Despite previous claims, a new study headed by researchers at Loyola Marymount University reports that smoking marijuana during adolescence might not lead to a decrease in intelligence; instead, this decrease could actually be a symptom of another dysfunction that is the root cause of the diminished brainpower found in other research. Although the team is not yet certain what this other dysfunctional factor is, Joshua Isen, one of the authors of the analysis, says that any teenager that is at risk for smoking pot "is probably going to show this IQ drop regardless of whether he or she is actually smoking marijuana," according to a press release.
The study aims to dispel fears brought on by previous research suggesting that the teenage brain is more vulnerable than other age groups to damage from marijuana, instead suggesting that these dangers are not rooted in marijuana smoking. The topic is particularly difficult to study due to the fact that children cannot be randomly chosen to take illicit drugs or abstain from taking them, making true experimental analysis impossible.
The new study analyzed data gained from two large U.S. twin studies, focusing on 3,066 subjects who participated in a variety of intelligence tests at the ages of 9 and 12, prior to marijuana use, and again at the ages of 17 to 20. The team followed changes in each participant's test scores and compared these patterns in terms of marijuana smokers and non-users, with most tests showing no difference between each group except for tests of vocabulary and general knowledge.
The researchers claim that if marijuana smoking truly affected intelligence and brought down test scores, marijuana smokers should show worse trends in comparison to those who smoke marijuana, but the data revealed that among users, there was no difference in test scoring between those who had smoked more than 30 times and those who had used it every day for more than six months at a time. Furthermore, upon examining 290 pairs of twins, one a marijuana user and the other a non-user, they found that despite sharing the same DNA, marijuana users showed no pattern toward poorer test scores.
Nora Volkow, director of the National Institute on Drug Abuse, believes that the findings show promise and should be followed up on in order to understand more about the effects of marijuana on adolescents, despite the limitations of the study.
The study was released in the Jan. 18 issue of the Proceedings of the National Academy of Sciences.
