Depersonalization as a symptom (not as a disorder) is quite common in college-age populations

Depersonalization disorder or dissociative identity disorder may be considered, as feeling detached from oneself while engaging in self-injuring behavior can be indicative of a dissociative disorder. It is important for the individual to seek a mental health professional for a proper evaluation and diagnosis.

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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.

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.