A new study led by McLean Hospital’s Staci Gruber, PhD, director of the Marijuana Investigations for Neuroscientific Discovery (MIND) program, is being conducted to determine the truth about cannabis’ effect on cognitive function. The preliminary results from the study, which have been published in Frontiers in Pharmacology journal, are showing a great deal of promise. Although there have been past studies that suggest the regular use of cannabis could have an adverse affect on brain functionality, the evidence yielded from Gruber’s longitudinal study thus far seems to suggest the contrary, as the patients involved are demonstrating an improvement in executive cognitive functioning after only 3-months time.

For the study, medical researchers from McLean Hospital, Harvard Medical School, and Tufts University will examine 24 patients certified for medical cannabis over the course of a year, testing neurocognition before their treatment, and again after 3 months, 6 months and 12 months of treatment. The study is still well underway with the team already having spoken with most of the 24 patients for their 3-month evaluation, producing the data presented here.

During the evaluations, patients are given an array of cognitive tests. Those who have received their 3-month evaluation have demonstrated an improvement in both their speed and accuracy as compared to the baseline results prior to treatment. An excerpt from the McLean Hospital report reads:

“After three months of medical marijuana treatment, patients actually performed better, in terms of their ability to perform certain cognitive tasks, specifically those mediated by the frontal cortex,” explained Gruber.

Study participants also reported improvements in their specific clinical conditions, sleep, and overall health as well as a decreased use of conventional medications, particularly opiates.

“We saw a 42 percent reduction in opioid use,” reported Gruber. “This is significant, particularly for those of us in Massachusetts and other areas of the country where the opioid epidemic is ravaging so many. This preliminary finding certainly warrants deeper and broader investigation.”


As of yesterday, November 8th, the states of Massachusetts, California and Nevada have officially approved recreational cannabis initiatives. On the medical side of things, the states of Arkansas, Florida and North Dakota have also just joined the party. This means that more than half of the states in the nation have adopted some degree of cannabis legalization, making the findings coming out of McLean Hospital, and other institutions, that much more impacting.

As McLean Hospital’s pilot study continues, the researchers will have the opportunity to further explore the favorable and unfavorable impacts of cannabis on adult brain cognition. As the investigation deepens and our understanding broadens, we may find the epidemic of opioid dependence to be a thing of the past.

Driven with passion and dedication, lead researcher Staci Gruber and her team will continue to press on with their investigation. Having already received recognition for the intelligence in their approach and their experiment model, their work is setting a new standard for cannabis research and opening a whole new window of information regarding the brain and how it is effected by exogenous substances. “People are going to use it,” Gruber says. “It’s up to us to figure out the very best and safest ways in which they can do that.”

Check back for more information, as we will have our eye out for developments on this and other upcoming cannabis news and research.

Gruber, Staci A., Kelly A. Sagar, Mary K. Dahlgren, Megan T. Racine, Rosemary T. Smith, and Scott E. Lukas. “Splendor in the Grass? A Pilot Study Assessing the Impact of Medical Marijuana on Executive Function.” Frontiers. N.p., n.d. Web. 07 Nov. 2016.

Peterson617.855.2110, Christopher. “McLean Hospital Study Finds That Medical Marijuana Use May Improve Cognitive Performance.” McLean Hospital, the Largest Psychiatric Affiliate of Harvard Medical School. N.p., n.d. Web. 07 Nov. 2016.