Abstract
Adult ADHD is associated with increased risk for suicide attempts, as indicated by investigations of population- and community-based cohorts. However, there is little data regarding suicide attempts in a clinical setting. To address this, we used a comprehensively phenotyped clinical adult ADHD (aADHD) cohort to assess to which extent comorbidity, psychosocial adversity, personality, and ADHD symptoms contribute to suicidal behavior in ADHD. Furthermore, we investigated a triallelic variation in the serotonin transporter-linked polymorphic region (5-HTTLPR), which has previously been associated with suicidal behavior. Depression, substance use, eating, and posttraumatic stress disorders were independently associated with past suicide attempts, whereas anxiety, somatoform, and obsessive-compulsive spectrum disorders showed no association. Pulmonary diseases also showed an association with suicidal behavior. Psychosocial factors including occupational status, marital status/living situation, externalizing behavior and psychiatric family history were strongly associated with past suicide attempts. ADHD symptoms of inattention and hyperactivity/impulsivity were not associated with past suicide attempts after adjustment for psychiatric comorbidity and psychosocial adversity. However, the personality trait of neuroticism fully mediated the association between depression and suicidal behavior. 5-HTTLPR was not associated with suicidal behavior, but an interaction with ADHD symptoms and subtype was found. Our data suggest that psychiatric comorbidity and psychosocial adversity are key factors for suicidal behavior in aADHD, with neuroticism representing a critical mediator of the association between depression and suicidality. Further research, preferentially with longitudinal study designs is needed to better understand causal factors for suicidal behavior to enable effective preventive action.