Dopaminergic syndromes of sleep, mood and mentation: Evidence from Parkinson's disease and related disorders

We reviewed sleep and dream-related clinical symptoms in a set of four neurologic disorders (Parkinson's Disease, REM Behavior Disorder, Narcolepsy and Depression) characterized by severe reductions in dopaminergic function. Sleep findings included excessive daytime sleepiness (EDS), increased rapid eye movement sleep times (REM%), increased REM density or bursts of REMs, reduced REM latency periods, and sleep onset REM (SOREM). Clinical symptoms included perseverative or rigid thinking and personality styles, frontal lobe impairment, increased complaints of, or vulnerability to negative affect, and increased vivid and unpleasant dreams. The increased vulnerability to unpleasant dreams was particularly interesting as descriptions of dream content were strikingly similar across all 4 disorders. Dreams of feeling threatened or being attacked by animals or dangerous creatures were very frequent. We hypothesize that the cluster of sleep, dream and cognitive changes associated with these four disorders can be explained by assuming that lowered dopaminergic tone leads to a disinhibition of REM physiology and amygdalar activity and that this disinhibition of REM and amygdalar function yields unpleasant dreams, negative affect, and frontal lobe impairment. Careful study of the cluster of co-occurring symptoms identified here may illuminate 1) the ways in which dopamine might function in regulation of sleep states, and 2) aspects of the neurology of dream content.