Jokes about smoking pot are really funny. Movies with stoners in them are even funnier. Sure, you wouldn’t want your daughter to date one, but when a slow-moving, laconic, glassy-eyed, long-haired, character pops up on the screen—big or small—we’re all likely to crack a smile. I have a friend who smokes a lot of weed, and she even trained her parrot to say, “Where’s my marijuana?” over and over. Okay, that’s pretty dang funny.
But now that marijuana is legal in Washington state, my fear is that people who never would have considered lighting up will now actually start smoking pot. Based upon 20 of practicing medicine, I think this is a bad idea. For full disclosure, I should point out that although I grew up in the seventies, I have actually never tried marijuana—or any other illegal drug—and have no interest in doing so.
Some patients use marijuana for medical reasons. It’s always nice to see a well-conducted randomized trial of medical marijuana that shows a strong benefit, but there are few such trials. The number of patients who truly require medical marijuana and have failed the better studied alternatives is small and vastly overshadowed by recreational users who seek prescriptions as legal protection for their drug habit.
This article pertains strictly to the recreational use of marijuana, which is now legal in Washington state. Because marijuana has been illegal, and still is in a majority of the United States, it has been much tougher to study the hazards. The volume of research on the health risks of marijuana is pretty small compared to that of smoking cigarettes or drinking alcohol. Most of the research has examined the obvious areas of concern—lung cancer, poor mental health, impaired cognitive ability, lack of motivation, and gateway to other drugs of abuse.
Lung cancer would seem to be the most obvious place to start. A 2008 study from Australia looked at lung cancer in patients under age 55. Lung cancer is less common in this group, but there are more pot smokers, so it is a good cohort to investigate. The authors found that the increased risk of lung cancer from smoking one joint per day was about the same as smoking one pack of cigarettes per day. Marijuana smoke is unfiltered and held deeply in the lungs; this probably accounts for its increased cancer potential as compared to cigarettes.
On the other hand, a large study of 65,000 patients by Kaiser in Northern California did not show an increased risk of lung cancer in marijuana smokers, although it did find they were more likely to be in car accidents or to be hospitalized for injuries. Some studies suggest that there are anti-cancer compounds in marijuana which partly offset the cancer causing chemicals, but this point is controversial and may just be a hallucination.
In fact, marijuana smoke has many of the same carcinogens as cigarette smoke. If you biopsy the airways of marijuana smokers, you find that they have many of the same changes we see in cigarette smokers. A study from UCLA suggested no association between marijuana smoking and cancers of the mouth, throat, or lungs, but this result does contradict the basic science which shows that marijuana smoke is carcinogenic. Some experts believe that the reason we are not seeing a more obvious association between marijuana smoking and lung cancer is that the existing studies are pretty lousy. People lie about smoking pot and many other differences separate pot smokers from non-users. My own view, shared by many researchers in this field, is that we will ultimately see that smoking marijuana causes cancer of the lung, bladder, and throat.
Heart attack is another area of concern with marijuana use. A study which followed 1900 patients who suffered a heart attack showed that smoking marijuana doubles your risk of dying in the few years after a heart attack. The pot smokers in this study who did not die of a second heart attack died from lung cancer or car accidents, which could also have been related to marijuana, of course. There are also reports in the literature of young, otherwise healthy people, sometimes having a heart attack or sudden cardiac death from smoking marijuana.
Clearly, some but not all studies show an increased risk of lung cancer and heart disease from smoking dope. The existing research is not great, and science in this area is challenging because of the quasi-illegal nature of pot smoking and the lack of great studies. There are no good randomized trials of marijuana use over the long term in sufficient numbers of patients to determine the exact cancer risk. Certainly, if your parent or grandparent smoked cigarettes and dropped dead of lung cancer or a heart attack, you’d be a nut to smoke marijuana. People, really.
Brain damage is another concern, obviously. One of the worst mental health diagnoses you can imagine is schizophrenia. A study in the Netherlands followed 4,045 “normal” teens and found that the pot smokers were 2.75 times more likely to become psychotic or schizophrenic during follow up over three years. The absolute risk is small, since only about 1% of the population has psychosis, but this is still a finding of concern. A study from Sweden showed that smoking marijuana during the teen years led to a six fold increase in the risk of psychosis. Two studies from New Zealand showed the same thing. Marijuana use among teens leads to much higher risk of developing a permanent psychotic mental illness.
A recent study showed that kids who used marijuana before age 18 had about an 8-point drop in IQ. This is the difference between being an accountant and a night watchman. A study from the Journal of the American Medical Association in 2002 showed that pot smokers in drug treatment were substantially dumber than non-pot smokers. An analysis of three studies with 6,000 kids in Australia showed that smoking marijuana before age 18 was associated with lower educational success, including being less likely to attend or graduate from college. These studies suggest that marijuana is particularly toxic to the growing brain.
In adults, it is unclear if marijuana causes permanent brain damage. An analysis of over 30 different marijuana studies suggested that all effects in adults wore off after one month. One area which is often debated is the so-called marijuana amotivational syndrome. Since heavy pot smokers in popular culture are slack-jawed, slow-moving, spaced out, and often living in their parents’ basement, sort of like Jay and Silent Bob, that it must be the marijuana which is causing this behavior. Here, the research is really quite poor. One study was conducted by just randomly e-mailing a bunch of people on the internet who happened to be in the author’s address book and asking them about motivation. It makes you think the person doing the study was a heavy pot smoker who lacked motivation himself. The results showed no difference in the level of self-reported motivation between marijuana users and nonusers, but this kind of research is poorly conducted and of little value.
What we really don’t know is whether people of low motivation take up pot smoking and the pot has nothing to do with it, or if the regular use of marijuana makes people just not give a darn about things. There are many anecdotal reports of the amotivational syndrome among regular marijuana users, but no good science. My own experience as a physician is that daily or almost-daily marijuana users do sharpen up after they quit. The drug remains in the body in small amounts for several days, and this could be part of the problem. Google “improved energy after quitting marijuana” and read the message boards for some interesting answers pro and con. Also search “help can’t quit weed” to read some disturbing testimonials about this drug and its addictive properties.
There are other potential mental health effects of marijuana. One study of patients with bipolar illness showed that symptom control was more difficult if they were using marijuana. Other research suggests that people who are prone to depression do worse if they smoke pot.
Some people worry that marijuana is a gateway drug and leads to the use of cocaine and other substances. One study of twins, from The Netherlands showed that the pot smoking twin was 7 times more likely to use other drugs if they smoked before age 18. This was true even for identical twins. Another study from Yale found a higher risk of drug abuse among 18-25 year-olds who smoked marijuana as compared to those who didn’t.
The central weakness in all these studies is that they are epidemiological, not randomized trials. We look at hundreds or sometimes thousands of patients; we ask them if they smoke weed, we count the number of cases of the adverse health outcome we are interested in, such as lung cancer or lack of a job, and we use math and statistics to try and figure out if the marijuana smoking is really a factor. The better studies follow thousands of patients for many years. The worst just e-mail their buddies and then write up a paper or grab some undergrads in an introductory psychology course.
When you see a study that claims marijuana does not cause brain damage, low motivation, lung cancer, or heart disease, it is foolish to take the results at face value. You really must look at the methodology used to come to this conclusion. Similarly, although there may be risks from marijuana use, these are sometimes overstated by the anti-drug types as well. Often, it is a flawed, poorly-conducted study which is making headlines either way.
Some individuals choose to eat marijuana, typically baked into brownies, instead of smoking it. This might lower the cancer and cardiovascular risks, but there are differences in the experience. The high is much quicker smoking marijuana but takes 30-60 minutes when you ingest it. Also, a smoked marijuana high lasts about two hours, but eaten marijuana often lasts 4-8 hours. The reason marijuana is baked into brownies is that brownies taste good and this keeps you from getting the munchies. No, actually the real reason is that active ingredient in marijuana is THC, also called delta-9-tetrahydrocannabinol, and it needs to be extracted from the marijuana plant to have an effect on the body. The heat of smoking turns THC into a vapor which is inhaled. With baking, the idea is to heat marijuana with butter or oil which extracts the THC.
There is just too much worrisome information
out there about marijuana regarding possible
permanent damage to growing brains.
Here is what I suggest to my patients. Based on current research, I recommend strongly against ever using marijuana before age 18, and preferably before age 21. There is just too much worrisome information out there regarding possible permanent damage to growing brains. Adult patients in my practice who use marijuana either for medical purposes or recreationally should know that we don’t have a great handle on the exact risks. Some individuals really like smoking or eating weed, and they are going to continue doing so. Life is short and many people do things which may have health risks, like riding motorcycles, drinking lots of alcohol, eating ice cream, smoking cigarettes, and climbing Mt. Everest. Mature adults can examine both sides of the argument and make their own decision. In this way, legalization is a good thing for a free society.
But for the many people who never would have considered smoking marijuana and are now thinking about it because this activity is legal in Washington state, my advice is to not try pot. We should not let the legality of marijuana sway us. The human brain is a miracle of evolution. It is the most masterfully engineered object in the known universe. Taking in substances recreationally to induce an altered state of mood and consciousness is unwise. Some percentage of people are going to try marijuana and discover that they really, really like being high; thus begins a slippery slope toward addiction. Will marijuana use increase the risk of lung cancer or heart attack? Will it predispose users to mental illness? Will consumption get out of control and lead to other drugs of abuse? Will more people be in car wrecks or suffer other types of accidents? Consider the analogous case of alcohol. Imagine that we lived in a world where alcohol was illegal and most law-abiding citizens had never even tried it. Suddenly it is legalized and a million people decide to have a drink and see what happens. Sure, some people will use it recreationally and not have a big problem, but we are going to uncover some alcoholics that way. We’ll see more car accidents. There will be an increase in head and neck cancers, as well as breast and esophageal cancer from alcohol. Most heavy drinkers who have tried to cut down would say they would have been much happier had they never tried alcohol in the first place. The same is true for every tobacco user who has ever tried to quit. I suspect this will prove true for marijuana as well.
With legalization, existing users of recreational marijuana will continue to smoke weed as they always have. Medical marijuana users will have to weigh the risks and benefits, as we do for all drugs. But for the neophyte considering giving it a try, I recommend saying absolutely no to this drug.