Background: Accumulating evidence indicates decreased melatonin levels in patients with schizophrenia. Insomnia, mainly difficulty in falling asleep at night, is commonly reported in this population. Association of insomnia with low or abnormal melatonin rhythms has been repeatedly documented. Melatonin is an endogenous sleep promoter in humans. We hypothesized that insomnia in patients with schizophrenia may be partially due to diminished melatonin output. In this study, we measured melatonin output in patients with chronic schizophrenia and assessed the effects of melatonin replacement on their sleep quality.
Method: In a randomized, double-blind, cross-over, clinically based trial, 19 patients with DSM-IV schizophrenia who were treated with the normal treatment regimen were given melatonin (2 mg, controlled release) or placebo for 2 treatment periods of 3 weeks each with 1 week washout between treatment periods (7 weeks total). For measuring endogenous melatonin production, urine was collected from each patient every 3 hours between 9:00 p.m. and 9:00 a.m. Actigraphy was performed for 3 consecutive nights at the end of each period. Activity- and rest-derived sleep parameters were compared for the whole population with treatment arm as the intervening variable. A separate analysis was performed for patients subgrouped into high versus low sleep efficiency.
Results: All patients had low melatonin output. Melatonin replacement significantly improved rest-derived sleep efficiency compared with placebo (83.5% vs. 78.2%, p = .038) in this population. Improvement of sleep efficiency was significantly greater (p < .0014) in low-efficiency (80% vs. 67%) than high-efficiency sleepers (88% vs. 90%). In addition, during melatonin therapy, tendencies toward shortened sleep latency (by 40 minutes, p < .056) and increased sleep duration (by 45 minutes, p < .078) were observed in low- but not high-efficiency sleepers.
Conclusion: Melatonin improves sleep efficiency in patients with schizophrenia whose sleep quality is low.