Long-Term Cannabis Use Linked to Impaired Automatic Movement Learning

Observational study comparing 30 regular cannabis users and 32 non-users. Measures: serial reaction time task (implicit motor learning), Corsi block-tapping test (visuospatial memory), and resting-state EEG (cortical activity in beta and gamma bands). Duration of cannabis use correlated with learning and EEG outcomes.

Implicit motor learning is fundamental to daily life — it underlies the ability to learn movement sequences for everything from typing to driving to social interaction. This is the first study to link chronic cannabis use to impairment in this specific type of learning, and the EEG data offer a potential brain-level explanation for why it happens.

Most cannabis cognition research focuses on explicit memory, attention, and executive function. This study adds implicit motor learning to the list of affected domains — a type of learning that operates below conscious awareness and may therefore be harder for users to notice or compensate for. The elevated resting brain activity finding connects to the neuroscience of tolerance (RTHC-00249) and the broader cognitive impact literature, suggesting that chronic cannabis use may alter baseline neural dynamics in ways that cascade across multiple cognitive functions.

Cross-sectional design cannot establish that cannabis caused the learning impairment — it may reflect pre-existing differences. Small sample size limits statistical power. Cannot control for all confounders (other substance use, sleep quality, education). Cannabis use was self-reported and varied in frequency and potency.