Epidemiology
The prevalence of personality disorder in the general community was largely unknown until surveys starting from the 1990s. In 2008 the median rate of diagnosable PD was estimated at 10.6%, based on six major studies across three nations. This rate of around one in ten, especially as associated with high use of cocaine, is described as a major public health concern requiring attention by researchers and clinicians.[85] The prevalence of individual personality disorders ranges from about 2% to 8% for the more common varieties, such as obsessive-compulsive, schizotypal, antisocial, borderline, and histrionic, to 0.5–1% for the least common, such as narcissistic and avoidant.[86][47]
A screening survey across 13 countries by the World Health Organization using DSM-IV criteria, reported in 2009 a prevalence estimate of around 6% for personality disorders. The rate sometimes varied with demographic and socioeconomic factors, and functional impairment was partly explained by co-occurring mental disorders.[87] In the US, screening data from the National Comorbidity Survey Replication between 2001 and 2003, combined with interviews of a subset of respondents, indicated a population prevalence of around 9% for personality disorders in total. Functional disability associated with the diagnoses appeared to be largely due to co-occurring mental disorders (Axis I in the DSM).[88] This statistic has been supported by other studies in the US, with overall global prevalence statistics ranging from 9% to 11%.[89][90]
A UK national epidemiological study (based on DSM-IV screening criteria), reclassified into levels of severity rather than just diagnosis, reported in 2010 that the majority of people show some personality difficulties in one way or another (short of threshold for diagnosis), while the prevalence of the most complex and severe cases (including meeting criteria for multiple diagnoses in different clusters) was estimated at 1.3%. Even low levels of personality symptoms were associated with functional problems, but the most severely in need of services was a much smaller group.[91] Personality disorders (especially Cluster A) are found more commonly among homeless people.[92]
There are some sex differences in the frequency of personality disorders which are shown in the table below.[93]: 206 The known prevalence of some personality disorders, especially borderline PD and antisocial PD are affected by diagnostic bias. This is due to many factors including disproportionately high research towards borderline PD and antisocial PD, alongside social and gender stereotypes, and the relationship between diagnosis rates and prevalence rates.[86] Since the removal of depressive PD, self-defeating PD, sadistic PD and passive-aggressive PD from the DSM-5, studies analysing their prevalence and demographics have been limited.