A population-based family study of minor depression.

Background: There is a paucity of research on whether minor depression is a familial disorder.

Methods: We conducted a population-based family study of minor depression in which subjects were interviewed using the Diagnostic Interview Schedule (DIS). Minor depression only (MDO) was diagnosed if there was a lifetime history of what the DIS refers to as a depressive "spell" and no lifetime history of either Diagnostic and Statistical Manual of Mental Disorders, Third Edition, major depression or dysthymia. There were 71 probands with a lifetime history of MDO; 577 controls with no lifetime history of MDO, major depression, or dysthymia; and 1,539 first-degree relatives (FDRs). Logistic regression was performed with the presence/absence of MDO in a proband/control as the "exposure" and MDO in an FDR as the "outcome".

Results: The odds ratio for the association between MDO in a proband and MDO in an FDR, after adjusting for age and sex of the FDR, was 1.55 (95% confidence interval: 0.93-2.58; P=.093). The study had 80% power to detect an odds ratio as small as 1.97, which is in the range of odds ratios seen for the familial aggregation of major depression.

Conclusions: MDO does not appear to be a familial disorder, raising questions about the validity of "minor depression" as a distinct psychiatric syndrome.