Impulse control deficits among patients with nonsuicidal self-injury: a mediation analysis based on structural imaging

Nonsuicidal self-injury (NSSI) is posited to arise from a complex interaction of biopsychosocial factors, with impulsivity playing a critical role. Given that current research on the neural mechanisms underlying this hypothesis remains inconsistent and limited in scope, we sought to explore how NSSI behaviours are associated with impulsivity resulting from structural brain alterations. We recruited patients with NSSI behaviours and healthy controls from 11 psychiatric hospitals. We assessed the differences in impulse control between the 2 groups using the Barratt Impulsiveness Scale version 11 and the Attention Network Test. We also conducted T 1-weighted magnetic resonance imaging (MRI) and diffusion tensor imaging. Finally, we analyzed the associations among brain structure, psychological characteristics, and self-injurious behaviour among patients with NSSI. We included 293 patients with NSSI behaviours and 140 healthy controls. Among them, 182 patients with NSSI and 95 controls underwent the T 1-weighted MRI and diffusion tensor imaging. Patients with NSSI showed increased impulsivity and alerting function, with the strongest correlation between NSSI frequency and motor impulsivity. Compared with controls, patients with NSSI exhibited decreased grey matter volume and increased white matter volume, with no significant difference in cortical thickness. Pathway analysis demonstrated that motor impulsivity significantly mediated the association between white matter volume and the NSSI frequency in the right superior frontal gyrus and right inferior parietal lobe. When examining the connecting fibre tracts in the right frontoparietal area, patients with NSSI showed decreased integrity of white matter microstructure in the right cingulum, right superior corona radiata, and the splenium of the corpus callosum. Accurately measuring executive control linked to NSSI is challenging in cognitive behavioural tasks, as impulsive tendencies during NSSI occurrence are not effectively captured. Our findings suggested that motor impulsivity, a prominent psychopathological characteristic of NSSI, is primarily modulated by the frontoparietal regions. These results provide empirical neuroimaging evidence for the impaired impulse control observed in NSSI.