Risk factors in the use of medical marijuana for rheumatic diseases include impact on cognition, and possible increases in depression and lung cancer, according to a presentation at the American College of Rheumatology annual meeting. There has been limited evidence to date on the efficacy or risks for using medical marijuana for treating patients with rheumatic conditions, Mary-Ann Fitzcharles, MB, ChB, MD, clinical rheumatologist, McGill University, Montreal, said. See more Rheumatology videos at http://www.healio.com/rheumatology/video