Figure 19.1 indicates the prevalence rates of the 10 personality disorders. Prevalence is a term that refers to the total number of cases that are present within a given population during a particular period of time. The data in Figure 19.1 are based on summaries of several community samples (Mattia & Zimmerman, 2001) and refer to prevalence rates at the time of sampling, e.g., at any given time, how many people are diagnosable with paranoid personality disorder? These results show that obsessive-compulsive personality disorder is the most common, at just over 4 percent prevalence rate. Next most common are the schizotypal, histrionic, and dependent personality disorders, approximately 2 percent prevalence each. The least common is narcissistic personality disorder, affecting only 0.2 percent of the population. However , these diagnoses were all based on interviews, and it may be that narcissists are least likely to admit to the more disordered features of their condition. In fact, Oltmanns and colleagues have shown that self-reports of narcissism correlate weakly with peer reports of narcissism, even though with most other personality traits there are modest to substantial correlations between self-report and peer report (Clifton, Turkheimer, & Oltmanns, in press; Klonsky , Oltmanns, & Turkheimer, 2002; Oltmanns, Friedman, Fiedler, & Turkheimer, in press). These findings suggest that because the data in Figure 19.1 are based on self-report through structured interviews, they may actually underestimate the prevalence of some of the disorders, especially narcissism.
Prevalence of Personality Disorders
Estimates of the prevalence of personality disorders.
Source: Adapted from J. I. Mattia and M. Zimmerman, "Epidemiology." In W. J. Livesley (ed), Handbook of Personality Disorders: Theory, Research, and Treatment. New York: Guilford, 2001. Reprinted with permission.
The total prevalence rate for having at least one personality disorder is about 13 percent. That is, at any given time, approximately 13 percent of the population is diagnosable with a personality disorder of one or more types. This brings up the issue of comorbidity, which we also mentioned in our A Closer Look on the Unabomber . A substantial proportion, between 25 and 50 percent, of the people who meet the criteria for a diagnosis on one personality disorder will also meet the criteria for diagnosis on another personality disorder (Oltmanns & Emery , 2004). Many of the personality disorders contain common features. For example, several disorders involve social isolation, including schizotypal, schizoid, avoidant, and, in many cases, obsessive-compulsive disorder. Uninhibited and irresponsible behavior is one of the criteria for a diagnosis of borderline, histrionic, and antisocial personality disorders. As such, dif ferential diagnoses are often challenging in personality disorders. A differential diagnosis is one in which, out of two or more possible diagnoses, the clinician searches for evidence in support of one diagnostic category over all the others.
Was this article helpful?