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Is Your Teen Smoking Pot?

Marijuana is bad for teens, and the damage can last

No, your son isn’t necessarily on the fast road to failure if you find a stash of pot in his closet. “For most young people, recreational cannabis use is essentially harmless, a rite of passage ending as young people settle into careers and adult intimate relationships,” writes Mayo Clinic psychiatrist Michael Bostwick. “For 10 percent, however, the drug becomes addictive, its relaxing properties transforming into a constant need that interferes with interpersonal and occupational advancement.”

Pot is better than the most common other drugs. The chances of becoming “hooked” on nicotine are 32 percent and, to alcohol, 15 percent. Drinking alcohol at parties isn't better than smoking pot: alcohol is not only more addictive but, especially in large binges, is clearly damaging to the teen brain.

The truth is that your kids should stay away from pot, alcohol and cigarettes. If your teen finds pot helps her function, she needs to know that over time it's likely to make her problems worse.

In a study of more than 1,600 Australian girls recruited at ages 14 and 15, researchers concluded that those who smoked daily were five times more likely to report depression or anxiety over the next seven years. Weekly use doubled the risk.

Some teens clearly use marijuana to manage pain, get to sleep, or relieve anxiety, but it’s a risky strategy, as anxious “self-medicating” teens are much more likely to develop a drug problem later.

Teens who are vulnerable to psychosis may be pushed over the edge by cannabis. About 3 percent of heavy users develop schizophrenia.

Some brain scan research has found that smoking marijuana regularly as a teenager shrinks parts of the brain linked to memory, learning and impulse control.

Does the damage from marijuana’s effect on the brain last into adulthood? Maybe. Two large longitudinal studies suggest that smoking marijuana impairs mental functioning over time. Among nearly 3,000 people recruited between the ages of 18 to 30 and tested 25 years later, the more years you had smoked, the worse you scored on a vocabulary test, even after the researchers removed the effects of other drug and alcohol use and depression. In another study, researchers followed more than 1,000 babies born in 1972 and 1973 until they turned 38. They were tested at 13 and again at 38. Those who began smoking regularly as teens lost 6 to 8 points on an IQ test, even if they stopped smoking as adults. On the other hand, a study with twins tested at ages 9 to 12 and again at ages 17 to 20 concluded that if one twin smoked pot and the other didn’t, the pot didn’t lower IQ scores. The authors suggested that some other factor — for example, lack of parental encouragement — might explain both the pot-smoking and lower scores over time.

But basic science suggests that marijuana could have important effects. The “endocannabinoid system” in the brain, which gives marijuana its power to affect us, is known to be important in early brain development and may also be key during the teen years, when our brains prune down connections to become more efficient.

Over the next decade, the National Institutes of Health is funding the Adolescent Brain Cognitive Development (ABCD) study — tracking a large sample of young Americans from late childhood (before first use of drugs) to early adulthood, using brain scans and other tools to clarify marijuana’s effect on the brain.

A version of this story appears on Your Care Everywhere.

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