Depressed REM Sleep Behavior Disorder Patients Are Less Likely to Recall Enacted Dreams than Non-Depressed Ones

OBJECTIVE: REM sleep behavior disorder (RBD) is associated with psychiatric symptoms, such as anxiety and alexithymia. However, only a few studies on the relationship between depression and RBD have been published. In this study, we investigated the occurrence of depression and associated factors in patients with RBD. METHODS: In total 94 patients (mean age: 61.9±12.7 years, male: 70.2%) diagnosed as RBD were examined using detailed clinical histories, the Beck Depression Inventory (BDI), the Epworth Sleepiness Scale (ESS), and nocturnal polysomnography (PSG). RESULTS: The mean BDI score of all patients was 12.4±10.3 and 44.7% of RBD patients showed depressed mood (BDI >11 points). Depressed RBD patients were less able to recall enacted dreams than were non-depressed patients (61.9% vs. 86.5%, p=0.008). Logistic regression analysis showed that failure to recall enacted dreams was significantly associated with depression, after controlling for confounding variables including the respiratory disturbance index and a history of psychiatric disorders (odds ratio=0.323, p=0.041). CONCLUSION: In this study, 44.7% of RBD patients were found to suffer from depressed mood. And, depression was found to be associated with reduced ability to recall enacted dreams. We suggest that routine evaluation of depression be performed in RBD patients, particularly when failure to recall enacted dreams is evident. We speculate that such failure may be associated with emotional dysregulation or neurodegeneration.