Disassociated identity disorder (DID), formerly known as multiple personality disorder is a complex psychological disorder where the affected person can have multiple personalities or personas with little to no interconnection with each other or the original personality of the person. It is also commonly accompanied by episodes of memory gaps where the affected person has no recollection of what happened in the time period missing from their memory. It is so named because a person suffering from DID dissociates so severely that they lose track of emotions, memories, feelings, thoughts and their identity.
Each personality has their own individuality including age, sex, manners and emotions. The over powering of these personalities on the affected person simultaneously is known as ‘switching’.

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Causes:

it is difficult to pinpoint a definitive cause for mental disorders because of the complexity of our brain which enables it to react unpredictably in every individual case. However, we can trace common patterns. In the case of DID, patients usually share a common history of neglect, abuse and trauma. It is believed that DID is a result of early childhood trauma that interfered with personality development, usually before age of six.
DID is not limited to people who have a history of physical abuse or physical trauma but can also be easily happen to people who have suffered with emotional neglect and emotional abuse in their tender abuse. Although these reasons are unfortunately a common history of a large population, they do not usually cause DID as statistics show only 1% of population suffers from DID.

Social sigma:

Mainstream entertainment industry has heavily played its part in portraying a very negative image of people who suffer from DID, usually depicting them as serial killers who cannot be held accountable for their actions. All of this for the sole purpose of adding a thriller element. This is false because although a person with DID can have a few personalities that are not notoriously good, those people do not end up as a psychopathic killer.