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Neurocognitive consequences of marihuana--a comparison with pre-drug performance
P A Fried1, B Watkinson, R Gray
1Department of Psychology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6. peter_fried@carleton.ca
Neurotoxicology and Teratology
|March 1, 2005
Summary
Regular heavy marijuana use in young adults is linked to lasting cognitive deficits, including lower IQ and memory issues. However, these cognitive impairments in marijuana smokers appear to resolve after 3 months of abstinence.
Area of Science:
- Neuroscience
- Psychology
- Addiction Medicine
Background:
- Assessing the long-term neurocognitive effects of marijuana use is challenging due to a lack of pre-drug baseline data.
- Previous studies often lack prospective, longitudinal data on cognitive function before and after marijuana initiation.
Purpose of the Study:
- To investigate the neurocognitive effects of current and past regular marijuana use in young adults.
- To determine if cognitive deficits persist after cessation of marijuana use.
Main Methods:
- A prospective, longitudinal study of 113 young adults assessed since infancy.
- Neurocognitive tests administered, with pre-drug performance data available.
- Participants categorized into light current users, heavy current users, and former users based on self-report and urinalysis.
Main Results:
- Current regular heavy marijuana users showed significant deficits in overall IQ, processing speed, and immediate/delayed memory compared to non-users.
- These cognitive impairments were evident after accounting for pre-drug performance and confounding factors.
- Former marijuana smokers, abstinent for at least 3 months, did not exhibit significant cognitive impairments.
Conclusions:
- Residual neurocognitive effects are associated with current heavy marijuana use, persisting beyond acute intoxication.
- Cognitive deficits observed in heavy marijuana users appear to be reversible upon cessation of use.
- Abstinence from marijuana for at least 3 months mitigates previously observed cognitive impairments.
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