Nightmares

Nightmares are vivid, disturbing dreams that wake the sleeper, usually from REM sleep in the second half of the night, and are remembered clearly on waking.

Occasional nightmares are common at every age and are typically triggered by stress, illness, irregular sleep, alcohol withdrawal or certain medications, including some antidepressants and blood pressure drugs. Nightmare disorder is diagnosed when they are frequent, cause significant distress or fear of going to sleep, and impair daytime functioning. They are distinguished from sleep terrors, which arise from deep non-REM sleep early in the night, involve screaming and confusion, and are not remembered, and from REM sleep behavior disorder, in which dreams are physically acted out. Recurring trauma-related nightmares are a core feature of post-traumatic stress disorder.

Assessment relies on the sleeper's account and, when useful, a sleep diary or overnight sleep study to rule out breathing disorders that can fragment REM sleep. Imagery rehearsal therapy, in which the person rewrites the dream while awake and rehearses the new version, is the best-supported treatment, and prazosin is sometimes prescribed for trauma-related nightmares. THC suppresses REM sleep and has been examined in small studies of PTSD nightmares, and cannabidiol has been reported in case series for REM-related parasomnias, but the research is limited, rebound dreaming can follow THC discontinuation, and no cannabinoid has an approved use for nightmares.