disorder in which a child displays hyperactive, impulsive, and/or inattentive behavior that is age-inappropriate.
ADHD is a result of an atypical chemical balance in
the brain, which means that ADHD is a physical problem, not an emotional problem. Outside factors, such as poor parenting, a chaotic home situation, divorce, or school stresses may affect how the symptoms come to light, but they do not cause ADHD. In order to diagnose ADHD (according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision [DSM-IV-TR]), problems of inattention and/or hyperactivity and impulsivity must interfere with a child’s functioning in at least two settings (home, school, or social situations). In addition, the guidelines state that at least some symptoms must have been present before the age of 7 years.
How common is ADHD?
ADHD is quite common; it is conservatively estimated
to affect 3% to 5% of school-age children. Some reports
suggest that as many as 4% to 8% or even an amazing
10% to 18% of children have ADHD. Thus, somewhere
between 2 and 13 million American children
have ADHD. Put another way, on the average, at least
one child in every classroom has ADHD. ADHD
results in millions of physician visits per year.
Approximately 60% of children with ADHD have
symptoms that persist into adulthood. This means that
close to 8 million adults (about 4% of the U.S. adult
population) have ADHD. However, as ADHD is a
behavioral disorder still lacking a specific biological
marker, estimates of its frequency can be affected by a
number of factors.
The method for making the diagnosis most certainly
affects the estimated frequency. The current DSM-IV-TR
standards, which allow both hyperactive–impulsive and
inattentive subtypes, have resulted in higher rates of
diagnosis than previous DSM standards, which placed a
higher emphasis on hyperactivity as a diagnostic criterion.
In other words, the frequency of the diagnosis
increases when hyperactivity is not regarded as a necessary
characteristic for ADHD diagnosis. The looser the
requirements are, the greater the number of individuals
included under the diagnostic umbrella.
The estimated frequency of ADHD also depends on
who provides the information to make the diagnosis:
parent, teacher, child, or physician. All have their own
agendas to report. Teachers are seeing children through
the lens of the classroom, where there are specific academic
and behavioral expectations. In a class full of
children, disruption by a single student can have a ripple
effect. On the other hand, in a large class full of
children, teachers may not notice the quietly inattentive
child. Children may be less aware of their own
symptoms. Adolescents, in particular, are notorious for
underreporting and minimizing their symptoms. Parents
view their children’s behavior from the perspective
of day-in, day-out living. Their perspective is intensive
as well as long-term. On the one hand, they may minimize
symptoms that they have been living with for
years. On the other hand, the behavior seen under the
intensive lens of daily living may make them keenly
aware of things that go unnoticed by others. Physicians
see children in a rather artificial setting, where
the child is the focus of attention and may be on his or
her best behavior. Conversely, some children are stressed
by a visit to the doctor and will immediately demonstrate
ADHD-like signs by wandering around the office, touching
and picking up everything in sight.
The problem of varying perspectives is highlighted in
one study that asked parents, teachers, and physicians
to rate children with school problems as having or not
having ADHD. Results indicated that approximately
10% were rated a unanimous “yes” and 30% a unanimous
“no.” However, parents, teachers, and physicians
disagreed on the diagnosis of almost two-thirds of the
children.
Studies using quantitative questionnaires to assess the
level of agreement between parents, teachers, and children
demonstrate more consistency among raters, but
the specific questionnaire used affects the level of agreement.
Some of the shorter questionnaires tend to diagnose
ADHD less frequently because they emphasize
hyperactivity and, subsequently, miss the inattentive
children. Longer questionnaires, which consider multiple
situations in which attention is required, yield greater
agreement among raters and are probably more reliable
diagnostic tools.
The child’s age at evaluation also makes a difference.
Younger children tend to have more classic symptoms
and more hyperactivity. Thus, the diagnosis is more
likely to be made in these younger children than in
older inattentive, nonhyperactive children.
ADHD seems to occur with differing frequency in
different cultures. For example, ADHD appears to be
more common in the United States than in Britain. A
large British national study found the prevalence of
hyperkinetic disorder (the British term for hyperactivity)
to be only 1.4%. In Japan, a study that based diagnosis
on an older version of the DSM (which places a
greater emphasis on hyperactivity for diagnosis) determined
that 8% of children in the general population
met the standards for ADHD. The frequency of
ADHD in two South American countries, Colombia
and Venezuela, ranged from 7% to 11%. Studies coming
out of Germany suggest a frequency of approximately
16%. The differences could be a reflection of
different thresholds for diagnosis among different cultures
or different diagnostic criteria (or both). For
example, in Britain, hyperactivity appears to be a more
important symptom for diagnosis than in the United
States. The variation in frequency could also be a
reflection of differing gene pools in these countries,
with more ADHD genes in one population than in another.
Read More: What is attention deficit hyperactivity disorder (ADHD)?
