Psychiatric Comorbidities Modify the Association Between Childhood ADHD and Risk for Suicidality: A Population-Based Longitudinal Study

Objective: The objective of this study was to evaluate the effect of psychiatric comorbidities on the association between childhood ADHD and suicidality among adults. Method: Subjects were recruited from a population-based birth cohort. Participating adult subjects with childhood ADHD and non-ADHD controls were administered a structured psychiatric interview to assess suicidality and psychiatric comorbidities. Associations were assessed using logistic regression. Results: Compared with controls, ADHD cases were significantly more likely to meet criteria for suicidality. Subjects with childhood ADHD who met criteria for generalized anxiety disorder had a higher than expected risk of suicidality with an observed odds ratio of 10.94 (95% confidence interval [4.97, 24.08]) compared with an expected odds ratio of 4.86, consistent with a synergistic interaction effect. Significant synergistic interactions were also observed for hypomanic episode and substance-related disorders. Conclusion: Childhood ADHD is significantly associated with adult suicidal risk. Comorbidity between ADHD and some psychiatric disorders is associated with a higher suicidal risk than expected.