Multiple reasons to better diagnose personality disorders
Previously known as multiple personality disorder, DID affects about one per cent of the population but Amy Wong, a psychologist and QUT Faculty of Health PhD researcher, said the number of people suffering from the disorder was likely to be much higher.
Ms Wong said DID, a condition highlighted in the popular television show United States of Tara, bears striking similarities to schizophrenia, and, on a lesser scale, bipolar disorder and borderline personality disorder.
"There are a lot of overlapping symptoms such as hallucinations or delusions and there isn't much research exploring the cognitive differences and similarities between DID and schizophrenia," she said.
"One of the main differences between these two conditions is memory loss. We've seen patients who can't remember significant events in their lives because they were being experienced by another personality."
Though some sectors of the psychological fraternity remain skeptical about the validity of the condition, Ms Wong said it was not uncommon for people to have distinct physiological changes with each personality. In some cases MRI scans and EEG have been significantly different between dominant personalities, as have blood and cholesterol tests. Changes in handwriting are also common.
While each case is individual, Ms Wong said it wasn't unusual for patients with DID to present with about 100 different personalities, but usually only a few are dominant - some with distinctly different names, ages and characteristics.
"Part of the therapy is to raise the awareness of the other personalities and help these personalities to 'speak to each other'," she said.
"We have seen cases on the extreme end of the spectrum where people have studied in a field but can't carry on in that line of work because they have no memory of their training, or have forgotten big events such as graduations, weddings or children because another personality has lived that event.
"The stories we see on TV are obviously more dramatic. In real life some of the switches are so subtle that you wouldn't even pick it up and are often put down to mood swings, but the nature of the illness makes it very hard to be able to lead a normal life."
Ms Wong said the condition was not genetic but was usually linked to deep trauma, particularly experienced in the very early stages of life and was likely formed as a way of escape.
"There is no medication to treat DID. There are high rates of other symptoms such as depression or anxiety among people with DID so we can medicate those conditions," she said.
"The major goal for treatment is to help people take responsibility of behavior of all personalities, understand why they're going through what they're going through, as well as mapping the shared knowledge of the personalities so they have better awareness of their own condition."
Ms Wong is looking for participants who have been diagnosed with DID to complete a one-off cognitive test and questionnaire. The results will be compared with cognitive testing undertaken by people diagnosed with schizophrenia.