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36 J. H. Reich and G. de Girolamo
PD. and it accounted for 45% of the total sample. The next most wmmon
was asthenic PD.
In the US on a selected day in 1986, there were a total of 3893 persons
under care in some in-patient psychiatric facility, with a primary diagnosis
of PD. This corresponded to 2.4% of the total number of in-patients
on that date.41 In the same year there were 29,910 admissions with a primary
diagnosis of PD. 1.9% of all admissions. The median length of hospital
stay for in-patients with a diagnosis of PD was nine days. Among
all those under out-patient care on the same day, there were 81,731 or
5.9% of the total, with a diagnosis of PD. In the same year 136,903 people
or 6.4% were admitted to out-patient care with a PD diagnosis.
The epidemiological findings in treated samples are especially important
if we bear in mind that the presence of a PD among those suffering
from other mental disorders can be a major predictor of the natural history
and treatment o~tcome.~
Conclusions
The epidemiology of PDs has not received the same amount of attention
as that of many other psychiatric disorders. In the last few years the situation
has changed, and we now have data on the prevalence of PD in the
community and in psychiatric facilities. Community data come primarily
from three studie~l~-~~ with a total sample of about 1300 subjects from
two countries, Germany and the US. There are excellent national and
cross-national epidemiological data on antisocial personality disorder,
based on the same diagnostic methods. There are almost no data on other
PDs from countries other than Germany and the US. The lack of studies
from developing countries is especially noteworthy because the role of
sociocultural factors has yet to be determined.
One important methodological problem is that some PDs have a very
low prevalence rate. Consequently, epidemiological surveys carried out
among the general population may require very large samples in order to
identify a sufficient number of cases to study demographic correlates and
the association of PD with other psychiatric disorders.
Many of the PDs are at an early stage of construct validation. Further
research should probably follow the general recommendations for validating
a psychiatric disorder. These include the need to delineate a proposed
disorder from other disorders. Given the overlap of the PDs, this
will be a challenging task. Another criterion is external validation, and
there are a number of psychological tests and behavioural indicators that