A personality disorder (PD) is a mental disorder characterized by enduring maladaptive patterns of behavior, cognition, and inner experience, exhibited across many contexts and deviating from those accepted by the culture. Personality, defined psychologically, is the set of enduring behavioral and mental traits that distinguish individual humans. Hence, personality disorders are characterized by experiences and behaviors that deviate from social norms and expectations. Those diagnosed with a personality disorder may experience difficulties in cognition, emotiveness, interpersonal functioning, or impulse control. These patterns develop early, are inflexible, and are associated with significant distress or disability.
Official criteria for diagnosing personality disorders are listed in the sixth chapter of the International Classification of Diseases (ICD) and in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM). The definitions vary by source and remain a matter of controversy. For psychiatric patients, the prevalence of personality disorders is estimated between 40 and 60%. The behavior patterns of personality disorders are typically recognized by adolescence, the beginning of adulthood or sometimes even childhood and often have a pervasive negative impact on the quality of life.