Disorders of Attention and Activity 57else. What particularly distinguishes an individual with ADHD is his or her
inability to suppress activity when stillness is required, for example, in
the classroom or at the meal table. Children and adolescents with ADHD
are also likely to be impulsive: acting without due reflection, engaging
in rash and sometimes dangerous behaviours, blurting out answers in
class, interrupting others, and not waiting their turn in games. However,
impulsiveness is also a common feature of most disruptive behavioural
disorders (see Box 6.3 on p. 71), so it is not as useful as over-activity and
inattention when trying to distinguish ADHD from disruptive behavioural
disorders.
Pervasiveness
If symptoms and impact only occur in a single setting, this is not enough for
an ADHD diagnosis. Thus DSM-IV stipulates that the symptoms must have
an impact in different settings, for example, both at home and at school.
ICD-10 has a similar requirement for pervasive symptoms. It is important
to note, however, that ADHD symptoms may not be evident during a brief
clinic visit since the child or adolescent may be intimidated by unfamiliar
professionals, or may be happy to settle to interesting tasks when given
plenty of adult attention.
Chronicity and early onset
Both ICD-10 and DSM-IV require chronicity (at least six months of
symptoms) and early onset (by or before 7 years of age). Though ADHD
generally dates back to the preschool years, referral is often delayed until
the early school years. This is the period when the child’s inattentiveness,
learning problems and disruptiveness become increasingly troublesome.
Exclusion criteria
According to the rules, autistic spectrum disorders (ASDs) are meant to
take precedence over ADHD. Though individuals with ASDs can also be
restless and inattentive, they should never officially be given an additional
ADHD diagnosis. Sometimes this rule makes sense. For instance, a boy
with an ASD may be extremely restless and inattentive both at home and
at school because he is not interested in doing what his parents or teachers
want him to do – so he will have a lot of ADHD symptoms reported by
both parents and teachers. However, if careful enquiry establishes that he
has excellent attention when lining up toys or memorizing timetables, he
should not be diagnosed as having ADHD as well as an ASD.
In other instances, though, the exclusion rule makes much less sense
and may be dropped in future revisions of DSM and ICD. This is because
some individuals do seem to have mixed features of ASDs and ADHD
(perhaps because of shared genes), and both conditions need treating.
Additional exclusion rules specify that ADHD should not be diagnosed
when restlessness and poor concentration are due to a mood disorder, an
anxiety disorder, or schizophrenia.