Extended Effects of Cannabis Abstinence on Clinical Symptoms and Cognition in Depression

This study examines how stopping cannabis (marijuana) use over an extended period affects mood, thinking, and depression symptoms in adults who both use cannabis heavily and have major depression. **You may be eligible if...** - You are between 18 and 55 years old - You have been diagnosed with cannabis use disorder (moderate or severe) - You have also been diagnosed with major depressive disorder (clinical depression) - You are currently on a stable dose of antidepressant medication for at least 3 months - Your depression symptoms are in the moderate range (HDRS-17 score 12-25) - You are not currently seeking treatment to quit cannabis **You may NOT be eligible if...** - You have a substance use disorder involving alcohol or other drugs (not cannabis) - You have a history of psychosis or other major psychiatric conditions - You are pregnant - You have a significant neurological condition Talk to your doctor to see if this trial is right for you.