Ketamine works quickly as an antidepressant but also causes temporary dissociative symptoms. In everyday clinical settings, it is unclear how much of the antidepressant effect comes from patients' expectations versus from the dissociative experience itself, and how these factors relate to changes in depression over time.
Dreams during REM sleep are emotionally fluid and fast-changing, with positive and negative emotions alternating frequently. In a study of 24 lucid dreamers with narcolepsy who reported emotional valence in real-time using facial codes during daytime naps monitored with polysomnography, 62 of 126 naps contained at least one emotional code during REM sleep, yielding 191 codes total. Positive and negative codes were evenly balanced per nap, and over half of naps with at least two codes showed opposite valences. The average duration of a given emotional valence was about one minute, with positive emotions emerging earlier than negative ones. These findings suggest that the emotional dynamics of REM sleep dreams may contribute to understanding how dreams help regulate emotions.