The case for prescription-only marijuana

As an epidemiologist and a parent, I am perplexed with the recent momentum toward legalizing marijuana. Of all the arguments I have heard, I have yet to hear any that are compelling enough to remove the drug from prescription status.

One argument I have heard is that marijuana is harmless. This argument ignores the fact that numerous studies have reported harm in peer-reviewed academic journals. A summary of the evidence, published in the New England

Journal of Medicine in 2014, concluded, “Marijuana use has been associated with substantial adverse effects, some of which have been determined with a high level of confidence.” Some of those effects were addiction to marijuana and other substances, motor vehicle accidents and chronic bronchitis.

Other effects were reported with either high or medium confidence. Some of the medium-confidence effects were schizophrenia and abnormal brain development in young people. In order to believe the harmless argument, you have to believe that all of the studies reporting harms were wrong.

Even from people who don’t think marijuana is harmless, you still hear the argument that it should be legal because it is not as bad as alcohol. The not-as-bad type of argument is also known as the fallacy of relative privation. The fallacy is that pointing to something worse does not justify anything. The not-as-bad argument asks people to dismiss one bad thing by asking them to focus on another bad thing. It is a show of falling dominoes with all of two tiles.

Society is replete with awful things it tolerates, like poverty, while it puts its foot down on much more minor things, like deer in urban Victoria. The only time the not-as-bad argument holds water is when only one bad thing has to be chosen from multiple bad options. But the government is not suggesting prohibition in exchange for allowing people to light up or eat up. The plan is to pile vice on top of vice.

Another argument is that marijuana is a medicinal herb and therefore should be freely available. If you think so, can I interest you in a warfarin brownie? Warfarin is a blood thinner that doctors have prescribed for decades to prevent life-threatening clots. Its discovery came after cattle were observed bleeding to death after eating feed derived from sweet clover. Warfarin has been shown to be a life-saving drug in some people at the right dose. Too much and it can kill.

A good therapy can also cause harm, which is why many drugs are available by prescription. If marijuana is removed from prescription status, then what other drugs should be exempted? Antibiotics? Anticoagulants? Analgesics (like opioids)? Antipsychotics? I could keep going with the A’s but what is really needed is a framework for these decisions.

Then we have the ‘I’m not hurting anyone’ argument. This is no different than arguing we can get rid of seat belt and helmet laws. While marijuana won’t split your skull open like a fall from a motorcycle, driving a motorcycle before work won’t degrade your cognitive performance for the day. Governments sometimes have to protect people from their own judgment, and from imposing a financial burden on society.

Harm reduction is the argument the federal government appears to be backing, perhaps because it has a veneer of edification which cannot be mustered from the other arguments. The Achilles heel of this argument is an assumption that legalization will not increase demand and swamp any trumpeted benefits with additional adverse events.

Data coming in from Washington state, which voted to legalize marijuana in 2012, suggests this concern should be taken seriously here. The National Survey on Drug Use and Health in the U.S., which has collected data on the use of tobacco, alcohol and illicit drugs since 1971, showed that marijuana use in Washington increased almost 30 per cent since legalization. By comparison, the proportion of the total U.S. population using marijuana increased by about 10 per cent (the total is inflated with states where marijuana was legalized).

During the same period, the Washington Poison Center reported that marijuana-related poisonings, such as accidental ingestion by children, increased by more than 50 per cent. The Washington Traffic Safety Commission reported the percentage of DUI cases testing positive for THC, the main psychoactive component of cannabis, increased by a similar amount.

Finally, to anyone who thinks we should legalize marijuana because it is happening in the United States, can I interest you in amending the Charter of Rights and Freedoms to allow us all to keep and bear arms?

A good therapy can also cause harm, which is why many drugs are available by prescription. If marijuana is removed from prescription status, then what other drugs should be exempted?