Jean-Martin Charcot argued that hysteria was caused by "a hereditary degeneration of the nervous system, namely a neurological disorder".In the 19th century, hysteria moved from being considered a neurological disorder to being considered a psychological disorder, when Pierre Janet argued that "dissociation appears autonomously for neurotic reasons, and in such a way as to adversely disturb the individuals everyday life". However, as early as 1874, doctors including W. B. Carpenter and J. A. Omerod began to speak out against the hysteria phenomenon as there was no evidence to prove its existence.Sigmund Freud referred to the condition as both hysteria and conversion disorder throughout his career. He believed those with the condition could not live in a mature relationship, and that those with the condition were unwell in order to achieve a "secondary gain", in that they are able to manipulate their situation to fit their needs or desires. He also found that both men and women could have the disorder.Freuds model suggested the emotional charge deriving from painful experiences would be consciously repressed as a way of managing the pain, but that the emotional charge would be somehow "converted" into 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".Pierre Janet, the other great theoretician of hysteria, argued that symptoms arose through the power of suggestion, acting on a personality vulnerable to dissociation.
Conversion disorder is typically seen in people aged 10 to 35, and affects between 0.011% and 0.5% of the general population.Conversion disorder can present with motor or sensory symptoms including any of the following:
Motor symptoms or deficits:

Impaired coordination or balance
Weakness/paralysis of a limb or the entire body (hysterical paralysis or motor conversion disorders)
Impairment or loss of speech (hysterical aphonia)
Difficulty swallowing (dysphagia) or a sensation of a lump in the throat
Urinary retention
Psychogenic non-epileptic seizures or convulsions
Persistent dystonia
Tremor, myoclonus or other movement disorders
Gait problems (astasia-abasia)
Loss of consciousness (fainting)Sensory symptoms or deficits:

Impaired vision (hysterical blindness), double vision
Impaired hearing (deafness)
Loss or disturbance of touch or pain sensationConversion symptoms typically do not conform to known anatomical pathways and physiological mechanisms. It has sometimes been stated that the presenting symptoms tend to reflect the patients own understanding of anatomy and that the less medical knowledge a person has, the more implausible are the presenting symptoms. However, no systematic studies have yet been performed to substantiate this statement. Diagnosis
Definition
Conversion disorder is now contained under the umbrella term functional neurological symptom disorder. In cases of conversion disorder, there is a psychological stressor. The diagnostic criteria for functional neurological symptom disorder, as set out in DSM-5, are:

Specify type of symptom or deficit as:

With weakness or paralysis
With abnormal movement (e.g. tremor, dystonic movement, myoclonus, gait disorder)
With swallowing symptoms
With speech symptoms (e.g. dysphonia, slurred speech)
With attacks or seizures
With amnesia or memory loss
With special sensory loss symptoms (e.g.