Neurophysiological and subjective profile of marijuana with varying concentrations of cannabinoids

Smoking marijuana with delta9-tetrahydrocannabinol (THC) produces expected effects on mood, behavior, and brain activity, but varying the concentrations of other cannabinoids like cannabichromene (CBC) and cannabidiol (CBD) does not change responses. Twenty-three healthy marijuana users (12 men, 11 women) participated in four sessions, randomly assigned to low or high THC groups (1.8% versus 3.6%). Under blinded conditions, they smoked placebo or THC cigarettes with low or high levels of CBC (0.1% versus 0.5%) and CBD (0.2% versus 1.0%). Active THC cigarettes decreased performance, reduced EEG power, and attenuated ERP components reflecting attentional processes during working and episodic memory tests, mostly without dose dependence. CBC and CBD concentrations did not alter any outcomes, consistent with THC being the primary active constituent.

Study at a glance

Abstract

This study investigated the contribution of different cannabinoids to the subjective, behavioral and neurophysiological effects of smoked marijuana. Healthy marijuana users (12 men, 11 women) participated in four sessions. They were randomly assigned to a low or a high delta9-tetrahydrocannabinol group (THC; 1.8% versus 3.6%). In the four sessions under blinded conditions subjects smoked marijuana cigarettes containing placebo (no active cannabinoids), or cigarettes containing THC with low or high levels of cannabichromene (CBC; 0.1% versus 0.5%) and low or high levels of cannabidiol (CBD; 0.2% versus 1.0%). Dependent measures included subjective reports, measures of cognitive task performance and neurophysiological measures [electroencephalographic (EEG) and event-related potential (ERP)]. Compared to placebo, active THC cigarettes produced expected effects on mood, behavior and brain activity. A decrease in performance, reduction in EEG power and attenuation of ERP components reflecting attentional processes were observed during tests of working memory and episodic memory. Most of these effects were not dose-dependent. Varying the concentrations of CBC and CBD did not change subjects' responses on any of the outcome measures. These findings are consistent with previous studies indicating that THC and its metabolites are the primary active constituents of marijuana. They also suggest that neurophysiological EEG and ERP measures are useful biomarkers of the effects of THC.