Marijuana Matters: Reviewing the Impact of Marijuana on Cognition, Brain Structure and Function, & Exploring Policy Implications and Barriers to Research
Kelly A. Sagar, Staci A Gruber
International Review of Psychiatry May 4, 2018 DOI: 10.1080/09540261.2018.1460334 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Review Peer reviewed |
|---|---|
| Topics | Cannabis |
| Key findings | The authors conclude that chronic, heavy recreational marijuana use is associated with cognitive decrements and neural changes, particularly when use begins in adolescence, but argue these findings may not generalize to medical marijuana patients given differences in demographics, product selection, and reasons for use. They contend that current evidence is beginning to inform public policy on age limits, cannabinoid limits, and use guidelines, while research barriers persist. |
Abstract
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.
Comparable studies
Other narrative reviews on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Causal association between cannabis and psychosis: examination of the evidence | 2004 | Review | |
| Cannabis sativa: A comprehensive ethnopharmacological review of a medicinal plant with a long history. General (historical and pharmacological review) | 2018 | Review | |
| Psychiatric effects of cannabis | 2001 | Review | |
| Beyond THC: The New Generation of Cannabinoid Designer Drugs | 2011 | Review | |
| Cannabidiol, a Cannabis sativa constituent, as an antipsychotic drug | 2006 | Review |
Citations in the library
Cited by 12
- Effects of inhaled cannabis high in Δ9-THC or CBD on the aging brain: A translational MRI and behavioral study Frontiers in Aging Neuroscience February 1, 2023
- Differences in Inhibitory Control and Resting Brain Metabolism between Older Chronic Users of Tetrahydrocannabinol (THC) or Cannabidiol (CBD)—A Pilot Study Brain Sciences June 23, 2022
- EEG-based network dynamics in cannabis and polydrug use: a directed transfer function approach. Psychopharmacology October 20, 2025
- A longitudinal study of cannabis use and risk for cognitive and functional decline among older adults with HIV AIDS and behavior May 8, 2023
- A Meta-Analysis of fMRI Studies of Youth Cannabis Use: Alterations in Executive Control, Social Cognition/Emotion Processing, and Reward Processing in Cannabis Using Youth Brain Science September 23, 2022
and 7 more in the library
Cites 22
- Cannabis use before age 15 and subsequent executive functioning The British Journal of Psychiatry May 31, 2011
- The Grass Might Be Greener: Medical Marijuana Patients Exhibit Altered Brain Activity and Improved Executive Function after 3 Months of Treatment Frontiers in Pharmacology January 17, 2018
- Acute and Chronic Effects of Cannabinoids on Human Cognition-A Systematic Review. Biological Psychiatry April 1, 2016
- Hippocampal harms, protection and recovery following regular cannabis use. Translational Psychiatry January 12, 2016
- The impact of initiation: Early onset marijuana smokers demonstrate altered Stroop performance and brain activation. Developmental Cognitive Neuroscience December 2015
and 17 more in the library