UNLABELLED: Recent epidemiologic studies have reported an association between migraine and major depression. Little is known about the mechanisms that link the two disorders, or the natural history of their co-occurrence. We examined the association between migraine and major depression in a sample of young adults, using longitudinal data. METHOD: A random sample of 1,007 young adults (21-30 years of age) members of a large HMO in Southeast Michigan was interviewed in 1989; 97% of the sample were reinterviewed 3.5 years later, in 1992. A structured diagnostic interview was used to elicit information on DSM-III-R major depression and IHS migraine in lifetime (in the 1989 interview) and during the 3.5 year follow-up interval (in the 1992 interview). Using Cox-proportional hazards models with time-dependent covariates, we estimated the relative risk for major depression associated with prior migraine and the relative risk for migraine associated with prior major depression. RESULTS: In this sample of young adults, the incidence of migraine per 1,000 person years, based on the prospectively gathered data, was 5.0 in males and 22.0 in females. The estimated relative risk for major depression associated with prior migraine, adjusted for sex and education, was 3.2 (95% CI 2.3-4.6). The adjusted relative risk for migraine associated with prior major depression was 3.1 (95% CI 2.0-5.0). CONCLUSIONS: The study provides the first body of evidence that the previously observed cross-sectional association between migraine and major depression can result from bidirectional influences, with each disorder increasing the risk for first onset of the other. The explanation that major depression in persons with migraine represents a psychologic response to migraine attacks would have been more plausible had we found an influence only from migraine to depression. By diminishing the plausibility of a simple causal explanation for the migraine-depression comorbidity, the findings favor the shared mechanisms explanation.
UNLABELLED: Recent epidemiologic studies have reported an association between migraine and major depression. Little is known about the mechanisms that link the two disorders, or the natural history of their co-occurrence. We examined the association between migraine and major depression in a sample of young adults, using longitudinal data. METHOD: A random sample of 1,007 young adults (21-30 years of age) members of a large HMO in Southeast Michigan was interviewed in 1989; 97% of the sample were reinterviewed 3.5 years later, in 1992. A structured diagnostic interview was used to elicit information on DSM-III-R major depression and IHS migraine in lifetime (in the 1989 interview) and during the 3.5 year follow-up interval (in the 1992 interview). Using Cox-proportional hazards models with time-dependent covariates, we estimated the relative risk for major depression associated with prior migraine and the relative risk for migraine associated with prior major depression. RESULTS: In this sample of young adults, the incidence of migraine per 1,000 person years, based on the prospectively gathered data, was 5.0 in males and 22.0 in females. The estimated relative risk for major depression associated with prior migraine, adjusted for sex and education, was 3.2 (95% CI 2.3-4.6). The adjusted relative risk for migraine associated with prior major depression was 3.1 (95% CI 2.0-5.0). CONCLUSIONS: The study provides the first body of evidence that the previously observed cross-sectional association between migraine and major depression can result from bidirectional influences, with each disorder increasing the risk for first onset of the other. The explanation that major depression in persons with migraine represents a psychologic response to migraine attacks would have been more plausible had we found an influence only from migraine to depression. By diminishing the plausibility of a simple causal explanation for the migraine-depression comorbidity, the findings favor the shared mechanisms explanation.