There are many subjects in medicine that are quite clear as long as one has to handle the separate cases in practice. But if one sits down to explain them they become confused in many aspects. Hysteria is one of these subjects. Since Charcot described the different symptoms of this illness, it has become a recognized part of medicine. One can now diagnose special symptoms as hysterical and know that no physical reason for them can be found. So far, everything is clear.
But if one asks for an explanation of the symptoms, and especially for an explanation which would enable one to treat them with success, the matter becomes very complicated. Charcot himself believed that a special form of degeneration of the nervous system was the cause of hysteria. But he failed to indicate what that form was. The same explanation was used for many other neuroses and psychoses
JAN H. VAN DER HOOP. PSYCHOLOGY AND HYSTERIA. Arch NeurPsych. 1930;24(2):324–334. doi:10.1001/archneurpsyc.1930.02220140100006