OBJECTIVE: This study aimed to comprehensively evaluate the efficacy and safety of olanzapine in the treatment of individuals with schizophrenia. METHODS: A retrospective study was conducted on 150 individuals with schizophrenia treated with olanzapine at a tertiary psychiatric hospital from January 2015 to December 2020. The efficacy was assessed using the Positive and Negative Syndrome Scale (PANSS), Clinical Global Impression-Severity (CGI-S), Personal and Social Performance (PSP) scale, and Brief Psychiatric Rating Scale (BPRS). Safety was evaluated based on the incidence of adverse events. Data were analyzed using descriptive statistics, paired t-tests, chi-square tests, and multiple regression analysis. RESULTS: The mean PANSS total score significantly decreased from 92.3 ± 13.8 at baseline to 56.9 ± 11.5 after 12 weeks of treatment (p <
0.001). Significant improvements were observed in positive symptoms, negative symptoms, and general psychopathology subscales (p <
0.001). CGI-S, PSP, and BPRS scores also demonstrated significant enhancements in overall clinical status, social functioning, and psychiatric symptoms (p <
0.001). The most common adverse events were weight gain (28 %), somnolence (22 %), dizziness (18 %), and dry mouth (15 %). Mild elevations in metabolic parameters were observed. The incidence of EPS was low (6 %), and prolactin levels increased mildly. Higher baseline symptom severity and younger age as predictors of greater improvement in PANSS scores (p <
0.01). CONCLUSIONS: Olanzapine demonstrated significant efficacy in reducing a wide range of schizophrenia symptoms, improving clinical status, enhancing social functioning, and alleviating overall psychiatric symptoms. The safety profile was generally manageable, with mild to moderate adverse events.