A 38-year-old man repeatedly tries to force his wife to have sex in the middle of the night but has no memory of his actions when he wakes up.

A married woman in her mid-20s often tears off her clothing and masturbates but remembers nothing when her partner rouses her.

For a dozen years, a 31-year-old man masturbates while asleep, at times injuring his groin. Embarrassed due to his unconscious behavior, he avoids relationships for eight years.

These are all clinically documented cases of sleep sex, or sexsomnia, part of a family of sleep disorders called parasomnias that include sleepwalking, sleep talking, sleep eating and sleep terrors.