Here's some basic information from the Diagnostic and Statistical Manual (DSM) of the American Psychiatric Association (APA).
- Dissociative Identity Disorder (DID) is diagnosed three to nine times more frequently in women than in men and may be even more than that
- Females also tend to have more identities (15 or more on average) wheras men average approximately 8.
- DID diagnosis is on the rise in the US, but the cause (increased awareness vs. increased prevalence) is unknown.
- It is often 6 to 7 years from when the first symptom appears until the diagnosis has been made. It may be come less likely to manifest beyond the late 40's, and may re-emerge during episodes of stress, trauma, or substance abuse.
In the DSM and the ICD, the diagnosis is 300.14 - a google for this should turn up some additional information, such as diagnostic criteria and a lot of editorial on the subject. (such as "DSM 300.14 Dissociative Identity Disorder")
Sorry I don't have much data regarding treatment, but a decent library with access to medical journals should have at least some information for you.