MSbP is rare. A recent systematic study in Italy found that in a series of over 700 patients admitted to a pediatric ward, 4 cases met the diagnostic criteria for MSbP (0.53%). In this study, stringent diagnostic criteria were used, which required at least one test outcome or event that could not possibly have occurred without deliberate intervention by the MSbP person.

One study showed that in 93 percent of MSbP cases, the abuser is the mother or another female guardian or caregiver. This may be attributed to the prevalent socialization pattern that places females in the primary care-taking role. Of course, it could also be a gender trait rooted in genetics, as it is easy to see how females who seek attention as victims could gain an evolutionary advantage, while men seeking the same would be unfavoured for physical protection and mating. A psychodynamic model of this kind of maternal abuse exists.

MSbP may be more prevalent in the parents of those with a learning difficulty or mental incapacity, and as such the apparent patient could, in fact, be an adult.

Fathers and other male caregivers have been the perpetrators in only 7% of the cases studied. When they are not actively involved in the abuse, the fathers or male guardians of MSbP victims are often described as being distant, emotionally disengaged, and powerless. These men play a passive role in MSbP by being frequently absent from the home and rarely visiting the hospitalized child. Usually, they vehemently deny the possibility of abuse, even in the face of overwhelming evidence or their child's pleas for help.

Overall, male and female children are equally likely to be the victim of MSbP. In the few cases where the father is the perpetrator, however, the victim is three times more likely to be male.

Factitious disorder imposed on another, also known as Munchausen syndrome by proxy (MSbP), is a condition where a caregiver or spouse fabricates, exaggerates, or induces mental or physical health problems in those who are in their care, with the primary motive of gaining attention or sympathy from others. The name is derived from the term Munchausen syndrome, a psychiatric factitious disorder wherein those affected feign disease, illness, or psychological trauma to draw attention, sympathy, or reassurance to themselves. However, unlike Munchausen syndrome, in MSbP, the deception involves not themselves, but rather someone under the person's care. MSbP is primarily distinguished from other forms of abuse or neglect by the motives of the perpetrator. Some experts consider it to be an elusive, potentially lethal, and frequently misunderstood form of child abuse or medical neglect. However, others consider the concept to be problematic, since it is based largely on supposition regarding a person's motives, which can be open to radically different interpretations.

Factitious disorder imposed on another has also spawned much heated controversy within the legal and social services communities. In a handful of high-profile cases, mothers who have had several children die from sudden infant death syndrome have been declared to have MSbP. Based on MSbP testimony of an expert witness, they were tried for murder, convicted, and imprisoned for several years. In some cases, that testimony was later impeached, resulting in exoneration of those defendants.

Because there is uncertainty in treating suspected factitious disorder imposed on self, some advocate that health care providers first explicitly rule out the possibility that the person has another early-stage disease. Then they may take a careful history and seek medical records to look for early deprivation, childhood abuse, or mental illness. If a person is at risk to themself, psychiatric hospitalization may be initiated.

Healthcare providers may consider working with mental health specialists to help treat the underlying mood or disorder as well as to avoid countertransference. Therapeutic and medical treatment may center on the underlying psychiatric disorder: a mood disorder, an anxiety disorder, or borderline personality disorder. The patient's prognosis depends upon the category under which the underlying disorder falls; depression and anxiety, for example, generally respond well to medication and/or cognitive behavioral therapy, whereas borderline personality disorder, like all personality disorders, is presumed to be pervasive and more stable over time, and thus offers a worse prognosis.

People affected may have multiple scars on their abdomen due to repeated "emergency" operations.

In factitious disorder imposed on self, the affected person exaggerates or creates symptoms of illnesses in themselves to gain examination, treatment, attention, sympathy, and/or comfort from medical personnel. In some extreme cases, people suffering from Munchausen syndrome are highly knowledgeable about the practice of medicine and are able to produce symptoms that result in lengthy and costly medical analysis, prolonged hospital stays, and unnecessary operations. The role of "patient" is a familiar and comforting one, and it fills a psychological need in people with this syndrome. This disorder is distinct from hypochondriasis and other somatoform disorders in that those with the latter do not intentionally produce their somatic symptoms. Munchausen syndrome is distinct from other psychiatric disorders such as malingering in that Munchausen does not fabricate symptoms for material gain such as financial compensation, absence from work, or access to drugs.

Risk factors for developing factitious disorder include childhood traumas, growing up with parents/caretakers who were emotionally unavailable due to illness or emotional problems, a serious illness as a child, failed aspirations to work in the medical field, personality disorders, and low self-esteem. Factitious disorder is more common in men and is seen in young or middle-aged adults. Those with a history of working in healthcare are also at greater risk of developing it.

Arrhythmogenic Munchausen syndrome describes individuals who simulate or stimulate cardiac arrhythmias to gain medical attention.

A similar behavior called factitious disorder imposed on another has been documented in the parent or guardian of a child. The adult ensures that his or her child will experience some medical affliction, therefore compelling the child to suffer through treatments and spend a significant portion of their youth in hospitals. Furthermore, a disease may actually be initiated in the child by the parent or guardian. This condition is considered distinct from Munchausen syndrome. There is growing consensus in the pediatric community that this disorder should be renamed "medical abuse" to highlight the harm caused by the deception and to make it less likely that a perpetrator can use a psychiatric defense when harm is done.

The symptoms most commonly feigned include those associated with mild head injury, fibromyalgia, chronic fatigue syndrome, and chronic pain. Generally, malingerers complain of psychological disorders such as anxiety. Malingering may take the form of dishonest complaints of chronic whiplash pain from automobile accidents. The psychological symptoms experienced by survivors of disaster (post-traumatic stress disorder) are also faked by malingerers.

Individuals use a variety of methods to feign symptoms of illness. Some of these include harming oneself, trying to convince medical professionals one has a disease after learning about its details (such as symptoms) in medical textbooks, taking drugs that provoke certain symptoms common in some diseases, performing excess exercise to induce muscle strain or other physical types of ailments, and overdosing on drugs.

There are many possible causes for this disorder. One such possibility is an underlying personality disorder. Individuals with FD may be trying to repeat a satisfying childhood relationship with a doctor. Perhaps also an individual has a desire to deceive or test authority figures. The underlying desire to resume the role of a patient and be cared for can also be considered an underlying personality disorder. Abuse, neglect, or abandonment during childhood are also probable causes.

These individuals may be trying to reenact unresolved issues with their parents. A history of frequent illnesses may also contribute to the development of this disorder. In some cases, individuals afflicted with FD are accustomed to actually being sick, and thus return to their previous state to recapture what they once considered the 'norm.' Another cause is a history of close contact with someone (a friend or family member) who had a severe or chronic condition. The patients found themselves subconsciously envious of the attention said relation received, and felt that they themselves faded into the background. Thus medical attention makes them feel glamorous and special.

Malingering is the fabricating of symptoms of mental or physical disorders for a variety of reasons such as financial compensation (often tied to fraud); avoiding school, work or military service; obtaining drugs; or as a mitigating factor for sentencing in criminal cases. It is not a medical diagnosis. Malingering is typically conceptualized as being distinct from other forms of excessive illness behaviour such as somatization disorder and factitious disorder, e.g., in DSM-5, although not all mental health professionals agree with this formulation.

Failure to detect actual cases of malingering imposes an economic burden on health care systems; workers compensation programs; and disability programs, e.g., Social Security Disability Insurance (United States) and U.S. Department of Veterans Affairs disability benefits. False attribution of malingering often harms genuine patients or claimants.

Some individuals experience only a few outbreaks of the disorder. However, in most cases, factitious disorder is a chronic and long-term condition that is difficult to treat. There are relatively few positive outcomes for this disorder; in fact, treatment provided a lower percentage of positive outcomes than did treatment of individuals with obvious psychotic symptoms such as people with schizophrenia. In addition, many individuals with factitious disorder do not present for treatment, often insisting their symptoms are genuine. Some degree of recovery, however, is possible. The passage of time seems to help the disorder greatly. There are many possible explanations for this occurrence, although none are currently considered definitive. It may be that an FD individual has mastered the art of feigning sickness over so many years of practice that the disorder can no longer be discerned. Another hypothesis is that many times an FD individual is placed in a home, or experiences health issues that are not self-induced or feigned. In this way, the problem with obtaining the 'patient' status is resolved because symptoms arise without any effort on the part of the individual.

Risk factors for mental illness include genetic inheritance, such as parents having depression, or a propensity for high neuroticism or "emotional instability".

In depression, parenting risk factors include parental unequal treatment, and there is association with high cannabis use.

In schizophrenia and psychosis, risk factors include migration and discrimination, childhood trauma, bereavement or separation in families, and abuse of drugs, including cannabis, and urbanicity.

In anxiety, risk factors may include family history (e.g. of anxiety), temperament and attitudes (e.g. pessimism), and parenting factors including parental rejection, lack of parental warmth, high hostility, harsh discipline, high maternal negative affect, anxious childrearing, modelling of dysfunctional and drug-abusing behaviour, and child abuse (emotional, physical and sexual).

Environmental events surrounding pregnancy and birth have also been implicated. Traumatic brain injury may increase the risk of developing certain mental disorders. There have been some tentative inconsistent links found to certain viral infections, to substance misuse, and to general physical health.

Social influences have been found to be important, including abuse, neglect, bullying, social stress, traumatic events and other negative or overwhelming life experiences. For bipolar disorder, stress (such as childhood adversity) is not a specific cause, but does place genetically and biologically vulnerable individuals at risk for a more severe course of illness. The specific risks and pathways to particular disorders are less clear, however. Aspects of the wider community have also been implicated, including employment problems, socioeconomic inequality, lack of social cohesion, problems linked to migration, and features of particular societies and cultures.

During a period of 13 years (1980–1993) for which admissions to the Kfar Shaul Mental Health Centre in Jerusalem were analysed, it was reported that 1,200 tourists with severe, Jerusalem-themed mental problems were referred to this clinic. Of these, 470 were admitted to hospital. On average, 100 such tourists have been seen annually, 40 of them requiring admission to hospital. About three and a half million tourists visit Jerusalem each year. Kalian and Witztum note that as a proportion of the total numbers of tourists visiting the city, this is not significantly different from any other city.

Munchausen by Internet is a pattern of behavior akin to Munchausen syndrome (renamed factitious disorder imposed on self), a psychiatric disorder, wherein those affected feign disease, illness, or psychological trauma to draw attention, sympathy, or reassurance to themselves. In Munchausen by internet, users seek attention by feigning illnesses in online venues such as chat rooms, message boards, and Internet Relay Chat (IRC). It has been described in medical literature as a manifestation of factitious disorder imposed on self, or if claiming illness of a child or other family member, factitious disorder imposed on another. Reports of users who deceive Internet forum participants by portraying themselves as gravely ill or as victims of violence first appeared in the 1990s due to the relative newness of Internet communications. The pattern was identified in 1998 by psychiatrist Marc Feldman, who created the term "Münchausen by Internet" in 2000. It is not included in the fifth revision of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5).

The development of factitious disorders in online venues is made easier by the availability of medical literature on the Internet, the anonymous and malleable nature of online identities, and the existence of communication forums established for the sole purpose of giving support to members facing significant health or psychological problems. Several high-profile cases have demonstrated behavior patterns which are common among those who pose as gravely ill or as victims of violence, or whose deaths are announced to online forums. The virtual communities that were created to give support, as well as general non-medical communities, often express genuine sympathy and grief for the purported victims. When fabrications are suspected or confirmed, the ensuing discussion can create schisms in online communities, destroying some and altering the trusting nature of individual members in others.

The term "Munchausen by Internet" was first used in an article published in the "Southern Medical Journal" written by Marc Feldman in 2000. Feldman, a clinical professor of psychiatry at the University of Alabama at Birmingham, gave a name to the phenomenon in 2000, but he co-authored an article on the topic two years earlier in the "Western Journal of Medicine", using the description "virtual factitious disorder". Factitious disorders are described in the "Diagnostic and Statistical Manual of Mental Disorders: DSM-IV-TR" (DSM) as psychological disorders involving the production of non-existent physical or psychological ailments to earn sympathy. These illnesses are feigned not for monetary gain or to avoid inconvenient situations, but to attract compassion or to control others. Chronic manifestation of factitious disorder is often called Munchausen syndrome, after a book about the exaggerated accounts of the adventures of Baron Munchausen, a German cavalry officer in the Russian Army, that was written by Rudolf Erich Raspe. When the symptoms of another person, such as a child or an elderly parent, are purposely induced by the caregiver, it is called factitious disorder imposed on another, or Munchausen syndrome by proxy.

Feldman noted that the advent of online support groups, combined with access to vast stores of medical information, enabled individuals seeking to gain sympathy by relating a series of harrowing medical or psychological problems that defy comprehension to misuse the groups. Communication forums specializing in medical or psychological recovery were established to give lay users support in navigating often confusing and frustrating medical processes and bureaucracy. Communities often formed on those forums, with the goal of sharing information to help other members. Medical websites also became common, giving lay users access to literature in a way that was accessible to those without specific medical training. As Internet communication grew in popularity, users began to forgo the doctors and hospitals often consulted for medical advice. Frequenting virtual communities that have experience with a medical problem, Feldman notes, is easier than going through the physical pain or illness that would be necessary before visiting a doctor to get the attention sought. By pretending to be gravely ill, Internet users can gain sympathy from a group whose sole reason for existence is support. Health care professionals, with their limited time, greater medical knowledge, and tendency to be more skeptical in their diagnoses, may be less likely to provide that support.

Jerusalem syndrome is a group of mental phenomena involving the presence of either religiously themed obsessive ideas, delusions or other psychosis-like experiences that are triggered by a visit to the city of Jerusalem. It is not endemic to one single religion or denomination but has affected Jews, Christians, and Muslims of many different backgrounds.

The best known, although not the most prevalent, manifestation of Jerusalem syndrome is the phenomenon whereby a person who seems previously balanced and devoid of any signs of psychopathology becomes psychotic after arriving in Jerusalem. The psychosis is characterised by an intense religious theme and typically resolves to full recovery after a few weeks or after being removed from the area. The religious focus of Jerusalem syndrome distinguishes it from other phenomena, such as Stendhal syndrome in Florence or Paris syndrome for Japanese tourists.

In a 2000 article in the "British Journal of Psychiatry", Bar-El et al. claim to have identified and described a specific syndrome which emerges in tourists with no previous psychiatric history. However, this claim has been disputed by M. Kalian and E. Witztum. Kalian and Witztum stressed that nearly all of the tourists who demonstrated the described behaviours were mentally ill prior to their arrival in Jerusalem. They further noted that, of the small proportion of tourists alleged to have exhibited spontaneous psychosis after arrival in Jerusalem, Bar-El et al. had presented no evidence that the tourists had been well prior to their arrival in the city. Jerusalem syndrome is not listed or mentioned in the DSM nor in the ICD.

Despite public or media opinion, national studies have indicated that severe mental illness does not independently predict future violent behavior, on average, and is not a leading cause of violence in society. There is a statistical association with various factors that do relate to violence (in anyone), such as substance abuse and various personal, social and economic factors. A 2015 review found that in the United States, about 4% of violence is attributable to people diagnosed with mental illness, and a 2014 study found that 7.5% of crimes committed by mentally ill people were directly related to the symptoms of their mental illness. The majority of people with serious mental illness are never violent.

In fact, findings consistently indicate that it is many times more likely that people diagnosed with a serious mental illness living in the community will be the victims rather than the perpetrators of violence. In a study of individuals diagnosed with "severe mental illness" living in a US inner-city area, a quarter were found to have been victims of at least one violent crime over the course of a year, a proportion eleven times higher than the inner-city average, and higher in every category of crime including violent assaults and theft. People with a diagnosis may find it more difficult to secure prosecutions, however, due in part to prejudice and being seen as less credible.

However, there are some specific diagnoses, such as childhood conduct disorder or adult antisocial personality disorder or psychopathy, which are defined by, or are inherently associated with, conduct problems and violence. There are conflicting findings about the extent to which certain specific symptoms, notably some kinds of psychosis (hallucinations or delusions) that can occur in disorders such as schizophrenia, delusional disorder or mood disorder, are linked to an increased risk of serious violence on average. The mediating factors of violent acts, however, are most consistently found to be mainly socio-demographic and socio-economic factors such as being young, male, of lower socioeconomic status and, in particular, substance abuse (including alcoholism) to which some people may be particularly vulnerable.

High-profile cases have led to fears that serious crimes, such as homicide, have increased due to deinstitutionalization, but the evidence does not support this conclusion. Violence that does occur in relation to mental disorder (against the mentally ill or by the mentally ill) typically occurs in the context of complex social interactions, often in a family setting rather than between strangers. It is also an issue in health care settings and the wider community.

A monothematic delusion is a delusional state that concerns only one particular topic. This is contrasted by what is sometimes called "multi-thematic" or "polythematic" delusions where the person has a range of delusions (typically the case of schizophrenia). These disorders can occur within the context of schizophrenia or dementia or they can occur without any other signs of mental illness. When these disorders are found outside the context of mental illness, they are often caused by organic dysfunction as a result of traumatic brain injury, stroke, or neurological illness.

People who experience these delusions as a result of organic dysfunction often do not have any obvious intellectual deficiency nor do they have any other symptoms. Additionally, a few of these people even have some awareness that their beliefs are bizarre, yet they cannot be persuaded that their beliefs are false.

The delusions that fall under this category are:

- Capgras delusion: the belief that (usually) a close relative or spouse has been replaced by an identical-looking impostor.

- Fregoli delusion: the belief that various people whom the believer meets are actually the same person in disguise.

- Intermetamorphosis: the belief that people in one's environment swap identities with each other while maintaining the same appearance.

- Subjective doubles: a person believes there is a doppelgänger or double of him- or herself carrying out independent actions.

- Cotard delusion: the belief that oneself is dead or does not exist; sometimes coupled with the belief that one is putrefying or missing internal organs.

- Mirrored-self misidentification: the belief that one's reflection in a mirror is some other person.

- Reduplicative paramnesia: the belief that a familiar person, place, object, or body part has been duplicated. For example, a person may believe that they are, in fact, not in the hospital to which they were admitted, but in an identical-looking hospital in a different part of the country.

- Somatoparaphrenia: the delusion where one denies ownership of a limb or an entire side of one's body (often connected with stroke).

Note that some of these delusions are sometimes grouped under the umbrella term of delusional misidentification syndrome.

The hypothesis that those prone to extroversion or neuroticism, or those with low IQ scores, are more likely to be affected in an outbreak of hysterical epidemic has not been consistently supported by research. Bartholomew and Wesseley state that it “seems clear that there is no particular predisposition to mass sociogenic illness and it is a behavioural reaction that anyone can show in the right circumstances.”

Females are affected with mass psychogenic illness at greater rates than males. Adolescents and children are frequently affected in cases of MPI.

Diplomatic illness is the practice amongst diplomats and government ministers of feigning illness, or another debilitating condition, to avoid engaging in diplomatic or social engagements. The excuse of ill-health is designed to avoid formally offending the host or other parties. The term also refers to the period during which the "diplomatic illness" is claimed to persist.

The mental health community does not recognize work aversion as an illness or disease and therefore no medically recognized treatments exist. Those attempting to treat work aversion as an illness may use psychotherapy, counseling, medication, or some more unusual forms of treatment.

In the case where the person has not worked for a while due to a workplace injury, work-hardening can be used to build strength. The person works for a brief period of time in the first week, such as two hours per day and increases the amount of work each week until full-time hours are reached.

Pseudoneurotic schizophrenia is a postulated mental disorder categorized by the presence of two or more symptoms of mental illness such as anxiety, hysteria, and phobic or obsessive-compulsive neuroses. It is often acknowledged as a personality disorder. Patients generally display salient anxiety symptoms that disguise an underlying psychotic disorder.

In the 1940s, psychiatrists Paul Hoch and Philip Polatin created the term pseudoneurotic schizophrenia. This mental illness, however, is no longer acknowledged as a clinical entity. In 1972 it went on to be called borderline personality disorder, a term coined by Otto Friedmann Kernberg, which referred to an expansive range of issues.

Pseudoneurotic schizophrenia is in the Russian adapted version of the ICD-10 (code F21.3).

Work aversion usually occurs in persons who have previously been employed, and can have a variety of causes. These include:

- Boredom with work: Holding a boring job early in life can lead to the impression later that all work is boring.

Although medication is the first-line treatment for most psychiatric disorders, it does not always improve every aspect of a patient's life, and for the negative symptoms in schizophrenia, the responses to anti-psychotics are less favourable than for positive symptoms. As a result, psychotherapy might be an alternative for the treatment of these symptoms, even if medication has a good effect on other manifestations of the disorder.

Cognitive behavioural therapy (CBT), is the kind of psychotherapy that shows most promise in treating avolition (and other negative symptoms of schizophrenia), but more research is needed in the area. CBT focuses on understanding how thoughts and feelings influence behaviour, in order to help individuals develop methods and strategies to better handle the implications of their disorder. Some research suggests that CBT focusing on social skills and practice of interpersonal situations, like job interviews, seeing a doctor (to discuss medication, for example), or interacting with friends and co-workers, as well as seemingly simple things like riding a bus, might reduce negative symptoms of schizophrenia and be beneficial to patients with avolition.

Other forms of psychotherapy might also complement the role of medication and help patients, their families, and friends to work through emotional and other challenges of living with a chronic psychological disorder, including avolition.

Implications from avolition often result in social deficits. Not being able to initiate and perform purposeful activities can have many implications for a person with avolition. By disrupting interactions with both familiar and unfamiliar people, it jeopardizes the patient's social relations. When part of a severe mental illness, avolition has been reported, in first person accounts, to lead to physical and mental inability to both initiate and maintain relationships, as well as work, eat, drink or even sleep.

Clinically, it may be difficult to engage an individual experiencing avolition in active participation of psychotherapy. Patients are also faced with the stresses of coping with and accepting a mental illness and the stigma that often accompanies such a diagnosis and its symptoms. Regarding schizophrenia, the American Psychiatric Association reported in 2013 that there currently are "no treatments with proven efficacy for primary negative symptoms" (such as avolition). Together with schizophrenia's chronic nature, such facts added to the outlook of never getting well, might further implicate feelings of hopelessness and similar in patients as well as their friends and family.

Another theory is that there may be shared risk factors that can lead to both substance abuse and mental illness. Mueser hypothesizes that these may include factors such as social isolation, poverty, lack of structured daily activity, lack of adult role responsibility, living in areas with high drug availability, and association with people who already misuse drugs.

Other evidence suggests that traumatic life events, such as sexual abuse, are associated with the development of psychiatric problems and substance abuse.

Timothy F. Jones, of the Tennessee Department of Health, recommends the following action be taken in the case of an outbreak:

- Attempt to separate persons with illness associated with the outbreak.

- Promptly perform physical examination and basic laboratory testing sufficient to exclude serious acute illness.

- Monitor and provide oxygen as necessary for hyperventilation.

- Minimize unnecessary exposure to medical procedures, emergency personnel, media or other potential anxiety-stimulating situations.

- Notify public health authorities of apparent outbreak.

- Openly communicate with physicians caring for other patients.

- Promptly communicate results of laboratory and environmental testing to patients.

- While maintaining confidentiality, explain that other people are experiencing similar symptoms and improving without complications.

- Remind patients that rumors and reports of "suspected causes" are not equivalent to confirmed results.

- Acknowledge that symptoms experienced by the patient are real.

- Explain potential contribution of anxiety to the patient's symptoms.

- Reassure patient that long-term sequelae from current illness are not expected.

- As appropriate, reassure patient that thorough clinical, epidemiologic and environmental investigations have identified no toxic cause for the outbreak or reason for further concern.

Some responses by authorities to MPI are not appropriate. Intense media coverage seems to exacerbate outbreaks. Once it is determined that the illness is psychogenic, it should not be given credence by authorities. For example, in the Singapore factory case study, calling in a medicine man to perform an exorcism seemed to perpetuate the outbreak.