Diagnosis of personality disorders is very subjective; however, inflexible and pervasive behavioral patterns often cause serious personal and social difficulties, as well as a general functional impairment. Rigid and ongoing patterns of feeling, thinking and behavior are said to be caused by underlying belief systems and these systems are referred to as fixed fantasies or “dysfunctional schemata”
Personality disorders are defined by the American Psychiatric Association (APA) 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 systonic (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 late adolescence and the beginning of adulthood and, in rare instances, childhood.