Until World War II most psychiatrists believed that mental illness resulted from issues encountered in childhood. However, when it was discovered that the vast majority of concentration camp survivors reported a happy childhood, this theory needed to be revisited. Eventually it was concluded that chronic mental illness could develop in persons who had a harmonious childhood but who had been subjected to extreme physical and psychological stress. This created a paradigm shift in the field of psychology in their understanding of the way extreme stress could affect adults and how it should be treated.
Dissociation is the act of separating oneself from your awareness. It occurs naturally for most of us when performing uninteresting or monotonous tasks. However, dissociation exists on a continuous spectrum and when it occurs and there is an actual identify shift it is considered a mental disorder and referred to as Dissociative Identity Disorder (DID).
Almost all DID subjects are victims of severe and chronic childhood sexual and physical abuse. These subjects are also often diagnosed with Post Traumatic Stress Syndrome, or borderline personality, in addition to DID. Epidemiological studies have shown that DID exists in 1-3% of the general population.
The Diagnostic and Statistical Manual of Mental Disorders (DSM), fourth edition, in section 300.14, defines the essential features of DID as: “the presence of two or more distinct identities or personal states that recurrently take control of behavior. There is an inability to recall important personal information, the extent of which is too great to be explained by ordinary forgetfulness. The disturbance is not due to the direct physiological effects of a substance or general medical condition.”
I was unable to find statistically based information regarding the average number of alter states, but based upon my reading it would not be unusual to have a many as five to ten alters, each with distinctive emotional attributes, age, and physical demeanor. Each alter state has one of two identity states. Either a neutral identity state (NIS) that inhibits memory of the trauma or a traumatic identity state (TIS) that has access and responses to the trauma. The dissociation associated with this disorder acts as a defense and enables victims to maintain a relatively healthy level of functioning because traumatic memories are disconnected from other information in their minds
The most effective psychoanalytic treatment involves attempting to integrate the multiple states. As some patients progress with this treatment they are able to volitionally transfer between alter states. These subjects are very useful in experiments attempting to gather physiological data on this disorder.
To date, very little is known about the physiology of DID. Two reasons for this are because of its only recent acceptance as a disorder and the dynamic nature of the disorder. Alter state switches, which are of most interest, occur within seconds making analysis difficult.
Recent studies have focused on the limbic system and specifically the hippocampus. It is very sensitive to stress making it an excellent candidate for exploration. It is very important for remembering where you were and what you were doing when something important happened; in other words, providing context. Several studies have linked stress to reduced hippocampal volume.
Because of the excellent temporal and spatial resolution of magnetic resonance imaging (MRI), it is an excellent tool to study this type of disorder.
The Tsai et al. study performed a structural and functional MRI on a middle aged woman who was diagnosed with DID. The structural test measured the volume of the hippocampus and compared it to normal values. The functional test attempted to determine the area(s) of the brain that were active during the switching between alter states.
This study found that while the subject’s intracranial volume was normal, her hippocampal volume was 50% smaller than values for normal females. Additionally, during the state switch from NIS to TIS there was bilateral hippocampal inhabitation (less activity during switching than normal state) with more inhabitation on the right side (subject was right handed). The right parahippocampal and medial temporal regions were also inhabited. The switch from TIS to NIS created only right hippocampal activation. In addition to confirming other studies regarding the diminished hippocampus, the study concluded that the hippocampus and medial temporal could be involved in the switching of states.
The Vermetten et. al. study compared hippocampal and amygdalar volumes of approximately twenty female subjects with DID to a like number of healthy subjects.
The results showed the DID subjects had a 19.2% smaller hippocampal volume and a 31.6% smaller amygdalar volume than healthy subjects. They also measured the ratio of hippocampal to amygdalar volume and found it to be larger in the DID group. This finding is consistent with the findings of other experiments in which the subjects were victims of extreme abuse.
This study suggested that since the hippocampus is a major target for glucocorticoids, which are release during stressful experiences, this could be the source of atrophy of the hippocampus. No rational was attempted for difference in amygdalar volume, nor was the difference in the ratio of volumes explained.
The Reinders study measured the emotional response of eleven DID subjects first in the NIS state and then in the TIS state. Each alter was read two sets of information. One that was neutral and the other trauma related. The premise was that the TIS when listening to trauma related information would: 1) exhibit emotional processing similar to patients with PTSD, 2) have more emotional and sensorimotor reactions, and 3) have higher heart rate and blood pressure. PET diagnosis was used to gather the data. The measurements used by the study were changes in regional cerebral blood flow and autonomic reactions.
The finding verified their premise. When the alter was in the TIS state the reaction to trauma related information showed completely different brain areas were effected than when read the same information in the NIS state.
Since it is believed that DID subjects exhibit anomalies in memory, consciousness, and perception the Dorahy et al study attempted to determine whether subjects had working memory processing problems that are not present in normal subjects. Also, if there were problems did they exist in both the NIS state and the TIS state.
This study performed three tests to determine the capability of working memory to process in a normal manner for all subjects. While results were quite technical, the findings were somewhat surprising in that no significant differences existed in the function of working memory between DID subjects and non-clinical ones.
The DSM is the gold standard for US mental health professionals for describing and diagnosing mental disorders. The latest version was published in 1994 included the description of DID previously referred to. This inclusion should be enough to extinguish doubts about this disorder. For evidence that it is a very conservative publication, it was not until the 1970s that it removed homosexuality from its list of mental disorders.
In spite of this, the disorder remains somewhat controversial. A vocal minority of psychologists don’t believe that it is possible for a person to have multiple personalities without some prompting. In my opinion they are like the European doctors in the second half of the 19th century who after being told by Ignac Semmelweis to wash their hands before delivering a baby, scoffed at the advice and continued killing their patients with their germ infected hands. Others are not sure exactly how to differentiate this disorder from others such as PTSD or borderline subjects. This conclusion is understandable and will be resolved as we learn more about the impact of trauma.
In addition resistance comes from several sources such as: resistance to the recognition of the widespread physical and sexual abuse of children by parents; resistance to a paradigm shift in treating emotional ill patients differently than physically ill ones; resistance as a result of personal investment of professionals to a different outcome; and resistance because its treatment is difficult, intense, and long term.