Marijuana Legalization And Use: What We Know and Do Not Know

Marijuana Legalization And Use: What We Know and Do Not Know

Laws and norms about marijuana are shifting rapidly. Starting with medical use legalization several years ago, laws have now been passed or are being considered in many states, including Maine, to decriminalize possession and use. Will that be a good thing for the public health of Vienna and Mt. Vernon?

At the risk of sounding like an old fuddy duddy, I have reservations; my greatest is the likely impact on youth. We know they already use marijuana commonly (50% have tried it by 12th grade), and that use will likely increase if it is more available, even if use by minors is prohibited. There will be more around. Several case-controlled studies over the last decade indicate permanent cognitive damage to users under 18, even after they grow up and stop smoking weed. The permanent deficits are in executive function, memory, and reaction times. Those deficits are measurably worse than those in non-users. And many studies of chronic users show functional and anatomical brain scan changes in the hippocampus and frontal lobes, just those areas still maturing in teenagers. And there are a worrisome number of case reports of marijuana use acutely inducing a first episode of schizophrenia in teens. However, overall schizophrenia prevalence in users is no higher than in non-users, so it may be just that the disease is triggered in young adults already predisposed to develop it?

I also have concerns about the potential bad effects of smoking the marijuana. Because that delivery method is so quick and effective, it is unlikely users will ever prefer to ingest it, let alone use suppositories. We know tobacco smoking clearly kills people at least 10 years prematurely from chronic bronchitis/emphysema, heart disease and cancers. It cannot be good to inhale hemp smoke either, as Dennis Keschl pointed out at the mid-February Mt. Vernon Community Center open meeting with local legislators. What little research we now have suggests there is less damage and risk in smoking marijuana than tobacco. But I’d like more research; it took 40-50 years for the grim data on cigarette smoking to become clear. I also suspect that smoking dope increases the likelihood that a person will also continue or take up tobacco smoking.

As the chairman of the Bureau of Motor Vehicles Medical Advisory Committee, I’m also concerned about marijuana-related driving crashes in all age groups. Acute intoxication clearly impairs reaction times and distance judgments. Unlike alcohol however, marijuana tends to slow driving speeds and recklessness down, so crash rates are a tenth as frequent as in alcohol drunk drivers, but still about twice those of sober drivers. Unfortunately we don’t have good screening tests for police to use in the field and there is no consensus about what constitutes an intoxicating blood level of tetra-hydro-cannabinol, the measurable marijuana psychoactive component. So identifying dangerous marijuana intoxication is going to become an increasing public health issue that needs work now.

Assertions that marijuana is a “gateway” drug to narcotic and other illicit drug use are reassuringly unsupported by the medical literature. But the published research on the drug is still pretty meager, reflecting, for the most part, the total Federal prohibition. Scientific investigators can’t get standardized doses to study; plants and their various parts vary greatly in the cannabinoid concentrations. Most of the reports available now are only case control studies. But one large 40-year study from New Zealand is a continuous study of 1000 children (a cohort) born in the 1970s who were tested for IQ and other cognitive skills throughout the study period. However, even with a cohort study, we can’t be sure that those who use marijuana aren’t doing so to self-treat a learning disorder or because of a particular behavioral trait. In other words, the study may still suffer from selection bias because participants decide themselves if they choose to use marijuana. We need a lot more research ASAP!  

So I favor legalization, control, and standardization. We would never let a pharmaceutical drug go to market with so many unknowns and potential risks. Medically marijuana has its uses; I’ve always encouraged my patients on chemotherapy to try it for their nausea. But the current environment in which it is only available legally with a doctor’s prescription, results in recreational users pressuring clinicians to prescribe it for questionable symptoms, a waste of everyone’s time. If it hurts teens, we need to know that and develop more effective ways to prevent their using it. The current prohibition system is not working well to protect the potentially most vulnerable or to encourage further research in the many other areas of possible unintended consequences. We need more research and data fast, and that’s most likely to happen in a controlled legalization.


Dan Onion, MD, MPH

Vienna Health Officer


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