Therapeutic Effects and Safety of Mirtazapine for Insomnia in Major Depressive Disorder: Findings from a 6-Week Open-Label Pre- and Post-Intervention Study

Introduction: Insomnia is one of the most common symptoms of depression, estimated to occur in approximately 75% of adult patients with depression, and it may persist even after remission from depressive episodes. Our objectives were to evaluate the efficacy of mirtazapine in reducing insomnia and depression symptom severity, assess side effects, and compare quality of life before and after intervention in major depressive disorder (MDD) patients with insomnia. Methods: This was a single-center, prospective, open-label, quasi-experimental pre-post intervention trial of six weeks. The Hamilton Depression Rating Scale (HDRS), Insomnia Severity Index (ISI), Antidepressant Side-Effect Checklist (ASEC), and World Health Organization Quality of Life (WHOQOL-BREF) tools were used during the assessment. Results: Out of the 135 recruited patients, 109 (80.7%) completed the trial. On day 14, with a mean dose of 18.9 mg/day, 24.8% of patients experienced remission for insomnia, while 7.3% showed remission for depression. By day 42, with a mean dose of 18.7 mg/day, these figures increased to 62.4% for insomnia and 41.3% for depression. The reduction in the ISI score (mean±SD) from baseline to day 14 and day 42 was 8.74±6.16 and 13.55±5.32, respectively. Similarly, the reduction in the HDRS score from baseline on day 14 and 42 was 10.30±6.89 and 17.78±6.26, respectively. The most commonly reported adverse effects (>10%) included increased appetite, drowsiness, weight gain, dry mouth, headache, and constipation. Regarding QoL, the differences were significant for all four domains with the highest improvement observed in the physical (mean difference 25.67±13.95) and psychological domains (mean difference 26.35±16.42) of QoL. Conclusion: Mirtazapine treatment was associated with significant improvements in depression, insomnia, and all QoL parameters, with increased appetite and weight gain being the most common adverse effects. Further randomized controlled comparator studies will be beneficial for healthcare providers to improve the clinical care of MDD patients with insomnia.