MARIJUANA INTOXICATION AND BRAIN ACTIVATION IN MARIJUANA SMOKERS

Objective and Method: The acute effects of delta(9) tetrahydrocannabin ol (THC) on cerebral blood flow (CBF) were studied in human subjects. Regional CBF was measured with O-15-water and Positron Emission Tomogr aphy (PET) in 32 volunteers with a history of exposure to marijuana. S cans were performed before and after intravenous (IV) infusion of eith er of two doses of THC or a placebo, given under double blind conditio ns. Results: THC but not placebo increased CBF especially in the front al regions bilaterally, insula and cingulate gyrus and sub-cortical re gions with somewhat greater effects in the right hemisphere. While mos t regions showed significant change at 60 minutes for the lower dose g roup, the higher dose group had significant change at 30 and 60 minute s. There was a highly significant change in the anterior/posterior rat io for the two THC groups reflecting minimal change in occipital flow but significant increases in frontal flow. Self ratings of THC intoxic ation showed significant effects, and regression analysis indicated it correlated most markedly with the right frontal region. Conclusion: B ehavioral manifestations of marijuana intoxication may be associated w ith increased functional activity of the brain especially the frontal cortex, insula and cingulate gyrus.