Study Confirms Marijuana Use Harmful To Adolescents

Despite ongoing campaigns across the country in favor of legalizing recreational marijuana use, most of us in the addictions field continue to have concerns about its long-term effects on users, particularly on those 18 and under. In fact, one of the specific areas of interest at this year’s APA conference was heavy marijuana use by adolescents.

I attended a four-hour session where papers were presented on the topic. One presentation by Krista Lisdahl really caught my attention. Lisdahl is the director of the brain imaging and neuropsychology lab at University of Wisconsin, Milwaukee, and she asserts that it’s detrimental for teenagers to engage in regular marijuana use.

During her presentation on marijuana use by adolescents, she cited several studies that support this view. Some even show that using marijuana once a week or more actually changes the structure of the human brain, especially the areas pertaining to cognitive reasoning and memory.

She referenced a study conducted by researchers at Duke University that found a direct correlation between marijuana use in teenage years and loss of IQ. They analyzed data gathered from people living in New Zealand and compared their IQs in childhood through age 38 among marijuana users and nonusers.

They found that individuals who began using marijuana in their teenage years and continued to use it for many years lost approximately eight IQ points between childhood and adulthood. In contrast, those who never used marijuana didn’t lose any IQ points.

This is one of the most reputable studies about marijuana use by adolescents. It supports the need for aggressive prevention efforts for teenage use of marijuana, especially in states where laws are being relaxed. Given the evidence that habitual marijuana use has a greater impact on the developing brains of youth than it does on adults, public health efforts should be aimed at delaying the onset of underage marijuana use.

Both Colorado and Washington have laws in place prohibiting use before age 21, but it remains to be seen how well they will be enforced. As a clinical community, even if we don’t treat youth, we have a role to play in dispelling the myth that smoking doesn’t hurt anyone.