Conversion disorder is a medical condition in which sufferers experience neurological symptoms such as paralysis, numbness, blindness, or seizures without a known neurological factor. Conversion disorder, formerly known as hysteria, is considered a psychiatric disorder by the Diagnostic and Statistical Manual of Mental Disorders, which classifies it as a somatoform disorder. In contrast, the World Health Organization's International Classification of Diseases (ICD-10) classifies it as a dissociative disorder. The diagnosis of this neurological disorder has been problematic in the past, as doctors have conceptually and practically differentiated its symptoms from those of the neurological diseases for which it is known to be so. Most psychologists assume that conversion disorder is a psychological disorder, but the psychological mechanism and how this varies from conscious simulation has eluded most of them. Current diagnostic systems require that simulation or conscious pretense be excluded and that symptoms be explained psychologically. The truth is during diagnosis, conscious simulation is very difficult to prove and in most cases it is not possible to find a psychological explanation. Studies of childhood and adult psychological precipitants tend to support the idea that stressful life events occurred before the onset of symptoms, but in individual cases, stressful life events are not a major cause. Therefore, these contradictions highlight serious practical and theoretical issues in current diagnostic systems and in the very concept of disorder. Advanced physiology, psychology and functional imaging techniques have been applied from the top side in an attempt to clearly explain the neurobiology of conversion disorder and to differentiate it from... middle of paper... nge, dissociative stupor (F44.2) – absence of voluntary movement, trance disorders and possession (F44.3) – temporary loss of sense of personal identity. The DSM IV also lists five types of dissociative disorder which are depersonalization disorders (DSM-IV Code 300.6) - characterized by periods of detachment from oneself and the surrounding environment, Dissociative Amnesia (DSM-IV code 300.12) - impairment of recall due to emotional trauma, Dissociative fugue (DSM-IV code 300.13) - impairment of recollection of the past and the surrounding environment, Dissociative identity disorder (DSM - IV code 300.14) - alternation of two or more distinct personality states. To conclude, a review done in 2007 found that conversion and dissociative disorders are statistically similar with common underlying causes. Therefore, conversion disorder should be reclassified from a somatoform disorder to a dissociative disorder.