Medication for Attention-Deficit/Hyperactivity Disorder and Risk for Depression: A Nationwide Longitudinal Cohort Study

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) is associated with high rates of psychiatric comorbidity, including depression. However, it is unclear whether ADHD medication increases or decreases the risk for depression. METHODS: We studied all individuals with a diagnosis of ADHD born between 1960 and 1998 in Sweden (N = 38,752). We obtained data for prescription of ADHD medication, diagnosis of depression and other psychiatric disorders, and sociodemographic factors from population-based registers. The association between ADHD medication and depression was estimated with Cox proportional hazards regression. RESULTS: After adjustment for sociodemographic and clinical confounders, ADHD medication was associated with a reduced long-term risk (i.e., 3 years later) for depression (hazard ratio = 0.58;95% confidence interval, 0.51-0.67). The risk was lower for longer duration of ADHD medication. Also, ADHD medication was associated with reduced rates of concurrent depression; within-individual analysis suggested that occurrence of depression was 20% less common during periods when patients received ADHD medication compared with periods when they did not (hazard ratio = 0.80; 95% confidence interval, 0.70-0.92). CONCLUSIONS: Our study suggests that ADHD medication does not increase the risk of later depression; rather, medication was associated with a reduced risk for subsequent and concurrent depression.