Challenging the myth of REM sleep behavior disorder: no evidence of heightened aggressiveness in dreams.

Objectives: Dreams are commonly described as violent, threatening, and aggressive in patients with REM behavior disorder (RBD), but very few studies have directly investigated dream content in this population. We systematically assessed dreams in subjects with a confirmed diagnosis of idiopathic RBD (iRBD) and explored psychological traits within the group with specific focus on aggressiveness.

Methods: A total of 129 dream reports was collected, of which 77 belonged to 12 iRBD patients and 52 belonged to 12 control subjects. Transcripts were analyzed with measures of both form and content. The Thematic Apperception Test was used to assess patients' personality traits and to yield information on formal aspects of waking thought processes.

Results: No statistically significant differences were found between the dreams of iRBD patients and those of normal controls in any of the applied measures. In wakefulness, passivity was found to differ between the two populations and was being higher in the iRBD group (F(9,14)=4.84, p<0.05).

Conclusions: Our results do not support the anecdotal view that dreams of RBD patients contain more aggressive elements than those of the general population. However, over 80% of the patients were on treatment at the time of data collection. The "mild" waking temperament could be interpreted as an early subtle sign of the apathy that is commonly described in the context of neurodegenerative disorders.