Attempts have been made to establish objective diagnostic criteria for
psychiatric disorders in persons with mental retardation. This paper
describes the clinical features of the most important psychiatric diso
rders in mentally retarded adolescents: mood disorders, psychotic diso
rders, severe behavioral disorders, personality disorders, anxiety dis
orders, and attention deficit disorder with hyperactivity. The impact
of mental retardation on personality development is confirmed by the h
igh psychopathological vulnerability of the mentally retarded. All typ
es of mental disorders can be observed, with an incidence estimated to
be at least three or four times higher than in the general population
. Adolescence is a particularly important phase for the mentally retar
ded, since adolescent turmoil can increase the risk of psychopathology
.