Heritable variations in gray matter concentration as a potential endophenotype for psychopathic traits.

CONTEXT Genetic vulnerability to psychopathic traits is likely to also manifest at the neural level. We have recently reported increased gray matter concentration in several brain areas in boys with psychopathic traits. OBJECTIVE To explore whether these gray matter concentration differences can be regarded as endophenotypes for psychopathic traits by (1) assessing their heritability and (2) examining the etiology of the co-occurrence of psychopathic traits and increased gray matter concentration. DESIGN Community twin sample. SETTING On-campus neuroimaging facility. PATIENTS OR OTHER PARTICIPANTS One hundred twenty-three male twins (56 monozygotic and 67 dizygotic individuals; mean age 11.55 years; range, 10-13 years). MAIN OUTCOME MEASURES We analyzed structural magnetic resonance imaging scans. Voxel-based morphometry analyses were used to obtain gray matter concentration values that were analyzed in a biometrical genetic twin model. RESULTS Left posterior cingulate and right dorsal anterior cingulate gray matter concentrations were found to be the strongest endophenotype markers, with heritability estimates of 46% and 37%, respectively, and common genes explaining the phenotypic relationship between these regions and psychopathic traits. No significant heritabilities were found for several regions, including the right orbitofrontal cortex and insula. CONCLUSIONS These findings suggest that structural endophenotypes, in the form of variations in gray matter concentration, reflect genetic vulnerability for psychopathic traits. Specifically, gray matter concentration in the left posterior cingulate and right dorsal anterior cingulate, brain areas implicated in empathy, moral processing, and introspection, are potential candidate endophenotypes for psychopathic traits.