is a condition where patients present with neurological symptoms such as numbness
, or fits
, but where no neurological explanation can be found. It is thought that these problems arise in response to difficulties in the patient's life, and conversion is considered a psychiatric disorder
in the International Statistical Classification of Diseases and Related Health Problems (ICD-10
) and Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV
). Formerly known as 'hysteria
', the disorder has arguably been known for millennia, though it came to greatest prominence at the end of the 19th century, when the neurologist Jean-Martin Charcot
, and psychiatrists Pierre Janet
and Sigmund Freud
made it the focus of their study. The term 'conversion' has its origins in Freud's doctrine that anxiety is 'converted' into physical symptoms. Though previously thought to have vanished from the west in the 20th century, new research has suggested it is as common as ever. As one expert Peter Halligan comments, the fundamental problem of linking symptoms with emotional disturbance remains to be solved thus leaving the term "conversion disorder" as one of dubious semantic accuracy and doubtful scientific reliability.
DSM-IV defines conversion disorder as follows:
- One or more symptoms or deficits are present that affect voluntary motor or sensory function suggestive of a neurologic or other general medical condition.
- Psychological factors are judged, in the clinician's belief, to be associated with the symptom or deficit because conflicts or other stressors precede the initiation or exacerbation of the symptom or deficit. A diagnosis where the stressor precedes the onset of symptoms by up to 15 years is not unusual.
- The symptom or deficit is not intentionally produced or feigned (as in factitious disorder or malingering).
- The symptom or deficit, after appropriate investigation, cannot be explained fully by a general medical condition, the direct effects of a substance, or as a culturally sanctioned behavior or experience.
- The symptom or deficit causes clinically significant distress or impairment in social, occupational, or other important areas of functioning or warrants medical evaluation.
- The symptom or deficit is not limited to pain or sexual dysfunction, does not occur exclusively during the course of somatization disorder, and is not better accounted for by another mental disorder.
The nature of the association between the psychological factors and the neurological symptoms remains unclear. Earlier versions of the DSM-IV employed psychodynamic concepts, but these have been incrementally removed from successive versions. The ICD-10 classifies conversion disorder as dissociative (conversion) disorder, which suggests the symptoms arise through the process of dissociation.
In the 19th century, physicians such as Silas Weir Mitchell
in the US and Paul Briquet
and Jean-Martin Charcot
in France developed ideas about patients sharing unexplained neurological symptoms. Charcot specialised in treating patients who were suffering from a variety of unexplained physical symptoms including paralysis, contractures (muscles which contract and cannot be relaxed) and seizures. Some of these patients sporadically and compulsively adopted a bizarre posture (christened arc-de-cercle
) in which they arched their body backwards until they were supported only by their head and their heels.
The term "Conversion disorder" originated with Freud and the psychotherapy movement. He viewed these apparently neurological symptoms as a result of the conversion of intrapsychic distress in to physical symptoms. Much of Freud's work is now viewed with scepticism, and it has been suggested that at least some of the classic psychoanalytic cases of hysteria, such as "Anna O., may actually have suffered from organic illness.
Historically, conversion disorder was thought to manifest itself in many different ways. Conversion disorders were thought to be triggered by acute psychosocial stress that the individual could not process psychologically. This overwhelming distress was thought to cause the brain to unconsciously disable or impair a bodily function which would relieve or prevent the patient from experiencing this stressor again. This is in contrast to a more modern understanding that patients remain distressed by their symptoms in the long term.
Conversion disorder can present with any motor or sensory symptom including
The diagnosis of conversion disorder involves three elements - the exclusion of neurological disease, the exclusion of feigning, and the determination of a psychological mechanism. Each of these has difficulties.
Exclusion of neurological disease
Conversion disorder presents with symptoms that typically resemble a neurological disorder such as stroke, multiple sclerosis, or epilepsy. The neurologist must carefully exclude neurological disease, through examination and appropriate investigations. However, it is not uncommon for patients with neurological disease to also have conversion disorder, in which case the task becomes to determine how much of the patient's problem is due to conversion.
In excluding neurological disease, the neurologist has traditionally relied partly on the presence of positive signs of conversion disorder - certain aspects of the presentation that were thought to be rare in neurological disease, but common in conversion. The validity of many of these signs has been questioned, however, by a study showing that they also occurred in neurological disease. One such symptom, for example, is La belle indifférence, described in DSM-IV as "a relative lack of concern about the nature or implications of the symptoms". In a later study no evidence was found that patients with 'functional' symptoms are any more likely to exhibit this than patients with a confirmed organic disease. Another feature thought to be important was that symptoms would tend to be more severe on the non-dominant (usually left) side; there were a variety of theories such as the relative involvement of cerebral hemispheres in emotional processing, or more simply just that it was "easier" to live with a functional deficit on the non-dominant side. However, a literature review of 121 studies established that this was not true, with publication bias the most likely explanation for this commonly held view.
The process of exclusion is not perfect, so misdiagnoses will occur. However, in a highly influential study from the 1960s, Eliot Slater demonstrated that misdiagnoses had occurred in one third of his 112 patients with conversion disorder. Later authors have argued that the paper was flawed, however , and a meta-analysis has shown that misdiagnosis rates since that paper are around 4%, the same as for other neurological diseases.
Exclusion of feigning
Conversion disorder is unique in DSM-IV in explicitly requiring the exclusion of deliberate feigning. Unfortunately, this is only likely to be demonstrable where the patient confesses, or is 'caught out' in a broader deception, such as a false identity. One neuroimaging study suggested that feigning may be distinguished from conversion by the pattern of frontal lobe activation; however this is a research, rather than a clinical technique. True rates of feigning in medicine remain unknown, though neurological presentations of feigning may be among the more common
Establishing a psychological mechanism
The psychological mechanism can be the most difficult aspect of the conversion diagnosis. DSM-IV requires that the clinician believe preceding stressors or conflicts to be associated with the development of the disorder, though how
this might come about is still the subject of debate. The original Freudian model suggested that the emotional charge of painful experiences would be consciously repressed as a way of managing the pain, but this emotional charge would be somehow 'converted' into the neurological symptoms. Freud later argued that the repressed experiences were of a sexual nature. Janet, the other great theoretician of hysteria, argued that symptoms arose through the power of suggestion, acting on a personality vulnerable to dissociation. In this hypothetical process, the subject's experience of their leg, for example, is split-off from the rest of their consciousness, resulting in paralysis or numbness in that leg. Later authors have attempted to combine elements of these models, but none of them has a firm empirical basis. Some support for the Freudian model comes from findings of high rates of childhood sexual abuse in conversion patients and from a recent neuroimaging study showing abnormal emotion processing of a traumatic event linked to motor processing of the affected limb, in a patient with conversion. Support for the dissociation model comes from studies showing heightened suggestibility in conversion patients, and in abnormalities in motor imagery.
There has been much recent interest in functional neuroimaging in conversion. As researchers identify the mechanisms which underlie conversion symptoms it is hoped these will allow the development of a neuropsychological model. A number of such studies have been performed, including some which suggest that blood flow in patients brains may be abnormal while they are unwell. These have all been too small to be confident of the generalisability of their findings, however, so that no neuropsychological model has been clearly established.
Information on the prevalence of conversion disorder in the West is limited, in part due to the complexities of the diagnostic process. In neurological settings, rates of unexplained symptoms are very high, at between 30 and 60%,, which suggests conversion to be more common than most neurological diseases. However, the diagnosis of conversion typically requires an additional psychiatric evaluation, yet few patients will see a psychiatrist so an unknown fraction of those unexplained symptoms will be due to conversion. Large scale psychiatric registers in the US and Iceland found rates of 22 and 11 per 100000 per year, respectively, but it is unclear what proportion of unexplained symptoms these represent.
It is often thought that rates are higher outside of the West, perhaps related to cultural and medical attitudes, though evidence for this is again limited. A community survey of urban Turkey found a rate of 5.6%. Many authors have found rates to be higher in rural and lower socio-economic groups.
'Hysteria' was originally understood to be a condition exclusively affecting women, though it has increasingly been recognised in men. In recent, larger studies, women continue to predominate, with between 2 and 6 female patients for every male.
Conversion disorder may present at any age but is rare in children younger than 10 years or in the elderly. Studies suggest a peak onset in the mid-to-late 30s .
Treatment may include the following:
- Explanation. This must be clear and coherent. It must emphasise the genuineness of the condition, that it is common, potentially reversible and does not mean that the sufferer is a 'psycho'. Taking an aetiologically neutral stance by describing the symptoms as functional may be helpful but further studies are required. Ideally the patient should be followed up neurologically for a while to ensure that the diagnosis has been understood.
- Physiotherapy where appropriate;
- Treatment of comorbid depression or anxiety if present.
There is little evidence-based treatment of conversion disorder. Other treatments such as cognitive behavioral therapy, hypnosis, EMDR, and psychodynamic psychotherapy need further trials.