Personality traits have always been of interest to people.  We often hear others described in terms of their personality characteristics.  Although the combination of these characteristics is unique to the individual, the basic descriptors have evolved to be understandable to us all.  The early Greeks employed a literary form begun by Aristotle, which exaggerated 'good' and 'bad' traits to communicate an individual's personality, often with humorous effect (Millon and Davis in Livesley,1995, pp.3-4).  The word personality has its origins in Latin; persona originally meant the mask worn by actors in a drama.  Although the term mask connotes "pretense and illusion" it has evolved to represent a person's observable qualities and characteristics (ibid, p. 2).  Conceptions of personality and its related pathology have continued to evolve since the ancient Greeks and Romans first began their attempts to describe the complexities of human character and behavior. 

    By the mid 19th century, psychiatrists began to believe that "one could be insane without a confusion of mind" (Millon and Davis in Livesley,1995, p.6).  This was perhaps the first time that personality traits were pathologized.  In 1952 with the publication of the first Diagnostic and Statistical Manual of Mental Disorders the term "personality disorders" included five broad categories each with several smaller subclasses.  These personality disturbances were considered to be unaffected by therapy and included things we do not currently consider to be related to personality such as learning disabilities and post-traumatic stress disorder (Millon and Davis in Livesley,1995, pp. 14-15). 

    A major change in the conceptualization of personality disorders occurred in the DSM-II (APA,1968), which "stipulated that these disorders must involve both impaired functioning and personally experienced distress."  Further, personality disorders should not overlap with other neurotic and psychotic disorders (Millon and Davis in Livesley,1995, p.16).  Another major structural overhaul occurred with the publication of the DSM III (APA, 1980), and the development of the multiaxial model.  Personality disorders were hence separated from clinical disorders and placed on a separate axis.  This shift in conceptualization and structure recognized that "lifelong coping styles and emotional vulnerabilities comprising personality can provide a context within which the more salient and usually transient clinical states are likely to arise and be understood" (Millon and Davis in Livesley, pp.16-17). 

    The current edition of the DSM (IV-TR), defines personality disorders as "an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the individual's culture, is pervasive and inflexible, has an onset in adolescence or early adulthood, is stable over time, and leads to distress or impairment."  The ten currently recognized personality disorders are grouped into three clusters based on "descriptive similarities" (APA, p. 685).