A personality disorder is an enduring pattern of inner experience and behavior that is abnormal, that starts by adolescence or early adulthood, that is stable and enduring, and that interferes with life.  It must be independent of any mood or anxiety disorder although some patients will have both.  Some psychiatrists love to diagnosis personality disorder and give such diagnoses to almost everyone who walks in the door.  Others use the diagnoses much more sparingly.  Personality disorder are very difficult to treat since they are part of a person's basic make-up.  However, Antisocial and Borderline Personality Disorders do tend to remit with age. 

The personality disorders listed in the DSM-IV diagnostic manual are: Cluster A (odd and eccentric): 1) Paranoid Personality Disorder, 2) Schizoid Personality Disorder, and 3) Schizotypal Personality Disorder; Cluster B (dramatic, emotional, erratic): 1) Antisocial Personality Disorder, 2) Borderline Personality Disorder, 3) Histrionic Personality Disorder, and 4) Narcissistic Personality Disorder; and Cluster C (anxious and fearful): 1) Avoidant Personality Disorder, 2) Dependent Personality Disorder, and 3) Obsessive-Compulsive Personality Disorder, and, finally, Personality Disorder Not Otherwise Specified, which means the person has a combination of features not fitting any one diagnosis.  A person may have more than one personality disorder diagnosis.

Personality disorders are not traditionally thought to be benefited by medication, although there are a fair number of studies showing some benefit.  Consequently, pharmaceutical companies have not funded much research in this area.  Whether personality disorders benefit from psychotherapy is also uncertain.  I think that they can, but it takes a very skilled therapist and a lot of time.  The cost-effectiveness of psychotherapy is open to question, because most of us are not very skilled therapists, even those of us that are good as convincing people to keep coming back over and over again.

Only Low to Moderate Stability of Personality Diagnoses in Depression: A 30 month follow-up study found personality disorder diagnoses had only a low to moderate stability over a 30-month period in depressed outpatients. Ferro, SUNY Stony Brook, Am J Psychiatry 155:653-9 5/98. (Ed: What this study is saying is that many psychiatrists in New York were jumping to conclusions, misdiagnosing patients as suffering from personality disorders in addition to depression only to have the so-called personality disorder disappear as the depression improved.  Personality disorders should not become too mild to diagnose when the depression lifts.)

Fluoxetine No Benefit for Depersonalization Disorder: In a 50-patient 10-week DB PC trial of individuals with depersonalization disorder of fluoxetine 10-60 mg/day or placebo, the Dissociative Experiences Scale - Depersonalization Factor, the Depersonalization Severity Scale and the Clinical Global Impression - Improvement (CGI-I) scale using an Intention-to-treat analysis revealed that fluoxetine (mean dosage 48 mg/day) was not superior to placebo except for a clinically minimal but statistically significantly greater improvement in CGI-I score in the fluoxetine group prior to covarying for anxiety and depression (2.9 v. 3.6). Depersonalization was significantly more likely to improve if comorbid anxiety disorder improved. Fluoxetine therapy in depersonalisation disorder: randomised controlled trial. Simeon D, Guralnik O, Schmeidler J, Knutelska M. Mount Sinai School of Medicine, Br J Psychiatry. 2004 Jul;185:31-6.  

Shyness Usually Outgrown: In the US National Comorbidity, Survey  of 5877 adults, 26% of women and 19% of men described themselves as 'very shy' when they were growing up. Of these shy individuals, 53% of women and 40% of men met criteria for a lifetime diagnosis of one or more anxiety or mood disorders [this is about twice as high as the national average suggesting that the shyness is the cause for only half in the disorders]. Shyness in childhood was linked to the complex subtype of social phobia in adulthood with lesser links to posttraumatic stress disorder in women and for major depressive disorder in men. Excessive shyness does not appear to be strongly associated with other anxiety and mood disorders when related psychosocial and developmental dimensions are statistically controlled. Finally, many individuals who report excessive childhood shyness do not meet criteria for any anxiety or mood disorder. Also, 50% of individuals with a lifetime history of complex social phobia did not view themselves as very shy when growing up. Psychiatric correlates of childhood shyness in a nationally representative sample. Cox BJ, et al. University of Manitoba. . Behav Res Ther. 2005 Aug;43(8):1019-27 

Schizotypal Personality Disorder

Helped by Risperidone: DB PC titrated to 2mg/d 25 pt 9 weeks. PANSS. Hamilton, CGI, & Schizotypal Personality Questionnaire. Risperidone in the Treatment of Schizotypal Personality Disorder. Koenigsberg HW, Reynolds D, Goodman M, New AS, Mitropoulou V, Trestman RL, Silverman J, Siever LJ. J Clin Psychiatry. 2003 Jun;64(6):628-34