Conversion disorder was formally called 'hysteria'. The disorder's diagnosis requires undergoing neurological symptoms that cannot be attributed to strictly medical causes. The person experiencing these symptoms does not just ‘imagine’ them, they actually go through them; it could influence how they function or sense things.
Experts have not yet found a cause and yet, they have identified several factors that might pave the way towards this psychological condition. Among these are stress, childhood abuse and genetics. Furthermore if a person has a conversion disorder, they are already more susceptible to acquire another psychological condition or a movement disorder.