 248), they were more often men, were older, and had lower levels of depression, but there were no significant differences in exercise or education. Conclusions Positive expectations on the effect of exercise as a self-help strategy did not alter the effect on the association between exercise and having fewer symptoms of psychological distress at the followup. The study findings were consistent with previous studies that have found that levels of physical exercise are associated with depressive symptoms. The results of this study are important to further comprehension of the role of expectations when using exercise to alleviate psychological distress such as depressive symptoms. Additional knowledge on this subject could help health care professionals’

Helgadóttir et al advise and encourage their patients as well as assist with the design of interventions targeting individuals experiencing from psychological distress.

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Human Subjects Statement Ethical permission for the study came from the Karolinska Institutet ethical committee dnr: 96:260, 01-218, 04-528/3 and from the Regional ethical review board of Stockholm (Reginala etikprövningsnämden i Stockholm) dnr: 09-880. Conflict of Interest Statement All authors declare that they have no conflicts of interest. Acknowledgement The PART study was funded by the Swedish Medical Research Council [50211123] and the Stockholm County Council [LS0901-0004]. References

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Impact of expectations on the effects of exercise on psychological distress.

To evaluate the influence of expectations on effectiveness of exercise in reducing psychological distress...
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