|Classification and external resources|
Conversion disorder (CD) is a diagnostic category previously used in some psychiatric classification systems. It is sometimes applied to patients who present with neurological symptoms, such as numbness, blindness, paralysis, or fits, which are not consistent with a well-established organic cause, and which cause significant distress. It is thought that these symptoms arise in response to stressful situations affecting a patient's mental health or an ongoing mental health condition such as depression. Conversion disorder was retained in DSM-5, but given the subtitle functional neurological symptom disorder. The new criteria cover the same range of symptoms, but remove the requirements for a psychological stressor to be present and for feigning to be disproved.
The theory of conversion disorder stems from ancient Egypt, and was formerly known as "hysteria". The concept of conversion disorder came to prominence at the end of the 19th century, when the neurologists Jean-Martin Charcot and Sigmund Freud and psychologist Pierre Janet focused their studies on the subject. Before their studies, people with hysteria were often believed to be malingering. 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, some research has suggested that conversion disorder is as common as ever.
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-V, are:
- The patient has ≥1 symptoms of altered voluntary motor or sensory function.
- Clinical findings provide evidence of incompatibility between the symptom and recognised neurological or medical conditions.
- The symptom or deficit is not better explained by another medical or mental disorder.
- The symptom or deficit causes clinically significant distress or impairment in social, occupational, or other important areas of functioning or warrants medical evaluation.
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 symptom (e.g. visual, olfactory, or hearing disturbance)
- With mixed symptoms.
- Acute episode: symptoms present for less than six months
- Persistent: symptoms present for six months or more.
- Psychological stressor
- No psychological stressor
Signs and symptoms
Conversion disorder begins with some stressor, trauma, or psychological distress. Usually the physical symptoms of the syndrome affect the senses or movement. Common symptoms include blindness, partial or total paralysis, inability to speak, deafness, numbness, difficulty swallowing, incontinence, balance problems, seizures, tremors, and difficulty walking. These symptoms are attributed to conversion disorder when a medical explanation for the afflictions cannot be found. Symptoms of conversion disorder usually occur suddenly. Conversion disorder is typically seen in individuals 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 sensation
Conversion 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 patient's 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.
The first evidence of functional neurological symptom disorder dates back to 1900 BC, when the symptoms were blamed on the uterus moving within the female body. The treatment varied "depending on the position of the uterus, which must be forced to return to its natural position. If the uterus had moved upwards, this could be done by placing malodorous and acrid substances near the woman’s mouth and nostrils, while scented ones were placed near her vagina; on the contrary, if the uterus had lowered, the document recommends placing the acrid substances near her vagina and the perfumed ones near her mouth and nostrils."
In Greek mythology, hysteria, the original name for functional neurological symptom disorder, was thought to be caused by a lack of orgasms, uterine melancholy and not procreating. Plato, Aristotle and Hippocrates believed that a lack of sex upset the uterus. The Greeks believed that it could be prevented and cured with wine and orgies. Hippocrates argued that a lack of regular sexual intercourse led to the uterus producing toxic fumes and caused it to move in the body, and that this meant that all women should be married and enjoy a satisfactory sexual life.
From the 13th century, women with hysteria were exorcised, as it was believed that they were possessed by the devil. It was believed that if doctors could not find the cause of a disease or illness, it must be caused by the devil.
At the beginning of the 16th century, women were sexually stimulated by midwives in order to relieve their symptoms. Gerolamo Cardano and Giambattista della Porta believed that polluted water and fumes caused the symptoms of hysteria. Towards the end of the century, however, the role of the uterus was no longer thought central to the disorder, with Thomas Willis discovering that the brain and central nervous system were the cause of the symptoms. Thomas Sydenham argued that the symptoms of hysteria may have an organic cause. He also proved that the uterus is not the cause of symptom.
During the 18th century, there was a move from the idea of hysteria being caused by the uterus to it being caused by the brain. This led to an understanding that it could affect both sexes. 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 individual's 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.
Freud referred to the condition as both hysteria and conversion disorder throughout his career. He believed that 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 suffer from the disorder. However, throughout his career, Freud admitted that "he had not succeeded in curing a single patient, and there was no clinical evidence that his theory had any merit whatsoever". Freud frequently made serious diagnostic errors due to his theory of hysteria. In 1901, a patient died of a sarcoma of the abdominal glands, which had given her abdominal pain. One key feature of hysteria was said to be abdominal pain, and so Freud treated her for this, and claimed her condition had "cleared up". After her death, he then claimed that hysteria had caused her tumour, but there is no evidence to support his claim.
Freud's model suggested that 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".
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 various models, but none of them has a firm empirical basis. In 1908, Steyerthal predicted that: "Within a few years the concept of hysteria will belong to history ... there is no such disease and there never has been. What Charcot called hysteria is a tissue woven of a thousand threads, a cohort of the most varied diseases, with nothing in common but the so-called stigmata, which in fact may accompany any disease." However, the term "hysteria" was still being used well into the 20th Century.
Some support for the Freudian model comes from findings of high rates of childhood sexual abuse in conversion patients. Support for the dissociation model comes from studies showing heightened suggestibility in conversion patients,. However, critics argue that it can be challenging to find organic pathologies for all symptoms, and so the practice of diagnosing patients who suffered with such symptoms as having hysteria led to the disorder being meaningless, vague and a sham-diagnosis, as it does not refer to any definable disease. Furthermore, throughout its history, many patients have been misdiagnosed with hysteria or conversion disorder when they had organic disorders such as tumours or epilepsy or vascular diseases. This has led to patient deaths, a lack of appropriate care and suffering for the patients. Eliot Slater, after studying the condition in the 1950s, stated: "The diagnosis of 'hysteria' is all too often a way of avoiding a confrontation with our own ignorance. This is especially dangerous when there is an underlying organic pathology, not yet recognised. In this penumbra we find patients who know themselves to be ill but, coming up against the blank faces of doctors who refuse to believe in the reality of their illness, proceed by way of emotional lability, overstatement and demands for attention ... Here is an area where catastrophic errors can be made. In fact it is often possible to recognise the presence though not the nature of the unrecognisable, to know that a man must be ill or in pain when all the tests are negative. But it is only possible to those who come to their task in a spirit of humility. In the main the diagnosis of 'hysteria' applies to a disorder of the doctor–patient relationship. It is evidence of non-communication, of a mutual misunderstanding ... We are, often, unwilling to tell the full truth or to admit to ignorance ... Evasions, even untruths, on the doctor’s side are among the most powerful and frequently used methods he has for bringing about an efflorescence of 'hysteria'".
Much recent work has been done to identify the underlying causes of conversion and related disorders and to better understand why conversion and hysteria appear more commonly in women. Current theoreticians tend to believe that there is no single cause for these disorders. Instead, the emphasis tends to be on the individual understanding of the patient and a variety of therapeutic techniques. In some cases, the onset of conversion disorder correlates to a traumatic or stressful event. There are also certain populations that are considered at risk for conversion disorder, including people suffering from a medical illness or condition, people with personality disorder, and individuals with dissociative identity disorder. However, no biomarkers have yet been found to support the idea that conversion disorder is caused by a psychiatric condition.
There has been much recent interest in using functional neuroimaging to study conversion. As researchers identify the mechanisms which underlie conversion symptoms, it is hoped that they will enable the development of a neuropsychological model. A number of such studies have been performed, including some which suggest that the blood-flow in patients' brains may be abnormal while they are unwell. However, the studies have all been too small to be confident of the generalisability of their findings, so no neuropsychological model has been clearly established.
An evolutionary psychology explanation for conversion disorder is that the symptoms may have been evolutionarily advantageous during warfare. A non-combatant with these symptoms signals non-verbally, possibly to someone speaking a different language, that she or he is not dangerous as a combatant and also may be carrying some form of dangerous infectious disease. This can explain that conversion disorder may develop following a threatening situation, that there may be a group effect with many people simultaneously developing similar symptoms (as in mass psychogenic illness), and the gender difference in prevalence.
The Lacanian model accepts conversion as a common phenomenon inherent in specific psychical structures. The higher prevalence of it among women is based on somewhat different intrapsychic relations to the body from those of typical males, which allows the formation of conversion symptoms.
Exclusion of neurological disease
Conversion disorder presents with symptoms that typically resemble a neurological disorder such as stroke, multiple sclerosis, epilepsy or hypokalemic periodic paralysis. 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 excluding neurological disease, the neurologist has traditionally relied partly on the presence of positive signs of conversion disorder, i.e. 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 occur 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. In DSM-V, la belle indifférence was removed as a diagnostic criteria.
Another feature thought to be important was that symptoms tended to be more severe on the non-dominant (usually left) side of the body. There have been a number of theories about this, such as the relative involvement of cerebral hemispheres in emotional processing, or more simply, 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. Although agitation is often assumed to be a positive sign of conversion disorder, release of epinephrine is a well-demonstrated cause of paralysis from hypokalemic periodic paralysis.
Misdiagnosis does sometimes occur. 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 was published are around 4%, the same as for other neurological diseases.
Exclusion of feigning
Conversion disorder is unique in ICD-10 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 was a piece of research, rather than a clinical technique. True rates of feigning in medicine remain unknown. However, it is believed that feigning of conversion disorder is no more likely than of other medical conditions.
The psychological mechanism of conversion can be the most difficult aspect of a conversion diagnosis. Even if there is a clear antecedent trauma or other possible psychological trigger, it is still not clear exactly how this gives rise to the symptoms observed. Patients with medically unexplained neurological symptoms may not have any psychological stressor, hence the use of the term "functional neurological symptom disorder" in DSM-V as opposed to "conversion disorder", and DSM-V's removal of the need for a psychological trigger.
There are a number of different treatments that are available to treat and manage conversion syndrome. Treatments for conversion syndrome include hypnosis, psychotherapy, physical therapy, stress management, and transcranial magnetic stimulation. Treatment plans will consider duration and presentation of symptoms and may include one or multiple of the above treatments. This may include the following:
- Explanation. This must be clear and coherent as attributing physical symptoms to a psychological cause is not accepted by many educated people in western cultures. It must emphasize the genuineness of the condition, that it is common, potentially reversible and does not mean that the sufferer is psychotic. Taking an etiologically 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;
- Occupational Therapy to maintain autonomy in activities of daily living;
- 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, EEG brain biofeedback need further trials. Psychoanalytic treatment may possibly be helpful. However, most studies assessing the efficacy of these treatments are of poor quality and larger, better controlled studies are urgently needed. Cognitive Behavioural Therapy is the most common treatment, however boasts a mere 13% improvement rate.
Empirical studies have found that the prognosis for conversion disorder varies widely, with some cases resolving in weeks, and others enduring for years or decades. There is also evidence that there is no cure for Conversion Disorder, and that although patients may go into remission, they can relapse at any point. Furthermore, many patients who are 'cured' continue to have some degree of symptoms indefinitely.
Information on the frequency of conversion disorder in the West is limited, in part due to the complexities of the diagnostic process. In neurology clinics, the reported prevalence of unexplained symptoms among new patients is very high (between 30 and 60%). However, diagnosis of conversion typically requires an additional psychiatric evaluation, and since few patients will see a psychiatrist it is unclear what proportion of the unexplained symptoms are actually due to conversion. Large scale psychiatric registers in the US and Iceland found incidence rates of 22 and 11 newly diagnosed cases per 100,000 person-years, respectively. Some estimates claim that in the general population, between 0.011% and 0.5% of the population have conversion disorder.
Although it is often thought that the frequency of conversion may be higher outside of the West, perhaps in relation to cultural and medical attitudes, evidence of this is limited. A community survey of urban Turkey found a prevalence of 5.6%. Many authors have found occurrence of conversion to be more frequent in rural, lower socio-economic groups, where technological investigation of patients is limited and individuals may be less knowledgeable about medical and psychological concepts.
Historically, the concept of 'hysteria' was originally understood to be a condition exclusively affecting women, though the concept was eventually extended to men. In recent surveys of conversion disorder (formerly classified as "hysterical neurosis, conversion type"), females predominate, with between 2 and 6 female patients for every male.
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. He viewed these apparently neurological symptoms as a result of the conversion of intrapsychic distress into physical symptoms. This distress was thought to cause the brain to unconsciously disable or impair a bodily function as a side effect of the original repression, which served to relieve the patient's anxiety. However, some have claimed that patients do remain distressed by their symptoms in the long term.
Many of the early cases of conversion disorder or hysteria had organic conditions as opposed to a psychiatric illness. Anna O., one of the first documented case studies of conversion disorder may not have been suffering with conversion disorder at all, as her symptoms are consistent with temporal lobe epilepsy. Despite claiming that she had been cured, Anna O. continued to be unwell until she died. "A year after Breuer had broken off his treatment of Anna O., he had confided to Freud that the patient he had supposedly cured 'was quite unhinged and that he wished she would die and so be released from her suffering'." In fact, in Studies On Hysteria in which Breuer's Anna O. case was first presented, Freud wrote this: "Others of the patient's symptoms were not of a hysterical nature at all. This is true, for example, of the neck cramps, which I consider a modified version of migraine and which as such are not to be classified as a neurosis but as an organic disorder. Hysterical symptoms, however, regularly become attached to these." Freud believed that all hysterical symptoms ultimately have some organic components.
- Sigmund Freud, "Charcot", In The Complete Psychological Works of Sigmund Freud, Book I
- Josef Breuer & Sigmund Freud, "Studies in Hysteria", 1895
- Akagi, H. & House, A.O., 2001, The epidemiology of hysterical conversion. In P. Halligan, C. Bass, J. Marshall (Eds.) Hysterical Conversion: clinical and theoretical perspectives (pp. 73–87). Oxford: Oxford University Press.
- International Statistical Classification of Diseases and Related Health Problems, 10th Revision. F44.9
- "Conversion and somatic symptom disorders". Retrieved 25 November 2015.
- "Conversion disorder". National Center for Biotechnology Information, U.S. National Library of Medicine. 2012-11-17. Retrieved 25 October 2013.
- Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, American Psychiatric Association
- Tollison, C. David; Satterthwaite, John R.; Tollison, Joseph W. (2002-01-01). Practical Pain Management. Lippincott Williams & Wilkins. ISBN 9780781731607.
- Tasca, Cecilia; Rapetti, Mariangela; Carta, Mauro Giovanni; Fadda, Bianca (2012-10-19). "Women And Hysteria In The History Of Mental Health". Clinical Practice and Epidemiology in Mental Health : CP & EMH. 8: 110–119. doi:10.2174/1745017901208010110. ISSN 1745-0179. PMC 3480686. PMID 23115576.
- Webster, Richard. "The hysteria diagnosis: Freud, Charcot, Breuer and Anna O". www.richardwebster.net. Retrieved 2016-02-29.
- Webster, Richard. "The hysteria diagnosis: Freud, Charcot, Breuer and Anna O". www.richardwebster.net. Retrieved 2016-02-21.
- Freud S (1905). Fragment of an analysis of a case of hysteria.
- Halligan PW, Bass C, Wade DT (2000). "New approaches to conversion hysteria". BMJ. 320 (7248): 1488–9. doi:10.1136/bmj.320.7248.1488. PMC 1118088. PMID 10834873.
- Janet P (1920). The Major Symptoms of Hysteria (2nd ed.).
- Brown RJ (2004). "Psychological mechanisms of medically unexplained symptoms: an integrative conceptual model". Psychol Bull. 130 (5): 793–812. doi:10.1037/0033-2909.130.5.793. PMID 15367081.
- Webster, Richard. "Sigmund Freud: hysteria, somatization, medicine and misdiagnosis". www.richardwebster.net. Retrieved 2016-02-21.
- Roelofs K, Keijsers GP, Hoogduin KA, Näring GW, Moene FC (2002). "Childhood abuse in patients with conversion disorder". Am J Psychiatry. 159 (11): 1908–13. doi:10.1176/appi.ajp.159.11.1908. PMID 12411227.
- Roelofs K, Hoogduin KA, Keijsers GP, Näring GW, Moene FC, Sandijck P (2002). "Hypnotic susceptibility in patients with conversion disorder". J Abnorm Psychol. 111 (2): 390–5. PMID 12003460.
- Bracha HS (2006). "Human brain evolution and the "Neuroevolutionary Time-depth Principle:" Implications for the Reclassification of fear-circuitry-related traits in DSM-V and for studying resilience to warzone-related posttraumatic stress disorder". Progress in Neuro-Psychopharmacology and Biological Psychiatry. 30 (5): 827–853. doi:10.1016/j.pnpbp.2006.01.008. PMID 16563589.
- Fink B (2000). A Clinical Introduction to Lacanian Psychoanalysis: Theory and Technique (3 ed.). Cambridge, Mass.: Harvard University Press. ISBN 978-0674135369.
- Stone J, Carson A, Sharpe M (2005). "Functional symptoms and signs in neurology: assessment and diagnosis". J. Neurol. Neurosurg. Psychiatr. 76 Suppl 1: i2–12. doi:10.1136/jnnp.2004.061655. PMC 1765681. PMID 15718217.
- Eames P (1992). "Hysteria following brain injury". J. Neurol. Neurosurg. Psychiatr. 55 (11): 1046–53. doi:10.1136/jnnp.55.11.1046. PMC 1015291. PMID 1469401.
- Gould R, Miller BL, Goldberg MA, Benson DF (1986). "The validity of hysterical signs and symptoms". J. Nerv. Ment. Dis. 174 (10): 593–7. doi:10.1097/00005053-198610000-00003. PMID 3760849.
- Stone J, Smyth R, Carson A, Warlow C, Sharpe M (2006). "La belle indifférence in conversion symptoms and hysteria: systematic review". Br J Psychiatry. 188: 204–9. doi:10.1192/bjp.188.3.204. PMID 16507959.
- Stone J, Sharpe M, Carson A, Lewis SC, Thomas B, Goldbeck R, Warlow CP (2002). "Are functional motor and sensory symptoms really more frequent on the left? A systematic review". J. Neurol. Neurosurg. Psychiatr. 73 (5): 578–81. doi:10.1136/jnnp.73.5.578. PMC 1738113. PMID 12397155.
- "Segal MM, Jurkat-Rott K, Levitt J, Lehmann-Horn F, Hypokalemic periodic paralysis - an owner's manual". Uni-ulm.de. 2009-06-05. Retrieved 2013-11-30.
- Slater E (1965). "Diagnosis of Hysteria". Br Med J. 1 (5447): 1395–9. doi:10.1136/bmj.1.5447.1395. PMC 2166300. PMID 14286998.
- Slater ET, Glithero E (1965). "A follow-up of patients diagnosed as suffering from "hysteria"". J Psychosom Res. 9 (1): 9–13. doi:10.1016/0022-3999(65)90004-8. PMID 5857619.
- Stone J, Warlow C, Carson A, Sharpe M (2005). "Eliot Slater's myth of the non-existence of hysteria". J R Soc Med. 98 (12): 547–8. doi:10.1258/jrsm.98.12.547. PMC 1299341. PMID 16319432.
- Ron M, "The Prognosis of Hysteria" In P. Halligan, C. Bass, J. Marshall (Eds.) Hysterical Conversion: clinical and theoretical perspectives (pp. 73–87). Oxford: Oxford University Press.
- Krahn LE, Li H, O'Connor MK (2003). "Patients who strive to be ill: factitious disorder with physical symptoms". Am J Psychiatry. 160 (6): 1163–8. doi:10.1176/appi.ajp.160.6.1163. PMID 12777276.
- Spence SA, Crimlisk HL, Cope H, Ron MA, Grasby PM (2000). "Discrete neurophysiological correlates in prefrontal cortex during hysterical and feigned disorder of movement". Lancet. 355 (9211): 1243–4. doi:10.1016/S0140-6736(00)02096-1. PMID 10770312.
- "Conversion disorder". Mayo Foundation for Medical Education and Research. Retrieved 25 October 2013.
- Stone J, Carson A, Sharpe M (2005). "Functional symptoms in neurology: management". J. Neurol. Neurosurg. Psychiatr. 76 Suppl 1: i13–21. doi:10.1136/jnnp.2004.061663. PMC 1765682. PMID 15718216.
- Ruddy R, House A (2005). "Psychosocial interventions for conversion disorder". Cochrane Database Syst Rev (4): CD005331. doi:10.1002/14651858.CD005331.pub2. PMID 16235402.
- Feinstein A (2011). "Conversion disorder: advances in our understanding". CMAJ. 183: 915–20. doi:10.1503/cmaj.110490. PMC 3091899. PMID 21502352.
- Mace, CJ; Trimble, MR (September 1996). "Ten-year prognosis of conversion disorder.". The British Journal of Psychiatry. 169 (3): 282–8. doi:10.1192/bjp.169.3.282. PMID 8879713.
- Couprie, W; Wijdicks, EF; Rooijmans, HG; van Gijn, J (June 1995). "Outcome in conversion disorder: a follow up study.". Journal of neurology, neurosurgery, and psychiatry. 58 (6): 750–2. doi:10.1136/jnnp.58.6.750. PMID 7608683.
- Carson AJ, Ringbauer B, Stone J, McKenzie L, Warlow C, Sharpe M (2000). "Do medically unexplained symptoms matter? A prospective cohort study of 300 new referrals to neurology outpatient clinics". J. Neurol. Neurosurg. Psychiatr. 68 (2): 207–10. doi:10.1136/jnnp.68.2.207. PMC 1736779. PMID 10644789.
- Nimnuan C, Hotopf M, Wessely S (2001). "Medically unexplained symptoms: an epidemiological study in seven specialities". J Psychosom Res. 51 (1): 361–7. PMID 11448704.
- Snijders TJ, de Leeuw FE, Klumpers UM, Kappelle LJ, van Gijn J (2004). "Prevalence and predictors of unexplained neurological symptoms in an academic neurology outpatient clinic--an observational study". J. Neurol. 251 (1): 66–71. doi:10.1007/s00415-004-0273-y. PMID 14999491.
- Crimlisk HL, Bhatia KP, Cope H, David AS, Marsden D, Ron MA (2000). "Patterns of referral in patients with medically unexplained motor symptoms". J Psychosom Res. 49 (3): 217–9. doi:10.1016/s0022-3999(00)00167-7. PMID 11110993.
- Stefánsson JG, Messina JA, Meyerowitz S (1976). "Hysterical neurosis, conversion type: clinical and epidemiological considerations". Acta Psychiatr Scand. 53 (2): 119–38. doi:10.1111/j.1600-0447.1976.tb00066.x. PMID 1251758.
- Deveci A, Taskin O, Dinc G, Yilmaz H, Demet MM, Erbay-Dundar P, Kaya E, Ozmen E (2007). "Prevalence of pseudoneurologic conversion disorder in an urban community in Manisa, Turkey". Soc Psychiatry Psychiatr Epidemiol. 42 (11): 857–64. doi:10.1007/s00127-007-0233-9. PMID 17639308.
- Tomasson K, Kent D, Coryell W (1991). "Somatization and conversion disorders: comorbidity and demographics at presentation". Acta Psychiatr Scand. 84 (3): 288–93. doi:10.1111/j.1600-0447.1991.tb03146.x. PMID 1950631.
- Kuloglu M, Atmaca M, Tezcan E, Gecici O, Bulut S (2003). "Sociodemographic and clinical characteristics of patients with conversion disorder in Eastern Turkey". Soc Psychiatry Psychiatr Epidemiol. 38 (2): 88–93. doi:10.1007/s00127-003-0608-5. PMID 12563551.
- Breuer and Freud, "Studies in Hysteria", 1895
- ( Breuer and Freud, *Studies on Hysteria* Basic Books, Inc. 2000, pg.96).