A comprehensive review of human brain imaging reveals how cannabis affects executive function, emotion, memory, and reward
A major review synthesizing all human neuroimaging research on cannabis found acute and chronic effects across executive, emotional, reward, and memory processing systems, with adolescent use carrying particular risk for lasting changes.
Quick Facts
What This Study Found
Cannabis and THC acutely affect executive, emotional, reward, and memory processing through direct CB1 effects and indirect effects on glutamate, GABA, and dopamine systems. CBD may partially offset some acute effects. Heavy chronic use, especially during adolescence, is associated with persistent alterations that increase risk for addiction and psychosis.
Key Numbers
THC acts as partial agonist at CB1 receptors. Indirect effects on glutamate, GABA, and dopamine systems. CBD found in some cannabis forms may offset certain acute effects. Adolescent exposure carries higher risk for lasting changes.
How They Did This
Comprehensive state-of-the-art review synthesizing all available human neuroimaging research on acute and chronic cannabis effects, including PET, SPECT, and fMRI studies.
Why This Research Matters
This is the most comprehensive neuroimaging review of cannabis effects available, synthesizing evidence across multiple brain systems and imaging modalities to create a unified picture of how cannabis affects the human brain.
The Bigger Picture
Understanding how cannabis alters brain function at the systems level is critical for informed policy, clinical guidance, and harm reduction. This review provides the scientific foundation for discussions about cannabis that are often conducted without it.
What This Study Doesn't Tell Us
Imaging studies have variable methods, sample sizes, and definitions of cannabis use. Most studies are cross-sectional, limiting causal conclusions. Many confounds (tobacco, alcohol, mental health) are difficult to control. Publication bias may affect the literature.
Questions This Raises
- ?Which brain changes are reversible and which are permanent?
- ?Can neuroimaging identify individuals most vulnerable to cannabis-related harms?
- ?How do different cannabis products (varying THC:CBD ratios) affect the brain differently?
Trust & Context
- Key Stat:
- All major brain systems affected
- Evidence Grade:
- Rated strong because this is a comprehensive review in a high-impact pharmacology journal synthesizing the full scope of human neuroimaging evidence.
- Study Age:
- Published in 2019. Cannabis neuroimaging research continues to expand rapidly.
- Original Title:
- The neuropsychopharmacology of cannabis: A review of human imaging studies.
- Published In:
- Pharmacology & therapeutics, 195, 132-161 (2019)
- Authors:
- Bloomfield, Michael A P(7), Hindocha, Chandni(13), Green, Sebastian F(3), Wall, Matthew B, Lees, Rachel, Petrilli, Katherine, Costello, Harry, Ogunbiyi, M Olabisi, Bossong, Matthijs G, Freeman, Tom P
- Database ID:
- RTHC-01951
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
What does cannabis do to the brain?
It affects four major systems: executive function (planning, decision-making), emotional processing, reward/motivation, and memory. These effects occur through direct action on CB1 receptors and indirect changes in glutamate, GABA, and dopamine signaling.
Is the adolescent brain more vulnerable?
Yes. Heavy cannabis use during adolescence is associated with more persistent brain changes and increased risk for addiction and psychosis compared to adult-onset use.
Does CBD protect the brain from THC effects?
Some evidence suggests CBD may offset certain acute THC effects, but the extent of this protection and whether it applies to chronic use is unclear.
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Cite This Study
https://rethinkthc.com/research/RTHC-01951APA
Bloomfield, Michael A P; Hindocha, Chandni; Green, Sebastian F; Wall, Matthew B; Lees, Rachel; Petrilli, Katherine; Costello, Harry; Ogunbiyi, M Olabisi; Bossong, Matthijs G; Freeman, Tom P. (2019). The neuropsychopharmacology of cannabis: A review of human imaging studies.. Pharmacology & therapeutics, 195, 132-161. https://doi.org/10.1016/j.pharmthera.2018.10.006
MLA
Bloomfield, Michael A P, et al. "The neuropsychopharmacology of cannabis: A review of human imaging studies.." Pharmacology & therapeutics, 2019. https://doi.org/10.1016/j.pharmthera.2018.10.006
RethinkTHC
RethinkTHC Research Database. "The neuropsychopharmacology of cannabis: A review of human i..." RTHC-01951. Retrieved from https://rethinkthc.com/research/bloomfield-2019-the-neuropsychopharmacology-of-cannabis
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.