Teenagers love to complain their parents are too critical of marijuana and that little harm can come from smoking pot. However, a new study suggests that teenagers who use marijuana regularly are at greater risk for long-term brain damage and declines in both IQ and cognitive functioning years later.

Daily cannabis use is on the rise among adolescents who are now smoking marijuana at younger ages than ever before, many of them on a daily basis. This rise in marijuana use is caused in part because most teenagers do not believe that smoking marijuana is harmful to their health. However, a new 38 year-long study might make them and their parents think again.

Tracking Teenagers’ Marijuana Use Over 25 Years

The new study followed participants from birth till the age of 38. Researchers administered cognitive testing (that measures intellectual abilities such as IQ) at two time periods: when the participants were 13—before they began regular marijuana use, and when they were 38 years-old. Participants’ marijuana use was ascertained via interviews at four other time periods as well; when the subjects were 18, 21, 26, and 32 years-old.

The researchers assumed that because the teenage brain is still developing, regular marijuana use would affect the brains of teenagers and adults differently. Their data allowed them to compare any cognitive/intellectual changes that occurred in chronic marijuana users who began smoking in their teens to changes that occurred among chronic users who started smoking pot as young adults or adults.

The Findings

Researchers found that participants who began chronic marijuana use in adolescence showed significant cognitive and intellectual declines by age 38, with heavy users dropping as much as 8 IQ points. Chronic users who began later in life showed significantly smaller declines across all measures. In addition, the more persistent their marijuana use was in adolescence, the greater the cognitive declines the participants exhibited later in life. Further, ceasing marijuana use in adulthood did not fully restore these declines among users who started in their teens.

The Conclusion

Although these findings need to be replicated by other studies, they contribute to a growing body of research demonstrating the vulnerability of the teenage brain, in this case, to the neurotoxic effects of chronic cannabis use. The study does not suggest regular marijuana use has no detremental affects for adults, only that cognitive declines were more significant for users who began smoking in their teens.

Since developing dependence might have extremely damaging and non-reversible affects in adolescents (especially when chronic use persists into adulthood), parents, educators, and especially teenagers should become informed about the potential harm of initiating marijuana use at young ages. Parents who need advice about talking to their teens about drugs can find many useful articles on this site (using the search function at the top right of this page) or go to theantidrug.com.

View my short and quite personal TED talk about Psychological Health here:

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Copyright 2012 Guy Winch

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