Relationship of type 1 cannabinoid receptor availability in the human brain to novelty-seeking temperament.

CONTEXT Brain neurochemistry can partially account for personality traits as a variance of normal human behavior, as has been demonstrated for monoamine neurotransmission. Positron emission tomography using fluorine 18-labeled MK-9470 now enables quantification of type 1 cannabinoid receptors (CB1R) in the brain. OBJECTIVE To investigate whether there is a relationship between human temperament traits and regional cerebral CB1R availability. DESIGN Forty-seven [(18)F]MK-9470 baseline scanning sessions were performed and correlated with the temperament dimensions and subdimensions of the 240-item Cloninger Temperament and Character Inventory. SETTING Academic brain imaging center. PARTICIPANTS Forty-seven nonsmoking, healthy volunteers (paid). Main Outcome Measure Voxel-based correlation of temperament variables of the inventory with regional CB1R availability. RESULTS Novelty seeking was inversely correlated with global CB1R availability (r = -0.33, P = .02), with the most significant correlation in the left amygdala (r = -0.41, P = .005). In particular, the subdimension extravagance showed a highly significant inverse correlation to global CB1R availability (r = -0.53, P <.001), most pronounced in the amygdala, anterior cingulate, parietal cortex, and precuneus. Also, disorderliness was inversely correlated with global CB1R availability (r = -0.31, P = .04). CONCLUSIONS Low baseline cerebral CB1R availability is related to a high novelty-seeking personality, in particular to extravagance, most pronounced in the amygdala. Further investigation of the functional role of the CB1R is warranted in pathological behavior known to be strongly related to novelty seeking, such as addiction and eating disorders.