Dissociative and somatoform disorders

Dissociative (conversion) disorders

Dissociative disorders present with physical or cognitive signs that have no organic cause. They have a sudden onset and are triggered by a traumatic event, insoluble or intolerable problems, or disturbed relationships. ICD10 describes various types of dissociative disorders.

Dissociative amnesia presents with loss of all memory for personal information and events. Patients present saying that they do not know who they are, where they are from or what has happened to them. They have no evidence of organic brain disorder and retain the ability to learn new information. The pattern of memory loss is therefore very different from a typical organic amnesia, where new information is not recalled but long-term memory for personal details is usually retained. Dissociative fugue presents with dissociative amnesia and, in addition, the affected person travels away from their usual environment, sometimes ending up many miles from home with no memory for the period of travel.

Dissociative stupor presents with reduced or absent movement and responsiveness, but it is clear that the patient is neither asleep or unconscious and physical examination and investigations are normal. Dissociative disorders of movement and sensation present with physical signs that do not conform to recognised neurological syndromes and often vary in severity, depending on whether the person is being observed and their emotional state. A variant is Dissociative convulsions, also known as pseudoseizures, in which there are generalised tonic–clonic movements, usually without tongue biting, incontinence of urine or true loss of consciousness.

Aetiology

Dissociative disorders are said to develop as a result of two psychological defence mechanisms, dissociation and conversion, that are used to cope with trauma or emotional conflict that is so painful or distressing it cannot be allowed into the conscious mind. Dissociation results in a loss of integration between mental functions. In conversion, distressing thoughts are transformed (‘converted’) into physical symptoms, sometimes in a way that symbolises the trauma or conflict that caused them. For example, a boy who witnessed the murder of his mother developed dissociative sensory loss that presented with blindness.

Dissociation and conversion can lead to primary and secondary gain, as shown in Figure 1. In chronic cases, secondary gain is often a maintaining factor.

Fig. 1 Primary and secondary gain in dissociative disorder.

Management

Dissociative disorder must always be a positive diagnosis, based upon a history that provides some reasonable psychological explanation of how and why the problem developed. The patient may deny recent stressful events and problems or disturbed relationships, so it is important to seek information from others. Great care must be taken to exclude organic pathology and it should be remembered that follow-up studies of people diagnosed with dissociative disorders have found that many turned out to have an underlying physical condition. Catatonic schizophrenia and severe depressive episodes should be considered in cases of stupor. Two further differential diagnoses are factitious disorder, also known as Munchausen’s syndrome, and malingering, the major features of which are shown in Figure 2.

Fig. 2 Comparison of dissociative disorder, factitious disorder and malingering.

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