A comprehensive review of human brain imaging reveals how cannabis affects executive function, emotion, memory, and reward | Research

The takeaway

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.

Neuroscientists, psychiatrists, cannabis policy researchers, and anyone wanting a thorough understanding of cannabis effects on the human brain.

All major brain systems affected

What the researchers 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.

Why it 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 numbers in context

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 the study worked

Comprehensive state-of-the-art review synthesizing all available human neuroimaging research on acute and chronic cannabis effects, including PET, SPECT, and fMRI studies.

What this study cannot 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.

How to read the evidence

Rated strong because this is a comprehensive review in a high-impact pharmacology journal synthesizing the full scope of human neuroimaging evidence.

When this study was published

Published in 2019. Cannabis neuroimaging research continues to expand rapidly.

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.

Questions still open

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?

Common 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.

Read the original research

The neuropsychopharmacology of cannabis: A review of human imaging studies.

Pharmacology & therapeutics, 195, 132-161

View on PubMed ↗Publisher’s paper ↗

Citation

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