Key Points Question What are the risks and benefits of obtaining a medical marijuana card for adults who seek medical marijuana for pain, insomnia, and anxiety or depressive symptoms? Findings In this randomized clinical trial involving 186 participants, immediate acquisition of a medical marijuana card increased the incidence and severity of cannabis use disorder (CUD) and resulted in no significant improvement in pain, anxiety, or depressive symptoms, but improved self-reported sleep quality. Meaning Findings from this study suggest the need for further investigation into the benefits of medical marijuana card ownership for insomnia symptoms and the risk of CUD, particularly for those with anxiety or depressive symptoms....