A Preliminary Study of the Opioid System and Personality Traits Using Positron Emission Tomography.

Background: Personality traits, such as Neuroticism and Extraversion, have been implicated in the processing of emotion. The neural correlates most often associated with Neuroticism and Extraversion are the insular cortex, orbitofrontal cortex, amygdala, and ventral striatum.

Objective: The aim of the current study was to explore neurotransmitter systems underlying those neural correlates and investigate the relationship between personality traits and opioid receptor binding potential.

Method: Twelve healthy participants completed an [11C]diprenorphine positron emission tomography scan at rest. Endogenous opioid levels as indicated by opioid receptor binding potential was examined in relation to personality phenotype.

Results: A high score of Neuroticism, a personality trait characterized by negative affect, was found to be associated with high opioid receptor binding in the right anterior insula. Conversely, a high score of Extraversion, a personality trait characterized by positive affect, was found to be associated with low opioid receptor binding in the left posterior insula.

Conclusions: While preliminary, the results of this study suggest that the expression of Neuroticism and Extraversion is related to baseline function of the opioid neurotransmitter system in the insular cortex. These findings may help elucidate the neural mechanisms underlying the expression of personality traits, particularly those implicated in affective processing.