Common and distinct morphometric correlates of the Dark Triad traits: machiavellianism, narcissism and psychopathy in a healthy male sample

There is an ongoing debate about the common and distinct nature of the Dark Triad (DT) and its traits machiavellianism, narcissism, and psychopathy. Up to date, neurobiological data regarding this discussion has been scarce. We collected T1-weighted high-resolution structural magnetic resonance brain images from 24 healthy male subjects with high DT scores and 27 with low DT scores. Images were analyzed with voxel-based morphometry, compared between the two groups and correlated with DT subscales for machiavellianism, narcissism and psychopathy within the group with high DT scores. The group comparison revealed reduced gray matter volumes (GMV) in the precentral gyrus extending to the dorsolateral frontal gyrus, and the cerebellar crus II in individuals with high DT scores compared to those with low scores. In the regression analysis, we found negative associations between GMV in the dorsolateral prefrontal cortex and both machiavellianism and psychopathy. In addition, GMV in the anterior cingulate cortex was negatively associated with psychopathy and narcissism. Furthermore, GMV in the medial orbitofrontal cortex, insula, and superior temporal sulcus showed negative associations with narcissism. Our study revealed both common, overlapping as well as distinct GMV alterations related to DT traits. GMV alterations were primarily found in regions associated with empathy and social cognition. These structural differences may reflect neural substrates contributing to interpersonal dysfunction and antisocial tendencies observed in individuals with elevated DT traits.