Disrupted structural-functional coupling in adolescents and young adults with major depressive disorder and non-suicidal self-injury.

BACKGROUND: Major depressive disorder (MDD) is consistently associated with an elevated risk of suicidal behaviours, including non-suicidal self-injury (NSSI). Neuroimaging evidence suggests that MDD patients with NSSI exhibit alterations in both brain structure and function, warranting further investigation into the underlying mechanisms linking these changes. METHODS: A total of 291 participants were recruited for this study: 141 drug-naïve individuals with MDD, who were divided into an MDD + NSSI group and an MDD-NSSI group based on the presence of self-injurious behaviour, and 150 healthy controls (HC). All participants underwent resting-state functional magnetic resonance imaging and diffusion tensor imaging data acquisition. Impulsivity traits were assessed using the short UPPS-P Impulsive Behaviour Scale, and covariance analysis was performed to compare structural-functional (SC-FC) coupling across the groups. Spearman's correlation analysis was conducted to confirm the relationship between SC-FC coupling and clinical characteristics. RESULTS: Widespread functional connectivity alterations were observed across groups, especially in key cortical regions. Relative to the MDD-NSSI and HC groups, the MDD + NSSI group displayed increased SC-FC coupling in the left middle temporal pole (TPOmid.L). In addition, the MDD-NSSI group exhibited weakened coupling in the left putamen compared to the HC group. Notably, SC-FC coupling in the TPOmid.L was significantly correlated with impulsivity traits and NSSI frequency, but not with anxiety or depression severity. CONCLUSION: Altered SC-FC coupling in the TPOmid.L reflects disrupted structure-functional interactions in MDD patients with NSSI and is linked to their impulsivity traits and NSSI frequency, revealing a neurobiological link between these behavioural features in this region.