PTSD definitely affects sleep. There are three symptom categories found in PTSD: re-experiencing the trauma, avoiding thinking or feeling about the trauma, and being hyperaroused as a result of the trauma. Two of those are reflected in sleep difficulties. People with PTSD may have disrupted sleep, or avoid going to sleep, because of nightmares (this is considered a re-experiencing symptom). They may also be unable to relax enough to sleep, instead attending to every noise in their environment or being concerned about being safe enough to sleep (this is a hyperarousal symptom).

I hope this information helps. There is more information at the National Center for PTSD.