Study evaluates effects of marijuana ingredients on brain functioning

DIFFERENT ingredients in marijuana appear to affect regions of the brain differently during brain processing functions involving responses to certain visual stimuli and tasks, according to a report in the January issue of Archives of General Psychiatry, one of the JAMA/Archives journals.Dr. Sagnik Bhattacharyya, at the Institute of Psychiatry, King's College in London, and colleagues studied 15 healthy men, who were occasional marijuana users, to examine the effects of '9-tetrahydrocannabinol ('9-THC) and cannabidiol (CBD) on regional brain function during salience processing, which is how people perceive things around them.The authors used functional MRI images to study each participant on three occasions after administration of '9-THC, CBD or placebo. Study participants performed a visual oddball task of pressing buttons according to the direction arrows on a screen were pointing, as a measure of attentional salience processing.'Pairwise comparisons revealed that '9-THC significantly increased the severity of psychotic symptoms compared with placebo and CBD whereas there was no significant difference between the CBD and placebo conditions,' the authors conclude.'9-THC had a greater effect than placebo on reaction time to nonsalient relative to salient stimuli. This was associated with modulation of both prefrontal and striatal function by '9-THC, augmenting (increasing) activation in the former region and attenuating (weakening) it in the latter.
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