Key PointsQuestionWhat is the comparative effectiveness of pharmacological treatments on the risk of suicidal behavior among individuals with borderline personality disorder (BPD)?FindingsIn this comparative effectiveness research study of 22 601 individuals with BPD, the use of attention-deficit/hyperactivity (ADHD) medication was associated with a reduced risk of suicidal behavior. No other pharmacotherapy (ie, antidepressants, antipsychotics, mood stabilizers, or benzodiazepines) was associated with a reduced risk of suicidal behavior.MeaningThese findings suggest that ADHD medication should be the preferred choice for individuals with BPD with ADHD symptoms and suicidal behavior.