Marijuana Poses Risks to Teenagers’ Brains

Research links adolescent pot smoking to increased risk of mental health woes and even brain damage.

These days, teens aren’t abusing prescription pain drugs, smoking cigarettes, or drinking alcohol as much as they used to. Yet, while they haven’t been smoking more marijuana, either, they think pot is harmless.

The latest rates of teen drug use – and attitudes toward drug use – were published by the National Institute on Drug Abuse (NIDA) following their 2014 Monitoring the Future survey. Eighth, 10^th, and 12-graders aren’t abusing prescription pain drugs, smoking cigarettes, and drinking alcohol as much as they were previously. But their somewhat cavalier attitude toward pot is troubling, with experts warning that carefree teens could wind up smoking more marijuana and put themselves at risk for mental health problems and even brain damage.

For example, a study by British scientists, published in the journal Biological Psychiatry, found that adolescent marijuana use can contribute to the development of schizophrenia later in adult life, if a young person has a specific genetic vulnerability to the disorder. In fact, daily users of marijuana with a specific gene variant have a seven times higher risk of developing psychosis than infrequent marijuana users or those who have never indulged.

Other studies have reported an association between marijuana use and lack of motivation, depression, anxiety, personality disorders, and even suicidal thoughts in teens, according to the NIDA. Because marijuana affects areas of the brain that regulate mood and reward, scientists have hypothesized the drug could cause changes in the brain, resulting in negative psychological effects.

A study published in the Proceedings of the National Academy of Sciences suggests that’s true, especially for chronic marijuana users who start abusing the drug as teens. Marijuana may literally change brain structure – and the consequences could be serious for some young people.

Using multiple MRI techniques, researchers at the Center for BrainHealth at the University of Texas found that people who started smoking marijuana as early as age 14 had less brain volume in the orbitofrontal cortex, a part of the brain associated with addiction.

Chronic marijuana users, who smoked pot an average of three times a day, scored lower on IQ tests when compared to age- and gender-matched controls. However, the scientists couldn’t make a direct link between the lower IQ and the brain abnormalities found in the study.

The research team also discovered evidence that chronic marijuana usage may trigger a complex “rewiring” of neurons (brain cells that process and transmit information) in order to compensate for the loss of the orbitofrontal cortex’s gray matter volume. “Eventually, however, the structural connectivity or ‘wiring’ of the brain starts degrading with prolonged marijuana use,” said Sina Aslan, co-author of the paper and a Center for BrainHealth neuroimaging expert.

Scientists admit many questions still need to be answered about marijuana’s impact on the brain, including whether the effects are a direct result of the drug, or some other unrecognized predisposing factor, and whether any changes in the brain caused by marijuana revert back to normal when people stop the drug for a long period.

However, one thing is clear: Young people appear to be at greatest risk from any potential ill effects of marijuana.

“While our study does not conclusively address whether any or all of the brain changes are a direct consequence of marijuana use, these effects do suggest that these changes are related to age of onset and duration of use,” said Francesca Filbey, director of the Center for BrainHealth’s Cognitive Neuroscience Research in Addictive Disorders.

The NIDA is urging a greater awareness of pot’s potential risks in order to counteract the notion among many young people that marijuana is harmless. “It is now more important than ever for the public health community to continue to educate teens, parents, teachers, community leaders, the media, and healthcare providers about the specific harms of drug use among teens, whose brains are still developing,” NIDA Director Nora D. Volkow, MD said.