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Chronic cannabis users have increased risk for memory distortions, despite abstinence

Study findings in Molecular Psychiatry indicate an increased risk for memory distortions among cannabis users, even if they have abstained from use for one month, suggesting the drug has long-term effects on memory and cognition.

“Despite changing attitudes in the perceived risks associated with [cannabis] and decriminalization initiatives taking place in many U.S. states and countries, the health implications of long-term cannabis consumption are still a matter of concern,” study researcher Jordi Riba, PhD, of Sant Pau Institute of Biomedical Research in Barcelona, and colleagues wrote.

Researchers tasked chronic cannabis users and healthy controls to learn a series of words. After a few minutes, study participants were shown the original word series with additional new words that were semantically related or unrelated. Study participants were then asked to identify the original word series. Researchers defined chronic cannabis use as daily use for the at least the last two years. Study participants abstained from cannabis use one month prior to the study.

Cannabis users were more likely to report seeing the semantically related new words compared with controls.

MRI screening indicated that cannabis users had lower activity levels in areas of the brain related to memory and the general control of cognition.

“The present results indicate that long-term heavy cannabis users are at an increased risk of experiencing memory errors even when abstinent and drug-free. These deficits show a neural basis and suggest a subtle compromise of brain mechanisms involved in reality monitoring,” Riba and colleagues wrote. “Though subtle, the deficits found bear similarities with alterations observed in psychiatric and neurologic conditions and also with age-related cognitive decline. This lingering diminished ability to tell true from false may have medical and legal implications.” – by Amanda Oldt

Disclosure: The researchers report no relevant financial disclosures.