Marijuana matters: reviewing the impact of marijuana on cognition, brain structure and function, & exploring policy implications and barriers to research

Abstract

The neurobiologic effects of cannabis, commonly referred to as ‘marijuana’ (MJ), have been studied for decades. The impact of recreational MJ use on cognition and measures of brain function and structure is outlined, and variables influencing study results are discussed, including age of the consumer, patterns of MJ use, variations in MJ potency, and the presence of additional cannabinoids. Although evidence suggests that chronic, heavy recreational MJ use is related to cognitive decrements and neural changes, particularly when use begins in adolescence, findings from studies of recreational MJ users may not be applicable to medical marijuana (MMJ) patients given differences in demographic variables, product selection, and reasons for use. Although additional research is needed to fully understand the impact of MJ and individual cannabinoids on the brain, current findings are beginning to inform public policy, including considerations for age limits, potential limits for some cannabinoids, and guidelines for use. However, barriers continue to impede researchers’ ability to conduct studies that will guide policy change and provide vital information to consumers and patients regarding best practices and safest methods for use. The need for information is critical, as legalization of MJ for medical and recreational use is increasingly widespread.

Keywords:

• Marijuana
• cannabis
• medical marijuana
• cognition
• neuroimaging
• MRI
• policy

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

During manuscript preparation, SG and KS were supported by the NIDA-funded grant R01DA032646 and private donations made to the Marijuana Investigations for Neuroscientific Discovery (MIND) program.