11. Sleep Walking
Also known as somnambulism, sleepwalking is just what its name suggests – someone walks around while asleep. It usually occurs at night, though it can also occur during a daytime nap. Experts recommend using care when waking a sleepwalker, as some have been known to attack. Source: American Academy of Sleep Medicine.
12. Non-24-Hour Sleep-Wake Syndrome
Most people have a sort of built-in body clock that is closely tied to the 24-hour day. But the body clocks of people with non-24-hour sleep-wake syndrome – one of the rarest of all sleep disorders – are out of whack. For example, someone on a 72-hour cycle might be awake for a full 48 hours and sleep for 24. Interestingly, the disorder often affects the blind.