Sustained Use of Medical Cannabis Is Not Associated With Changes in Either Brain Morphology or Cognitive Performance

Adults who regularly consume medical cannabis products do not experience any significant adverse changes in either brain morphology or cognitive performance, according to longitudinal data published in the journal JAMA (Journal of the American Medical Association) Network Open.

Researchers affiliated with Harvard Medical School and the McGovern Institute for Brain Research at the Massachusetts Institute of Technology collected structural and functional brain imaging (fMRI) data from a cohort of newly authorized medical cannabis patients at baseline and one-year later. Similar data was also collected for healthy controls (non-cannabis consumers).

Investigators “did not observe functional differences between baseline and brain activation at one-year during working memory, reward processing, or inhibitory control tasks,” nor did they identify “an association between changes in cannabis use frequency and brain activation.”

The findings are consistent with numerous prior studies concluding that cannabis exposure is not negatively associated with significant changes in either brain morphology or cognitive functioning in either young people or adults. Other studies have determined that medical cannabis patients “exhibit enhanced rather than impaired executive function over time,” likely as a result of clinical improvements in their conditions.

The study’s authors concluded: “In this cohort study of adults obtaining MCCs [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 use frequency was noted. 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.”

Commenting on the study’s findings, NORML’s Deputy Director Paul Armentano said, “These study’s findings reinforce the fact that medical cannabis use is both safe and effective and they belie longstanding claims that cannabis exposure is either uniquely or significantly damaging to the brain.”

The full text of the study, “Year-long cannabis use for medical symptoms and brain activation during cognitive processes,” appears in JAMA Network Open. Additional information is available from the NORML Fact Sheet, “Marijuana Exposure and Cognitive Performance.”