Abstract
RATIONALE: Asthma is associated with depression, but the temporality of the association has not been established. OBJECTIVES: To examine the association between prevalent elevated depressive symptoms and incident asthma, and between prevalent asthma and incident elevated depressive symptoms in a cohort of young and middle-aged adults. METHODS: We examined the longitudinal association between asthma and depressive symptoms bidirectionally in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort. First, 3,614 participants, free of asthma, were classified by elevated depressive symptoms at the CARDIA Year-5 exam (n = 856 elevated vs. 2,758 not elevated; ages 23-35 yr) and followed for 20 years to incident asthma. Then, 3,016 participants, free of elevated depressive symptoms, were classified by self-reported current asthma status (n = 188 prevalent vs. 2,828 not prevalent) at the CARDIA Year-5 exam and followed for 20 years until onset of elevated depressive symptoms. MEASUREMENTS AND MAIN RESULTS: The relative hazard of incident asthma among those with elevated depressive symptoms was 1.26 (95% confidence interval [CI] = 1.02-1.56) after adjustment for covariates. When depressive status was modeled as the total number of reports of elevated depressive symptoms before the onset of asthma, the adjusted hazard ratio was 1.15 (95% CI = 1.02-1.29). The hazard of incident elevated depressive symptoms for those with asthma was no different than the hazard in those without asthma (adjusted hazard ratio = 0.92; 95% CI = 0.70-1.20). CONCLUSIONS: This longitudinal observational study points to depression as a marker of risk for incident adult-onset asthma. On the other hand, prevalent asthma is not associated with incident adult-onset depression.