Prevention: an achievable goal in personalized medicine.

In the past 15 years a considerable number of studies
have found evidence that it may be possible to prevent
the onset of some mental disorders. Most evidence is
available for depressive disorders, but a growing number
of studies have focused on anxiety disorders and
psychotic disorders. This paper reviews the studies which
have examined the effects of preventive interventions
on the incidence of mental disorders in people who do
not meet criteria for a mental disorder at baseline. More
than 20 studies have examined prevention of depressive
disorders, and they have found an overall reduction in
the incidence of about 25% compared with control
groups. The problem of identifying the most optimal
target groups for preventive interventions is also illustrated.
This is a problem because most risk indicators
have a low specificity, and most people with a risk indicator
do not develop a mental disorder. Finally, this
paper will show how other statistics, such as the exposure
rate, the attributable fraction, and the number
needed to treat can help in identifying the most optimal
target groups for preventive interventions.