Missouri medical marijuana is legal for patients with qualifying medical conditions. To become a registered medical marijuana patient in Missouri, you must have a qualifying medical condition, such as cancer, epilepsy, glaucoma, PTSD, or a chronic medical disease that causes severe, persistent pain or muscle spasms. A licensed physician must certify in writing that you have a qualifying medical condition. You can apply for a medicinal marijuana card from the Missouri Department of Health after receiving a certificate. It's crucial to remember that marijuana usage and possession are still prohibited in Missouri for non-medical purposes.