" Negative Neurophysiological and cognitive effects of smoked marijuana in frequent users "

Negative Neurophysiological and cognitive effects of smoked marijuana in frequent users.

7-08-10

Negative Experienced Marijuana Consumers Exhibit Virtually No Change In
Cognitive Task Performance After Smoking, Study Says

Division on Substance Abuse, New York State Psychiatric Institute and Department of
Psychiatry, College of Physicians and Surgeons of Columbia University, USA;
Department of Psychology, Columbia University, USA.

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New York, NY: Experienced marijuana consumers exhibit nominal changes in cognitive performance after inhaling cannabis, according to clinical trial data published online this week in the journal Pharmacology, Biochemistry, and Behavior.

Investigators at Columbia University in New York and the San Francisco Brain Research Institute assessed acute marijuana-related effects on cognitive functioning in 24 volunteers who reported consuming the drug at least 24 times per week.

Researchers determined that participants' overall performance accuracy on episodic memory and working memory tasks "was not significantly altered by marijuana."

Abstract

RATIONALE: Previously, we reported that acute marijuana intoxication minimally affected complex cognitive performance of daily marijuana smokers. It is possible that the cognitive tests used were insensitive to marijuana-related cognitive effects. OBJECTIVES: In the current study, electroencephalographic (EEG) signals were recorded as daily marijuana users performed additional tests of immediate working memory and delayed episodic memory, before and after smoking marijuana. METHODS: Research volunteers (N=24), who reported smoking approximately 24 marijuana cigarettes/week, completed this study. Participants completed baseline computerized cognitive tasks, smoked a single marijuana cigarette (0%, 1.8%, or 3.9% (9)-THC w/w), and completed additional cognitive tasks; sessions were separated by at least 72-hours. Cardiovascular and subjective effects were also assessed throughout sessions. RESULTS: Overall performance accuracy was not significantly altered by marijuana, although the drug increased response times during task performance and induced a response bias towards labeling "new" words as having been previously seen in the verbal episodic memory task. Marijuana reduced slow wave evoked potential amplitude in the episodic memory task and decreased P300 amplitude and EEG power in the alpha band in the spatial working memory task. Heart rate and "positive" subjective-effect ratings were increased in a (9)-THC concentration-dependent manner. CONCLUSIONS: Relative to previous findings with infrequent marijuana users, the frequent users in the current study exhibited similar neurophysiological effects but more subtle performance effects. These data emphasize the importance of taking into account the drug-use histories of research participants and examining multiple measures when investigating marijuana-related effects on cognitive functioning. Copyright � 2010 Elsevier Inc. All rights reserved.

PMID: 20600251 [PubMed - as supplied by publisher]

Negative Neurophysiological and cognitive effects of smoked marijuana in frequent users.

Negative Experienced Marijuana Consumers Exhibit Virtually No Change In Cognitive Task Performance After Smoking, Study Says

Division on Substance Abuse, New York State Psychiatric Institute and Department of Psychiatry, College of Physicians and Surgeons of Columbia University, USA; Department of Psychology, Columbia University, USA.

Return Back To Main Medical Reports Page

Abstract

Negative Experienced Marijuana Consumers Exhibit Virtually No Change In
Cognitive Task Performance After Smoking, Study Says

Division on Substance Abuse, New York State Psychiatric Institute and Department of
Psychiatry, College of Physicians and Surgeons of Columbia University, USA;
Department of Psychology, Columbia University, USA.