An article in The New York Times elaborates on Dr. Jodi Gilman’s research on the neurological impact of marijuana on the brains of casual users, which I summarized in a previous post (http://goo.gl/gogPV7). However, this article is interesting because it explains how and why even moderate use may be particularly damaging to young people. Again, this was a small study (40 subjects) but it found that the seven participants who smoked only once or twice a week had structural differences in the nucleus accumbens, a key reward structure in the brain, and in the amygdala, which is a fundamental structure for processing emotions, memories and fear responses. Moreover, the more marijuana subjects smoked, the greater these differences were.
In this interview Dr. Gilman expressed particular concern about college students, whose brains are still developing and who, as she noted, are making major life decisions, including “choosing a major (and) making long-lasting friendships.” It was already known that THC interferes with working memory, decision making and motivation for about 24 hours. But the structural changes that Gilman found indicate “that the effects of THC are longer lasting than we previously thought.” The article cites other research that points to adverse and long-lasting effects of marijuana smoking, including a study released in 2012 that showed that teenagers who were found to be dependent on pot before age 18 and continued using it into adulthood lost an average of eight I.Q. points by age 38. It also notes that Hans Breiter, a co-author on the Gilman research, found in a study last year that changes in the nucleus accumbens persisted in young adults who had smoked daily for three years but had stopped for at least two years. His subjects had impaired working memories as well. Dr. Breiter commented that, “Working memory is key for learning. “If I were to design a substance that is bad for college students, it would be marijuana.”