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

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.

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.

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.

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.

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.