Around 60% of Americans experience insomnia a couple times of week. I believe women are like 1/3 more likely to have it than guys. Experiencing insomnia from time to time doesn't make you an insomniac though. A true insomniac is someone that can't sleep, even when they are tired, exhausted, drunk, etc. When my parents dragged me to a psychiatrist when I had trouble sleeping for nights in a row, I was diagnosed with chronic insomnia, but I refused to take the pills I was prescribed, because they really do alter your mind. I chose to deal with it myself, and eventually was able to get back to a normal sleep schedule without anything, not that I see anything wrong with using a pill to fix your problem, just I personally noticed the way it altered my mind.
In this age though...every flaw in people is considered a disorder, or a disease, or a mental weakness. If your circadian rhythm is fucked because you spent spring break partying all night long then you go back to school and can't fall asleep the night classes start, you have a "circadian rhythm disorder". If you understand how people feel, and you sympathize with people that are in pain or are upset, then you'll be labeled as depression. If you're just not an outgoing person, you have a disorder. If you can't concentrate, you have a disorder. I find it rather pathetic that we have to blame everything that's "wrong with us" according to society on a "chemical imbalance" or "a poor mental condition". It's such a load of crap.