Introduction
BSESSIVE-compulsive disorder accounts for between 0.1%
vand 4.60%o of psychiatrically disturbed individuals.'
However, minor obsessional traits are observed far more often,
being found in 14%o of a sample of normal people in the United
States of America.2 A genetic predisposition seems likely, since
obsessionality is more prevalent in first degree relatives of
obsessive-compulsive patients than in the population at large.3
Furthermore, monozygotic twin pairs show frequent concordance for symptoms of obsessive-compulsive disorder compared
with a virtual absence of concordance in dizygotic twin pairs.4
Neurological factors may occasionally contribute to the disorder.
However, they are present in only a minority of cases. Successful
behavioural treatment is independent of such factors.5 The
outlook for sufferers is variable and depends on the severity and
duration of disturbance. Seventy per cent of mild cases improve
substantially after one to five years although only 33% of
hospitalized patients improve over a similar time period.