Circadian Rhythm Sleep Disorder

My sleep study is not for two more weeks, but I'm researching everything I can to better understand possible outcomes for my sleep issue. Today I Googled "Sleep Disorders and Brain Injury." I learned some interesting facts.
A recent study, found that a brain injury may increase your likelihood of developing circadian rhythm sleep disorder (CRSD), which is something I'd never heard of--but then again I'd never heard of a brain injury until I had one myself.
CRSD is more than insomnia, it's a disorder of the sleep cycle, affecting the timing of your sleep. The timing of your sleep is governed by certain hormones which make you sleepy or alert. Maybe my body no longer releases these hormones? I'm not trying to self-diagnose, since this is what the sleep study is for (I'm so thankful that my doctor is smart enough to send me for a study, rather than just saying, "here's some Ambien, sweet dreams"). I have no problem feeling tired at night, just a problem getting and staying asleep. The human brain is extremely complex, and it affects everything. As a result, my brain injury is somehow related to every part of my lifestyle--even my sleep.