Psychopathy

Psychopathy was, until 1980, the term used for a personality disorder characterized by an abnormal lack of empathy combined with strongly amoral conduct but masked by an ability to appear outwardly normal. The publication of DSM-III changed the name of this mental disorder to Antisocial Personality Disorder, and also broadened the diagnostic criteria considerably by shifting from clinical inferences to behavioral diagnostic criteria. However, the DSM-V working party is recommending a revision of Antisocial Personality Disorder to include "Antisocial/Psychopathic Type", with the diagnostic criteria having a greater emphasis on character than on behavior. The ICD-10 diagnostic criteria of the World Health Organization also lacks psychopathy as a personality disorder, its 1992 manual including Dissocial (Antisocial) Personality Disorder, which encompasses amoral, antisocial, asocial, psychopathic, and sociopathic personalities.

Despite being currently unused in diagnostic manuals, psychopathy and related terms such as psychopath are still widely used by mental health professionals and laymen alike. In particular, NATO has funded a series of Advanced Study Institutes on psychopathy, both before and after to the publication of DSM-III. Researcher Robert Hare has been a particular champion of the term; his Hare Psychopathy Checklist is the standard tool for differentiating between those with Antisocial Personality Disorder (APD) and the subset who are psychopaths. According to this scale, the prevalence of APD is two to three times that of psychopathy.

According to Christopher J. Patrick in his Handbook of Psychopathy, clinicians generally believe that there is neither a cure nor any effective treatment for psychopathy; there are no medications that can instill empathy, while psychopaths who undergo traditional talk therapy only become more adept at manipulating others. However, other researchers suggest that psychopaths may benefit as much as others from psychological treatment, at least in terms of effect on behavior. According to Hare, the consensus among researchers in this area is that psychopathy stems from a specific neurological disorder which is biological in origin and present from birth, although a 2008 review indicated multiple causes and variation between individuals. Hare estimates that about one percent of the population are psychopaths.

Classification
The classification of mental disorders, also known as psychiatric nosology or taxonomy, is a key aspect of psychiatry and other mental health professions and an important issue for consumers and providers of mental health services. There are currently two widely established systems for classifying mental disorders &mdash; Chapter V of the International Classification of Diseases (ICD-10) produced by the World Health Organization (WHO) and the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) produced by the American Psychiatric Association (APA). Both list categories of disorders thought to be distinct types, and have deliberately converged their codes in recent revisions so that the manuals are often broadly comparable, although significant differences remain. Other classification schemes may be in use more locally, for example the Chinese Classification of Mental Disorders. Other manuals have some limited used by those of alternative theoretical persuasions, such as the Psychodynamic Diagnostic Manual.

Characteristics
The prototypical psychopath has deficits or deviances in several areas: interpersonal relationships, emotion, and self-control. Psychopaths gain satisfaction through antisocial behavior, and do not experience shame, guilt, or remorse for their actions. Psychopaths lack a sense of guilt or remorse for any harm they may have caused others, instead rationalizing the behavior, blaming someone else, or denying it outright. Psychopaths also lack empathy towards others in general, resulting in tactlessness, insensitivity, and contemptuousness. All of this belies their tendency to make a likable first impression; psychopaths have a superficial charm about them, enabled by a willingness to say anything without concern for accuracy or truth. Shallow affect also describes the psychopath's tendency for genuine emotion to be short-lived and egocentric, with an overall cold demeanor. Their behavior is impulsive and irresponsible, often failing to keep a job or defaulting on debts. Psychopaths also have a markedly distorted sense of the potential consequences of their actions, not only for others, but also for themselves. They do not deeply recognize the risk of being caught, disbelieved or injured as a result of their behaviour.

Researcher Robert Hare, whose Hare Psychopathy Checklist is widely used, describes psychopaths as "intraspecies predators". Also R.I. Simon uses the word predator to describe psychopaths. Elsewhere Hare and others write that psychopaths "use charisma, manipulation, intimidation, sexual intercourse and violence"   to control others and to satisfy their own needs. Hare states that: "Lacking in conscience and empathy, they take what they want and do as they please, violating social norms and expectations without guilt or remorse". He previously stated that: "What is missing, in other words, are the very qualities that allow a human being to live in social harmony".

According to Hare, many psychopaths are superficially charming, and can excellently mimic normal human emotion; some psychopaths can blend in, undetected, in a variety of surroundings, including corporate environments.

Facial affect recognition
In a 2002 study, David Kosson and Yana Suchy, et al. asked psychopathic inmates to name the emotion expressed on each of 30 faces; compared to the control group, psychopaths had a significantly lower rate of accuracy in recognizing disgusted facial affect but a higher rate of accuracy in recognizing anger. Additionally, when "conditions designed to minimize the involvement of left-hemispheric mechanisms" (i.e. sadness) were used, psychopaths had more difficulty accurately identifying emotions. This study did not replicate Blaire, et al. (1997)'s findings that psychopaths are specifically less sensitive to nonverbal cues of fear or distress.

Vocal affect recognition
In a 2002 experiment, Blair, Mitchell, et al. used the Vocal Affect Recognition Test to measure psychopaths' recognition of the emotional intonation given to connotatively neutral words. Psychopaths tended to make more recognition errors than controls with a particularly high rate of error for sad and fearful vocal affect.

Stroop tasks
A 2004 experiment tested the hypothesis of overselective attention in psychopaths using two forms of the Stroop color-word and picture-word tasks: with color/picture and word separated and with color/picture and word together. Psychopaths performed significantly worse than controls in the separated Stroop tasks, but performed as well as the controls on standard Stroop tasks.

When split into low-anxious and high-anxious groups, low-anxious psychopaths and low-anxious controls showed less interference on the separated Stroop tasks than their high-anxious counterparts; for low-anxious psychopaths, interference was very nearly zero. Researchers concluded the inability to integrate contextual cues depends on the cues' relationship to "the deliberately attended, goal-relevant information."

Causes
One twin study suggests that psychopathy has a strong genetic component. The study demonstrates that children with anti-social behavior can be classified into two groups: those who were also callous acquired their behavior by genetic influences, and those who were not callous acquired it from their environment. "The amygdala is crucial for stimulus-reinforcement learning and responding to emotional expressions, particularly fearful expressions that, as reinforcers, are important initiators of stimulus-reinforcement learning. Moreover, the amygdala is involved in the formation of both stimulus-punishment and stimulus-reward associations. Individuals with psychopathy show impairment in stimulus-reinforcement learning (whether punishment or reward based) and responding to fearful and sad expressions. It is argued that this impairment drives much of the syndrome of psychopathy"(Blair, 2008).

People scoring ≥25 in the Psychopathy Checklist Revised, with an associated history of violent behavior, appear to have significantly reduced microstructural integrity in their uncinate fasciculus &mdash; white matter connecting the amygdala and orbitofrontal cortex. The more extreme the psychopathy, the greater the abnormality.

Pathophysiology
Recent studies have triggered theories on determining whether there is a biological relationship between the brain and psychopathy. One theory suggests that psychopathy is associated with both the amygdala, which is associated with emotional reactions and emotion learning, and the prefrontal cortex, associated with impulse control, decision-making, emotional learning and behavioral adaptation. Some studies have shown there is less "gray matter" in these areas in psychopaths than in non-psychopaths.

There is DT-MRI evidence of breakdowns in the white matter connections between these two important areas in a small British study of nine criminal psychopaths. This evidence suggests that the degree of abnormality was significantly related to the degree of psychopathy and may explain the offending behaviors.

A 2008 review found various abnormalities (based on group differences from average) reported in the literature, centred on a prefrontal-temporo-limbic circuit &mdash; regions that are involved in emotional and learning processes, as well as many other processes. However, the authors report that the people classed as "psychopathic" cannot in fact be seen as a homogeneous group (i.e. as all having the same characteristics), and that the associations between structural changes and psychopathic characteristics do not enable causal conclusions to be drawn. They conclude that psychopathic characteristics involve multifactorial processes including neurobiological, genetic, epidemiological, and sociobiographical (the person's life in society) factors.

Diagnosis
Currently, there are no diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders for psychopathy. Labeling a person as a psychopath involves forensic measurement, using a diagnostic tool such as the Hare Psychopathy Checklist (PCL-R). The PCL-R is widely considered the "gold standard" for assessing psychopathy. Psychopathy is most strongly correlated with DSM-IV antisocial personality disorder (ASPD), and the ICD-10 antisocial personality disorder and dissocial personality disorder (DPD). However, the PCL-R criteria for identifying a psychopath are stricter than the diagnostic criteria for ASPD or DPD; psychopaths represent a subset of those with ASPD, and psychopaths' traits are more severe.

One issue related to the assessment of individuals who may exhibit affective, interpersonal, and behavioral features associated with psychopathy is the ability to overcome gender myths when the psychopathy features are present in females. The Hare Psychopathy Checklist-Revised has both percentiles and T-score tables for male and female offenders.

Hare Psychopathy Checklist
Psychopathy is most commonly assessed with the PCL-R, which is a clinical rating scale with 20 items. Each of the items in the PCL-R is scored on a three-point (0, 1, 2) scale according to two factors. PCL-R Factor 2 is associated with reactive anger, anxiety, increased risk of suicide, criminality, and impulsive violence.

PCL-R Factor 1, in contrast, is associated with extraversion and positive affect. Factor 1, the so-called core personality traits of psychopathy, may even be beneficial for the psychopath (in terms of nondeviant social functioning). A psychopath will score high on both factors, whereas someone with ASPD will score high only on Factor 2. Both case history and a semi-structured interview are used in the analysis.

Because an individual's scores may have important consequences for his or her future, the potential for harm if the test is used or administered incorrectly is considerable. The test can only be considered valid if administered by a suitably qualified and experienced clinician under controlled conditions.

PCL-R items
The following findings are for research purposes only, and are not used in clinical diagnosis. These items cover the affective, interpersonal, and behavioral features. Each item is rated on a score from zero to two. The sum total determines the extent of a person's psychopathy.


 * Factor 1: Aggressive narcissism
 * 1) Glibness/superficial charm
 * 2) Grandiose sense of self-worth
 * 3) Pathological lying
 * 4) Cunning/manipulative
 * 5) Lack of remorse or guilt
 * 6) Emotionally shallow
 * 7) Callous/lack of empathy
 * 8) Failure to accept responsibility for own actions


 * Factor 2: Socially deviant lifestyle
 * 1) Need for stimulation/proneness to boredom
 * 2) Parasitic lifestyle
 * 3) Poor behavioral control
 * 4) Promiscuous sexual behavior
 * 5) Lack of realistic, long-term goals
 * 6) Impulsiveness
 * 7) Irresponsibility
 * 8) Juvenile delinquency
 * 9) Early behavioral problems
 * 10) Revocation of conditional release


 * Traits not correlated with either factor


 * 1) Many short-term marital relationships
 * 2) Criminal versatility

Comorbidity
Psychopaths may have various mental conditions, although, in contrast to people with antisocial personality disorder, comorbidity among psychopaths is generally found to be low.

Substance abuse has been associated with psychopathy, particularly Factor 2 (anti-social behaviour), but not Factor 1 (emotional) scores of the PCL-R. Conduct disorder and ADHD have both been associated with psychopathy; which may be explained by disruption to dorsolateral prefrontal cortex. This area is associated with executive function, which is affected in all three disorders.

There is some evidence of an association between ASPD and other personality disorders (i.e. histrionic, narcissistic and borderline personality disorders), however, evidence for a link with psychopathy is more tentative.

Anxiety may be associated positively with antisocial behaviour, but it is inversely associated with Factor I (emotional) scores on the PCL-R. Depression is inversely associated with psychopathy. Although violence may be associated with schizophrenia, there is no conclusive evidence for a link between psychopathy and schizophrenia.

It has been suggested that psychopathy may be comorbid with several other diagnoses than these, however limited work on comorbidity has been carried out. This may be because of difficulties in using inpatient groups from certain institutions to assess comorbidity, owing to the likelihood of some bias in sample selection. Furthermore, comorbidity may be more reflective of poor discriminant validity of categories in the DSM-IV than reflective of underlying aetiologically separate conditions.

No evidence for propensity to sexually-oriented murder
No clinical definition of psychopathy indicates that psychopaths are especially prone to commit sexually-oriented murders, and scientific studies do not suggest that a large proportion of psychopaths have committed these crimes. Although some claim a large proportion of such offenders have been classified as psychopathic, this evidence comes from a single, unrepeated research study using the Rorschach Inkblot Test, an invalid test for psychopathy and for sex offenders, references not considering psychopathy, and studies concerning sexual homicide, a somewhat different population than the general class of sex offenders and not from meta-studies combining repeatable results.

As a discrete disorder
Hare believes that the Diagnostic and Statistical Manual of Mental Disorders should list psychopathy as a unique disorder, given that psychopathy has no precise equivalent in either the DSM-IV-TR, where it is most strongly correlated with the diagnosis of antisocial personality disorder, or the ICD-10, which has a partly similar condition called dissocial personality disorder.

Primary-secondary distinction
Primary psychopathy was defined by those following this theory as the root disorder in patients diagnosed with it, whereas secondary psychopathy was defined as an aspect of another psychiatric disorder or social circumstances. Today, primary psychopaths are considered to have mostly Factor 1 traits from the PCL-R (arrogance, callousness, manipulativeness, lying) whereas secondary psychopaths have a majority of Factor 2 traits (impulsivity, boredom proneness, irresponsibility, lack of long-term goals).

Secondary psychopaths show normal to above-normal physiological responses to (perceived) potential threats; their crimes tend to be unplanned and impulsive with little thought of the consequences. According to those using this theory, this type have hot tempers and are prone to reactive aggression. They experience normal to above-normal levels of anxiety but are nevertheless highly stimulus-seeking and have trouble tolerating boredom. Their lifestyle may lead to depression and even suicide.

Mealey uses the term "primary psychopathy" to differentiate between psychopathy that is biological in origin and "secondary psychopathy" that results from a combination of genetic and environmental influences. Lykken prefers sociopathy to describe the latter.

Sellbom and Ben-Porath (2005) describe the distinction:

This distinction closely resembles the distinction between instrumental and impulsive/reactive crime/violence in the field of criminology.

Joseph P. Newman et al., who use this concept of psychopathy, have validated David T. Lykken's conceptualization of psychopathy subtypes in relation to Gray's behavioral activation system and behavioral inhibition system. Newman et al. found measures of primary psychopathy to be negatively correlated with Gray's behavioral inhibition system, a construct intended to measure behavioral inhibition from cues of punishment or nonreward. In contrast, measures of secondary psychopathy to be positively correlated with Gray's behavioral activation system, a construct intended to measure sensitivity to cues of behavioral approach.

Psychopathy vs. sociopathy
Hare writes that the difference between sociopathy and psychopathy may "reflect the user's views on the origins and determinates of the disorder."

In the preface to the fifth edition of The Mask of Sanity, Cleckly stated, "... revisions of the nomenclature have been made by the American Psychiatric Association. The classification of psychopathic personality was changed to that of sociopathic personality in 1958", suggesting that he did not recognise any difference between the conditions.

David T. Lykken proposes psychopathy and sociopathy are two distinct kinds of antisocial personality disorder. He believes psychopaths are born with temperamental differences such as impulsivity, cortical underarousal, and fearlessness that lead them to risk-seeking behavior and an inability to internalize social norms. On the other hand, he claims sociopaths have relatively normal temperaments; their personality disorder being more an effect of negative sociological factors like parental neglect, delinquent peers, poverty, and extremely low or extremely high intelligence. Both personality disorders are the result of an interaction between genetic predispositions and environmental factors, but psychopathy leans towards the hereditary whereas sociopathy tends towards the environmental.

Three-factor model
Recent statistical analysis using confirmatory factor analysis by Cooke and Michie indicated a three-factor structure, with those items from factor 2 strictly relating to antisocial behaviour (criminal versatility, juvenile delinquency, revocation of conditional release, early behavioural problems, and poor behavioural controls) removed from the final model. The remaining items are divided into three factors: Arrogant and Deceitful Interpersonal Style, Deficient Affective Experience, and Impulsive and Irresponsible Behavioural Style.

Hare and colleagues have published detailed critiques of the Cooke & Michie hierarchical ‘three’-factor model, citing severe statistical problems. Hare and colleagues note that the Cooke & Michie model actually contains ten factors, and results in impossible parameters (negative variances). Hare and colleagues also note conceptual problems with this model.

Discrete vs. continuous
As part of the larger debate on whether personality disorders are distinct from normal personality, or if they are extremes on various dimensions of normal personality, is the debate on whether psychopathy represents something "qualitatively different" from normal personality, or a "continuous dimension" shading from normality into severely psychopathic. Otto Kernberg believed psychopathy should fall under a spectrum of pathological narcissism, that ranged from narcissistic personality on the low end, malignant narcissism in the middle, and psychopathy at the high end.

Early taxonometric analysis from Harris and colleagues indicated a discrete category may underlie psychopathy, but this was only found for the behavioural Factor 2 items, indicating this analysis may be related to Antisocial Personality Disorder rather than psychopathy per se. Marcus, John, and Edens more recently performed a series of statistical analysis on previously attained PCL–R and PPI scores and concluded psychopathy may best be conceptualized as having a "dimensional latent structure" like depression.

Childhood precursors
Psychopathic tendencies can sometimes be recognized in childhood or early adolescence. If recognized, a diagnosis of Conduct Disorder, or possibly the related Oppositional Defiant Disorder, may be given. However, while these childhood signs have been found in a significantly higher proportion of psychopaths than in the general population, it must be stressed that not all such childhood diagnoses turn out to be psychopaths as adults, or even disordered at all. Therefore, psychopathy is not normally diagnosed in children or adolescents, and some jurisdictions explicitly forbid diagnosing minors with psychopathy and similar personality disorders. This is because such a diagnosis "fails to capture the emotional, cognitive, and interpersonality traits — egocentricity and lack of remorse, empathy, or guilt - that are so important in the diagnosis of psychopathy."

Children showing strong psychopathic precursors often appear immune to punishment; nothing seems to modify their undesirable behavior. Consequently parents usually give up, and the behavior worsens.

The following childhood indicators are to be seen not as to the type of behavior, but as to its relentless and unvarying occurrence. Not all must be present concurrently, but at least a number of them need to be present over a period of years. These indicators are sufficient - but not necessary - indicators of possible psychopathy.


 * An extended period of bedwetting past the preschool years not due to any medical problem.
 * Precocious sadism, often expressed as profound animal abuse.
 * Pathological firesetting lacking in obvious homicidal intent. Not to be confused with playing with matches, which is not uncommon for preschoolers. This is the deliberate setting of destructive fires with utter disregard for the property and lives of others.
 * Lying, often without discernible objectives, extending beyond a child's normal impulse not to be punished. These lies are so extensive it is often impossible to know lies from truth.
 * Theft and truancy.
 * Aggression to peers and relatives, which can include physical and verbal abuse, getting others into trouble, or a campaign of psychological torment.

The three indicators &mdash; bedwetting, cruelty to animals and firestarting, known as the Macdonald triad &mdash; were first described by J.M. MacDonald as "red flag" indicators of psychopathy and future episodic aggressive behavior. However, subsequent research has found that bedwetting is not a significant factor. Moreover, as mentioned previously, these indicators are sufficient - but not necessary - indicators of possible psychopathy.

The question of whether young children with early indicators of psychopathy respond poorly to intervention compared to conduct disordered children without these traits have only recently been examined in controlled clinical research. The empirical findings from this research have been consistent with broader anecdotal evidence, pointing to poor treatment outcomes.

Clinical management
In practice, mental health professionals rarely treat psychopathic personality disorders as they are often considered untreatable and no interventions have proved to be effective. However, some of the difficulty has been attributed to the lack of clarity around the concept and diagnosis of psychopathy; the threat of danger to staff, or deceit or poor motivation from patients; and a lack of follow-up to test effectiveness. Despite pessimism, as of 1999, treatment of patients still takes place in a variety of psychiatric hospitals and secure units, and the research has indicated that some individuals do show some improvements when the right treatment is identified, and that longer periods of therapy often produce better results.

It has been shown that punishment and behavior modification techniques do not improve the behavior of psychopaths. Psychopathic individuals have been regularly observed to become more cunning and better able to hide their behaviour. It has been suggested that traditional therapeutic approaches actually make psychopaths more adept at manipulating others and concealing their behavior. They are generally considered to be not only incurable but also untreatable.

However, some researchers suggest that psychopaths can benefit as much as others from psychological treatment, at least in terms of criminal behaviors. For example, one therapeutic approach to juveniles reports reduced re-offending over a two year period compared to usual care.

United Kingdom
In the United Kingdom, "Psychopathic Disorder" was legally defined in the Mental Health Act (UK) as, "a persistent disorder or disability of mind (whether or not including significant impairment of intelligence) which results in abnormally aggressive or seriously irresponsible conduct on the part of the person concerned." This term, which did not equate to psychopathy, was intended to reflect the presence of a personality disorder, in terms of conditions for detention under the Mental Health Act 1983. With the subsequent amendments to the Mental Health Act 1983 within the Mental Health Act 2007, the term 'psychopathic disorder' has been abolished, with all conditions for detention (e.g. mental illness, personality disorder, etc.) now being contained within the generic term of 'mental disorder'.

In England and Wales, the diagnosis of dissocial personality disorder is grounds for detention in secure psychiatric hospitals under the Mental Health Act if they have committed serious crimes, but since such individuals are disruptive for other patients and not responsive to treatment this alternative to prison is not often used.

United States
Psychopathy has quite separate legal and judicial definitions that should not be confused with the medical definition. The American Psychiatric Association is vigorously opposing any non-medical or legal definition of what purports to be a medical condition "without regard for scientific and clinical knowledge." Various states and nations have at various times enacted laws specific to dealing with psychopaths.

In the United States, approximately 20 states currently have provisions for the involuntary civil commitment for sex offenders or sexual predators, under Sexually violent predator acts, avoiding the use of the term "psychopath." These statutes and provisions are controversial and are being reviewed by the U.S. Supreme Court as a violation of a person's Fourteenth Amendment rights. (See Foucha v. Louisiana for an example. )

Washington State Legislature defines a "Psychopathic personality" to mean "the existence in any person of such hereditary, congenital or acquired condition affecting the emotional or volitional rather than the intellectual field and manifested by anomalies of such character as to render satisfactory social adjustment of such person difficult or impossible." The same statute defines the "sexual psychopath" as "any person who is affected in a form of psychoneurosis or in a form of psychopathic personality, which form predisposes such person to the commission of sexual offenses in a degree constituting him a menace to the health or safety of others" for prison sentencing purposes in the Sentencing Reform Act of 1981.
 * Washington

California enacted a psychopathic offender law in 1939, since greatly outmoded and revised, that defined a psychopath solely in terms of offenders with a predisposition "to the commission of sexual offenses against children." A 1941 law attempted to further clarify this to the point where anyone examined and found to be psychopathic was to be committed to a state hospital and anyone else was to be sentenced by the courts. However, these laws were enacted years before the American Psychiatric Association began publishing the Diagnostic and Statistical Manual of Mental Disorders which is used today for diagnosis and does not include "psychopathic offender". Hence, these laws are of historical interest only.
 * California

Release rate among convicted criminals
Findings indicate psychopathic convicts have a 2.5 time higher probability of being released from jail than undiagnosed convicts, even though they are more likely to recidivate.

Epidemiology
It is estimated that approximately one percent of the general population are psychopaths. According to an unsourced article in popular science magazine Scientific American, studies indicate that about 25% of prison inmates meet diagnostic criteria for psychopathy. However, recent British studies have reported a community prevalence of 0.6%, consistent with the estimate given by the screening version of the psychopathy checklist and a prisoner prevalence of 7.7% in men and 1.9% in women.

History
The current concept of psychopathy has been thematically linked to writings by Theophrastus, a student of Aristotle in Ancient Greece, whose description of The Unscrupulous Man is said to embody the characteristics of psychopathy:


 * "The Unscrupulous Man will go and borrow more money from a creditor he has never paid ... When marketing he reminds the butcher of some service he has rendered him and, standing near the scales, throws in some meat, if he can, and a soup-bone. If he succeeds, so much the better; if not, he will snatch a piece of tripe and go off laughing."

In 1801, Philippe Pinel described patients who were mentally unimpaired but nonetheless engaged in impulsive and self-defeating acts. He saw them as la folie raisonnante ("insane without delirium") meaning they fully understood the irrationality of their behavior but continued with it anyway.

The scientific study of individuals thought to lack a conscience flourished in the latter half of the 19th century. Notably, Cesare Lombroso rejected the view that criminality could occur in anyone and instead sought to identify particular "born criminals" whom he thought showed certain physical defects.

By the turn of the 20th century, Henry Maudsley had begun writing about the "moral imbecile", and was arguing such individuals could not be rehabilitated by the correctional system. Maudsley included the psychopath's immunity to the reformational effects of punishment, owing to their refusal to anticipate further failure, and punishment. In 1904, Emil Kraepelin described four types of personalities similar to antisocial personality disorder. By 1915 he had identified them as defective in either affect or volition, dividing the types further into different categories, only some of which correspond to the current descriptions of antisocial personality disorder.

In 1909, Birnbaum introduced the term "sociopathic", intended to emphasize the social causes of antisocial behavior.

The Mask of Sanity by Hervey M. Cleckley, M.D., first published in 1941, is considered a seminal work which provided a vivid series of case studies of individuals (mostly prisoners) described by Cleckley as psychopathic. Cleckley proposed 16 characteristics of psychopathy. The title refers to the "mask" of normality that Cleckley thought concealed the disorganization or mental disorder of what he saw as the psychopathic person.

A 1977 study, however, found little relationship with the characteristics commonly attributed to psychopaths and concluded that the concept was being used too widely and loosely.

The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders incorporated various concepts of psychopathy/sociopathy/antisocial personality in early versions but, starting with the DSM-III in 1980, used instead a diagnosis of antisocial personality disorder. This was based on some of the criteria put forward by Cleckley but operationalized in behavioral terms and more specifically related to conduct and criminality. The World Health Organization's ICD incorporates a similar diagnosis of Dissocial Personality Disorder. Both the DSM and the ICD state that psychopathy (or sociopathy) are synonyms of their diagnosis.

However, there remained no international agreement on the diagnosis of psychopathy. One author referred to it in 1987 as an "infinitely elastic, catch-all category". In 1988, Blackburn wrote in the British Journal of Psychiatry that the concept as commonly used in psychiatry is little more than a moral judgement masquerading as a clinical diagnosis, and argued that it should be scrapped.

Robert Hare developed a Psychopathy Checklist in 1980 based on the psychopath construct advanced by Cleckley, and later revised it in the 1990s (including the removal of two items). While the official diagnostic manuals had moved away from the concept as being too vague and difficult to reliably assess, Hare's questionnaire would be increasingly used in research studies on psychopathy mainly in forensic (criminal) settings.

In other animals
Several studies note the role of serotonergic functioning in impulsive aggression and antisocial behavior in animals.