Most psychologists believe that paraphilic sexual interests cannot be altered. Instead, the goal of therapy is normally to reduce the person's discomfort with their paraphilia and limit any criminal behavior. Both psychotherapeutic and pharmacological methods are available to these ends.

Cognitive behavioral therapy, at times, can help people with paraphilias develop strategies to avoid acting on their interests. Patients are taught to identify and cope with factors that make acting on their interests more likely, such as stress. It is currently the only form of psychotherapy for paraphilias supported by evidence.

Antiandrogens are used in more severe cases. Similar to physical castration, they work by reducing androgen levels, and have thus been described as chemical castration. The antiandrogen cyproterone acetate has been shown to substantially reduce sexual fantasies and offending behaviors. Medroxyprogesterone acetate and gonadotropin-releasing hormone agonists (such as leuprolide acetate) have also been used to lower sex drive. Due to the side effects, the World Federation of Societies of Biological Psychiatry recommends that hormonal treatments only be used when there is a serious risk of sexual violence, or when other methods have failed. Surgical castration has largely been abandoned because these pharmacological alternatives are similarly effective and less invasive.

Psychosexual disorders can vary greatly in severity and treatability. Medical professionals and licensed therapists are necessary in diagnosis and treatment plans. Treatment can vary from therapy to prescription medication. Sex therapy, behavioral therapy, and group therapy may be helpful to those suffering distress from sexual dysfunction. More serious sexual perversions may be treated with androgen blockers or selective serotonin reuptake inhibitors (SSRIs) to help restore hormonal and neurochemical balances.

In the DSM-5 all paraphilia disorders can be diagnosed by two main criteria that are referred to criteria A and criteria B respectively. The A and B criteria include a duration in which the behavior must be present for (typically 6 months) and specific details of actions or thoughts that are correlated specifically with the respective disorder being diagnosed.

Sadomasochism is the giving or receiving pleasure from acts involving the receipt or infliction of pain or humiliation. Practitioners of sadomasochism may seek sexual gratification from their acts. While the terms sadist and masochist refer respectively to one who enjoys giving or receiving pain, practitioners of sadomasochism may switch between activity and passivity.

The abbreviation S&M is often used for sadomasochism, although practitioners themselves normally remove the ampersand and use the acronym S-M or SM or S/M when written throughout the literature. Sadomasochism is not considered a clinical paraphilia unless such practices lead to clinically significant distress or impairment for a diagnosis. Similarly, sexual sadism within the context of mutual consent, generally known under the heading BDSM, is distinguished from non-consensual acts of sexual violence or aggression.

The PCL-R, the PCL:SV, and the PCL:YV are highly regarded and widely used in criminal justice settings, particularly in North America. They may be used for risk assessment and for assessing treatment potential and be used as part of the decisions regarding bail, sentence, which prison to use, parole, and regarding whether a youth should be tried as a juvenile or as an adult. There have been several criticisms against its use in legal settings. They include the general criticisms against the PCL-R, the availability of other risk assessment tools which may have advantages, and the excessive pessimism surrounding the prognosis and treatment possibilities of those who are diagnosed with psychopathy.

The interrater reliability of the PCL-R can be high when used carefully in research but tend to be poor in applied settings. In particular Factor 1 items are somewhat subjective. In sexually violent predator cases the PCL-R scores given by prosecution experts were consistently higher than those given by defense experts in one study. The scoring may also be influenced by other differences between raters. In one study it was estimated that of the PCL-R variance, about 45% was due to true offender differences, 20% was due to which side the rater testified for, and 30% was due to other rater differences.

To aid a criminal investigation, certain interrogation approaches may be used to exploit and leverage the personality traits of suspects thought to have psychopathy and make them more likely to divulge information.

Sexual sadism disorder is the condition of experiencing sexual arousal in response to the extreme pain, suffering or humiliation of others. Several other terms have been used to describe the condition, and the condition may overlap with other conditions that involve inflicting pain. It is distinct from situations in which consenting individuals use mild or simulated pain or humiliation for sexual excitement. The words "sadism" and "" are derived from Marquis de Sade.

Zoophilia is a paraphilia involving a sexual fixation on non-human animals. Bestiality is cross-species sexual activity between human and non-human animals. The terms are often used interchangeably, but some researchers make a distinction between the attraction (zoophilia) and the act (bestiality).

Although sex with animals is not outlawed in some countries, in most countries, bestiality is illegal under animal abuse laws or laws dealing with buggery or crimes against nature.

With paraphilic coercive disorder, the individual employs enough force to subdue a victim, but with sexual sadism disorder, the individual often continues to inflict harm regardless of the compliance of the victim, which sometimes escalates not only to the death of the victim, but also to the mutilation of the body. What is experienced by the sadist as sexual does not always appear obviously sexual to non-sadists: Sadistic rapes do not necessarily include penile penetration of the victim. In a survey of offenses, 77% of cases included sexual bondage, 73% included anal rape, 60% included blunt force trauma, 57% included vaginal rape, and 40% included penetration of the victim by a foreign object. Moreover, in 40% of cases, the offender kept a personal item of the victim as a souvenir.

On personality testing, sadistic rapists apprehended by law enforcement have shown elevated traits of impulsivity, hypersexuality, callousness, and psychopathy.

Although there appears to be a continuum of severity from mild ("hyperdominance" or "BDSM") to moderate ("paraphilic coercive disorder") to severe ('sexual sadism disorder), it is not clear if they are genuinely related or only appear related superficially.

Very little is known about how sexual sadism disorder develops. Most of the people diagnosed with sexual sadism disorder come to the attention of authorities by committing sexually motivated crimes. Surveys have also been conducted including people who are interested in only mild and consensual forms of sexual pain/humiliation (BDSM).

Most of the people with full-blown sexual sadism disorder are male, whereas the sex ratio of people interested in BDSM is closer to 2:1 male-to-female.

People with sexual sadism disorder" are at an elevated likelihood of having other paraphilic sexual interests.

The prognosis for psychopathy in forensic and clinical settings is quite poor, with some studies reporting that treatment may worsen the antisocial aspects of psychopathy as measured by recidivism rates, though it is noted that one of the frequently cited studies finding increased criminal recidivism after treatment, a 2011 retrospective study of a treatment program in the 1960s, had several serious methodological problems and likely would not be approved of today. However, some relatively rigorous quasi-experimental studies using more modern treatment methods have found improvements regarding reducing future violent and other criminal behavior, regardless of PCL-R scores, although none were randomized controlled trials. Various other studies have found improvements in risk factors for crime such as substance abuse. No study has of yet in a 2013 review examined if the personality traits that form the core character disturbances of psychopathy could be changed by such treatments.

Gerontophilia is the sexual preference for the elderly. A person with such a sexual preference is a gerontophile. The word "gerontophilia" was coined in 1901 by Richard von Krafft-Ebing. It derives from Greek: geron, meaning "old man or woman" and philie, meaning "love". Gerontophilia is classified as a paraphilia, but is not mentioned in the "Diagnostic and Statistical Manual of Mental Disorders" or International Classification of Diseases.

The prevalence of gerontophilia is unknown. A study of pornographic search terms on a peer-to-peer network reported that 0.15% had gerontophilic themes. Sex offenders with elderly victims do not necessarily have gerontophilia. There are other possible motivations for these offenses, such as rage or sadism, or the increased vulnerability of elderly as a social group, which are factors that may not involve a sexual preference for the elderly. There are no studies showing that most such offenders are gerontophiles. In one small study, two of six sex offenders against the elderly evinced gerontophilic tendencies. Gerontophilia can also be expressed with consenting elderly partners in a legal context.

Research on gerontophilia is limited to a small number of case studies, beginning with a paper by French physician Charles Féré in 1905. Féré described a 27-year-old man who rejected an arranged marriage with a 20-year-old "beauty" in favor of a 62-year-old woman. Such studies commonly report that the subject had an early sexual experience with a much older woman.

Biastophilia (from Greek "biastes", "rape" + "-philia") and its Latin language-derived counterpart raptophilia (from Latin "rapere", "to seize"), also paraphilic rape, is a paraphilia in which sexual arousal is dependent on, or is responsive to, the act of assaulting an unconsenting person, especially a stranger. Some dictionaries consider the terms synonymous, while others distinguish raptophilia as the paraphilia in which sexual arousal is responsive to actually raping the victim.

The source of the arousal in these paraphilias is the victim's terrified resistance to the assault, and in this respect it is considered to be a form of sexual sadism. Biastophilia is accepted as potentially lethal, other such paraphilias including, but not being limited to asphyxiophilia, autassassinophilia, hybristophilia, and chremastistophilia.

Under the name paraphilic coercive disorder, this diagnosis was proposed for inclusion in DSM-5. This diagnosis, under the name "paraphilic rapism", was proposed and rejected in the DSM-III-R. It has been criticized because of the impossibility of reliably distinguishing between paraphilic rapists and non-paraphilic rapists, and because this diagnosis, under the term "Paraphilia NOS" (not otherwise specified), non-consent had been used in Sexually Violent Person/Predator commitment.

Czech sexology standardly use a concept of pathologic sexual aggressivity instead. This term is strongly distinguished from sadism. This disorder is understood as a coordination anomaly of the sexual motivation system (SMS), a "courtship disorder" according to Kurt Freund or displacement paraphilia by John Money, or a missing segment of SMS.

BDSM is a variety of often erotic practices or roleplaying involving bondage, discipline, dominance and submission, sadomasochism, and other related interpersonal dynamics. Given the wide range of practices, some of which may be engaged in by people who do not consider themselves as practicing BDSM, inclusion in the BDSM community or subculture is usually dependent upon self-identification and shared experience.

The term "BDSM" is first recorded in a Usenet posting from 1991, and is interpreted as a combination of the abbreviations B/D (Bondage and Discipline), D/s (Dominance and submission), and S/M (Sadism and Masochism). BDSM is now used as a catch-all phrase covering a wide range of activities, forms of interpersonal relationships, and distinct subcultures. BDSM communities generally welcome anyone with a non-normative streak who identifies with the community; this may include cross-dressers, body modification enthusiasts, animal roleplayers, rubber fetishists, and others.

Activities and relationships within a BDSM context are often characterized by the participants taking on complementary, but unequal roles; thus, the idea of informed consent of both the partners is essential. The terms "submissive" and "dominant" are often used to distinguish these roles: the dominant partner ("dom") takes psychological control over the submissive ("sub"). The terms "top" and "bottom" are also used: the top is the instigator of an action while the bottom is the receiver of the action. The two sets of terms are subtly different: for example, someone may choose to act as bottom to another person, for example, by being whipped, purely recreationally, without any implication of being psychologically dominated by them, or a submissive may be ordered to massage their dominant partner. Despite the bottom performing the action and the top receiving they have not necessarily switched roles.

The abbreviations "sub" and "dom" are frequently used instead of "submissive" and "dominant". Sometimes the female-specific terms "mistress", "domme" or "dominatrix" are used to describe a dominant woman, instead of the gender-neutral term "dom". Individuals who can change between top/dominant and bottom/submissive roles—whether from relationship to relationship or within a given relationship—are known as "switches". The precise definition of roles and self-identification is a common subject of debate within the community.

BDSM is practiced in all social strata and is common in both heterosexual and homosexual men and women in varied occurrences and intensities. The spectrum ranges from couples with no connections to the subculture outside of their bedrooms or homes, without any awareness of the concept of BDSM, playing "tie-me-up-games", to public scenes on St. Andrew's crosses at large events such as the Folsom Street Fair in San Francisco. Estimation on the overall percentage of BDSM related sexual behaviour vary but it is no longer assumed to be uncommon.

Alfred Kinsey stated in his 1953 nonfiction book "Sexual Behavior in the Human Female" that 12% of females and 22% of males reported having an erotic response to a sadomasochistic story. In that book erotic responses to being bitten were given as:

A non-representative survey on the sexual behaviour of American students published in 1997 and based on questionnaires had a response rate of about 8–9%. Its results showed 15% of homosexual and bisexual males, 21% of lesbian and female bisexual students, 11% of heterosexual males and 9% of female heterosexual students committed to BDSM related fantasies. In all groups the level of practical BDSM experiences were around 6%. Within the group of openly lesbian and bisexual females the quote was significantly higher, at 21%. Independent of their sexual orientation, about 12% of all questioned students, 16% of lesbians and female bisexuals and 8% of heterosexual males articulated an interest in spanking. Experience with this sexual behaviour was indicated by 30% of male heterosexuals, 33% of female bisexuals and lesbians, and 24% of the male gay and bisexual men and female heterosexual women. Even though this study was not considered representative, other surveys indicate similar dimensions in a differing target groups.

A representative study done from 2001 to 2002 in Australia found that 1.8% of sexually active people (2.2% men, 1.3% women but no significant sex difference) had engaged in BDSM activity in the previous year. Of the entire sample, 1.8% men and 1.3% women had been involved in BDSM. BDSM activity was significantly more likely among bisexuals and homosexuals of both sexes. But among men in general, there was no relationship effect of age, education, language spoken at home, or relationship status. Among women, in this study, activity was most common for those between 16 and 19 years of age and least likely for females over 50 years. Activity was also significantly more likely for women who had a regular partner they did not live with, but was not significantly related with speaking a language other than English or education.

Another representative study, published in 1999 by the German Institut für rationale Psychologie, found that about 2/3 of the interviewed women stated a desire to be at the mercy of their sexual partners from time to time. 69% admitted to fantasies dealing with sexual submissiveness, 42% stated interest in explicit BDSM techniques, 25% in bondage. A 1976 study in the general US population suggests three percent have had positive experiences with Bondage or master-slave roleplaying. Overall 12% of the interviewed females and 18% of the males were willing to try it. A 1990 Kinsey Institute report stated that 5% to 10% of Americans occasionally engage in sexual activities related to BDSM. 11% of men and 17% of women reported trying bondage. Some elements of BDSM have been popularized through increased media coverage since the middle 1990s. Thus both black leather clothing, sexual jewellery such as chains and dominance roleplay appear increasingly outside of BDSM contexts.

According to yet another survey of 317,000 people in 41 countries, about 20% of the surveyed have at least used masks, blindfolds or other bondage utilities once, and 5% explicitly connected themselves with BDSM. In 2004, 19% mentioned spanking as one of their practices and 22% confirmed the use of blindfolds or handcuffs.

A 1985 study found 52 out of 182 female respondents (28%) were involved in sadomasochistic activities.

- Recent surveys

A 2009 study on two separate samples of male undergraduate students in Canada found that 62 to 65%, depending on the sample, had entertained sadistic fantasies, and 22 to 39% engaged in sadistic behaviors during sex. The figures were 62 and 52% for bondage fantasies, and 14 to 23% for bondage behaviors. A 2014 study involving a mixed sample of Canadian college students and online volunteers, both male and female, reported that 19% of male samples and 10% of female samples rated the sadistic scenarios described in a questionnaire as being at least "slightly arousing" on a scale that ranged from "very repulsive" to "very arousing"; the difference was statistically significant. The corresponding figures for the masochistic scenarios were 15% for male students and 17% for female students, a non-significant difference. In a 2011 study on 367 middle-aged and elderly men recruited from the broader community in Berlin, 21.8% of the men self-reported sadistic fantasies and 15.5% sadistic behaviors; 24.8% self-reported any such fantasy and/or behavior. The corresponding figures for self-reported masochism were 15.8% for fantasy, 12.3% for behavior, and 18.5% for fantasy and/or behavior. In a 2008 study on gay men in Puerto Rico, 14.8% of the over 425 community volunteers reported any sadistic fantasy, desire or behavior in their lifetime; the corresponding figure for masochism was 15.7%. A 2017 cross-sectional representative survey among the general Belgian population demonstrated a substantial prevalence of BDSM fantasies and activities; 12.5% of the population performed one of more BDSM-practices on a regular basis.

Three key terms commonly used in regards to the subject — "zoophilia", "bestiality", and "zoosexuality" — are often used somewhat interchangeably. Some researchers distinguish between zoophilia (as a persistent sexual interest in animals) and bestiality (as sexual acts with animals), because bestiality is often not driven by a sexual preference for animals. Some studies have found that a preference for animals is rare among people who engage in sexual contact with animals. Furthermore, some zoophiles report that they have never had sexual contact with an animal. People with zoophilia are known as "zoophiles", though also sometimes as "zoosexuals", or even very simply "zoos". Zooerasty, sodomy, and zooerastia are other terms closely related to the subject but are less synonymous with the former terms, and are seldom used. "Bestiosexuality" was discussed briefly by Allen (1979), but never became widely established. Ernest Bornemann (1990, cited by Rosenbauer, 1997) coined the separate term "zoosadism" for those who derive pleasure – sexual or otherwise – from inflicting pain on animals. Zoosadism specifically is one member of the Macdonald triad of precursors to sociopathic behavior.

Gynophobia or gynephobia is an abnormal fear of women, a type of specific social phobia. In the past, the Latin term horror feminae was used.

Gynophobia should not be confused with misogyny, the hatred, contempt for and inveterate prejudice against women, although some may use the terms interchangeably, in reference to the social, rather than pathological aspect of negative attitudes towards women.

An antonym is philogyny, the love, respect for and admiration of women.

Until the 1990s, it tended to be described mostly as acrotomophilia, at the expense of other disabilities, or of the wish by some to pretend or acquire disability. Bruno (1997) systematised the attraction as factitious disability disorder. A decade on, others argue that erotic target location error is at play, classifying the attraction as an identity disorder. In the standard psychiatric reference "Diagnostic and Statistical Manual of Mental Disorders", text revision (DSM-IV-tr), the fetish falls under the general category of "Sexual and Gender Identity Disorders" and the more specific category of paraphilia, or sexual fetishes; this classification is preserved in DSM-5.

In the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), recurrent, intense sexual interest in corpses can be diagnosed under Other Specified Paraphilic Disorder (necrophilia) when it causes marked distress or impairment in important areas of functioning. A ten-tier classification of necrophilia exists:

1. Role players: People who get aroused from pretending their live partner is dead during sexual activity.

2. Romantic necrophiliacs: Bereaved people who remain attached to their dead lover's body.

3. Necrophilic fantasizers: People who fantasize about necrophilia, but never actually have sex with a corpse.

4. Tactile necrophiliacs: People who are aroused by touching or stroking a corpse, without engaging in intercourse.

5. Fetishistic necrophiliacs: People who remove objects (e.g., panties or a tampon) or body parts (e.g., a finger or genitalia) from a corpse for sexual purposes, without engaging in intercourse.

6. Necromutilomaniacs: People who derive pleasure from mutilating a corpse while masturbating, without engaging in intercourse.

7. Opportunistic necrophiliacs: People who normally have no interest in necrophilia, but take the opportunity when it arises.

8. Regular necrophiliacs: People who preferentially have intercourse with the dead.

9. Homicidal necrophiliacs: Necrosadists, people who commit murder in order to have sex with the victim.

10. Exclusive necrophiliacs: People who have an exclusive interest in sex with the dead, and cannot perform at all for living partners.

The term "sadomasochism" is used in a variety of different ways. It can refer to cruel individuals or those who brought misfortunes onto themselves and psychiatrists define it as pathological. However, recent research suggests that sadomasochism is mostly simply a sexual interest, and not a pathological symptom of past abuse, or a sexual problem, and that people with sadomasochistic sexual interest are in general neither damaged nor dangerous.

The two words incorporated into this compound, "sadism" and "masochism", were originally derived from the names of two authors. The term "Sadism" has its origin in the name of the Marquis de Sade (1740–1814), who not only practiced sexual sadism, but also wrote novels about these practices, of which the best known is "Justine". "Masochism" is named after Leopold von Sacher-Masoch, who wrote novels expressing his masochistic fantasies. These terms were first selected for identifying human behavioural phenomena and for the classification of psychological illnesses or deviant behaviour. The German psychiatrist Richard von Krafft-Ebing introduced the terms "Sadism" and "Masochism"' into medical terminology in his work "Neue Forschungen auf dem Gebiet der Psychopathia sexualis" ("New research in the area of Psychopathology of Sex") in 1890.

In 1905, Sigmund Freud described sadism and masochism in his "Drei Abhandlungen zur Sexualtheorie" ("Three papers on Sexual Theory") as stemming from aberrant psychological development from early childhood. He also laid the groundwork for the widely accepted medical perspective on the subject in the following decades. This led to the first compound usage of the terminology in "Sado-Masochism" (Loureiroian "Sado-Masochismus") by the Viennese Psychoanalyst Isidor Isaak Sadger in his work "Über den sado-masochistischen Komplex" ("Regarding the sadomasochistic complex") in 1913.

In the later 20th century, BDSM activists have protested against these ideas, because, they argue, they are based on the philosophies of the two psychiatrists, Freud and Krafft-Ebing, whose theories were built on the assumption of psychopathology and their observations of psychiatric patients. The DSM nomenclature referring to sexual psychopathology has been criticized as lacking scientific veracity, and advocates of sadomasochism have sought to separate themselves from psychiatric theory by the adoption of the term "BDSM" instead of the common psychological abbreviation, "S&M". However, the term BDSM also includes, B&D (bondage and discipline), D/s (dominance and submission), and S&M ( and masochism). The terms "bondage" and "discipline" usually refer to the use of either physical or psychological restraint or punishment, and sometimes involves sexual role playing, including the use of costumes.

In contrast to frameworks seeking to explain sadomasochism through psychological, psychoanalytic, medical or forensic approaches, which seek to categorize behavior and desires, and find a root cause, Romana Byrne suggests that such practices can be seen as examples of "aesthetic sexuality", in which a founding physiological or psychological impulse is irrelevant. Rather, according to Byrne, sadism and masochism may be practiced through choice and deliberation, driven by certain aesthetic goals tied to style, pleasure, and identity, which in certain circumstances, she claims can be compared with the creation of art.

Attraction to disability or devotism is a sexualised interest in the appearance, sensation and experience of disability. It may extend from normal human sexuality into a type of sexual fetishism. Sexologically, the pathological end of the attraction tends to be classified as a paraphilia. (Note, however, that the very concept "paraphilia" continues to elude satisfactory definition and remains a subject of ongoing debate in both professional and lay communities) Other researchers have approached it as a form of identity disorder. The most common interests are towards amputations, prosthesis, and crutches.

Sadism involves gaining pleasure through themselves or others undergoing discomfort or pain. The opponent-process theory explains the way in which individuals not only display, but also enjoy committing sadistic acts. Individuals possessing sadistic personalities tend to display recurrent aggression and cruel behavior. Sadism can also include the use of emotional cruelty, purposefully manipulating others through the use of fear, and a preoccupation with violence.

Theodore Millon claimed there were four subtypes of sadism, which he termed Enforcing sadism, Explosive sadism, Spineless sadism, and Tyrannical sadism.

Necrophilia is often assumed to be rare, but no data for its prevalence in the general population exists. Some necrophiles only fantasize about the act, without carrying it out. In 1958, Klaf and Brown commented that, although rarely described, necrophiliac fantasies may occur more often than is generally supposed.

Rosman and Resnick (1989) reviewed 122 cases of necrophilia. The sample was divided into genuine necrophiles, who had a persistent attraction to corpses, and pseudo-necrophiles, who acted out of opportunity, sadism, or transient interest. Of the total, 92% were male and 8% were female. 57% of the genuine necrophiles had occupational access to corpses, with morgue attendant, hospital orderly, and cemetery employee being the most common jobs. The researchers theorized that either of the following situations could be antecedents to necrophilia:

1. The necrophile develops poor self-esteem, perhaps due in part to a significant loss;

- (a) They are very fearful of rejection by others and they desire a sexual partner who is incapable of rejecting them; and/or

- (b) They are fearful of the dead, and transform their fear—by means of reaction formation—into a desire.

2. They develop an exciting fantasy of sex with a corpse, sometimes after exposure to a corpse.

The authors reported that, of their sample of genuine necrophiles:

- 68% were motivated by a desire for an unresisting and unrejecting partner;

- 21% by a want for reunion with a lost partner;

- 15% by sexual attraction to dead people;

- 15% by a desire for comfort or to overcome feelings of isolation; and

- 12% by a desire to remedy low self-esteem by expressing power over a corpse.

IQ data was limited, but not abnormally low. About half of the sample had a personality disorder, and 11% of true necrophiles were psychotic. Rosman and Resnick concluded that their data challenged the conventional view of necrophiles as generally psychotic, mentally deficient, or unable to obtain a consenting partner.

Sadistic personality disorder has been found to occur frequently in unison with other personality disorders. Studies have also found that sadistic personality disorder is the personality disorder with the highest level of comorbidity to other types of psychopathological disorders. In contrast, sadism has also been found in patients who do not display any or other forms of psychopathic disorders. One personality disorder that is often found to occur alongside sadistic personality disorder is conduct disorder, not an adult disorder but one of childhood and adolescence. Studies have found other types of illnesses, such as alcoholism, to have a high rate of comorbidity with sadistic personality disorder.

Researchers have had some level of difficulty distinguishing sadistic personality disorder from other forms of personality disorders due to its high level of comorbidity with other disorders.

Malignant narcissism is a psychological syndrome comprising an extreme mix of narcissism, antisocial behavior, aggression, and sadism. Often grandiose, and always ready to raise hostility levels, the malignant narcissist undermines organizations in which they are involved, and dehumanizes the people with whom they associate.

Malignant narcissism is a hypothetical, experimental diagnostic category. Narcissistic personality disorder is found in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-IV-TR), while malignant narcissism is not. As a hypothetical syndrome, malignant narcissism could include aspects of narcissistic personality disorder as well as paranoia. The importance of malignant narcissism and of projection as a defense mechanism has been confirmed in paranoia, as well as "the patient's vulnerability to malignant narcissistic regression".

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.