Aggressiveness in the dreams of drug-naïve and clonazepam-treated patients with isolated REM sleep behavior disorder

Background: Although aggressive dream content is considered a distinctive feature of REM Sleep Behavior Disorder (RBD) and patients often report violent dreams during medical interviews, nonviolent behaviors (eating, drinking, urinating) and pleasant actions (e.g laughing, singing, dancing) or simply elemental, jerky limb movements are frequently observed during video-polysomnography. As a first-line pharmacological treatment, clonazepam has been shown to reduce motor symptoms during REM sleep, but its effect on dream content remains unclear. Here, we aimed to prospectively assess the dream content of individuals with drug-naïve isolated RBD (iRBD) and iRBD patients treated with clonazepam. Methods: Thirteen (12 Male, 1 Female; age 65.38 ± 10.95) iRBD patients treated with clonazepam (iRBD-T), eleven (9 M, 2 F; age 68.90 ± 6.8) drug-naïve patients (iRBD-NT) and twelve (8 M, 1 F; age 63.33 ± 12.88) healthy control subjects of comparable age kept a dream diary over a 3-week period. Dream content analysis was conducted according to the Hall and Van de Castle method (HVdC). The Threat Simulation Scale (TSS) was employed to assess the frequency of threatening contents. Results: A total of 214 dream reports were collected. No significant differences were found in the frequency of threatening dream contents between the iRBD subsamples and healthy control subjects (p = 0.732). The HVdC analysis detected higher levels of Friendliness in iRBD patients compared to the control group (p = 0.036). Increased levels of Aggressiveness were only observed when differentiating dreams in which dream enactment behaviors (DEB) were present compared to dreams without DEBs, both in the iRBD-T group (p = 0.007) and the iRBD-NT group (p = 0.012). Conclusion: Our study shows no difference in the frequency of violent or threatening dreams in drug-naïve iRBD patients, clonazepam-treated iRBD patients and healthy control individuals. Aggressiveness is more frequent when DEBs are reported, suggesting motor disinhibition could require sufficiently dramatic and emotionally intense dreams, independent of clonazepam treatment.