I'd have to call it dysomnia. It's not that I can't sleep, it's that I don't sleep regularly. Like last night I was up until 5:30 A.M. and I woke up at 8:30. And in another couple of hours, I'll probably be smacked down again for a couple more hours. I don't think I've had an unbroken night's sleep for three months.
I suppose it's structure. I work better at night, and I work better in long stretches. So given the opportunity, I tend to work late into the night and sleep late in the morning.

Side note: I find Klan members that appear on the Jerry Springer show to be amusing.