Rick Nauert reports on PsychCentral about a study by investigators from Northwestern University concerning the adverse impact of teens’ daily marijuana smoking on the shape and function of the hippocampus, a brain structure that plays a key role in the preservation of long-term memories.
The study was published in the journal Hippocampus and 97 subjects participated. Healthy control subjects were matched with individuals who had a marijuana use disorder, schizophrenic subjects with no history of a substance use disorder, and schizophrenic subjects with a marijuana use disorder. Subjects with marijuana use disorders started using the drug between the ages of 16 and 17 and used it daily for about three years. They did not abuse other drugs and, at the time of the study, had been marijuana free for approximately two years.
Structural MRIs of the participants’ brains revealed that that subjects with a history of daily marijuana smoking had abnormally shaped hippocampi, despite the two years of abstinence from the drug. The longer these subjects had engaged in heavy use of marijuana, the more abnormal the shape of their hippocampus, according to the researchers. These subjects also “performed about 18 percent worse on long-term memory tests than young adults who never abused cannabis”.
Nauert correctly reports that, “In the U.S., marijuana is the most commonly used illicit drug, and young adults have the highest — and growing — prevalence of use.”