What's wrong with having morbid thoughts?
There are lots of things that cause insomnia and I will agree that depression and anxiety are top causes. I think several insomniacs on here would agree that they would rather not sleep than take anti-depressants, though.
My sleep disturbances are neither caused by depression nor anxiety, but more from a hyper-active, overly-analytical mind that will not stop. Usually, the only way to get my brain to slow down and concentrate (or stop) is by shaking my foot/leg. Redirecting the excess energy gives my brain a rest long enough to sleep and I will do that the entire time I'm sleeping. I've also been yelled at multiple times for doing it through exams.
I'd rather not sleep than be on a bunch of pills. Through deep-breathing and mediation, I've learned how to be in a waking-sleep that usually gets me the rest I need. Cutting out caffeine has helped a lot as well, too.