My 32-year-old son has had a mood disorder since he was 18. He and so many other people I see use marijuana chronically. Is it possible that the heavy marijuana use is the cause of mood disorders and not just the way some individuals choose to cope?

Claims made by supporters of medical marijuana and the legal changes in many states suggest that marijuana could be good for your health. But marijuana is very different from prescription medications. It contains over 70 known cannabinoid chemicals and we do not understand the effects of many of them. Varying types and amounts of these chemicals are found in the marijuana products sold in recreational marijuana stores and medical marijuana dispensaries, unlike prescription medications whose makeup is uniform no matter where you buy them. Additionally, medical researchers typically conduct studies comparing prescription medications to a placebo or other active medications to determine whether or not they are effective in treating a health condition. There is no comparable information that tells us whether or not marijuana products are effective.

Is marijuana ever an effective or appropriate treatment for a mood disorder?

What we know about marijuana use and its effects on depression and bipolar disorder comes mostly from studies where people were interviewed several times over a number of years about their health, including mental health and substance use. No studies of marijuana or its components have shown them to be helpful for depression or bipolar disorder.

Can marijuana cause or exacerbate a mood disorder?

Some studies show that marijuana use has no effect on depression while others have found depression to be worse when marijuana is used. A review of these studies indicates that more frequent and heavier marijuana use is associated with worse depression. For example, a 13-year study in Norway found that people using marijuana once a month or more had a greater likelihood of suicidal thoughts or suicide attempts. Similarly, studies about bipolar disorder showed that marijuana use is associated with worse symptoms, including duration and severity of manic episodes. A study of adults with bipolar disorder indicated that those who reported using marijuana had developed bipolar disorder at an earlier age and had had more manic episodes, hospitalizations, and suicide attempts. Stopping marijuana use appeared to reverse these effects.

How could I know if marijuana is contributing to my mood symptoms?

In addition to worsening mood, marijuana use may also be associated with worsening memory problems and motivation, such as worse attention and short-term memory. People who use marijuana may also experience lower energy and motivation which can impact school and work performance.

About the Doc

About the Doc

Dr. Ryan Caldeiro is an addiction psychiatrist. He is the Chief of Chemical Dependency Services and Consultative Psychiatry at Group Health in Seattle, Washington.