Medical cannabis could improve quality of life, executive functioning for patients

By Sarah Wolpoff

BOSTON – Medical use of marijuana is fully legal in 28 states, with another 17 states allowing limited use in specified cases. But policy has outpaced research and investigation into cannabis’s effects on the brain — both positive and negative. Although recreational users can face negative cognitive effects such as slowed reaction time, the herb may provide some benefit to people who partake for medical reasons, according to research presented Feb. 19 at the American Association for the Advancement of Science (AAAS) annual meeting.

Marijuana flower

Marijuana flower and leaves. Credit: fotobias /Pixabay

When marijuana was used to treat medical conditions such as chronic pain, anxiety, depression and attention disorders, patients reported improved quality of life, in terms of sleep, depression levels and social functions. After starting cannabis use, the patients also decreased their use of traditional prescription medications such as opioids. And preliminary research suggests that cannabis may improve executive functioning for such medical users.

While most studies regarding medical marijuana have focused on treatment outcomes and symptom relief, few, if any, have looked specifically at the effect of medically used marijuana on the ability to perform cognitive tasks. Cognitive studies are important because recreational users who consume with the intent to get “high” are known to do so at the expense of efficient thinking, said Staci Gruber, an associate professor of psychiatry at Harvard Medical School.

Two years ago, this problem inspired her to initiate the Marijuana Investigations for Neuroscientific Discovery, or M.I.N.D, program, which focuses on the drug’s impacts on cognition, quality of life and brain structure and function. The program follows patients for up to 24 months to document their experiences.

Last October, her group published findings from its first trial of 28 patients whose ailments included chronic pain, depression, anxiety/PTSD, attention problems and seizures. Patients had either never used cannabis before, or had not used it in at least 10 years. Patients participated in executive functioning tests, including digit symbol substitution tasks that involve categorizing and recording symbols with numbers as quickly as possible; and trail-making tests, a numerical ordering speed test that increases in difficulty as patterns change.

After three months of cannabis use, patients saw improved ability in most of these tasks, and no declines. Supplementary fMRI data indicated that activity in the brain’s frontal lobe in these cannabis users more closely resembled that of healthy individuals than the brain activity of non-using patients with the same medical conditions.

In addition to these cognitive boosts, study participants also showed improvements in depression symptoms, quality of sleep, social functioning and energy and fatigue, based on responses to inventory scale questionnaires. Research on these effects is ongoing.

But alongside these potential benefits for patients, medical marijuana can also produce negative effects such as dizziness, nausea, sleepiness, fatigue or agitation, said Ryan Vandrey, associate professor of psychiatry and behavioral sciences at John Hopkins Bayview Medical Center, who has studied effects of dosages and THC levels in marijuana and different routes of administration. Some of those adverse effects were attributed to products that had higher concentrations of the psychoactive ingredient in cannabis, called tetrahydrocannabinol or THC. To better advise doctors and improve safety for patients, further research is needed, experts say.

Such research is hindered currently, given the drug’s federal classification as a Schedule 1 drug with no accepted medical use. But to determine whether to remove it from Schedule 1 would take further research. It’s a Catch 22, Vandrey said.

Sarah Wolpoff is a senior studying journalism and psychology at Central Michigan University in Mount Pleasant, Michigan. She is a news editor at Central Michigan Life, an award-winning college media company. Previously, she served as a beat reporter at the paper, covering science and research at CMU. Reach her at or read her work at