Chronic cannabis use consistently alters cerebellum structure and function, affecting memory and decision-making | Research

The takeaway

A systematic review of 40 studies found chronic cannabis use is consistently associated with increased cerebellar gray matter volume, altered resting brain activity, and deficits in memory, decision-making, and associative learning.

Neuroscientists, cannabis researchers, and clinicians interested in cognitive effects of cannabis use.

40 studies, 3 consistent findings

What the researchers found

The three most consistent findings across 40 studies were: (1) increased cerebellar gray matter volume after chronic use, (2) altered cerebellar resting state activity after acute or chronic use, and (3) deficits in memory, decision-making, and associative learning (cerebellar-dependent tasks). Earlier age of onset and greater exposure were associated with more alterations.

Why it matters

The cerebellum is increasingly recognized as important for cognition, emotion, and learning, not just motor coordination. Its high density of CB1 receptors makes it a prime target for cannabis effects, yet it has been understudied compared to cortical regions.

The numbers in context

40 studies included from 348 screened. High CB1 receptor density in cerebellum. 3 main findings: increased gray matter volume, altered resting activity, deficits in memory/decision-making/learning. Earlier onset and higher exposure = more alterations.

How the study worked

Systematic review searching three databases for studies on cannabis effects on cerebellar structure, function, and cerebellar-dependent behavioral tasks. 348 records screened, 40 included in qualitative synthesis.

What this study cannot tell us

Included studies had variable methods for assessing cannabis use. Tobacco was a confounding factor in many studies. The review could not determine causality. Increased cerebellar volume could be compensatory rather than pathological.

How to read the evidence

Rated moderate because this is a thorough systematic review of a substantial body of literature, though individual study quality varied.

When this study was published

Published in 2019 reviewing literature through March 2018.

The bigger picture

Most cannabis brain research focuses on frontal cortex and hippocampus. This review shifts attention to the cerebellum, which may play a larger role in cannabis-related cognitive effects than previously appreciated, particularly for learning and decision-making.

Questions still open

Is increased cerebellar volume compensatory or reflecting a different type of tissue change? Do cerebellar effects recover with abstinence? Could cerebellar function tests be used as monitoring tools for cannabis-related impairment?

Common questions

Does cannabis affect the cerebellum?

Yes. A review of 40 studies found consistent changes including increased gray matter volume, altered resting activity, and impaired learning and decision-making. The cerebellum has one of the highest densities of cannabinoid receptors in the brain.

Does it matter when you start using cannabis?

Earlier age of onset and greater total exposure were both associated with more cerebellar alterations, suggesting the developing brain may be particularly vulnerable.

Read the original research

Cerebellar alterations in cannabis users: A systematic review.

Addiction biology, 24(6), 1121-1137

View on PubMed ↗Publisher’s paper ↗

Citation

Blithikioti, Chrysanthi; Miquel, Laia; Batalla, Albert; Rubio, Belen; Maffei, Giovanni; Herreros, Ivan; Gual, Antoni; Verschure, Paul; Balcells-Oliveró, Mercedes. (2019). Cerebellar alterations in cannabis users: A systematic review.. Addiction biology, 24(6), 1121-1137. https://doi.org/10.1111/adb.12714