Acta psychiat. scand. (1975) 51, 77-87 Department of Social Medicine (Head: Professor B. Lindegdrd), University of Gothenburg, Gothenburg, Sweden

D E P R E S S I O N : P R E D I S P O S I N G FACTORS

s. NYSTROM AND B. LINDEG~RD Factors predisposing to a depressive state had been investigated in a prospective study on a stratified population, accounted for in the preceding article (Nystrorn & Lindegdrd (1975a)). Of the 114 persons seeking psychiatric care during the period of observation, 37 had a depression as the main diagnosis. As compared to their 370 matched controls, these patients showed a significant overrepresentation of psychasthenic traits (subvalidity according to Sjobring), a tendency to ruminate, shyness in company and lack of endurance, certain asthenic subclinical symptoms such as habitual fatigue and irritability, certain depressive subclinical phenomena, various expressions of anxiousness, all kinds of insomnia, and certain forms of medical care and examinations. The findings can be used for mental hygienic purposes. It can be recommended that the environmental pressure within occupational as well as within private life, should be kept as low as possible, especially for persons with characteristics shown to indicate mental vulnerability. Key words. Depression - personality pattern - subclinical symptoms - anxiety - somatic symptoms - previous medical history environmental pressure.

This study is prospective and starts from a normal though selected population. The investigation aims at finding factors associated with the later appearance of a depressive syndrome. Such determinants might have a predisposing or only a pathoplastic influence on the disorder, The set-up of the investigation has been described in a previous paper (Lindeg i r d & Nystrom 1969), and here a presentation has also been given of the clinical phenomena during the period of observation and of the therapy given during that time. A second report dealt with factors predisposing to mental illness in general (Lindegird & Nystrom (1970)), and in a third study the specificity of various background factors has been analysed (Nystrom & Lindegird (1975a)). The present paper offers an example of that special use of epidemiological methods, where a more detailed nosological analysis is achieved.

78 Previous investigations

The papers on the premorbid characteristics of depressives are numerous. However, the possibilities to compare the present study with those mentioned are limited. Most earlier studies deal with psychotic patients, while the one here presented deals with patients whose depressions are of a moderate severity. The investigation by Laughlin (1956) forms an exception. The categorisation of the patients as to premorbid make-up is mostly carried out on the basis of clinical impression. The study of Perris (1966) is an exception in this respect, applying the same questionnaire on Sjobring variables as was used in the present investigation. As comparison groups, other sub-groups of depressives or other forms of mental illness are usually chosen. Titley (1936) in his study on involutional melancholia has used a different control group - healthy persons. This is undoubtedly necessary if conclusions as to predisposing power shall be allowed. Prospective studies are scanty in psychiatry, and there are none on factors predictive of a depressive case to the knowledge of the present authors. There are several drawbacks with such studies (cf. Reid (1960)), but if the difficulties as to size of material and methods of investigation of the individual person can be overcome, the results undoubtedly are more reliable than in retrospective studies.

MATERIAL AND METHODS As to the selection of the material, methods of sampling, investigation after the period of observation, and the delineation of the dependent variables the reader is referred to the preceding article (Nystrum & Lindegird (1975a)). In the study just mentioned, it was desirable to have as little overlapping as possible between the patient groups. Because of this, only those patients with depression as a main diagnosis were included. In only two of the cases, was the disturbance of a psychotic dimension. As the present study is an extension of the one just mentioned, the same delineation of the patient group has been used. In order to be able to confirm some of the results obtained, the giving of antidepressant (a-d) therapy was used as a dependent variable, parallel to depression. However, in the report of the results, the connections for a-d therapy with background factors will be commented upon only when they are of special interest. Analytical methods

This subject has also been dealt with in the preceding paper (Nystrom & Lindegird (1975a)). There are two supplementary remarks to take into account. As the studies for associations within the group of depressives ( n = 37, 370 controls) were compared with the associations in the total material of mentally

79 ill which was considerably larger (n = 114, 1140 controls), there was a need for a quantitative measure of the strength of the association in addition to the + d u e s , in order to permit comparisons. Therefore, from the x2-values, association coefficients were calculated according to the formula r2 = x 2 : n (Cram& (1946)). As a descriptive value of the patients' characteristics, the relationship for each non-continuous variable was determined by dividing the observed frequency among the patients, multiplied by ten, with the corresponding figure of the controls (the expected frequency). The reason for the multiplication was that ten controls were chosen for each patient. The value arrived at that way was called the O/E quotient (observed/expected).

RESULTS Social conditions

There is no association between income and the appearance of a depressive state. However, a connection, at an almost significant level, is present between this syndrome and previous financial support from the social welfare authorities (x2 = 3.77, d.f. l), as concerns mental illness in general. Only one of the depressives was registered for a traffic offence as compared to 20 in the control material.

Personality pattern Psychasthenic traits. The findings as to the Sjobring personality factors have been reported elsewhere (Nystrorn & Lindegbrd 1975a)). It will only be mentioned briefly here that there was an overrepresentation of patients with psychasthenic traits (sub-validity according to Sjobring (1913, 1973) among the depres= 7.17* d.f. 2). There was also a connection with psychasthenia for sives treatment with anti-depressants = 11.09**, d.f. 2). The finding on psychasthenia is in line with the statements of Sjobring (1919). The results are the same as those for mental disturbance in general (Lindegbrd & Nystrorn (1970)). As the depressives were almost all of the unipolar type, this result is also in line with that of Perris (1966) who demonstrated an overweight of subvalidity for unipolars when contrasted to bipolar cases. Angst (1966) also describes his depressives as conscientious, pedantic, and self-uncertain, and so does Laughlin (1956).

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(x*

Syntonia, hysteroid personality. For the variable syntonia (sub-stability according to Sjobring), no association with depression was found. Nor was there any association for hysteroid personality (sub-solidity according to Sjobring). An association between depression and syntonia has in general been assumed to exist. The negative result in this study might mean that earlier findings have been caused by bias. It should be recalled that syntonia has been proven to have importance for the response of depression to ECT (Nystrom (1964)).

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Mental illness (n=114)

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Patients (n=37)

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Depression y

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n=370)

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Depression: Predisposing factors.

Factors predisposing to a depressive state had been investigated in a prospective study on a stratified population, accounted for in the preceding art...
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