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Effects of frequent marijuana use on memory-related regional cerebral blood flow.

Robert I Block, Daniel S O'Leary, Richard D Hichwa, Jean Augustinack, Laura L. Boles Ponto, Mohamed M Ghoneim, Stephan Arndt, Richard R Hurtig, G Leonard Watkins, James A Hall, Peter E Nathan, Nancy C Andreasen

Pharmacology, Biochemistry, and Behavior May 2002 DOI: 10.1016/s0091-3057(01)00771-7 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational case-control study Peer reviewed
Population Frequent marijuana users and nonusing control subjects
Duration 26+ h of monitored abstention
Topics Cannabis
Key findings Frequent marijuana users, compared with nonusing control subjects, showed altered memory-related regional cerebral blood flow after 26+ hours of monitored abstinence, including prefrontal decreases, cerebellar increases, and altered hippocampal lateralization, with the largest differences during episodic memory encoding. They required 2.7 more presentations during initial word-list learning and 3.1 more during relearning, and in single-trial recall they recalled 23% more from the end of the list but 19% less from the middle, indicating altered memory-related brain function.

Abstract

It is uncertain whether frequent marijuana use adversely affects human brain function. Using positron emission tomography (PET), memory-related regional cerebral blood flow was compared in frequent marijuana users and nonusing control subjects after 26+ h of monitored abstention. Memory-related blood flow in marijuana users, relative to control subjects, showed decreases in prefrontal cortex, increases in memory-relevant regions of cerebellum, and altered lateralization in hippocampus. Marijuana users differed most in brain activity related to episodic memory encoding. In learning a word list to criterion over multiple trials, marijuana users, relative to control subjects, required means of 2.7 more presentations during initial learning and 3.1 more presentations during subsequent relearning. In single-trial recall, marijuana users appeared to rely more on short-term memory, recalling 23% more than control subjects from the end of a list, but 19% less from the middle. These findings indicate altered memory-related brain function in marijuana users.

Comparable studies

Other observational and cohort studies on cannabis, most cited first.

Study Year Design Participants
High-potency cannabis and the risk of psychosis People with first episode of psychosis and healthy controls from the local population 2009 Case-control study n = 454
Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada Rural aboriginal population 2013 Observational study
Impaired cognitive performance in drug free users of recreational ecstasy (MDMA) Otherwise healthy young people 2000 Observational
Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Individuals from the general population in Germany aged 14-24 at baseline 2011 Observational cohort n = 1,923
Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and... 2005 Observational cohort n = 535

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