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Severity of stressful life events in first and subsequent episodes of depression: the relevance of depressive subtype

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Abstract

Background: Recent studies have reignited debate concerning the relationship between stressful life events and depressive subtypes, particularly in relation to first versus subsequent episodes. Aims: To investigate the relationship between stressful life events and variably defined melancholic/non-melancholic depressive subtypes, and the import of such life events to first compared with subsequent episodes across those subtypes. Method: Acute and chronic stressful life events were rated in 270 patients with DSM-IV Major Depressive episodes who were allocated to melancholic and non-melancholic groups separately as defined by DSM-III-R, DSM-IV, the Newcastle criteria and the CORE system. Results: Severe stressful life events (both acute and chronic)—as defined by DSM-III-R axis IV—were more likely to occur prior to first rather than subsequent episodes, particularly for those with non-melancholic depression. Limitations: Dependence or independence of life events was not assessed. Genetic vulnerability to depression was not determined. Life events in first and subsequent depressive episodes were compared cross-sectionally between groups, not prospectively in the same cohort of patients. There were no differences in the number of severe life events—as defined by clinician consensus—between the first and subsequent episodes. Conclusions: These findings are consistent with other studies in suggesting an enhanced sensitisation of depressed patients to subsequent episodes of depression, but suggest that any such phenomenon is specific to non-melancholic depression, in comparison to one key previous study.

Introduction

While the ‘endogenous’ or ‘melancholic’ depressive disorder has been traditionally linked to an absence of life event stressors, formal studies of the association have not been unanimously supportive (Leff et al., 1970, Thomson and Hendrie, 1972, Bebbington et al., 1981, Paykel et al., 1984, Roy et al., 1985). Two recent studies have reopened this scientific debate. First, Frank et al. (1994), studying patients with recurrent illness, found a close relationship between severe life events and non-endogenous—but not endogenous—depression. They demonstrated that endogenous depressed patients defined by the Research Diagnostic Criteria (RDC) experienced significantly fewer severe life stresses in the 6 months prior to episode onset. In a contemporaneous paper, Brown et al. (1994) found no difference in the rate of severe life events between RDC or clinically defined endogenous and non-endogenous patients. That group did, however, report that severe life events were less common in those with a score of ≥6 on a ‘melancholic/psychotic index’ than in those with a score <6 (i.e. non-melancholic patients). Furthermore, they found severe life events to be more common prior to the first episode of melancholia than to later episodes. In contrast, non-melancholic non-psychotic patients were no more likely to experience severe events in their first than subsequent episodes. These varying results reflect another issue of note—that any demonstration of specificity may hinge upon the definition of ‘melancholia’. The finding by Brown et al. (1994) of a closer association between life events and first (rather than subsequent) episodes of depression is consistent with a growing body of literature. Post (1992) has proposed that both sensitisation to stressors and episode sensitisation occur, and become encoded at the level of gene expression.

Other groups have reported a modest relationship between life stress and relapse or recurrence in severe recurrent depressive disorders. For example, Andrew et al. (1993) studied a sample of female inpatients with severe depression and found a lack of an association between psychosocial stress and outcome 9 months later. Similarly, Paykel et al. (1996) found that psychosocial factors such as life events and marital relationships appeared to played little role in predicting the outcome of inpatients with recurrent depression.

The aims of this study were: first, to examine the relationship between life events and contrasting depressive subtypes (melancholic and non-melancholic); second, to investigate the import of life events to first compared with subsequent episodes across those depressive subtypes; and third, to determine whether any evidence of specificity is dependent upon the system for melancholic sub-typing.

Section snippets

Method

A total of 270 consecutive depressed inpatients or outpatients fulfilling DSM-IV criteria for a Major Depressive Episode (present for less than 2 years) were recruited from subjects attending a tertiary referral Mood Disorders Unit (MDU) in Sydney, and a number of non-specialist psychiatric units in several Sydney teaching hospitals.

The methodology used in the study is described in detail by Parker et al. (1998). Patients completed a set of self-report questionnaires including a rating of the

Results

The mean age of the 270 patients was 43.3 (±14.9) years. The sample comprised 63.7% female and 36.3% male patients. The percentages of the total group of patients defined as ‘melancholic’ according to the four diagnostic systems were: DSM-III-R 44.1%; DSM-IV 38.9%; Newcastle 29.6%; and CORE 27.4%. A total of 16 (22%) patients in the CORE melancholic group did not meet criteria for DSM IV melancholia.

A total of 190 (70%) patients had experienced a previous episode of depression, whilst 80 (30%)

Conclusions

This study found high rates of acute and chronic life events of all levels of severity in the 12 months preceding the onset of a depressive episode, with at least 75% of all patients experiencing at least one such stressor. Additionally, on top of that high baseline rate, non-melancholic patients had a higher likelihood of experiencing both acute and enduring events compared with melancholic subjects. These findings were consistent across patient self-report (though this alone is of limited

Acknowledgements

Thanks to Zora Vuckovic and Anne-Maree Austen for manuscript preparation and Kerrie Eyers for helpful comments. This study was supported by the Australian National Health and Medical Research Council Program Grant 993208 and a New South Wales Health Department Infrastructure Grant Program.

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