Three decades ago, I would have been over the moon to see marijuana legalized. I smoked throughout my teens and early 20s. Upon landing in a new city, my first order of business was to score a quarter-ounce. The thought of a concert or a vacation without weed was simply too bleak.
These days it’s hard to find anybody critical of marijuana. The drug enjoys broad acceptance by most Americans — 63 percent favored ending cannabis prohibition in a recent Quinnipiac poll — and legislators on both sides of the aisle are becoming more likely to endorse than condemn it. After years of loosening restrictions on the state level, there are signs that the federal government could follow suit: In April, Senate Minority Leader Charles Schumer became the first leader of either party to support decriminalizing marijuana at the federal level, and President Donald Trump (his attorney general notwithstanding) promised a Republican senator from Colorado that he would protect states that have legalized pot.
And why not? The drug is widely thought to be either benign or beneficial. Even many of those apathetic toward its potential health benefits are ecstatic about its commercial appeal, whether for personal profit or state tax revenue. Legalization in many cases, and for many reasons, can be a good thing. I’m sympathetic.
But I am also a neuroscientist, and I can see that the story is being oversimplified. The debate around legalization — which often focuses on the history of racist drug laws and their selective enforcement — is astoundingly naive about how the widespread use of pot will affect communities and individuals, particularly teenagers. In our rush to throw open the gate, we might want to pause to consider how well the political movement matches up with the science, which is producing inconveniently alarming studies about what pot does to the adolescent brain.
Of the many things I loved about getting high, the one I loved best was that it commuted the voice in my head — usually peevish or bored — to one full of curiosity and delight. Marijuana transformed the mundane into something dramatic. Family outings, school, work or just sitting on the couch became endlessly entertaining when I was stoned.
Although studies have not found that legalizing or decriminalizing marijuana leads to increased use among adolescents, perhaps this is because it is already so popular. More teenagers now smoke marijuana than smoke products with nicotine. Between 30 and 40 percent of high school seniors report smoking pot in the past year. About 20 percent got high in the past month, and about 6 percent admit to using virtually every day. The consequences are unlikely to be rare or trivial.
It’s not surprising that heavy-smoking teens show evidence of reduced activity in brain circuits critical for flagging newsworthy experiences, are 60 percent less likely to graduate from high school, and are at substantially increased risk for heroin addiction and alcoholism. Recent data is even more alarming: The offspring of partying adolescents, specifically those who used THC, may be at increased risk for mental illness and addiction.
Now, as a scientist, I’m unimpressed with many of the widely used arguments for the legalization of marijuana. “It’s natural!” So is arsenic. “It’s beneficial!” The best-documented medicinal effects of marijuana are achieved without the chemical compound that gets users high. “It’s not addictive!” This is false, because the brain adapts to marijuana as it does to all abused drugs, and these neural adjustments lead to tolerance, dependence and craving — the hallmarks of addiction.
Whether or not to legalize weed is the wrong question. The right one is: How will growing use of THC affect individuals and communities?
Instead of rushing to enact new laws that are as nonsensical as the ones they replace, let’s sort out the costs and benefits, using current scientific knowledge, while supporting the research needed to clarify the neural and social consequences of frequent use of THC.
Judith Grisel is a professor of psychology and neuroscience at Bucknell University.