You may not think of sleep disorders as a mental problem, but nothing can mess up the mind like a few sleepless nights. The fact is, not nearly enough is known about what goes on in our minds when we are asleep. Where do dreams come from? How about nightmares?
Let's look at a few sleep disorders. Perhaps the most common is insomnia. Lying awake hour after hour, night after night. That sort of behavior can lead to all sorts of problems. Many times the problem is either stress or depression. Of course, the more sleep we lose, the more stress and depression dominate our lives. If the problem goes on long enough, it can lead to a fear of going to bed because sleep is so elusive.
Sleep apnea is not only a destroyer of sleep; it's a destroyer of life. Imagine waking up in the night gasping for breath. Imagine this happening hundreds of times a night. The problem is, most of the time victims of sleep apnea don't come fully awake, but it's enough to cause broken sleep and sleep deprivation.
Narcolepsy causes hallucinations. You see things that aren't there. If that's not enough to boggle the mind, narcoleptics also suffer from cataplexy. They're unable to express any strong emotion - fear, grief, anger, even laughter without falling to the floor, their muscles no longer under their control.
Dreams, nightmares, night terrors. What causes these aberrations of the mind? Stress? Depression? Perhaps. But everyone dreams, even if the dreams aren't recalled. Science has proved this with the discovery of REM (rapid eye movement.) When we dream, the eyeball moves beneath the eyelid as our subconscious follows the movement of the dream. Dreams can take you to the weirdest places. Some dreams even prophecy the future. Nightmares and night terrors can jerk you, terrified and screaming, out of a sound sleep, not quite sure where you are. Sometimes, if you happen to sleep walk, the disorientation is even worse.
This brings us to sleep paralysis. Imagine awakening unable to move. Strange beings seem to have invaded your room. You hear sounds...footsteps, muffled voices, laughter. Sometimes it seems someone or something is sitting on your chest, making breathing difficult. Some people who think they've been abducted by aliens or possessed by a demon are merely the victims of sleep paralysis.
There are more sleep disorders, or variations on the ones I've mentioned. No matter what the disorder, sleep deprivation is often the result, and sleep deprivation does mess with the mind. It causes depression, loss of memory, inability to concentrate, irritability and mental dysfunction.
Add to that, the other things I've mentioned, cataplexy, hallucinations, sleep walking. I think any and all of the above merit sleep disorders a place on the pages of borderline personality disorders.