The term comes from the Greek for "uterus", and in ancient times doctors used it to describe females with convulsive attacks and random pains, which they believed to be the result of the womb wandering, unfettered, around the body. It entered modern thinking from the work of a French doctor, Jean-Martin Charcot, who in Paris in the 1880s became celebrated for his demonstrations of hysteria in his patients. The main characteristic in the patients was seizures, which he stopped by using hypnotism.
But it was Sigmund Freud, influenced by Charcot, who listened to the stories of the afflicted women and proposed that the bodily symptoms were the result of earlier, traumatic sexual experiences. It was Freud, too, who introduced the term "conversion", the implication being that psychological disorders were converted into bodily symptoms - somatisation.
The modern view of conversion hysteria is essentially that it is a set of bodily symptoms for which no medical explanation can be found; in its most typical form it results in the loss of some function of the voluntary nervous system, resulting in paralysis or seizures. Some patients have seizures that can easily be confused with epilepsy. There is no evidence, contrary to popular belief, that hysteria, difficult though it is to diagnose, is any less common than it used to be.
Indeed, in some neurological outpatient clinics as many as one-third of the patients have symptoms that do not seem to have a medical basis, and a significant number of these are examples of hysteria or somatisation. In some cases the disability may be feigned in order to get compensation for an accident or to gain some other advantage.
Contrary to Freud's ideas about childhood, sex and repression being the cause of hysterical symptoms, there is a strong association between a stressful life event and and the onset of symptoms. Indeed, the idea that psychological stress could result in bodily illness entered widely into the public consciousness with the description of soldiers in the First World War suffering from shell-shock, now known as post-traumatic stress disorder.
Somatisation of psychological stress is common, and, for example, patients with depression often have other symptoms such as loss of motor function, and so have difficulty walking. Is hysterical conversion really any different from somatisation?
It is now suggested that illnesses as diverse as irritable bowel syndrome and chronic fatigue syndrome are more similar than previously thought, and are examples of somatisation. Most cases of hysterical conversion can be included in this category. One distinction is that hysterical conversion is not chronic.
Among animals the nearest to hysterical conversion is tonic immobility in animals such as guinea-pigs and opossums. When in contact with a predator they become completely immobile, paralysed until the danger has passed. Different but related is the freezing paralysis of a rat induced when seeing a cat.
Many of the processes involved in hysteria are similar to those operating in hypnosis. Remarkably, it is claimed that most of the symptoms of hysteria can be induced under hypnosis, including paralysis of a limb. A new study has used this to compare brain activity in patients with paralysis with those who have had their paralysis induced by hypnosis. Similar brain regions seem to be involved in inhibiting the movement of limbs.
Psychoanalysts still stick to their belief that early childhood experiences play a crucial role. We may wonder how they would deal with someone whose paralysis had been induced by hypnosis; how long would they spend analysing childhood experiences? Nevertheless psychotherapy, particularly cognitive behaviour therapy, has begun to provide some encouraging results in treating hysterical conversion.
Our understanding of the interactions between emotions, thinking and the body still has a very long way to go.
The writer is professor of biology as applied to medicine at University College LondonReuse content