Objective.— To examine whether major depressive episodes (MDEs) are associated with an increased risk of migraine in the general population and to examine whether migraine is associated with an increase risk of MDE.
Background.— Population-based cross-sectional studies have consistently reported an association between migraine and depression. However, longitudinal studies about this potentially bidirectional association are inconsistent.
Methods.— This retrospective cohort study used 12 years of follow-up data from the Canadian National Population Health Survey (15,254 respondents, age >12). Stratified analysis, logistic regression, and proportional hazard modeling were used to quantify the effect of migraine on subsequent MDE status and vice versa.
Results.— After adjusting for sex, age, and other chronic health conditions, respondents with migraine were 60% more likely (HR 1.6, 95% confidence interval 1.3-1.9) to develop MDE compared with those without migraine. Similarly adjusting for sex and age, respondents with MDE were 40% more likely (HR 1.4, 95% confidence interval 1.0-1.9) to develop migraine compared with those without MDE. However, the latter association disappeared after adjustment for stress and childhood trauma.
Conclusions.— The current study provides substantial evidence that migraine is associated with the later development of MDEs, but does not provide strong causal evidence of an association in the other direction. Environmental factors such as childhood trauma and stress may shape the expression of this bidirectional relationship; however, the precise underlying mechanisms are not yet known.