Biological modulators of treatment outcome during psychiatric care: The interplay between inflammation and oxytocin

Background Although scientific advancements highlight the involvement of inflammatory processes in psychiatric disorders, few studies have explored how these processes relate to treatment outcomes. This study aimed to examine whether inflammation is associated with reduced treatment outcomes in inpatient psychiatric care, and whether oxytocin (OT) - a neuropeptide known for its anti-inflammatory properties - may buffer these effects. Methods Patients (N = 72, 76% females) who received intranasal OT or placebo twice daily for four weeks adjacent to standard inpatient care were examined for their pre-treatment inflammation, using the neutrophil-to-lymphocyte ratio (NLR). Baseline Depressive symptoms, anxiety, suicidal ideation, and distress were assessed using self-report measures at pre and post-treatment. Multilevel models were utilized to test the predictive effects of baseline NLR on treatment outcomes and its interaction with OT administration. Results Higher pre-treatment NLR was associated with reduced improvement in trait anxiety ( p = .02). A significant NLR × OT interaction emerged for depression ( p = .005), indicating that OT administration did not significantly improve depression outcomes for patients with high baseline NLR ( p = .35), but was associated with greater improvement among patients with low baseline NLR compared to placebo ( p = .001). Conclusions Inflammation is a potential biological factor shaping treatment outcome, however, OT administration benefits mostly those with low inflammation. Additional studies are needed to assess whether other anti-inflammatory agents may buffer its effects.