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Ten states and Washington, D.C., have now legalized marijuana for recreational use for adults ages 21 and older, and 33 states have legalized medical marijuana. Connecticut is among a handful of states seriously considering legalizing recreational use. We need to look before we leap.

It has been six years since Colorado and Washington legalized marijuana, and scientists continue to unearth more data on the effects of the drug. Very recently, research presented at the 2018 meeting of the Society for Neuroscience showed marijuana use in teenagers affects the development of areas of the brain responsible for self-control and planning, and a study recently published in the Journal of Clinical Psychiatry showed that abstinence for one month from cannabis improves the memory of adolescents and young.

Other articles have highlighted the effects of cannabis addiction, which is estimated to impact 9 percent of all overall users. These findings are often ignored as the legalization movement sweeps across the nation. A professor of psychiatry and behavioral sciences at Stanford University warned in an Atlantic article about its risks: “In large national surveys, about 1 in 10 people who smoke it say they have a lot of problems. They say things like, 'I have trouble quitting. I think a lot about quitting and I can't do it. I smoked more than I intended to. I neglect responsibilities.'”

Another professor of psychiatry—this one at University of Colorado School of Medicine who is co-leading a $5.5 million study of 5,000 sets of twins funded by the National Institute on Drug Abuse on the impact that legalization has on mental health and substance use—pleads that much-needed examination must proceed, as rigorous, large-scale research has been limited.

We do know that, if you start smoking pot as a teenager, you have a much higher likelihood of getting addicted, as the adolescent brain is far more sensitive to the effects than the brain of an adult. Some argue that marijuana can be a gateway to more detrimental substances, such as cocaine and prescription pills. According to a 2015 study conducted by researchers at Yale School of Medicine, a person who uses marijuana is 2½ times more likely to abuse prescription opioids.

And then there is the danger of becoming addicted to marijuana itself. It is estimated that three million people suffer from marijuana use disorder. The Diagnostic and Statistical Manual of Mental Disorders defines that as significant impairment of functioning and distress, as well as symptoms such as cravings and difficulty stopping resulting from using marijuana for at least a year.

Although studies have not determined that legalizing or decriminalizing marijuana leads inexorably to increased use among adolescents, this may be because it is already almost commonplace—more teenagers now smoke marijuana than products with nicotine. In fact, 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 potential consequences are unlikely to be rare or trivial.

So before the Legislature embraces Gov. Ned Lamont's invitation to legalize marijuana, we hope it does its homework to assess if indeed marijuana has both short- and long-term effects on the body and the brain.