The sleep disorders that predispose to trauma are: disorders associated with excessive daytime sleepiness, obstructive sleep apnea, upper airway resistance syndrome, periodic limb movement disorder, narcolepsy, cataplexy, sleep paralysis and hypnagogic hallucinations. The disorders associated with behaviors while asleep (parasomnias) are: sleep terrors and sleepwalking and REM sleep behavior disorder. Injury can result from behaviors that occur during sleep. The patient's ability to recall the episode depends partly on the type of the parasomnia (occurrence during non-REM versus REM sleep). The other sleep disorders are recurrent hypersomnia and insomnia. Insomnia can result from multiple causes including psychiatric or general medical disorders, medication effects, substance abuse, and other sleep disorders. Restless legs syndrome (RLS) is another important cause of insomnia. RLS is thought to be related to periodic limb movement disorder and is characterized by lower extremity dysesthesias that occur at rest.