Major Depression and Its Association With Long-Term Medical Conditions

Lisa M Gagnon, MSc, MD1, Scott B Patten, MD, FRCPC, PhD2

Objective: To replicate previously reported associations between major depressive episodes (MDEs) and long-term medical conditions in a Canadian community sample.

Methods: A sample of 2542 household residents was selected using random digit dialing (RDD). Data were collected by telephone interview. The Composite International Diagnostic Interview (CIDI)-Short Form for major depression (CIDI-SFMD) was used to identify MDEs occurring in the previous 12 months. Long-term medical conditions were identified by self-report.

Results: The prevalence of MDE was elevated in those subjects who reported 1 or more long-term medical conditions. The association was not due to confounding by age, sex, social support, or stressful recent life events.

Conclusion: This study replicates a previously reported association between depressive disorders and long-term medical conditions. These cross-sectional associations suggest that medical conditions may increase the risk of major depression or that major depression may increase the risk of medical conditions. Alternatively, comorbid medical conditions may influence the duration of depressive episodes, or vice versa. These explanations are not mutually exclusive.

(Can J Psychiatry 2002;47:149–152)

Clinical Implications

Having 1 or more chronic medical conditions is associated with an increased prevalence of major depression.
Major depression does not appear to be associated with hypertension.
Comorbid medical conditions may cause, perpetuate, or result from depression.
Limitations

Clinical Implications

The cross-sectional nature of the study limits its causal inference.
Major depression was measured using an abbreviated instrument rather than a clinical assessment or a fully structured research diagnostic interview.
Evaluation of medical conditions was limited to self-report.

Key Words: mood disorders, major depressive disorder, depressive disorder epidemiology, cross-sectional studies, comorbidity

Résumé : La dépression majeure en association avec les affections médicales de longue durée

Clinical studies have reported associations between depressive disorders and various medical conditions, such as heart disease (1), stroke (2), celiac disease (3), epilepsy (4), and many others. Only a few studies, however, have evaluated these associations in community populations. Community studies are important because clinical findings cannot always be generalized to nonclinical populations.

Two US community studies have examined the relation between depressive disorders and long-term medical conditions (5,6). In each study, an elevated prevalence was reported in subjects with 1 or more medical conditions. However, neither study found that hypertension was associated with major depression. Similar results were reported in an analysis of data from the Canadian National Population Health Survey (NPHS): there was a higher prevalence of major depression in subjects reporting 1 or more long-term medical conditions (7).

The objective of the current analysis was to replicate these findings using an additional Canadian data source.

Methods

Data collection was part of a telephone survey conducted in Calgary in 1998 and 1999. A description of the methods employed in this survey has been published previously (8). Major depression was evaluated using the Composite International Diagnostic Interview-Short Form for Major Depression (CIDI-SFMD) (9). Information about long-term medical conditions was collected by self-report using the following questions: “Do you have any long-term medical conditions diagnosed by a health professional, not including mental health problems?” An optional statement in the interview script clarified that a long-term condition is one that lasts, or is expected to last, longer than 6 months.