In a recent study sponsored by NIDA and the National Institute of Mental Health, teens who used marijuana lost IQ points relative to their nonusing peers. However, the drug appeared not to be the culprit. The new findings contribute to an ongoing scientific exploration of the drug’s impact on users’ cognition.
Mr. Nicholas Jackson from the University of Southern California, Dr. Joshua Isen from the University of Minnesota, and colleagues tested three hypotheses that should all be confirmed if marijuana causes cognitive impairment that persists beyond the period of acute intoxication. Their results did not support any of the hypotheses. Instead, their evidence suggests that some children’s genes and family environments set them on pathways that lead both to the use of marijuana and to IQ decline.