Neurophysiological functioning of occasional and heavy cannabis users during THC intoxication

Department of Neuropsychology and Psychopharmacology, Faculty of Psychology and Neuroscience, Maastricht University, P.O. Box 616, 6200MD Maastricht, The Netherlands.
Psychopharmacology (Impact Factor: 3.88). 10/2011; 220(2):341-50. DOI: 10.1007/s00213-011-2479-x
Source: PubMed


Experienced cannabis users demonstrate tolerance to some of the impairing acute effects of cannabis.
The present study investigates whether event-related potentials (ERPs) differ between occasional and heavy cannabis users after acute Δ9-tetrahydrocannabinol (THC) administration, as a result of tolerance.
Twelve occasional and 12 heavy cannabis users participated in a double-blind, placebo-controlled, crossover study. On two separate days, they smoked a joint containing 0 or 500 μg/kg body weight THC. ERPs were measured while subjects performed a divided attention task (DAT) and stop signal task (SST).
In the DAT, THC significantly decreased P100 amplitude in occasional but not in heavy cannabis users. P300 amplitude in the DAT was significantly decreased by THC in both groups. The N200 peak in the SST was not affected by treatment in neither of the groups. Performance in the SST was impaired in both groups after THC treatment, whereas performance in the DAT was impaired by THC only in the occasional users group.
The present study confirms that heavy cannabis users develop tolerance to some of the impairing behavioral effects of cannabis. This tolerance was also evident in the underlying ERPs, suggesting that tolerance demonstrated on performance level is not (completely) due to behavioral compensation.

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    • "Chronic cannabis users smoking cannabis cigarettes (joints; containing maximally 39 mg of THC) have been shown to demonstrate no accuracy deficiencies on a number of tasks tapping into different cognitive functions (Hart et al., 2001) and, in particular, on episodic and working memory tests (Hart et al., 2010). In addition, compared to infrequent users, chronic users did not display any behavioral impairments on tasks evaluating tracking error and divided attention (Ramaekers et al., 2009) or changes in an ERP indicative of early attentional processes (Theunissen et al., 2012), following smoking of a cannabis joint (with 500 μg/kg body weight THC). Conversely , inhibitory control has been identified to be equally diminished among both chronic and occasional users due to cannabis administration (Ramaekers et al., 2009). "
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    ABSTRACT: Cannabis has been suggested to impair the capacity to recognize discrepancies between expected and executed actions. However, there is a lack of conclusive evidence regarding the acute impact of cannabis on the neural correlates of error monitoring. In order to contribute to the available knowledge, we used a randomized, double-blind, between-groups design to investigate the impact of administration of a low (5.5 mg THC) or high (22 mg THC) dose of vaporized cannabis vs. placebo on the amplitudes of the error-related negativity (ERN) and error positivity (Pe) in the context of the Flanker task, in a group of frequent cannabis users (required to use cannabis minimally 4 times a week, for at least 2 years). Subjects in the high dose group (n =18) demonstrated a significantly diminished ERN in comparison to the placebo condition (n =19), whereas a reduced Pe amplitude was observed in both the high and low dose (n=18) conditions, as compared to placebo. The results suggest that a high dose of cannabis may affect the neural correlates of both the conscious (late), as well as the initial automatic processes involved in error monitoring, while a low dose of cannabis might impact only the conscious (late) processing of errors.
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    • "Using event-related potentials as a measure of brain functioning, Theunissen et al. (2012) found that THC significantly reduced P100 levels among heavy cannabis users. Similarly, Lane, Cherek, Tcheremissine, Lieving, and Pietras (2005) found that subjects exposed to a high dose of THC (3.6%) demonstrated significantly greater risk-taking than subjects receiving lower doses of THC. "

    Full-text · Dataset · Feb 2015
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    • "Administration of joints (containing up to 39 mg of THC) to regular cannabis users has been found to produce no accuracy impairments on a test battery assessing several cognitive functions (Hart et al. 2001) and, more specifically , on tasks related to episodic and working memory (Hart et al. 2010). Furthermore, after smoking a cannabis joint (containing 500 μg/kg body weight THC), chronic users did not display any behavioral deficiencies on tasks assessing tracking performance and divided attention (Ramaekers et al. 2009) or changes in an event-related potential (ERP) reflecting early attentional processes (Theunissen et al. 2012), compared to infrequent users. In addition, regular cannabis users were shown to display reduced sensitivity to the psychotomimetic effects of THC (administered as an intravenous dose up to 5 mg; D'Souza et al. 2008). "
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    ABSTRACT: Rationale Cannabis users often claim that cannabis has the potential to enhance their creativity. Research suggests that aspects of creative performance might be improved when intoxicated with cannabis; however, the evidence is not conclusive. Objective The aim of this study was to investigate the acute effects of cannabis on creativity. Methods We examined the effects of administering a low (5.5 mg delta-9-tetrahydrocannabinol [THC]) or high (22 mg THC) dose of vaporized cannabis vs. placebo on creativity tasks tapping into divergent (Alternate Uses Task) and convergent (Remote Associates Task) thinking, in a pop-ulation of regular cannabis users. The study used a random-ized, double-blind, between-groups design. Results Participants in the high-dose group (n=18) displayed significantly worse performance on the divergent thinking task, compared to individuals in both the low-dose (n=18) and placebo (n=18) groups. Conclusions The findings suggest that cannabis with low potency does not have any impact on creativity, while highly potent cannabis actually impairs divergent thinking.
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