Personality disorders have an early onset, and are associated with dysfunction over the course of adult life. Antisocial and borderline personality disorders tend to remit with age, but other categories do not usually show improvement. The chronicity of personality disorders is both a challenge and a frame for treatment planning. Psychotherapy for these patients can focus on rehabilitation and the development of social niches that match their personality profiles.
THE NATURE OF PERSONALITY DISORDERS
Patients with personality disorders are common in clinical practice (51). But this population presents a number of difficulties for effective treatment (17,29). These conditions are associated with strikingly low levels of functioning (23,44). Moreover, by definition, personality disorders begin early in development and go on to have a chronic course (1).
This degree of chronicity and dysfunction requires an explanation. It has long been assumed that "deep-seated" problems must originate in early childhood, and that problems present for years require years of therapy. This point of view has led to therapeutic approaches designed to discover and repair conflicts arising in early development.
However, recent evidence suggests that these etiological assumptions are, at least in part, mistaken. In medicine, diseases that begin early in life and go on to chronicity tend to be associated with higher genetic vulnerability (7), and similar principles apply to most mental disorders (25). Behavioral genetic studies show that about half the variance affecting personality traits (12), as well as personality disorders themselves (46), is accounted for by genetic factors. There is strong evidence that personality disorders are rooted in heritable traits that reflect temperament (40,43,29).
However, these findings do not mean that personality disorders are purely genetic, or that their causes lie only in "chemical imbalances." Environmental factors, most particularly childhood adversities, are also important (13). These risk factors have been most consistently identified in research on antisocial personality (38) and on borderline personality (50).
The real issue is that the impact of adverse events can only be understood in interaction with temperament. This principle is supported by research showing that in most cases, childhood trauma does not lead to pathological sequelae (41). In general, life events have greater effects on those who are vulnerable (25). The development of a diagnosable personality disorder depends on a complex combination of genetic and environmental factors, which are best formulated in a stress-diathesis model (22,25).
PRECURSORS, COURSE AND OUTCOME OF PERSONALITY DISORDERS
Personality disorders do not arise in adulthood de novo. These conditions have a continuous relationship with normal personality traits (17), and differences are only a matter of degree. These trait profiles also reflect patterns of vulnerability that can be identified prior to the onset of a diagnosable disorder.
Although personality disorders may only be present clinically at adolescence, they usually have childhood precursors. The best documented example concerns antisocial personality, for which conduct disorder is an established precursor (38). Patients who later develop borderline personality may also have had difficulties during childhood, probably a combination of externalizing and internalizing symptoms (27). Patients who develop avoidant personality disorder in adulthood may have been unusually shy ("behaviorally inhibited") as children (14,25). Finally, patients who develop schizoid or schizotypal personality disorders may show similar symptoms during childhood (48).
Childhood precursors reflect temperamental variations that shape trait profiles, and temperament also explains why personality is highly stable over the life course (18). But traits do not, by themselves, lead to psychopathology. …