Only when personality traits are inﬂexible and maladaptive and cause significant func- tional impairment or subjective distress do they constitute personality disorders. The essen- tial feature of a personality disorder is an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the individual’s culture and is manifested in at least two of the following areas: cognition, affectivity, interpersonal functioning, or im- pulse control (Criterion A). This enduring pattern is inﬂexible and pervasive across a broad range of personal and social situations (Criterion B) and leads to clinically significant dis- tress or impairment in social, occupational, or other important areas of functioning (Crite- rion C). The pattern is stable and of long duration, and its onset can be traced back at least to adolescence or early adulthood (Criterion D). The pattern is not better explained as a manifestation or consequence of another mental disorder (Criterion E) and is not attribut- able to the physiological effects of a substance (e.g., a drug of abuse, a medication, exposure to a toxin) or another medical condition (e.g., head trauma) (Criterion F). Specific diagnostic criteria are also provided for each of the personality disorders included in this chapter.
The diagnosis of personality disorders requires an evaluation of the individual’s long- term patterns of functioning, and the particular personality features must be evident by early adulthood. The personality traits that define these disorders must also be distin- guished from characteristics that emerge in response to specific situational stressors or more transient mental states (e.g., bipolar, depressive, or anxiety disorders; substance in- toxication). The clinician should assess the stability of personality traits over time and across different situations. Although a single interview with the individual is sometimes sufficient for making the diagnosis, it is often necessary to conduct more than one inter- view and to space these over time. Assessment can also be complicated by the fact that the the individual (i.e., the traits are often ego-syntonic). To help overcome this difficulty, sup- plementary information from other informants may be helpful.
The features of a personality disorder usually become recognizable during adolescence or early adult life. By definition, a personality disorder is an enduring pattern of thinking, feeling, and behaving that is relatively stable over time. Some types of personality disorder (notably, antisocial and borderline personality disorders) tend to become less evident or to remit with age, whereas this appears to be less true for some other types (e.g., obsessive- compulsive and schizotypal personality disorders).
Personality disorder categories may be applied with children or adolescents in those relatively unusual instances in which the individual’s particular maladaptive personality traits appear to be pervasive, persistent, and unlikely to be limited to a particular devel- opmental stage or another mental disorder. It should be recognized that the traits of a per- sonality disorder that appear in childhood will often not persist unchanged into adult life.
For a personality disorder to be diagnosed in an individual younger than 18 years, the fea- tures must have been present for at least 1 year. The one exception to this is antisocial per— sonality disorder, which cannot be diagnosed in individuals younger than 18 years. Al- though, by definition, a personality disorder requires an onset no later than early adulthood, individuals may not come to clinical attention until relatively late in life. A per- sonality disorder may be exacerbated following the loss of significant supporting persons (e.g., a spouse) or previously stabilizing social situations (e.g., a job). However, the devel- opment of a change in personality in middle adulthood or later life warrants a thorough evaluation to determine the possible presence of a personality change due to another med- ical condition or an unrecognized substance use disorder.