The basic modern concept of personality disorder dates back to French physician Philippe Pinel, who pioneered the humane treatment of mentally ill individuals. In 1801, Pinel characterized the condition manie sans d\u00e9lire (mania without delusion), as outbursts of rage and violence in the absence of any symptoms of psychosis (e.g. delusions and hallucinations). Kurt Schneider\u2019s seminal volume Psychopathic Personalities, first published in 1923, still forms the basis of current classifications of personality disorders. An estimated 9-10% of individuals worldwide suffer from any personality disorder with prevalence rates as high as 24% in primary care and more than 30% among individuals being treated for psychiatric disorders. The severity and chronic nature of these impairments causes serious suffering for impacted individuals and their families. Moreover, co-occurring mental illness and physical illnesses are common in individuals with personality disorders. Evolving Personality Disorder Classification A better understanding of underlying mechanisms, impairments and comorbidity have led to periodic changes in diagnostic criteria published in the Diagnostic and Statistical Manual of Mental Disorders, as well as fierce debate. In DSM-II (1968), influenced by psychoanalysis, some personality disorders were differentiated from neuroses of the same name (e.g. hysterical, obsessive-compulsive and neurasthenic personalities and neuroses). In DSM-3 (1980) and DSM-4 (1994), personality disorders were described as discrete types, grouped into three clusters, placed on a separate axis (axis II). Borderline and narcissistic personality disorders, new to DSM-3, were adapted from psychoanalytic concepts. This is still a nascent field relative to other psychiatric disorders such as schizophrenia, depression and bipolar disorder, with a paucity of research. Current Classification and Types of Personality Disorders The biggest change from DSM-4 to the current DSM-5, is that the concept of areas (axes) has been eliminated. Now, personality disorders are simply categorized by three Clusters: A, B and C, each of which includes similar or overlapping characteristics and symptoms. The prevalence rates for each of the 10 types of personality vary greatly, depending on the study. Cluster A This cluster is characterized by odd or eccentric behavior. Major disruptions in relationships can result from behavior perceived as peculiar, suspicious or detached. Cluster A personality disorders include: Schizotypal Personality Disorder This chronic and pervasive condition impacts an estimated 0.6-3.3% of the population and is characterized by social isolation and feelings of indifference toward other people. The words distant, withdrawn, aloof, cold and detached are used to describe people with this disorder and depression is the most frequent comorbidity. Unlike schizophrenia, paranoia and hallucinations rarely occur. Paranoid Personality Disorder This disorder impacts .07-5.1% of the population and as the name implies, involves pervasive distrust and suspicion of others. Individuals tend to be angry, secretive, guarded and isolate themselves due to unfounded issues they have with friends, family and significant others. Schizoid Personality Disorder Distant and withdrawn, individuals with this disorder are consumed by their thoughts and feelings and have difficulty expressing themselves and reading other people\u2019s social cues. Prevalence rates vary between 0.9-4.9%. Cluster B This cluster is characterized by dramatic or erratic behavior. Very intense emotions or extremely impulsive, theatrical, promiscuous or law-breaking behaviors may occur. Cluster B personality disorders include: Borderline Personality Disorder This disorder impacts .05-3.9% of the population and is characterized by unstable moods, relationships, behaviors and self-image. Impulsivity, attention-seeking, bouts of anger and volatility in interpersonal relationships are common. It is highly comorbid with other disorders, with 96% of individuals diagnosed with a lifetime mood disorder and 88% with an anxiety disorder. Histrionic Personality Disorder Individuals with this disorder suffer from low self-esteem, so they seek constant approval from others. They are prone to shallow and rapidly shifting emotions, with an excessive flair for the dramatic, although the underlying reasons for this behavior are vague. This disorder affects 0.2-.09% of the population. Antisocial Personality Disorder Individuals with this disorder often exhibit a blatant, longstanding disregard for other people\u2019s feelings or rights. They feel little or no empathy toward others and could care less about bending or breaking the law for their own needs or wants. Prevalence rates vary between 1.0-4.1%. Narcissistic Personality Disorder This disorder frequently co-occurs with borderline personality disorder and impacts an estimated 2.2% of the population. As the name implies, individuals have a grossly inflated opinion of themselves, need excessive admiration and believe only other \u201cspecial\u201d people like them are worthy. Clinically significant self-absorption and associated negative behaviors interfere with relationships, careers or other important areas of life. Cluster C This cluster is characterized by anxiety, with pervasive anxiety and\/or fearfulness common manifestations. Cluster C personality disorders include: Dependent Personality Disorder Considered the least prevalent, this disorder affects 0.1-.08% of the population. With a strong fear of being alone or rejected, individuals have difficulty accepting criticism or coping when a relationship ends. They may stay in an unhealthy or abusive relationship and avoid disagreeing with others for fear of rejection. Obsessive-Compulsive Personality Disorder Not to be confused with obsessive compulsive disorder, this disorder impacts 2.4-4.7% of the population. It is characterized by the need to be in complete control, a preoccupation with orderliness, perfectionism and rigidity. As a result, flexibility, openness, efficiency and the ability to adapt to change are severely compromised. Avoidant Personality Disorder Individuals with this disorder face such crippling stress in their day-day-day lives that their ability to socialize and maintain relationships is greatly compromised. They feel inferior to others and are so hypersensitive to criticism that they often isolate themselves to avoid it. Prevalence rates vary between 1.8-6.4%. Several types of therapeutic interventions for personality disorders can help people with personality orders regain control of their lives, including cognitive behavioral therapy, dialectical behavior therapy and experiential therapies. In addition, medications such as mood stabilizers, antidepressants and antipsychotics may be prescribed, although none are specifically approved for personality disorders. Because co-occurring substance disorders are common in individuals with personality disorders, these issues are also addressed in treatment.