Personality disorder

Personality disorder, formerly referred to as a Characterological disorder is a class of mental illness characterized by rigid and on-going patterns of thought and action. The underlying belief systems informing these patterns are referred to as fixed fantasies. The inflexibility and pervasiveness of these behavioral patterns often cause serious personal and social difficulties, as well as a general impairment of functioning.

Personality disorders are defined by the American Psychiatric Association as "an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the culture of the individual who exhibits it". These patterns, as noted, are inflexible and pervasive across many situations, due in large part to the fact that such behavior is ego-syntonic (i.e., the patterns are consistent with the ego integrity of the individual), and therefore, perceived to be appropriate by that individual. The onset of these patterns of behavior can typically be traced back to the beginning of adulthood, and, in rare instances, early adolescence.