Emotion regulation deficits in patients with major depressive disorder and nonsuicidal self-injury: evidence from self-report and neurophysiological indicators.

BACKGROUND: Major depressive disorder (MDD) and nonsuicidal self-injury (NSSI) are both characterized by emotion regulation (ER) deficits, yet the pathophysiological mechanisms underlying comorbid presentations remain unclear. The aim of this investigation was to evaluate the ER abilities in patients with MDD and NSSI (MDD + NSSI) using ER questionnaires and electroencephalography (EEG), and to clarify their intrinsic connections with NSSI behaviors. METHODS: A total of 58 MDD + NSSI patients, 72 patients with MDD and without NSSI (MDD - NSSI), and 45 healthy controls (HCs) completed the ER questionnaires. A subgroup of 21 MDD + NSSI patients, 18 MDD - NSSI patients, and 20 HCs underwent task-based EEG to measure late positive potential (LPP) during cognitive reappraisal. Group differences and potential associations of these indicators with NSSI behaviors were analyzed. RESULTS: Compared to MDD - NSSI patients and HCs, MDD + NSSI patients exhibited significantly reduced positive reappraisal ability, increased catastrophizing tendency, and significant difficulties in emotional acceptance, impulse control, and effective use of ER strategies. Moreover, task-based EEG indicated a significant impairment in LPP modulation during cognitive reappraisal in MDD + NSSI patients, and their difference waves were smaller than those of MDD - NSSI patients and HCs. No significant associations were observed between these indicators and NSSI behaviors. LIMITATIONS: Small sample size, cross-sectional design, uncontrolled medication status, and limited ER strategies assessed. CONCLUSIONS: MDD + NSSI patients demonstrate self-reported ER deficits and impaired capacity to alleviate negative emotions during ER tasks.