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Parasomnias are disorders involving abnormal behaviors or moving during sleep. In the case of REM parasomnias, these abnormal behaviors arise during rapid-eye-movement (REM) sleep. These conditions were once thought to indicate psychological disorders, but researchers now understand that parasomnias are common conditions that occur during the transitions between REM sleep, NREM sleep and wakefulness. Because REM parasomnias occur during lighter-stage REM sleep, they are most common in the second half of the night when they body spends more time in REM sleep.
In contrast to NREM parasomnias, which arise out of deeper, non-rapid-eye-movement sleep, REM parasomnias do not involve arousals from sleep. People experiencing a REM parasomnia (like a nightmare) are considered to be asleep, while people experiencing a NREM parasomnia (like a night terror) are considered to be partially awake.
Symptoms of REM parasomnias include unwanted behaviors or actions during REM sleep, often during the latter portion of the night or early hours of the morning. People experiencing REM parasomnias may or may not recall the event the next day.
REM sleep behavior disorder involves physically acting out dreams. In REM sleep behavior disorder, the mechanisms that disable motor activity during sleep don’t function normally, so movements aren’t inhibited during sleep. REM sleep behavior disorder occurs during sleep, not during an arousal from sleep.
People with REM sleep behavior rarely act out mild dreams; rather, the dreams acted out tend to be violent and intense, making this one of the more dangerous sleep disorders. Unlike other parasomnias, REM sleep behavior disorder is most common in older adults, usually beginning between age 50 and 60, and is more common in men. REM sleep behavior disorder with violence is rare, occurring in around .05 percent of the adult population.
During sleep paralysis (also called sleep atonia), motor activity is inhibited so the individual remembers being awake but is unable to move. These episodes are generally brief, lasting just a few moments, but they can be intense and frightening. Around 7 percent of adults have experienced sleep paralysis; in adults with a psychiatric disorder, rates are as high as 35 percent.
Nightmares (also called nightmare disorder) are intense, frightening dream experiences that occur during REM sleep. Unlike night terrors, nightmares are experienced while completely asleep and are often recalled the next day. In contrast to other types of parasomnias, nightmares don’t involve motor activity like sleepwalking, kicking, thrashing or eating. Nightmares are more common in children than adults; up to 40 percent of children experience nightmares compared to 1 to 5 percent of adults.
Like NREM parasomnias, REM parasomnias run in families. Stress, trauma, sleep deprivation and fragmented sleep can increase the risk of REM parasomnias, particularly nightmares. Because REM parasomnias arise out of lighter-stage REM sleep, conditions that increase REM sleep or fragmented, poor-quality sleep, like sleeping in warm environments or taking certain medications, can trigger REM parasomnias.
REM sleep behavior disorder is thought to relate to neurodegenerative conditions and has a strong link to Parkinson’s disease. Some antidepressants have been shown to trigger REM behavior disorder.
A sleep medicine physician can evaluate your health history and sleep patterns to diagnose REM parasomnias. In some cases, polysomnography may be used to help pinpoint whether you have an underlying sleep disorder, such as sleep apnea.
Treating REM parasomnias usually involves avoiding sleep deprivation, treating underlying sleep disorders, and adjusting the sleep environment to remove dangerous objects and tripping hazards.
For REM sleep behavior disorder, melatonin has been shown to be effective, either alone or in combination with clonazepam. Tricyclic antidepressants, levodopa, and dopamine agonists are also used to treat REM behavior disorder, though some antidepressants have been shown to trigger REM sleep behavior disorder symptoms.