HIGHS AND LOWS: CU Med School docs question risks of smoking pot


AURORA | Any pack of cigarettes features a warning from the Surgeon General about lung cancer, heart disease, emphysema and other risks associated with tobacco.

Coming up with a similar standard label for a pack of marijuana joints could be tricky, according to University of

CU Med School officials say more work needs to be done to determine the short and long term effects of smoking marijuana, or ingesting it in other ways.
CU Med School officials say more work needs to be done to determine the short and long term effects of smoking marijuana, or ingesting it in other ways.

Colorado School of Medicine professor Christian Hopfer. Hopfer, who works in the university’s Department of Psychiatry, said that while the passage of Amendment 64 in Colorado may have legalized the possession of small quantities of marijuana, it hasn’t resolved fundamental questions about the long-term health risks of the drug.

“It took 40 or 50 years for people smoking tobacco to really get a clue. The long-term effects aren’t often seen immediately,” Hopfer said. “We haven’t had a generation of chronic marijuana smokers that we’ve followed for a long time.”

Even so, Hopfer said there’s plenty of information about the basic science associated with using marijuana. Whether it’s smoked, ingested through edibles or taken into the body via a vaporizer, marijuana still works in the same, basic way. The chemical delta-9-tetrahydrocannabinol (better known as THC), resembles a chemical called anandamide that’s naturally made by the brain. When someone uses marijuana, the THC attaches itself to proteins called cannabinoid receptors (known as CBRs). The CBRs normally bond with anandamide, but THC stimulates these receptors

That’s the basic chemical process, no matter which way the marijuana and THC is ingested. Heavy marijuana users run the risk of messing with their brain chemistry, Hopfer said. That includes short-term impacts on memory, learning and cognition.

“It’s a substitute for natural cannabinoids that people have,” Hopfer said. “If you repeatedly smoke it, your brain is basically going to adapt to it (and) down the regulation of internal cannabinoids. That’s why some people could be addicted to it.”

Beyond the basic questions of brain chemistry, the use of marijuana carries other health risks, many of which depend on how the drug is ingested. A 2012 study out of the University of California, San Francisco explored the links between smoking marijuana and lung capacity. While smoking small quantities (the equivalent of about one marijuana cigarette a day) didn’t show damage to pulmonary function, the study indicated that heavier use led to diminished lung capacity. The study also showed that heavy marijuana smokers also suffered from coughing, wheezing and an increased risk of bronchitis similar to smoking cigarettes.

What’s more, a study from 2007 commissioned by the Canadian government indicates that marijuana smoke contains many of the same carcinogens found in cigarette smoke.

“Theoretically, it’s got the same compounds that you get from burning plant matter and inhaling,” Hopfer said. “There’s no reason to think there’s any magical properties that protect against it.”

Any dispensary in Colorado has other options for marijuana users, whether it’s in the form of edibles (brownies, cookies, etc.), vaporizers or tinctures. They’re different delivery systems for THC that leave the smoke, the tar and the wheezing. But those substances still contain THC, and the chemical still acts on the brain’s receptors in the same way. Plus, it stays in the body in the same way.

“The main organ that THC affects is the brain, and it’s a fat soluble substance,” Hopfer said. “You store it in your body for weeks, because it’s a lipid. It’s a substance that’s easily stored in fat tissue.”

Beyond the immediate effects on the lungs and the brain, Hopfer pointed to the rare risk of long-term impacts on mental health. Hopfer, who works in the Department of Psychiatry’s Division of Substance Dependence, cites a 2006 study that explores links between marijuana use and permanent mental illness. Hopfer admits that the risk is extremely slim — the study shows permanent damage in one out of every 1,000 users.

But he added that the study hinted at a bigger theme when it comes to looking at the adverse effects of the drug.

“It’s a dose-response thing,” Hopfer said. “The more and the more times you use, the bigger the issues. The younger you start, the bigger the issues … I think the negative consequences of marijuana are proportional to the amount and the length … It’s a matter of degree.”


Reach reporter Adam Goldstein at [email protected] or