Everything can feed into another. When people for example get depressed, their sleep pattern tend to change. Some people think it's just the depressed one not staying active and disciplined, when in fact it is something happening in that person's brain.

I have Asperger's and ADD, and both have a higher incident of circadian rhythm disorders than "normal" people.

I'm a night owl, but I also have to watch myself so I don't fall asleep later and later at night. I wish at least the cycle could be still...