Marijuana Trouble?

Two recent events have dimmed some of the glow of marijuana, the world’s most widely consumed illegal drug. The first event is a study showing possible adverse effects of chronic marijuana use, presented at the recent annual meeting of the Society for Nuclear Medicine (SNM) in San Antonio, Texas.

According to the scientists who conducted the study, chronic use of marijuana causes a decrease in some brain receptors that bind with THC, the psychoactive chemical in cannabis. Using a PET scan to capture images of the brain, the study leaders found that chronic consumption of marijuana can lead to a decreased number of cannabinoid CB1 receptors specifically. These receptors play roles in pleasure, appetite, pain tolerance and other psychological and physiological functions throughout the body. The extent to which this may cause mental or physical troubles remains to be determined.

Employing PET scan imaging, the researchers examined the brains of chronic marijuana users, and found that CB1 receptor activity was reduced by as much as 20 percent. Upon cessation of marijuana use, receptor activity returned to normal, suggesting no lasting adverse effects. The study involved injection of a radioactive isotope into the bodies of chronic marijuana users, and then observing cannabinoid CB1 receptor activity via the PET imaging, which takes a nuclear image of biological activity.

The decrease of CB1 activity is known as “downregulation.” And while no specific adverse effects of this occurrence in marijuana users has been identified by researchers, there is a presumption among them that the decrease is not good.

Yet the downregulation of CB1 receptor activity may hold promise for those who are overweight. In sharp contrast to the ominous undertones of the SNM research, a tantalizing study conducted in Europe and reported in the British medical journal Lancet in 2005, showed that downregulation of the CB1 receptor in obese people can lead to a leaner body type. In that study, suppression of CB1 activity in obese subjects resulted in reduced waist size, improved blood levels of HDL-cholesterol and triglycerides, and improved insulin activity and overall reduction of symptoms of metabolic syndrome. This study suggests that downregulation of CB1 activity, at least in obese people, may be a good thing. So can pot help overweight people to slim down? The jury is out on that one.

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Against of all of this science chatter about the negative or positive implications of reduced CB1 activity, another force is at work that may trouble pot smokers. The Dutch cabinet is moving to restrict access to the famed marijuana café’s of the Netherlands, limiting patronage to Dutch citizens, and forbidding access to foreigners. The Dutch bureau of tourism estimates that approximately twenty percent of all travelers to the Netherlands take advantage of the “coffee shops” that sell marijuana. Tourism officials in Amsterdam are fighting the proposed change of access, decrying that such a move would damage tourism to that city.

So what are we to conclude from all the activity around marijuana? There is an adage that the difference between a medicine and a poison is the dose. It is possible that very high use of marijuana may result in negative changes in overall function of the central nervous system, though this needs to be further established. At the same time, we may possibly have in pot a weight control agent. This seems to contradict the increase in appetite that most marijuana users experience. Further investigation into this is unquestionably needed.

Vilified by opponents and championed by users, marijuana remains a highly disputed drug. Studies show that occasional or medical marijuana use is far less harmful than use of either tobacco or alcohol, both of which are responsible for the deaths of hundreds of thousands of Americans each year. At present, not one marijuana-related death has ever been reported. Medical applications of marijuana, for pain, appetite and glaucoma are increasingly well established. And information from the U.S. government itself shows likely benefits of marijuana for the treatment of degenerative disorders of the nervous system.

The landscape for marijuana use is fluid, highly charged, and changing rapidly. Medical marijuana laws, medical marijuana dispensaries, and various scientific studies are pushing this medicine into the medical foreground, despite hue and cry from opponents. As investigators continue to explore the complexity of this age-old remedy and its use, we will likely discover more benefits and hazards associated with this highly popular drug.

Chris Kilham is a medicine hunter who researches natural remedies all over the world, from the Amazon to Siberia. He teaches ethnobotany at the University of Massachusetts Amherst, where he is Explorer In Residence. Chris advises herbal, cosmetic and pharmaceutical companies and is a regular guest on radio and TV programs worldwide. His field research is largely sponsored by Naturex of Avignon, France. Read more at