Key PointsQuestionAre general and specific factors of psychopathology associated with 7 clinically relevant outcomes within adult sibling and twin pairs at 10-year follow-up?FindingsIn this cohort study including 1 974 434 participants, general psychopathology was significantly associated with all 7 outcomes within sibling and dizygotic twin pairs and 3 outcomes within monozygotic twin pairs at 10 years. Within twin and sibling pairs, the specific factors were primarily associated with related outcomes.MeaningThe findings in this study suggest that associations cannot be attributed to unmeasured shared confounds, and interventions toward broad psychopathology dimensions might lead to a reduction in future clinically relevant events.