White Matter Correlates of Psychopathic Traits in a Japanese Community Sample: Sex Matters!

Psychopathy is a personality disorder marked by distinct interpersonal, affective and behavioural abnormalities. Relatively little is known about associations between psychopathic traits and white matter (WM) microstructure among community samples, as most diffusion tensor imaging (DTI) research has focused on small clinical and forensic samples. These studies are also often limited to males from Western populations, leaving gaps in the understanding of females and non-Western populations. This study uses DTI data from a large community sample (n = 97) of well-functioning Japanese adults (45 males, aged 21-39 years). We used tract-based spatial statistics to investigate WM microstructural integrity (whole brain corrected using threshold-free cluster enhancement (TFCE), p < 0.05). Psychopathy traits were measured using the Self-Report Psychopathy Scale (SRP-SF). Region of interest analysis showed that callous affect scores negatively correlated with fractional anisotropy and axial diffusivity in the left cingulum. Furthermore, analysis across the entire white matter skeleton revealed that sex acted as a moderator in the association between psychopathy trait scores and mean diffusivity (MD) in the right superior longitudinal fasciculus, anterior thalamic radiation, and corpus callosum. The interaction showed that psychopathy trait scores were positively associated with MD in females, whereas the opposite pattern was observed in males. Our findings offer novel insights into the white matter correlates of psychopathic traits.