Sibling alcohol use disorder is associated with increased risk for suicide attempt.

The association between having a sibling diagnosed with alcohol use disorder (AUD) and risk for suicide attempt may be attributable to shared genetic liability between AUD and suicidal behavior, effects of environmental exposure to a sibling's AUD, or both. To distinguish between these alternatives, we conducted a series of Cox regression models using data derived from Swedish population-based registers with national coverage. Among full sibling pairs (656,807 males and 607,096 females), we found that proband risk for suicide attempt was significantly elevated when their sibling was affected by AUD, even after accounting for the proband's AUD status. Further, risk for proband suicide attempt was consistently higher when the sibling's AUD registration had occurred more recently. Our findings provide evidence for exposure to sibling AUD as an environmental risk factor for suicide attempt and suggest that clinical outreach may be warranted following a sibling's diagnosis with AUD.