Researchers looking into the effects of medical marijuana use on brain processes say in a new federally funded paper published by the American Medical Association that cognitive attributes such as working memory, reward and inhibitory control were not significantly affected after a year of cannabis consumption.

The results appear to run contrary to long-held stereotypes about marijuana negatively affecting memory and other brain health indicators.

“Our results suggest that adults who use cannabis, generally with light to moderate use patterns, for symptoms of pain, anxiety, depression, or poor sleep, experience few significant long-term neural associations in these areas of cognition,” says the study, funded by the National Institute on Drug Abuse (NIDA) and published this week in the journal JAMA Network Open.

Researchers recruited 57 newly certified medical marijuana patients from the greater Boston area and used functional magnetic resonance imaging (fMRI) to monitor brain activity during a variety of mental tasks. Participants’ brains were then scanned again after a year of medical cannabis use to look for changes in activity.

“Working memory, reward, and inhibitory control tasks did not differ statistically from baseline to 1 year and were not associated with changes in cannabis use frequency.”

“In all groups and at both time points, functional imaging revealed canonical activations of the probed cognitive processes,” the report says. “No statistically significant difference in brain activation between the 2 time points (baseline and 1 year) in those with medical cannabis cards and no associations between changes in cannabis use frequency and brain activation after 1 year were found.”

“In this cohort study of adults obtaining [medical cannabis cards] for medical symptoms, brain activation during working memory, reward processing, and inhibitory control tasks was not significantly different after year-long cannabis use and no association with changes in cannabis