Volume CXXXIII, Number 16 February 15, 2002 f

Ask Dr. Jeff
JEFF BENSON, M.D.

Dear Dr. Jeff: I have a friend who gets stoned a lot. What's he doing to his brain? I know he's not doing very well academically. T.F.

Dear T.F.: An increasing body of research suggests that marijuana is neither the deadly toxin its foes portray, nor the benign herb its advocates promote. Heavy, regular use of marijuana may be more harmful and habit-forming than previously suspected.

The principal active ingredient in marijuana is delta-9-tetrahydrocannabinol - THC. Researchers have discovered THC-binding receptors throughout the body and brain, and naturally occurring, THC-like endogenous cannabinoids, or endocannabinoids, which bind to these receptors. Endocannabinoids appear to play an important role in regulating mood, appetite, pain, memory, and a variety of other sensations and functions.

Current research into these mechanisms is in part driven by the debate over medical marijuana use. For many people with AIDS, cancer and other debilitating diseases, marijuana offers substantial relief from pain, nausea and loss of appetite. Chronic marijuana use, however, may possibly have harmful effects as well.

THC seems to change the way in which sensory information is processed by the hippocampus, the part of our brains' limbic system which integrates sensory inputs with emotions and motivations, all components of memory formation and learning.

Longitudinal studies of high school students who smoke marijuana regularly, do show lower academic achievement and greater behavioral problems. Of course, it may be a little tricky here to sort out cause and effect.

A much-touted study of college students is reported to show that critical skills relating to attention, memory and learning are all impaired in people who use marijuana heavily. Researchers compared a large group of students who smoked marijuana daily, to a "matched" group of students who smoked less than once a month, if ever. They were all closely monitored for a nineteen to twenty-four hour abstinence period, and then administered a battery of standardized tests. The pot smokers scored more poorly on measures of attention, memory and new learning. It is unclear whether any of these effects might be long lasting.

This study might have several important flaws, especially around issues of matching and THC "washout." Whatever the shortcomings of research, it seems clear enough to me, for pretty obvious reasons, that getting stoned every day is likely to have a deleterious impact on one's academic performance. There may also be other health consequences to consider.
Heavy marijuana use is definitely associated with depressed libido, lower sperm counts and occasional breast enlargement in men, as well as with irregular menstrual cycles in women. Marijuana smoke contains more tar than tobacco smoke, and may be even more damaging to lung tissues. Daily users have more respiratory problems and more injuries from accidents. Smoking pot elevates your blood pressure, raises your heart rate (as much as 50 percent in the first hour), and has been shown to increase some people's risk of heart attack up to five-fold.

The question of marijuana's addictive potential is quite contentious. More than seventy-two million Americans have smoked marijuana at least once, and it remains the most commonly and casually used illicit substance across the nation. Many commentators point out that currently available marijuana is very much more potent than it used to be, and so is more likely to become abused. The National Institute on Drug Abuse (NIDA) reports that more than 120,000 people enter treatment each year for their primary marijuana addiction.

NIDA categorizes a drug as addicting "if it causes compulsive, at times uncontrollable drug craving, seeking and use, even in the face of negative health and social consequences," and argues that marijuana meets this criterion. Other researchers believe that a smaller segment of the population, in the ten to fifteen percent range, are in some manner vulnerable, and can become strongly dependent on marijuana. They may develop cravings for the drug, and develop tolerance, needing to smoke more of it to get the same effect. When they stop using marijuana regularly, they may develop withdrawal symptoms that last for weeks, such as reactive depression, anxiety, anger, insomnia or nausea. All of these features are considered characteristic of addictions.

If you have questions or concerns about marijuana use, you can always contact the Health Center or the Counseling Service. The Addictions Resource Center in Bath would be an excellent off-campus alternative. And there are many web-based sources of information, including NIDA and Go Ask Alice.

Stay informed, and take good care of yourselves!

Jeff Benson, M.D.
Dudley Coe Health Center