Antisocial personality disorder is defined by a pervasive and persistent disregard for morals, social norms, and the rights and feelings of others. Individuals with this personality disorder will typically have no compunction in exploiting others in harmful ways for their own gain or pleasure and frequently manipulate and deceive other people, achieving this through wit and a facade of superficial charm or through intimidation and violence. They may display , think lowly and negatively of others, and lack remorse for their harmful actions and have a callous attitude to those they have harmed. Irresponsibility is a core characteristic of this disorder: they can have significant difficulties in maintaining stable employment as well as fulfilling their social and financial obligations, and people with this disorder often lead exploitative, unlawful, or parasitic lifestyles.

Those with antisocial personality disorder are often impulsive and reckless, failing to consider or disregarding the consequences of their actions. They may repeatedly disregard and jeopardize their own safety and the safety of others and place themselves and others in danger. They are often aggressive and hostile and display a disregulated temper and can lash out violently with provocation or frustration. Individuals are prone to substance abuse and addiction, and the abuse of various psychoactive substances is common in this population. These behaviors lead such individuals into frequent conflict with the law, and many people with ASPD have extensive histories of antisocial behavior and criminal infractions stemming back before adulthood.

Serious problems with interpersonal relationships are often seen in those with the disorder. Attachments and emotional bonds are weak, and interpersonal relationships often revolve around the manipulation, exploitation, and abuse of others. While they generally have no problems in establishing relationships, they may have difficulties in sustaining and maintaining them. Relationships with family members and relatives are often strained due to their behavior and the frequent problems that these individuals may get into.

While antisocial personality disorder is a mental disorder diagnosed in adulthood, it has its precedent in childhood. The DSM-5's criteria for ASPD require that the individual have conduct problems evident by the age of 15. Persistent antisocial behavior as well as a lack of regard for others in childhood and adolescence is known as conduct disorder and is the precursor of ASPD. About 25-40% of youths with conduct disorder will be diagnosed with ASPD in adulthood.

Conduct disorder (CD) is a disorder diagnosed in childhood that parallels the characteristics found in ASPD and is characterized by a repetitive and persistent pattern of behavior in which the basic rights of others or major age-appropriate norms are violated. Children with the disorder often display impulsive and aggressive behavior, may be callous and deceitful, and may repeatedly engage in petty crime such as stealing or vandalism or get into fights with other children and adults. This behavior is typically persistent and may be difficult to deter with threat or punishment. Attention deficit hyperactivity disorder (ADHD) is common in this population, and children with the disorder may also engage in substance abuse." CD is differentiated from oppositional defiant disorder (ODD) in that children with ODD do not commit aggressive or antisocial acts against other people, animals, and property, though many children diagnosed with ODD are subsequently rediagnosed with CD.

Two developmental courses for CD have been identified based on the age at which the symptoms become present. The first is known as the "childhood-onset type" and occurs when conduct disorder symptoms are present before the age of 10 years. This course is often linked to a more persistent life course and more pervasive behaviors, and children in this group express greater levels of ADHD symptoms, neuropsychological deficits, more academic problems, increased family dysfunction, and higher likelihood of aggression and violence. The second is known as the "adolescent-onset type" and occurs when conduct disorder develops after the age of 10 years. Compared to the childhood-onset type, less impairment in various cognitive and emotional functions are present, and the adolescent-onset variety may remit by adulthood. In addition to this differentiation, the DSM-5 provides a specifier for a callous and unemotional interpersonal style, which reflects characteristics seen in psychopathy and are believed to be a childhood precursor to this disorder. Compared to the adolescent-onset subtype, the childhood onset subtype, especially if callous and unemotional traits are present, tends to have a worse treatment outcome.

Sadistic personality disorder is a personality disorder involving which appeared in an appendix of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-III-R). The later versions of the DSM (DSM-IV, DSM-IV-TR and DSM-5) do not include it.

The words "sadism" and "sadist" are derived from Marquis de Sade.

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.

Borderline personality disorder may be characterized by the following signs and symptoms:

- Markedly disturbed sense of identity

- Frantic efforts to avoid real or imagined abandonment and extreme reactions to such

- Splitting ("black-and-white" thinking)

- Impulsivity and impulsive or dangerous behaviours

- Intense or uncontrollable emotional reactions that often seem disproportionate to the event or situation

- Unstable and chaotic interpersonal relationships

- Self-damaging behavior

- Distorted self-image

- Dissociation

- Frequently accompanied by depression, anxiety, anger, substance abuse, or rage

The most distinguishing symptoms of BPD are marked sensitivity to rejection or criticism, and intense fear of possible abandonment. Overall, the features of BPD include unusually intense sensitivity in relationships with others, difficulty regulating emotions, and impulsivity. Other symptoms may include feeling unsure of one's personal identity, morals, and values; having paranoid thoughts when feeling stressed; dissociation and depersonalization; and, in moderate to severe cases, stress-induced breaks with reality or psychotic episodes.

The "Diagnostic and Statistical Manual of Mental Disorders" is a widely used manual for diagnosing mental disorders. DSM- 5 still includes schizoid personality disorder with the same criteria as in DSM-IV.

According to the DSM, those with SPD may often be unable to, or will rarely express aggressiveness or hostility, even when provoked directly. These individuals can seem vague or drifting about their goals and their lives may appear directionless. Others view them as indecisive in their actions, self-absorbed, absentminded and detached from their surroundings ("not with it" or "in a fog"). Excessive daydreaming is often present. In cases with severe defects in the capacity to form social relationships, dating and marriage may not be possible.

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".

Schizoid personality disorder (SPD) is a personality disorder characterized by a lack of interest in social relationships, a tendency towards a solitary or sheltered lifestyle, secretiveness, emotional coldness, detachment, and apathy. Affected individuals may be unable to form intimate attachments to others and simultaneously demonstrate a rich, elaborate, and exclusively internal fantasy world.

SPD is not the same as schizophrenia or schizotypal personality disorder, but there is some evidence of links and shared genetic risk between SPD, other cluster A personality disorders, and schizophrenia. Thus, SPD is considered to be a "schizophrenia-like personality disorder".

Critics argue that the definition of SPD is flawed due to cultural bias and that it does not constitute a mental disorder but simply an avoidant attachment style requiring more distant emotional proximity. If that is true, then many of the more problematic reactions these individuals show in social situations may be partly accounted for by the judgments commonly imposed on people with this style. However, it is important to note that impairment is mandatory for any behaviour to be diagnosed as a personality disorder. SPD seems to satisfy this criterion because it is linked to negative outcomes. These include a significantly compromised quality of life, smaller GAF scores even after 15 years and one of the lowest levels of "life success" of all personality disorders (measured as "status, wealth, and successful relationships").

Schizoid personality disorder is a poorly studied disorder, and there is little clinical data on SPD because it is rarely encountered in clinical settings. The effectiveness of psychotherapeutic and pharmacological treatments for the disorder have yet to be empirically and systematically investigated.

Premenstrual dysphoric disorder (PMDD) occurs in 3–8 percent of women. Symptoms begin 5–11 days before menstruation and cease a few days after it begins. Symptoms may include marked mood swings, irritability, depressed mood, feeling hopeless or suicidal, a subjective sense of being overwhelmed or out of control, anxiety, binge eating, difficulty concentrating, and substantial impairment of interpersonal relationships. People with PMDD typically begin to experience symptoms in their early twenties, although many do not seek treatment until their early thirties.

Although some of the symptoms of PMDD and BPD are similar, they are different disorders. They are distinguishable by the timing and duration of symptoms, which are markedly different: the symptoms of PMDD occur only during the luteal phase of the menstrual cycle, whereas BPD symptoms occur persistently at all stages of the menstrual cycle. In addition, the symptoms of PMDD do not include impulsivity.

Personality disorders (PD) are a class of mental disorders characterized by enduring maladaptive patterns of behavior, cognition, and inner experience, exhibited across many contexts and deviating markedly from those accepted by the individual's culture. These patterns develop early, are inflexible, and are associated with significant distress or disability. The definitions may vary somewhat, according to source. Official criteria for diagnosing personality disorders are listed in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM) and the of the "International Classification of Diseases" (ICD). The DSM-5 lists personality disorders in the same way as other mental disorders, rather than on a separate 'axis', as previously.

Personality, defined psychologically, is the set of enduring behavioral and mental traits that distinguish between individual humans. Hence, personality disorders are defined by experiences and behaviors that differ from societal norms and expectations. Those diagnosed with a personality disorder may experience difficulties in cognition, emotiveness, interpersonal functioning, or impulse control. In general, personality disorders are diagnosed in 40–60% of psychiatric patients, making them the most frequent of psychiatric diagnoses.

Personality disorders are characterized by an enduring collection of behavioral patterns often associated with considerable personal, social, and occupational disruption. Personality disorders are also inflexible and pervasive across many situations, largely due to the fact that such behavior may be ego-syntonic (i.e. the patterns are consistent with the ego integrity of the individual) and are therefore perceived to be appropriate by that individual. This behavior can result in maladaptive coping skills and may lead to personal problems that induce extreme anxiety, distress, or depression. These behaviour patterns are typically recognized in adolescence, the beginning of adulthood or sometimes even childhood and often have a pervasive negative impact on the quality of life.

Many issues occur with classifying a personality disorder. Because the theory and diagnosis of personality disorders occur within prevailing cultural expectations, their validity is contested by some experts on the basis of inevitable subjectivity. They argue that the theory and diagnosis of personality disorders are based strictly on social, or even sociopolitical and economic considerations.

Psychopathy, sometimes considered synonymous with sociopathy, is traditionally defined as a personality disorder characterized by persistent antisocial behavior, impaired empathy and remorse, and bold, disinhibited, egotistical traits. Different conceptions of psychopathy have been used throughout history. These conceptions are only partly overlapping and may sometimes be contradictory.

Hervey M. Cleckley, an American psychiatrist, influenced the initial diagnostic criteria for antisocial personality reaction/disturbance in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM), as did American psychologist George E. Partridge. The DSM and "International Classification of Diseases" (ICD) subsequently introduced the diagnoses of antisocial personality disorder (ASPD) and dissocial personality disorder (DPD) respectively, stating that these diagnoses have been referred to (or include what is referred to) as psychopathy or sociopathy. The creation of ASPD and DPD was driven by the fact that many of the classic traits of psychopathy were impossible to measure objectively. Canadian psychologist Robert D. Hare later repopularized the construct of psychopathy in criminology with his Psychopathy Checklist.

Although no psychiatric or psychological organization has sanctioned a diagnosis titled "psychopathy", assessments of psychopathic characteristics are widely used in criminal justice settings in some nations, and may have important consequences for individuals. The study of psychopathy is an active field of research, and the term is also used by the general public, popular press, and in fictional portrayals. While the term is often employed in common usage along with the related but distinct "crazy", "insane", and "mentally ill", there is a distinction between those with psychosis and psychopathy.

As with other mental disorders, psychopathy as a personality disorder may be present with a variety of other diagnosable conditions. Studies especially suggest strong comorbidity with antisocial personality disorder. Among numerous studies, positive correlations have also been reported between psychopathy and histrionic, narcissistic, borderline, paranoid, and schizoid personality disorders, panic and obsessive–compulsive disorders, but not neurotic disorders in general, schizophrenia, or depression.

Attention deficit hyperactivity disorder (ADHD) is known to be highly comorbid with conduct disorder (a theorized precursor to ASPD), and may also co-occur with psychopathic tendencies. This may be explained in part by deficits in executive function. Anxiety disorders often co-occur with ASPD, and contrary to assumptions, psychopathy can sometimes be marked by anxiety; this appears to be related to items from Factor 2 but not Factor 1 of the PCL-R. Psychopathy is also associated with substance use disorders.

It has been suggested that psychopathy may be comorbid with several other conditions than these, but limited work on comorbidity has been carried out. This may be partly due to difficulties in using inpatient groups from certain institutions to assess comorbidity, owing to the likelihood of some bias in sample selection.

The two major systems of classification are the ICD-10 published by the World Health Organization and the DSM-5 by the American Psychiatric Association. Both have deliberately merged their diagnoses to some extent, but some differences remain. For example, ICD-10 does not include narcissistic personality disorder as a distinct category, while DSM-5 does not include enduring personality change after catastrophic experience or after psychiatric illness. ICD-10 classifies the DSM-5 schizotypal personality disorder as a form of schizophrenia rather than as a personality disorder. There are accepted diagnostic issues and controversies with regard to distinguishing particular personality disorder categories from each other.

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.

Paranoid personality disorder (PPD) is a mental disorder characterized by paranoia and a pervasive, long-standing suspiciousness and generalized mistrust of others. Individuals with this personality disorder may be hypersensitive, easily insulted, and habitually relate to the world by vigilant scanning of the environment for clues or suggestions that may validate their fears or biases. Paranoid individuals are eager observers. They think they are in danger and look for signs and threats of that danger, potentially not appreciating other evidence.

They tend to be guarded and suspicious and have quite constricted emotional lives. Their reduced capacity for meaningful emotional involvement and the general pattern of isolated withdrawal often lend a quality of schizoid isolation to their life experience. People with PPD may have a tendency to bear grudges, suspiciousness, tendency to interpret others' actions as hostile, persistent tendency to self-reference, or a tenacious sense of personal right. Patients with this disorder can also have significant comorbidity with other personality disorders.

While narcissists are common, malignant narcissists are less common. A notable difference between the two is the feature of sadism, or the gratuitous enjoyment of the pain of others. A narcissist will deliberately damage other people in pursuit of their own selfish desires, but may regret and will in some circumstances show remorse for doing so, while a malignant narcissist will harm others and enjoy doing so, showing little empathy or regret for the damage they have caused.

The definition and classification of mental disorders are key issues for researchers as well as service providers and those who may be diagnosed. For a mental state to classify as a disorder, it generally needs to cause dysfunction. Most international clinical documents use the term mental "disorder", while "illness" is also common. It has been noted that using the term "mental" (i.e., of the mind) is not necessarily meant to imply separateness from brain or body.

According to DSM-IV, a mental disorder is a psychological syndrome or pattern which is associated with distress (e.g. via a painful symptom), disability (impairment in one or more important areas of functioning), increased risk of death, or causes a significant loss of autonomy; however it excludes normal responses such as grief from loss of a loved one, and also excludes deviant behavior for political, religious, or societal reasons not arising from a dysfunction in the individual.

DSM-IV precedes the definition with caveats, stating that, as in the case with many medical terms, "mental disorder" "lacks a consistent operational definition that covers all situations", noting that different levels of abstraction can be used for medical definitions, including pathology, symptomology, deviance from a normal range, or etiology, and that the same is true for mental disorders, so that sometimes one type of definition is appropriate, and sometimes another, depending on the situation.

In 2013, the American Psychiatric Association (APA) redefined mental disorders in the DSM-5 as "a syndrome characterized by clinically significant disturbance in an individual's cognition, emotion regulation, or behavior that reflects a dysfunction in the psychological, biological, or developmental processes underlying mental functioning.”

The World Health Organization's ICD-10 lists paranoid personality disorder as "() Paranoid personality disorder".

It is a requirement of ICD-10 that a diagnosis of any specific personality disorder also satisfies a set of general personality disorder criteria. It is also pointed out that for different cultures it may be necessary to develop specific sets of criteria with regard to social norms, rules and other obligations.

Typical deficiencies may include problems identifying, processing, describing, and working with one's own feelings, often marked by a lack of understanding of the feelings of others; difficulty distinguishing between feelings and the bodily sensations of emotional arousal; confusion of physical sensations often associated with emotions; few dreams or fantasies due to restricted imagination; and concrete, realistic, logical thinking, often to the exclusion of emotional responses to problems. Those who have alexithymia also report very logical and realistic dreams, such as going to the store or eating a meal. Clinical experience suggests it is the structural features of dreams more than the ability to recall them that best characterizes alexithymia.

Some alexithymic individuals may appear to contradict the above-mentioned characteristics because they can experience chronic dysphoria or manifest outbursts of crying or rage. However, questioning usually reveals that they are quite incapable of describing their feelings or appear confused by questions inquiring about specifics of feelings.

According to Henry Krystal, individuals suffering from alexithymia think in an operative way and may appear to be superadjusted to reality. In psychotherapy, however, a cognitive disturbance becomes apparent as patients tend to recount trivial, chronologically ordered actions, reactions, and events of daily life with monotonous detail. In general, these individuals lack imagination, intuition, empathy, and drive-fulfillment fantasy, especially in relation to objects. Instead, they seem oriented toward things and even treat themselves as robots. These problems seriously limit their responsiveness to psychoanalytic psychotherapy; psychosomatic illness or substance abuse is frequently exacerbated should these individuals enter psychotherapy.

A common misconception about alexithymia is that affected individuals are totally unable to express emotions verbally and that they may even fail to acknowledge that they experience emotions. Even before coining the term, Sifneos (1967) noted patients often mentioned things like anxiety or depression. The distinguishing factor was their inability to elaborate beyond a few limited adjectives such as "happy" or "unhappy" when describing these feelings. The core issue is that people with alexithymia have poorly differentiated emotions limiting their ability to distinguish and describe them to others. This contributes to the sense of emotional detachment from themselves and difficulty connecting with others, making alexithymia negatively associated with life satisfaction even when depression and other confounding factors are controlled for.

Alexithymia is considered to be a personality trait that places affected individuals at risk for other medical and psychiatric disorders while reducing the likelihood that these individuals will respond to conventional treatments for the other conditions. Alexithymia is not classified as a mental disorder in the fourth edition of the "Diagnostic and Statistical Manual of Mental Disorders". It is a dimensional personality trait that varies in severity from person to person. A person's alexithymia score can be measured with questionnaires such as the Toronto Alexithymia Scale (TAS-20), the Bermond-Vorst Alexithymia Questionnaire (BVAQ), the Online Alexithymia Questionnaire (OAQ-G2) or the Observer Alexithymia Scale (OAS). It is distinct from the psychiatric personality disorders, such as antisocial personality disorder or borderline personality disorder, with which it shares some characteristics, and is likewise distinct from the abnormal conditions of sociopathy or psychopathy.

Alexithymia is defined by:

1. difficulty identifying feelings and distinguishing between feelings and the bodily sensations of emotional arousal

2. difficulty describing feelings to other people

3. constricted imaginal processes, as evidenced by a scarcity of fantasies

4. a stimulus-bound, externally oriented cognitive style.

In studies of the general population the degree of alexithymia was found to be influenced by age, but not by gender; the rates of alexithymia in healthy controls have been found at: 8.3%; 4.7%; 8.9%; and 7%. Thus, several studies have reported that the prevalence rate of alexithymia is less than 10%. A less common finding suggests that there may be a higher prevalence of alexithymia amongst males than females, which may be accounted for by difficulties some males have with "describing feelings", but not by difficulties in "identifying feelings" in which males and females show similar abilities.

Psychologist R. Michael Bagby and psychiatrist Graeme J. Taylor have argued that the alexithymia construct is strongly related (negatively) to the concepts of psychological mindedness and emotional intelligence and there is "strong empirical support for alexithymia being a stable personality trait rather than just a consequence of psychological distress". Other opinions differ and can show evidence that it may be state-dependent.

Bagby and Taylor also suggest that there may be two kinds of alexithymia, "primary alexithymia" which is an enduring psychological trait that does not alter over time, and "secondary alexithymia" which is state-dependent and disappears after the evoking stressful situation has changed. These two manifestations of alexithymia are otherwise called "trait" or "state" alexithymia.

Grandiosity refers to an unrealistic sense of superiority—a sustained view of oneself as better than others that causes the narcissist to view others with disdain or as inferior—as well as to a sense of uniqueness: the belief that few others have anything in common with oneself and that one can only be understood by a few or very special people. It also occurs in reactive attachment disorder.

Grandiosity is chiefly associated with narcissistic personality disorder, but also commonly features in manic or hypomanic episodes of bipolar disorder.

A spectrum disorder is a mental disorder that includes a range of linked conditions, sometimes also extending to include singular symptoms and traits. The different elements of a spectrum either have a similar appearance or are thought to be caused by the same underlying mechanism. In either case, a spectrum approach is taken because there appears to be "not a unitary disorder but rather a syndrome composed of subgroups". The spectrum may represent a range of severity, comprising relatively "severe" mental disorders through to relatively "mild and nonclinical deficits".

In some cases, a spectrum approach joins together conditions that were previously considered separately. A notable example of this trend is the autism spectrum, where conditions on this spectrum may now all be referred to as autism spectrum disorders. In other cases, what was treated as a single disorder comes to be seen (or seen once again) as comprising a range of types, a notable example being the bipolar spectrum. A spectrum approach may also expand the type or the severity of issues which are included, which may lessen the gap with other diagnoses or with what is considered "normal". Proponents of this approach argue that it is in line with evidence of gradations in the type or severity of symptoms in the general population, and helps reduce the stigma associated with a diagnosis. Critics, however, argue that it can take attention and resources away from the most serious conditions associated with the most disability, or on the other hand could unduly medicalize problems which are simply challenges people face in life.

A mood disorder (affective) spectrum or bipolar spectrum or depressive spectrum. These approaches have expanded out in different directions. On the one hand, work on major depressive disorder has identified a spectrum of subcategories and subthreshold symptoms which are prevalent, recurrent and associated with treatment needs. People are found to move between the subtypes and the main diagnostic type over time, suggesting a spectrum. This spectrum can include already recognised categories of minor depressive disorder, 'melancholic depression' and various kinds of atypical depression.

Going in another direction, numerous links and overlaps have been found between major depressive disorder and bipolar syndromes, including mixed states (simultaneous depression and mania or hypomania). Hypomanic ('below manic') and more rarely manic signs and symptoms have been found in a significant number of cases of major depressive disorder, suggesting not a categorical distinction but a dimension of frequency which is higher in bipolar II and higher again in bipolar I. In addition, numerous subtypes of bipolar have been proposed beyond the types already in the DSM (which includes a milder form called cyclothymia). These extra subgroups have been defined in terms of more detailed gradations of mood severity, or the rapidity of cycling, or the extent or nature of psychotic symptoms. Furthermore, due to shared characteristics between some types of Bipolar disorder and Borderline Personality Disorder, some researchers have suggested they may both lie on a spectrum of affective disorders, although others see more links to post-trauma syndromes.