here in my location reversing sleep cycles from night and day is not called a dissociative disorder of any kind. here where I am this is called a sleep disorder, another name for it is called Circadian Rhythm Sleep Disorder. here where I am located dissociation and depersonalization is things like feeling numb, spaced out, foggy minded, (you can read more about what my location goes by for depersonalization in my link at the bottom of my post)

as for your question can reversing sleep cycles be a sign of something more serious.. in my location it can be normal example when someone works nights their body naturally over time reverses their sleep cycles. or it can be a sign of more serious medical conditions like heart problems, sleep deprivation, diet and exercise problems,...

here in my location the treatment is having a regular bedtime, multi spectrum lighting, and in some cases medications like sleep aids.

my suggestion if this continues to bother you contact your medical doctor who can help you get your internal clock (Circadian Rhythm) back on track.