Depersonalization as a symptom (not as a disorder) is quite common in college-age populations
depersonalization disorder
If you are worried that you are suffering from depersonalization depression and bipolar disorder, you will need to see a doctor. A doctor can offer treatment.
Depersonalization disorder is present in Schizophrenics in most cases, But Schizophrenics tend to develop Psychosis which disables them completely from reality, thus Schizophrenics are not aware nor can tell the difference between the internal and external world. Whereas individuals with Depersonalization disorder temporarly have fragmentation of reality.
Derealization and depersonalization sindrom.
Heather Nichol has written: 'Depersonalization'
depersonalization disorder
Dementia.
The major dissociative symptoms experienced by DID patients are amnesia, depersonalization, derealization, and identity disturbances.
That is based on each individual case depending on how severe the disorder is.
There is no set period of time. I've heard cases of several hours to several months. It all depends on the situation.
You may wish to see a therapist. You could have repressed trauma or even depersonalization disorder. Or you could have up an emotional wall.