Intellectual Disability 235routinely necessary, but may be helpful for the high proportion of individ-
uals with intellectual disability who have co-existent psychiatric problems.
Psychiatric disorders in children and adolescents
with intellectual disability
In the multi-axial schemes of ICD-10 and DSM-IV, intellectual disability
and psychiatric disorders are coded on separate axes (see Chapter 2). While
intellectual disability is not itself a psychiatric disorder, it is a powerful
risk factor for psychiatric disorders. Roughly a third of all children and
adolescents with mild intellectual disability have psychiatric diagnoses, as
do roughly half of those with marked intellectual disability. This compares
with some 10–15% of children without intellectual disability when judged
by the same criteria. The combination of intellectual disability and psy-
chiatric disorder is particularly stressful for families, many of whom find
it harder to live with the psychiatric problems than with the problems
intrinsic to intellectual disability. Psychiatric problems are the commonest
reason for family placements breaking down.
Type of psychiatric disorder
Among children and adolescents with mild intellectual disability, the
mixture of psychiatric disorders is generally similar to that seen in children
without intellectual disability, being dominated by ADHD, emotional and
behavioural disorders. In marked intellectual disability, the mixture of
psychiatric disorder is more distinctive. Thus, although ADHD, emotional
and behavioural disorders are still common, so too are autistic spectrum
disorders (see Chapter 4). Thus, a substantial minority of children with
marked intellectual disability are socially aloof or relate to others in
a bizarre way; their imaginative play is characteristically impoverished,
and stereotypies can be prominent, and may be worsened by boredom,
isolation, blindness or deafness. Severe ADHD features sometimes occur
alone, and sometimes in association with simple stereotypies or features of
autism.
Self-injury, such as eye-poking, head banging or hand biting, is another
behavioural syndrome that is particularly common in marked intellectual
disability. These behaviours have a functional component that can be
shown to vary from individual to individual. Thus, in different individuals,
self-injury may serve to reduce boredom, to attract attention, or to discour-
age unwanted attention. Difficulties with the acquisition of self-help skills
(including feeding, toileting and dressing) are also common in marked in-
tellectual disability, as are sleep problems. For a range of reasons including
understandable frustration, poor impulse control, less good understanding
of why changes are occurring, a substantial minority of children and
adolescents with intellectual disability have fairly frequent temper out-
bursts, sometimes called ‘challenging behaviour’; as the individual grows
larger and stronger these may become increasingly hard to manage.