Major depression as a risk factor for chronic disease incidence: longitudinal analyses in a general population cohort

Abstract

Objective

Cross-sectional studies have consistently reported associations between major depression (MD) and chronic medical conditions. Such studies cannot clarify whether medical conditions increase the risk for MD or vice versa. The latter possibility has received relatively little attention in the literature. In this study, we evaluate the incidence of several important chronic medical conditions in people with and without MD.

Method

The data source was the Canadian National Population Health Survey (NPHS). The NPHS included the Composite International Diagnostic Interview Short Form to assess past-year major depressive episodes. The NPHS also collected self-report data about professionally diagnosed long-term medical conditions. A longitudinal cohort was interviewed every 2 years between 1994 and 2002. Proportional hazards models were used to compare the incidence of chronic conditions in respondents with and without MD and to produce age-, sex- and covariate-adjusted estimates of the hazard ratios.

Results

The adjusted hazard ratios associated with MD at baseline interview were elevated for several long-term medical conditions: heart disease (1.7), arthritis (1.9), asthma (2.1), back pain (1.4), chronic bronchitis or emphysema (2.2), hypertension (1.7) and migraines (1.9). The incidences of cataracts and glaucoma, peptic ulcers and thyroid disease were not higher in respondents with MD.

Conclusion

A set of conditions characterized particularly by pain, inflammation and/or autonomic reactivity has a higher incidence in people with MD.

Introduction

The association of chronic medical conditions with major depression (MD) has been well established by cross-sectional studies [1], [2], [3], [4], [5], [6]. While useful for descriptive purposes, cross-sectional estimates cannot clarify temporal relationships and are therefore difficult to interpret. In a few instances, longitudinal methods have been employed. Brown et al. [7] used administrative data to determine whether the incidence of diabetes is increased in people with MD, confirming earlier reports from the Baltimore Epidemiologic Catchment Area Follow-up Study [8]. A related analysis indicated that the incidence of MD was not increased in people with type II diabetes [9].

Migraines are another condition where longitudinal studies have been helpful in clarifying well-known cross-sectional associations [3], [4], [10], [11], [12] with MD. In a longitudinal investigation, Breslau et al. [13] found that MD increased the incidence of migraines and also that migraines increased the incidence of MD. An effect of migraine on depression incidence, but no effect of depression on migraine incidence, was seen in another prospective study conducted in Baltimore [12].

Depressive symptoms (as opposed to depressive disorders) were found to be associated with subsequent hypertension incidence in two studies. One of these studies analyzed data from the National Health and Nutrition Examination Survey [14], and the other analyzed data from the CARDIA study [15]. The only study to examine hypertension incidence in association with depressive disorders was the Baltimore study [16]. Here, an adjusted odds ratio of 2.16, suggesting an elevated risk of hypertension, was reported; however, the association did not achieve statistical significance.

A literature of cross-sectional studies has reported associations between back pain and depression [3], [4], [10]. Currie and Wang [17] used longitudinal data from two cycles of the Canadian National Population Health Survey (NPHS) to confirm whether there is an elevated incidence of MD in people with chronic back pain and also an elevated incidence of back pain in people with MD.

The objective of the current study was to compare age- and sex-adjusted incidences of several long-term medical conditions in people with and without MD. Migraines and hypertension were considered to be of particular importance in view of the inconclusive nature of the literature for these conditions. Another objective was to replicate the elevation in back pain incidence reported by Currie and Wang [17]. On exploratory analyses, the incidence of several other conditions in respondents with and without MD was assessed.