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How does pot affect depression, bipolar?

Asked by Sam Simpson, Victoria, British Columbia

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I was wondering where I would find information on how pot affects depression and bipolar disorder. I have looked at various sites on the Internet and found that the topic is rarely talked about by a doctor. And when it is, they mention chronic use. What is chronic use, and what is the opinion of workers in the mental heath field?

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Mental Health Expert Dr. Charles Raison Psychiatrist,
Emory University Medical School

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Dear Sam,

Before addressing pot and depression/bipolar disorder specifically, let me make a suggestion regarding how to find mental health information in general. The very best place to find the "raw science" is through a government-run Web site known as PubMed. This site provides abstracts for almost every scientific study and review article that has been published anywhere in the world over the last 50 years or so.

For example, in the search box I typed in "marijuana and major depression" and came up with 304 entries. If I use the more technical term "cannabis" and enter it as a single item to get a sense of everything that is known scientifically about pot, I come up with 12,294 entries -- more than enough to keep the most interested reader busy for quite a stretch.

To give you the best answer I can, I spent an hour or two reading through PubMed to see what scientific research says about effects of marijuana on major depression and bipolar disorder. As with many things in psychiatry, the studies do not all agree, so I cannot give you a completely conclusive answer based on sound science. But let me give you my overall impression of the situation.

Studies that have looked closely at whether marijuana use is associated with major depression suggest, in general, that any such association is either weak or nonexistent. Remember, too, that association does not prove causality -- meaning in this case that it is at least as likely that depressed people use pot, as that pot causes depression.

Indeed, studies that have attempted to clarify what causes what generally do not find that pot causes depression, even when used regularly. On the other hand, a number of studies do associate regular marijuana use with depression and anxiety in both adolescents and young adults.

Although there have been recent studies in animals suggesting that compounds that affect cannabinoid receptors in the brain may offer promise for the treatment of depression, I couldn't find any studies suggesting that regular marijuana use was associated with less depression. So I think we'd have to say that on the whole, marijuana is best avoided if one is concerned about -- or struggling with -- depression.

Interestingly, evidence is stronger that regular marijuana use is a risk factor for young people to develop psychosis (defined as loss of touch with reality, i.e. insanity). It also appears to increase the risk for mania, a disastrous state that frequently includes psychotic symptoms. Marijuana is also famous for giving a minority of people panic attacks. These attacks are so miserable that they usually end a person's marijuana use.

On the plus side, marijuana (or more technically cannabis) appears to be beneficial for nausea and a number of chronic pain conditions -- and has a medical indication for these uses in several states.

There is no hard-and-fast definition of chronic use, but most professionals would probably set the line somewhere in the neighborhood of daily use.

Cannabis dependence is more exactly defined and includes 1) developing tolerance so that over time more drug is needed to get the same effect; 2) withdrawal symptoms occur when the drug is discontinued (this has been demonstrated to occur with marijuana when used heavily); 3) using more or for longer periods than intended; 4) unsuccessful attempts to cut down on use; 5) a pattern of life centered around obtaining and using the drug; 6) the abandonment of important occupational or social facets of life to use the drug; and 7) continued use despite knowledge of significant problems caused by the drug.

More than whether use is chronic, the presence of these signs and symptoms of dependence clearly signal that one's marijuana use has become problematic.

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