Conversion Disorder - Causes

Causes

The original Freudian model suggested that the emotional charge of painful experiences would be consciously repressed as a way of managing the pain, but this emotional charge would be somehow "converted" into the neurological symptoms. Freud later argued that the repressed experiences were of a sexual nature. As Peter Halligan comments, conversion has 'the doubtful distinction among psychiatric diagnoses of still invoking Freudian mechanisms'

Janet, the other great theoretician of hysteria, argued that symptoms arose through the power of suggestion, acting on a personality vulnerable to dissociation. In this hypothetical process, the subject's experience of their leg, for example, is split-off from the rest of their consciousness, resulting in paralysis or numbness in that leg. Later authors have attempted to combine elements of these models, but none of them has a firm empirical basis.

Some support for the Freudian model comes from findings of high rates of childhood sexual abuse in conversion patients and from a recent neuroimaging study showing abnormal emotion processing of a traumatic event linked to motor processing of the affected limb, in a patient with conversion. Support for the dissociation model comes from studies showing heightened suggestibility in conversion patients, and in abnormalities in motor imagery.

There has been much recent interest in functional neuroimaging in conversion. As researchers identify the mechanisms which underlie conversion symptoms it is hoped these will allow the development of a neuropsychological model. A number of such studies have been performed, including some which suggest that blood flow in patients brains may be abnormal while they are unwell. These have all been too small to be confident of the generalisability of their findings, however, so no neuropsychological model has been clearly established.

A 2007 review stated that conversion disorder and dissociative disorders are statistically associated, share features such as a history of abuse and high suggestibility, and likely have common underlying causes. It recommended that DSM should follow ICD-10 and reclassify conversion disorder from a somatoform disorder to a dissociative disorder.

An evolutionary psychology explanation for conversion disorder is that the symptom may have been evolutionarily advantageous during warfare. A non-combatant with these symptoms signals non-verbally, possibly to someone speaking a different language, that she or he is not dangerous as a combatant and also may be carrying some form of dangerous infectious disease. This can explain that conversion disorder may develop following a threatening situation, that there may be a group effect with many people simultaneously developing similar symptoms (as in mass psychogenic illness), and the gender difference in prevalence.