In factitious disorder imposed on another, a caregiver makes a dependent person appear mentally or physically ill in order to gain attention. To perpetuate the medical relationship, the caregiver systematically misrepresents symptoms, fabricates signs, manipulates laboratory tests, or even purposely harms the dependent (e.g. by poisoning, suffocation, infection, physical injury). Studies have shown a mortality rate of between 6% and 10%, making it perhaps the most lethal form of abuse.

At the time of diagnosis, the average age of the persons affected was 4 years. Slightly over 50% were aged 24 months or younger, and 75% were under 6 years old. The average duration from onset of symptoms to diagnosis was 22 months. By the time of diagnosis, 6% of the affected persons were dead, mostly from apnea (a common result of smothering) or starvation, and 7% suffered long-term or permanent injury. About half of the affected had siblings; 25% of the known siblings were dead, and 61% of siblings had symptoms similar to the affected or that was otherwise suspicious. The mother was the perpetrator in 76.5% of the cases, the father in 6.7%.

Most present about 3 medical problems in some combination of the 103 different reported symptoms. The most frequently reported problems are apnea (26.8% of cases), anorexia / feeding problems (24.6% of cases), diarrhea (20%), seizures (17.5%), cyanosis (blue skin) (11.7%), behavior (10.4%), asthma (9.5%), allergy (9.3%), and fevers (8.6%). Other symptoms include failure to thrive, vomiting, bleeding, rash and infections. Many of these symptoms are easy to fake because they are subjective. A parent reporting that their child had a fever in the past 24 hours is making a claim that is impossible to prove or disprove. The number and variety of presented symptoms contribute to the difficulty in reaching a proper MSbP diagnosis.

Aside from the motive (which is to gain attention or sympathy), another feature that differentiates MSbP from "typical" physical child abuse is the degree of premeditation involved. Whereas most physical abuse entails lashing out at a child in response to some behavior (e.g., crying, bedwetting, spilling food), assaults on the MSbP victim tend to be unprovoked and planned.

Also unique to this form of abuse is the role that health care providers play by actively, albeit unintentionally, enabling the abuse. By reacting to the concerns and demands of perpetrators, medical professionals are manipulated into a partnership of child maltreatment. Challenging cases that defy simple medical explanations may prompt health care providers to pursue unusual or rare diagnoses, thus allocating, even more, time to the child and the abuser. Even without prompting, medical professionals may be easily seduced into prescribing diagnostic tests and therapies that are at best uncomfortable and costly, and at worst potentially injurious to the child. If the health practitioner instead resists ordering further tests, drugs, procedures, surgeries, or specialists, the MSbP abuser makes the medical system appear negligent for refusing to help a poor sick child and their selfless parent. Like those with Munchausen syndrome, MSbP perpetrators are known to switch medical providers frequently until they find one that is willing to meet their level of need; this practice is known as "doctor shopping" or "hospital hopping".

The perpetrator continues the abuse because maintaining the child in the role of patient satisfies the abuser's needs. The cure for the victim is to separate the child completely from the abuser. When parental visits are allowed, sometimes there is a disastrous outcome for the child. Even when the child is removed, the perpetrator may then abuse another child: a sibling or other child in the family.

Factitious disorder imposed on another can have many long-term emotional effects on a child. Depending on their experience of medical interventions, a percentage of children may learn that they are most likely to receive the positive maternal attention they crave when they are playing the sick role in front of health care providers. Several case reports describe Munchausen syndrome patients suspected of themselves having been MSbP victims. Seeking personal gratification through illness can thus become a lifelong and multi-generational disorder in some cases. In stark contrast, other reports suggest survivors of MSbP develop an avoidance of medical treatment with post-traumatic responses to it. This variation possibly reflects broad statistics on survivors of child abuse in general, where around 30% go on to also become abusers even though a significant percentage do not.

The adult care provider who has abused the child often seems comfortable and not upset over the child's hospitalization. While the child is hospitalized, medical professionals must monitor the caregiver's visits to prevent an attempt to worsen the child's condition. In addition, in many jurisdictions, medical professionals have a duty to report such abuse to legal authorities.

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.

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.

Diagnosing factitious disorder imposed on self requires a clinical assessment. Clinicians should be aware that those presenting with symptoms (or persons reporting for that person) may malinger, and caution should be taken to ensure there is evidence for a diagnosis. Lab tests may be required, including complete blood count (CBC), urine toxicology, drug levels from blood, cultures, coagulation tests, assays for thyroid function, or DNA typing. In some cases CT scan, magnetic resonance imaging, psychological testing, electroencephalography, or electrocardiography may also be employed. A summary of more common and reported cases of factitious disorder (Munchausen syndrome), and the laboratory tests used to differentiate these from authentic disease is provided below:

There are several symptoms that together point to factitious disorder, including frequent hospitalizations, knowledge of several illnesses, frequently requesting medication such as pain killers, openness to extensive surgery, few or no visitors during hospitalizations, and exaggerated or fabricated stories about several medical problems. Factitious disorder should not be confused with hypochondria, as people with factitious disorder syndrome do not really believe they are sick; they only want to be sick, and thus fabricate the symptoms of an illness. It is also not the same as pretending to be sick for personal benefit such as being excused from work or school.

People may fake their symptoms in multiple ways. Other than making up past medical histories and faking illnesses, people might inflict harm on themselves by consuming laxatives or other substances, self-inflicting injury to induce bleeding, and altering laboratory samples.” Many of these conditions do not have clearly observable or diagnostic symptoms and sometimes the syndrome will go undetected because patients will fabricate identities when visiting the hospital several times. Factitious disorder has several complications, as these people will go to great lengths to fake their illness. Severe health problems, serious injuries, loss of limbs or organs, and even death are possible complications.

Factitious disorder imposed on self, also known as Munchausen syndrome, is a factitious disorder wherein those affected feign disease, illness, or psychological trauma to draw attention, sympathy, or reassurance to themselves. Munchausen syndrome fits within the subclass of factitious disorder with predominantly physical signs and symptoms, but patients also have a history of recurrent hospitalization, travelling, and dramatic, extremely improbable tales of their past experiences. The condition derives its name from Baron Munchausen.

Factitious disorder imposed on self is related to factitious disorder imposed on another, which refers to the abuse of another person, typically a child, in order to seek attention or sympathy for the abuser. This drive to create symptoms for the victim can result in unnecessary and costly diagnostic or corrective procedures.

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.

"Jerusalem syndrome superimposed on and complicated by idiosyncratic ideas." This does not necessarily take the form of mental illness and may simply be a culturally anomalous obsession with the significance of Jerusalem, either as an individual, or as part of a small religious group with idiosyncratic spiritual beliefs.

The motives of the patient can vary: for a patient with factitious disorder, the primary aim is to obtain sympathy, nurturance, and attention accompanying the sick role. This is in contrast to malingering, in which the patient wishes to obtain external gains such as disability payments or to avoid an unpleasant situation, such as military duty. Factitious disorder and malingering cannot be diagnosed in the same patient, and the diagnosis of factitious disorder depends on the absence of any other psychiatric disorder. While they are both listed in the DSM-IV-TR, factitious disorder is considered a mental disorder, while malingering is not.

Ganser syndrome was once considered a separate factitious disorder. It is a disorder of extreme stress or an organic condition. The patient suffers from approximation or giving absurd answers to simple questions. The syndrome is sometimes diagnosed as merely malingering—however, it is more often defined as a factitious disorder. This has been seen in prisoners following solitary confinement, and the symptoms are consistent in different prisons, though the patients do not know one another.

Symptoms include a clouding of consciousness, somatic conversion symptoms, confusion, stress, loss of personal identity, echolalia, and echopraxia. Individuals also give approximate answers to simple questions such as, "How many legs on a cat?" "Three"; "What's the day after Wednesday?" "Friday"; and so on. The disorder is extraordinarily rare with fewer than 100 recorded cases. While individuals of all backgrounds have been reported with the disorder, there is a higher inclination towards males (75% or more). The average age of those with Ganser syndrome is 32, though it stretches from ages 15–62 years old.

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.

People who demonstrate factitious disorders often claim to have physical ailments or be recovering from the consequences of stalking, victimization, harassment, and sexual abuse. Several behaviors present themselves to suggest factors beyond genuine problems. After studying 21 cases of deception, Feldman listed the following common behavior patterns in people who exhibited Munchausen by Internet:

- Medical literature from websites or textbooks is often duplicated or discussed in great detail.

- The length and severity of purported physical ailments conflicts with user behavior. Feldman uses the example of someone posting in considerable detail about being in septic shock, when such a possibility is extremely unlikely.

- Symptoms of ailments may be exaggerated as they correspond to a user's misunderstanding of the nature of an illness.

- Grave situations and increasingly critical prognoses are interspersed with "miraculous" recoveries.

- A user's posts eventually reveal contradictory information or claims that are implausible: for example, other users of a forum may find that a user has been divulging contradictory information about occurrence or length of hospital visits.

- When attention and sympathy decreases to focus on other members of the group, a user may announce that other dire events have transpired, including the illness or death of a close family member.

- When faced with insufficient expressions of attention or sympathy, a forum member claims this as a cause that symptoms worsen or do not improve.

- A user resists contact beyond the Internet, such as by telephone or personal visit, often claiming bizarre reasons for not being able to accept such contact.

- Further emergencies are described with inappropriate happiness, designed to garner immediate reactions.

- The posts of other forum members exhibit identical writing styles, spelling errors, and language idiosyncrasies, suggesting that the user has created fictitious identities to move the conversation in their direction.

"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.

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.

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.

Pan-Neurosis is the existence of multiple neurotic symptoms such as:

- obsessions

- compulsions

- phobias

- hysteria

- depression

- hypochondriasis

- depersonalization

Diffuse anxiety is stimulated by a minor catalyst and may persist long after the catalyst disappears.

Qualities of MPI outbreaks often include:

- symptoms that have no plausible organic basis;

- symptoms that are transient and benign;

- symptoms with rapid onset and recovery;

- occurrence in a segregated group;

- the presence of extraordinary anxiety;

- symptoms that are spread via sight, sound or oral communication;

- a spread that moves down the age scale, beginning with older or higher-status people;

- a preponderance of female participants

Also, the illness may recur after the initial outbreak.

The likely course and outcome of mental disorders varies and is dependent on numerous factors related to the disorder itself, the individual as a whole, and the social environment. Some disorders are transient, while others may be more chronic in nature.

Even those disorders often considered the most serious and intractable have varied courses i.e. schizophrenia, psychotic disorders, and personality disorders. Long-term international studies of schizophrenia have found that over a half of individuals recover in terms of symptoms, and around a fifth to a third in terms of symptoms and functioning, with some requiring no medication. At the same time, many have serious difficulties and support needs for many years, although "late" recovery is still possible. The World Health Organization concluded that the long-term studies' findings converged with others in "relieving patients, carers and clinicians of the chronicity paradigm which dominated thinking throughout much of the 20th century."

Around half of people initially diagnosed with bipolar disorder achieve syndromal recovery (no longer meeting criteria for the diagnosis) within six weeks, and nearly all achieve it within two years, with nearly half regaining their prior occupational and residential status in that period. However, nearly half go on to experience a new episode of mania or major depression within the next two years. Functioning has been found to vary, being poor during periods of major depression or mania but otherwise fair to good, and possibly superior during periods of hypomania in Bipolar II.

The recognition and understanding of mental health conditions have changed over time and across cultures and there are still variations in definition, assessment and classification, although standard guideline criteria are widely used. In many cases, there appears to be a continuum between mental health and mental illness, making diagnosis complex. According to the World Health Organisation (WHO), over a third of people in most countries report problems at some time in their life which meet criteria for diagnosis of one or more of the common types of mental disorder. Mental health can be defined as an absence of mental disorder.

Work aversion (or aversion to work) is the state of avoiding or not wanting to work or be employed, or the extreme preference of leisure as opposed to work. It can be attributed to laziness, boredom or burnout. Work aversion is not a recognized psychological disorder in the DSM-IV.

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.

People with avolition often want to complete certain tasks but lack the ability to initiate behaviours necessary to complete them. Avolition is most commonly seen as a symptom of some other disorder, but might be considered a primary clinical disturbance of itself (or as a coexisting second disorder) related to disorders of diminished motivation. In 2006, avolition was identified as a negative symptom of schizophrenia by the National Institute of Mental Health (NIMH), and has been observed in patients with bipolar disorder as well as resulting from trauma.

Avolition is sometimes mistaken for other, similar symptoms also affecting motivation, such as aboulia, anhedonia and asociality, or strong general disinterest. For example, aboulia is also a restriction in motivation and initiation, but characterized by an inability to set goals or make decisions and considered a disorder of diminished motivation. In order to provide effective treatment, the underlying cause of avolition (if any) has to be identified and it is important to properly differentiate it from other symptoms, even though they might reflect similar aspects of mental illness.

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.

Psychogenic disease (or psychogenic illness) is a name given to physical illnesses that are believed to arise from emotional or mental stressors, or from psychological or psychiatric disorders. It is most commonly applied to illnesses where a physical abnormality or other biomarker has not yet been identified. In the absence of such "biological" evidence of an underlying disease process, it is often assumed that the illness must have a psychological cause, even if the patient shows no indications of being under stress or of having a psychological or psychiatric disorder.

Examples of diseases that are believed by many to be psychogenic include psychogenic seizures, psychogenic polydipsia, psychogenic tremor and psychogenic pain.

There are problems with the assumption that all medically unexplained illness must have a psychological cause. It always remains possible that genetic, biochemical, electrophysiological or other abnormalities may be present which we do not have the technology or background to identify.

The term psychogenic disease is often used in a similar way to psychosomatic disease. However, the term "psychogenic" usually implies that psychological factors played a key causal role in the development of the illness. The term "psychosomatic" is often used in a broader way to describe illnesses with a known medical cause where psychological factors may nonetheless play a role (e.g., asthma can be exacerbated by anxiety).