In China, traditional treatment based on the causes suggested by cultural beliefs are administrated to the patient. Praying to gods and asking Taoist priests to perform exorcism is common. If a fox spirit is believed to be involved, people may hit gongs or beat the person to drive it out. The person will receive a yang- or yin-augmenting Chinese medicine potion, usually including herbs, pilose antler (stag of deer) or deer tail, and tiger penis, deer penis, or fur seal penis. Other foods for therapy are pepper soup, ginger soup and liquor.

There is a general lack of consensus in the diagnosis and treatment of DID and research on treatment effectiveness focuses mainly on clinical approaches described in case studies. General treatment guidelines exist that suggest a phased, eclectic approach with more concrete guidance and agreement on early stages but no systematic, empirically-supported approach exists and later stages of treatment are not well described and have no consensus. Even highly experienced therapists have few patients that achieve a unified identity. Common treatment methods include an eclectic mix of psychotherapy techniques, including cognitive behavioral therapy (CBT), insight-oriented therapies, dialectical behavioral therapy (DBT), hypnotherapy and eye movement desensitization and reprocessing (EMDR). Medications can be used for comorbid disorders or targeted symptom relief. Some behavior therapists initially use behavioral treatments such as only responding to a single identity, and then use more traditional therapy once a consistent response is established. Brief treatment due to managed care may be difficult, as individuals diagnosed with DID may have unusual difficulties in trusting a therapist and take a prolonged period to form a comfortable therapeutic alliance. Regular contact (weekly or biweekly) is more common, and treatment generally lasts years—not weeks or months. Sleep hygiene has been suggested as a treatment option, but has not been tested. In general there are very few clinical trials on the treatment of DID, none of which were randomized controlled trials.

Therapy for DID is generally phase oriented. Different alters may appear based on their greater ability to deal with specific situational stresses or threats. While some patients may initially present with a large number of alters, this number may reduce during treatment—though it is considered important for the therapist to become familiar with at least the more prominent personality states as the "host" personality may not be the "true" identity of the patient. Specific alters may react negatively to therapy, fearing the therapist's goal is to eliminate the alter (particularly those associated with illegal or violent activities). A more realistic and appropriate goal of treatment is to integrate adaptive responses to abuse, injury or other threats into the overall personality structure. There is debate over issues such as whether exposure therapy (reliving traumatic memories, also known as abreaction), engagement with alters and physical contact during therapy are appropriate and there are clinical opinions both for and against each option with little high-quality evidence for any position.

Brandt et al., noting the lack of empirical studies of treatment effectiveness, conducted a survey of 36 clinicians expert in treating dissociative disorder (DD) who recommended a three-stage treatment. They agreed that skill building in the first stage is important so the patient can learn to handle high risk, potentially dangerous behavior, as well as emotional regulation, interpersonal effectiveness and other practical behaviors. In addition, they recommended "trauma-based cognitive therapy" to reduce cognitive distortions related to trauma; they also recommended that the therapist deal with the dissociated identities early in treatment. In the middle stage, they recommended graded exposure techniques, along with appropriate interventions as needed. The treatment in the last stage was more individualized; few with DD became integrated into one identity.

The International Society for the Study of Trauma and Dissociation has published guidelines to phase-oriented treatment in adults as well as children and adolescents that are widely used in the field of DID treatment. The first phase of therapy focuses on symptoms and relieving the distressing aspects of the condition, ensuring the safety of the individual, improving the patient's capacity to form and maintain healthy relationships, and improving general daily life functioning. Comorbid disorders such as substance abuse and eating disorders are addressed in this phase of treatment. The second phase focuses on stepwise exposure to traumatic memories and prevention of re-dissociation. The final phase focuses on reconnecting the identities of disparate alters into a single functioning identity with all its memories and experiences intact.

A study was conducted with the goal of developing an "expertise-based prognostic model for the treatment of complex posttraumatic stress disorder (PTSD) and dissociative identity disorder (DID)". Researchers constructed a two-stage survey and factor analyses performed on the survey elements found 51 factors common to complex PTSD and DID. The authors concluded from their findings: "The model is supportive of the current phase-oriented treatment model, emphasizing the strengthening of the therapeutic relationship and the patient's resources in the initial stabilization phase. Further research is needed to test the model's statistical and clinical validity."

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:

1. 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 a neutral-cause-based 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.

2. Physiotherapy where appropriate;

3. Occupational Therapy to maintain autonomy in activities of daily living;

4. 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.

Piblokto, also known as pibloktoq and Arctic hysteria, is a condition most commonly appearing in Inughuit (Greenlandic Inuit) societies living within the Arctic Circle. Piblokto is a culture-specific hysterical reaction in Inuit, especially women, who may perform irrational or dangerous acts, followed by amnesia for the event. Piblokto may be linked to repression of the personality of Inuit women. The condition appears most commonly in winter. It is considered to be a form of a culture-bound syndrome, although more recent studies (see "Skepticism" section) question whether it exists at all. Piblokto is also part of the glossary of cultural bound syndromes found in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

Electroconvulsive therapy (ECT) is sometimes used in severe cases when other interventions for severe intractable depression have failed. Psychosurgery is considered experimental but is advocated by some neurologists in certain rare cases.

Counseling (professional) and co-counseling (between peers) may be used. Psychoeducation programs may provide people with the information to understand and manage their problems. Creative therapies are sometimes used, including music therapy, art therapy or drama therapy. Lifestyle adjustments and supportive measures are often used, including peer support, self-help groups for mental health and supported housing or supported employment (including social firms). Some advocate dietary supplements.

Reasonable accommodations (adjustments and supports) might be put in place to help an individual cope and succeed in environments despite potential disability related to mental health problems. This could include an emotional support animal or specifically trained psychiatric service dog.

A major option for many mental disorders is psychiatric medication and there are several main groups. Antidepressants are used for the treatment of clinical depression, as well as often for anxiety and a range of other disorders. Anxiolytics (including sedatives) are used for anxiety disorders and related problems such as insomnia. Mood stabilizers are used primarily in bipolar disorder. Antipsychotics are used for psychotic disorders, notably for positive symptoms in schizophrenia, and also increasingly for a range of other disorders. Stimulants are commonly used, notably for ADHD.

Despite the different conventional names of the drug groups, there may be considerable overlap in the disorders for which they are actually indicated, and there may also be off-label use of medications. There can be problems with adverse effects of medication and adherence to them, and there is also criticism of pharmaceutical marketing and professional conflicts of interest.

Although there is no known cause for piblokto, Western scientists have attributed the disorder to the lack of sun, the extreme cold, and the desolate state of most villages in the region. A reason for this disorder present in this culture may be due to the isolation of their cultural group.

This culture-bound syndrome is possibly linked to vitamin A toxicity (hypervitaminosis A). The native Inughuit diet or Eskimo nutrition provides rich sources of vitamin A through the ingestion of livers, kidneys, and fat of arctic fish and mammals and is possibly the cause or a causative factor. This causative factor is through the disturbance that has been reported for males, females, adults, children, and dogs. The ingestion of organ meats, particularly the livers of some Arctic mammals, such as the polar bear and bearded seal, where the vitamin is stored in toxic quantities, can be fatal to most people.

Inughuit tradition states that it is caused by evil spirits possessing the living. Shamanism and animism are dominant themes in Inughuit traditional beliefs with the angakkuq (healer) acting as a mediator with the supernatural forces. Angakkuit use trance states to communicate with spirits and carry out faith healing. There is a view among the Inughuit that individuals entering trance states should be treated with respect given the possibility of a new "revelation" emerging as a result. Treatment in piblokto cases usually involves allowing the episode to run its course without interference. While piblokto can often be confused with other conditions, (including epilepsy) in which failure to intervene can lead to the victim coming to harm, most cases tend to be more typical.

In historical culture-bound cases, reassurance and talks on sexual anatomy are given. Patients are treated with psychotherapy distributed according to symptoms and to etiologically significant points in the past. Prognosis appears to be better in cases with a previously functional personality, a short history and low frequency of attacks, and a relatively uncomplicated sexual life.

For sporadic Western cases, careful diagnostic workup including searching for underlying sexual conflict is common. The choice of psychotherapeutic treatment is based on the psychiatric pathology found.

Individual therapy may be best suited to treat the individual's delusions. Persistence is needed in establishing a therapeutic empathy without validating the patient’s delusional system or overtly confronting the system. Cognitive techniques that include reality testing and reframing can be used. Antipsychotics and other therapeutic drugs have been used with relative success.

Another example of treatment besides coding is Functional Ideographic Assessment Template. The functional ideographic assessment template, also known as FIAT, was used as a way to generalize the clinical processes of functional analytic psychotherapy. The template was made by a combined effort of therapists and can be used to represent the behaviors that are a focus for this treatment. Using the FIAT therapists can create a common language to get stable and accurate communication results through functional analytic psychotherapy at the ease of the client; as well as the therapist.

As mentioned earlier, anti-anxiety, antidepressants and tranquilizers are treatment medications that do not cure, but help control the symptoms of dissociative disorders. The accepted mode of treatment are atypical neuroleptics such as Abilify, Zyprexa, Seroquel and Geodon. Newer-generation anticonvulsants are also highly effective. Quetiapine is initiated at 25–50 mg PO bid and increased by 50 mg PO bid q3d until symptom resolution is achieved. The higher dose should be administered nightly due to the strong sedation effects of the medicine. Other medications such as SSRIs and SNRIs may reduce the anxiety and apprehension of the dissociation.

Keppra may be effective in treating dissociation. Doses are usually kept much lower than for the treatment of seizure disorders. Lamotrigine started at 25 mg and increased by 25 mg every 2 weeks is another option. The effects of these novel anticonvulsants is thought to be secondary to GABA modulation.

Risk factors: People who experience chronic physical, sexual or emotional childhood abuse are at a greater risk of developing dissociative disorders. Children and adults experiencing other traumatic events (including war, natural disasters, kidnapping, torture and invasive medical procedures) also may develop these conditions.

No true psychiatric medications are prescribed for factitious disorder. However, selective serotonin reuptake inhibitors (SSRIs) can help manage underlying problems. Medicines such as SSRIs that are used to treat mood disorders can be used to treat FD, as a mood disorder may be the underlying cause of FD. Some authors (such as Prior and Gordon 1997) also report good responses to antipsychotic drugs such as Pimozide. Family therapy can also help. In such therapy, families are helped to better understand patients (the individual in the family with FD) and that person's need for attention.

In this therapeutic setting, the family is urged not to condone or reward the FD individual's behavior. This form of treatment can be unsuccessful if the family is uncooperative or displays signs of denial and/or antisocial disorder. Psychotherapy is another method used to treat the disorder. These sessions should focus on the psychiatrist's establishing and maintaining a relationship with the patient. Such a relationship may help to contain symptoms of FD. Monitoring is also a form that may be indicated for the FD patient's own good; FD (especially proxy) can be detrimental to an individual's health—if they are, in fact, causing true physiological illnesses. Even faked illnesses/injuries can be dangerous, and might be monitored for fear that unnecessary surgery may subsequently be performed.

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.

Folie à deux (; ; French for "madness of two"), or shared psychosis, is a psychiatric syndrome in which symptoms of a delusional belief and sometimes hallucinations are transmitted from one individual to another. The same syndrome shared by more than two people may be called "folie à trois", "folie à quatre", "folie en famille" ("family madness"), or even "folie à plusieurs" ("madness of many").

Recent psychiatric classifications refer to the syndrome as shared psychotic disorder (DSM-IV – 297.3) and induced delusional disorder (F24) in the ICD-10, although the research literature largely uses the original name. This disorder is not in the current DSM (DSM-5). The disorder was first conceptualized in 19th-century French psychiatry by Charles Lasègue and Jean-Pierre Falret and is also known as Lasègue-Falret syndrome.

Amafufunyana is an unspecified "culture-bound" syndrome named by the traditional healers of the Xhosa people that relates to claims of demonic possession due to members of the Xhosa people exhibiting aberrant behavior and psychological concerns. After study, it was discovered that this term is directed toward people suffering from varying types of schizophrenia. A similar term, ukuthwasa, is used to refer to positive types of claimed possession, though this event also involves those suffering from schizophrenia. It has also found cultural usage among some groups of Zulu peoples.

The direct translation of the term "amafufunyana" is nerves and is a part of a much more complex cultural ideology connecting varying types of psychosis with religious, social, and recently psychiatric beliefs and activities. In a 1998 interview with Xhosa people suffering from schizophrenia by Lund et al., it was determined that through interaction with scientists and psychological services, the preferred treatment for the cultural condition had shifted from relation to traditional healers to active psychiatric assessment.

Treatments for classic (winter-based) seasonal affective disorder include light therapy, medication, ionized-air administration, cognitive-behavioral therapy and carefully timed supplementation of the hormone melatonin.

Photoperiod-related alterations of the duration of melatonin secretion may affect the seasonal mood cycles of SAD. This suggests that light therapy may be an effective treatment for SAD. Light therapy uses a lightbox which emits far more lumens than a customary incandescent lamp. Bright white "full spectrum" light at 10,000 lux, blue light at a wavelength of 480 nm at 2,500 lux or green (actually cyan or blue-green) light at a wavelength of 500 nm at 350 lux are used, with the first-mentioned historically preferred.

Bright light therapy is effective with the patient sitting a prescribed distance, commonly 30–60 cm, in front of the box with her/his eyes open but not staring at the light source for 30–60 minutes. A study published in May 2010 suggests that the blue light often used for SAD treatment should perhaps be replaced by green or white illumination. Discovering the best schedule is essential. One study has shown that up to 69% of patients find lightbox treatment inconvenient and as many as 19% stop use because of this.

Dawn simulation has also proven to be effective; in some studies, there is an 83% better response when compared to other bright light therapy. When compared in a study to negative air ionization, bright light was shown to be 57% effective vs. dawn simulation 50%. Patients using light therapy can experience improvement during the first week, but increased results are evident when continued throughout several weeks. Most studies have found it effective without use year round but rather as a seasonal treatment lasting for several weeks until frequent light exposure is naturally obtained.

Light therapy can also consist of exposure to sunlight, either by spending more time outside or using a computer-controlled heliostat to reflect sunlight into the windows of a home or office. Although light therapy is the leading treatment for seasonal affective disorder, prolonged direct sunlight or artificial lights that don't block the ultraviolet range should be avoided due to the threat of skin cancer.

SSRI (selective serotonin reuptake inhibitor) antidepressants have proven effective in treating SAD. Effective antidepressants are fluoxetine, sertraline, or paroxetine. Both fluoxetine and light therapy are 67% effective in treating SAD according to direct head-to-head trials conducted during the 2006 Can-SAD study. Subjects using the light therapy protocol showed earlier clinical improvement, generally within one week of beginning the clinical treatment. Bupropion extended-release has been shown to prevent SAD for one in eight people, but has not been compared directly to other preventive options in trials.

Negative air ionization, which involves releasing charged particles into the sleep environment, has been found effective with a 47.9% improvement if the negative ions are in sufficient density (quantity).

Depending upon the patient, one treatment (e.g., lightbox) may be used in conjunction with another (e.g., medication).

Modafinil may be an effective and well-tolerated treatment in patients with seasonal affective disorder/winter depression.

Another explanation is that vitamin D levels are too low when people do not get enough Ultraviolet-B on their skin. An alternative to using bright lights is to take vitamin D supplements. However, studies did not show a link between vitamin D levels and depressive symptoms in elderly Chinese nor among elderly British women.

Physical exercise has shown to be an effective form of depression therapy, particularly when in addition to another form of treatment for SAD. One particular study noted marked effectiveness for treatment of depressive symptoms when combining regular exercise with bright light therapy. Patients exposed to exercise which had been added to their treatments in 20 minutes intervals on the aerobic bike during the day along with the same amount of time underneath the UV light were seen to make quick recovery.

Another way to treat histrionic personality disorder after identification is through functional analytic psychotherapy. The job of a Functional Analytic Psychotherapist is to identify the interpersonal problems with the patient as they happen in session or out of session. Initial goals of functional analytic psychotherapy are set by the therapist and include behaviors that fit the client's needs for improvement. Functional analytic psychotherapy differs from the traditional psychotherapy due to the fact that the therapist directly addresses the patterns of behavior as they occur in-session.

The in-session behaviors of the patient or client are considered to be examples of their patterns of poor interpersonal communication and to adjust their neurotic defenses. To do this, the therapist must act on the client's behavior as it happens in real time and give feedback on how the client's behavior is affecting their relationship during therapy. The therapist also helps the client with histrionic personality disorder by denoting behaviors that happen outside of treatment; these behaviors are termed "Outside Problems" and "Outside Improvements". This allows the therapist to assist in problems and improvements outside of session and to verbally support the client and condition optimal patterns of behavior". This then can reflect on how they are advancing in-session and outside of session by generalizing their behaviors over time for changes or improvement".

There are many different forms (modalities) of treatment used for personality disorders:

- Individual psychotherapy has been a mainstay of treatment. There are long-term and short-term (brief) forms.

- Family therapy, including couples therapy.

- Group therapy for personality dysfunction is probably the second most used.

- Psychological-education may be used as an addition.

- Self-help groups may provide resources for personality disorders.

- Psychiatric medications for treating symptoms of personality dysfunction or co-occurring conditions.

- Milieu therapy, a kind of group-based residential approach, has a history of use in treating personality disorders, including therapeutic communities.

- The practice of mindfulness that includes developing the ability to be nonjudgmentally aware of unpleasant emotions appears to be a promising clinical tool for managing different types of personality disorders.

There are different specific theories or schools of therapy within many of these modalities. They may, for example, emphasize psychodynamic techniques, or cognitive or behavioral techniques. In clinical practice, many therapists use an 'eclectic' approach, taking elements of different schools as and when they seem to fit to an individual client. There is also often a focus on common themes that seem to be beneficial regardless of techniques, including attributes of the therapist (e.g. trustworthiness, competence, caring), processes afforded to the client (e.g. ability to express and confide difficulties and emotions), and the match between the two (e.g. aiming for mutual respect, trust and boundaries).

Mass psychogenic illness (MPI), also called mass sociogenic illness or just sociogenic illness, is "the rapid spread of illness signs and symptoms affecting members of a cohesive group, originating from a nervous system disturbance involving excitation, loss, or alteration of function, whereby physical complaints that are exhibited unconsciously have no corresponding organic" cause. MPI is distinct from other collective delusions, also included under the blanket terms of mass hysteria, in that MPI causes symptoms of disease, though there is no organic cause.

There is a clear preponderance of female victims. The DSM-IV-TR does not have specific diagnosis for this condition but the text describing conversion disorder states that "In 'epidemic hysteria', shared symptoms develop in a circumscribed group of people following 'exposure' to a common precipitant."

"Jerusalem syndrome as a discrete form, uncompounded by previous mental illness." This describes the best-known type, whereby a previously mentally balanced person becomes psychotic after arriving in Jerusalem. The psychosis is characterised by an intense religious character and typically resolves to full recovery after a few weeks or after being removed from the locality. It shares some features with the diagnostic category of a "brief psychotic episode", although a distinct pattern of behaviors has been noted:

1. Anxiety, agitation, nervousness and tension, plus other unspecified reactions.

2. Declaration of the desire to split away from the group or the family and to tour Jerusalem alone. Tour guides aware of the Jerusalem syndrome and of the significance of such declarations may at this point refer the tourist to an institution for psychiatric evaluation in an attempt to preempt the subsequent stages of the syndrome. If unattended, these stages are usually unavoidable.

3. A need to be clean and pure: obsession with taking baths and showers; compulsive fingernail and toenail cutting.

4. Preparation, often with the aid of hotel bed-linen, of a long, ankle-length, toga-like gown, which is always white.

5. The need to shout psalms or verses from the Bible, or to sing hymns or spirituals loudly. Manifestations of this type serve as a warning to hotel personnel and tourist guides, who should then attempt to have the tourist taken for professional treatment. Failing this, the two last stages will develop.

6. A procession or march to one of Jerusalem's holy places, ex:The Western Wall.

7. Delivery of a sermon in a holy place. The sermon is typically based on a plea to humankind to adopt a more wholesome, moral, simple way of life. Such sermons are typically ill-prepared and disjointed.

8. Paranoid belief that a Jerusalem syndrome agency is after the individual, causing their symptoms of psychosis through poisoning and medicating.

Bar-El et al. reported 42 such cases over a period of 13 years, but in no case were they able to actually confirm that the condition was temporary.

"Jerusalem syndrome imposed on a previous psychotic illness." This refers to individuals already diagnosed as having a psychotic illness before their visit to Jerusalem. They have typically gone to the city because of the influence of religious ideas, often with a goal or mission in mind that they believe needs to be completed on arrival or during their stay. For example, an affected person may believe himself to be an important historical religious figure or may be influenced by important religious ideas or concepts (such as causing the coming of the Messiah or the second coming of Christ).

Dancing mania (also known as dancing plague, choreomania, St John's Dance and, historically, St. Vitus's Dance) was a social phenomenon that occurred primarily in mainland Europe between the 14th and 17th centuries. It involved groups of people dancing erratically, sometimes thousands at a time. The mania affected men, women, and children who danced until they collapsed from exhaustion. One of the first major outbreaks was in Aachen, in the Holy Roman Empire, in 1374, and it quickly spread throughout Europe; one particularly notable outbreak occurred in Strasbourg in 1518, also in the Holy Roman Empire.

Affecting thousands of people across several centuries, dancing mania was not an isolated event, and was well documented in contemporary reports. It was nevertheless poorly understood, and remedies were based on guesswork. Generally, musicians accompanied dancers, to help ward off the mania, but this tactic sometimes backfired by encouraging more to join in. There is no consensus among modern-day scholars as to the cause of dancing mania.

The several theories proposed range from religious cults being behind the processions to people dancing to relieve themselves of stress and put the poverty of the period out of their minds. It is, however, thought to have been a mass psychogenic illness in which the occurrence of similar physical symptoms, with no known physical cause, affect a large or small group of people as a form of social influence.

According to Balaratnasingam and Janca, “mass hysteria is to date a poorly understood condition. Little certainty exists regarding its” cause.

Besides the difficulties common to all research involving the social sciences, including a lack of opportunity for controlled experiments, mass sociogenic illness presents special difficulties to researchers in this field. Balaratnasingam and Janca report that the methods for “diagnosis of mass hysteria remains contentious. According to Timothy Jones of the Tennessee Department of Public Health, the effects resulting from MPI “can be difficult to differentiate from [those of] bioterrorism, rapidly spreading infection or acute toxic exposure.”

These troubles result from the residual diagnosis of MPI. Singer, of the Uniformed Schools of Medicine, puts the problems with such a diagnosis thus:

“[y]ou find a group of people getting sick, you investigate, you measure everything you can measure . . . and when you still can't find any physical reason, you say 'well, there's nothing else here, so let's call it a case of MPI.'” There is a lack of logic in an argument that proceeds: “There isn't anything, so it must be MPI.” It precludes the notion that an organic factor could have been overlooked. Nevertheless, running an extensive number of tests extends the probability of false positives.

British psychiatrist Simon Wesseley distinguishes between two forms of MPI:

- mass anxiety hysteria “consists of episodes of acute anxiety, occurring mainly in schoolchildren. Prior tension is absent and the rapid spread is by visual contact.”

- mass motor hysteria “consists of abnormalities in motor behaviour. It occurs in any age group and prior tension is present. Initial cases can be identified and the spread is gradual. . . . [T]he outbreak may be prolonged.”

While his definition is sometimes adhered to, others such as Ali-Gombe et al. of the University of Maiduguri, Nigeria contest Wesseley's definition and describe outbreaks with qualities of both mass motor hysteria and mass anxiety hysteria.

An evolutionary psychology explanation for this disorder, as well as for conversion disorder more generally, is that the symptom 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, and the gender difference in prevalence.

In Italy, a similar phenomenon was tarantism, in which the victims were said to have been poisoned by a tarantula or scorpion. Its earliest known outbreak was in the 13th century, and the only antidote known was to dance to particular music to separate the venom from the blood. It occurred only in the summer months. As with dancing mania, people would suddenly begin to dance, sometimes affected by a perceived bite or sting and were joined by others, who believed the venom from their own old bites was reactivated by the heat or the music. Dancers would perform a tarantella, accompanied by music which would eventually "cure" the victim, at least temporarily.

Some participated in further activities, such as tying themselves up with vines and whipping each other, pretending to sword fight, drinking large amounts of wine, and jumping into the sea. Some died if there was no music to accompany their dancing. Sufferers typically had symptoms resembling those of dancing mania, such as headaches, trembling, twitching and visions.

As with dancing mania, participants apparently did not like the color black, and women were reported to be most affected. Unlike dancing mania, tarantism was confined to Italy and southern Europe. It was common until the 17th century, but ended suddenly, with only very small outbreaks in Italy until as late as 1959.

A study of the phenomenon in 1959 by religious history professor Ernesto de Martino revealed that most cases of tarantism were probably unrelated to spider bites. Many participants admitted that they had not been bitten, but believed they were infected by someone who had been, or that they had simply touched a spider. The result was mass panic, with a "cure" that allowed people to behave in ways that were, normally, prohibited at the time. Despite their differences, tarantism and dancing mania are often considered synonymous.

This syndrome is most commonly diagnosed when the two or more individuals concerned live in proximity and may be socially or physically isolated and have little interaction with other people. Various sub-classifications of "folie à deux" have been proposed to describe how the delusional belief comes to be held by more than one person :

- Folie imposée is where a dominant person (known as the 'primary', 'inducer' or 'principal') initially forms a delusional belief during a psychotic episode and imposes it on another person or persons (known as the 'secondary', 'acceptor' or 'associate') with the assumption that the secondary person might not have become deluded if left to his or her own devices. If the parties are admitted to hospital separately, then the delusions in the person with the induced beliefs usually resolve without the need of medication.

- Folie simultanée describes either the situation where two people considered to suffer independently from psychosis influence the content of each other's delusions so they become identical or strikingly similar, or one in which two people "morbidly predisposed" to delusional psychosis mutually trigger symptoms in each other.

Folie à deux and its more populous cousins are in many ways a psychiatric curiosity. The current Diagnostic and Statistical Manual of Mental Disorders states that a person cannot be diagnosed as being delusional if the belief in question is one "ordinarily accepted by other members of the person's culture or subculture" (see entry for delusion). It is not clear at what point a belief considered to be delusional escapes from the "folie à..." diagnostic category and becomes legitimate because of the number of people holding it. When a large number of people may come to believe obviously false and potentially distressing things based purely on hearsay, these beliefs are not considered to be clinical delusions by the psychiatric profession and are labelled instead as mass hysteria.