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One
controversial aspect of current diagnostic criteria for ADHD is the
requirement that in addition to displaying a certain number of inattentive
and/or hyperactive-impulsive symptoms, some of these symptoms must have been
present and caused some impairment prior to the age of 7.
This age-of-onset criteria was included in DSM-IV (the diagnostic manual for
all psychiatric disorders, including ADHD) based on findings that most
children with ADHD first exhibited symptoms in early childhood, and in
response to concerns that when ADHD symptoms appear after age 7, they often
may be due to school failure or stress rather than to ADHD. Thus, by
requiring ADHD symptoms to have been evident and causing impairment before
the age of 7 for the diagnosis to be appropriate, it was hoped that children
whose symptoms first emerged at later ages for a variety of other reasons
would not be misdiagnosed as having ADHD.
This age-of-onset criteria assumes that there is a meaningful difference
between children whose ADHD symptoms emerge relatively early in life from
those whose symptoms first become evident later on. Several ADHD experts (in
particular, Dr. Joseph Biederman and Dr. Russell Barkley) have questioned the
validity of this assumption and suggested that the age 7 cutoff is arbitrary
and not based in science. As a result, there are concerns that this may
actually deny diagnoses and services to youths who suffer from ADHD-related
difficulties.
For example, a child who met all symptomatic criteria for ADHD except for the
age-of-onset criteria currently would not be given the diagnosis and could
thus be denied access to educational services that would otherwise be
provided. In addition, treatment options typically considered for a child
with ADHD might be discarded. Clearly, it is potentially problematic to have
this unsubstantiated age-of-onset cutoff in the official diagnostic criteria
for ADHD. Research to establish the validity of this requirement is needed.
A study published in a recent issue of the Journal of the
American Academy
of Child and Adolescent Psychiatry offers the best data currently available
on this important issue (Willoughby,
M.T., et al., 39, 1512-1519, 2000). Participants in the study were part of a
large study designed to determine the prevalence of a variety of childhood
psychiatric disorders and the impact of different disorders on children and
their families.
A representative sample of 4500 students, grouped by ages 9, 11, and 13, was
recruited from 11 counties in western
North
Carolina. Parents completed an initial screening
instrument designed to detect child behavior problems. When this score
exceeded a pre-determined cutoff, these parents and children were invited to
participate in a more detailed assessment that involved thorough psychiatric
interviews of both parents and children over a 4–year span. In addition, a
sample of children whose behavior problem screening score fell below the
cutoff was recruited to serve as comparison subjects.
The authors identified children who met symptomatic criteria for ADHD based
on the results of an extensive parental interview. Parents also provided
information about the age at which their child’s symptoms first became
evident. These ADHD participants were then divided into 6 mutually exclusive
groups:
· Those with the inattentive subtype of ADHD with onset of symptoms before
age 7
· Those with the inattentive subtype of ADHD with onset of symptoms after age
7
· Those with the combined subtype of ADHD with onset of symptoms before age 7
· Those with the combined subtype of ADHD with onset of symptoms after age 7
· Those with the hyperactive-impulsive subtype of ADHD with onset of symptoms
before age 7
· Those with the hyperactive-impulsive subtype of ADHD with onset of symptoms
after age 7
Note: The inattentive subtype refers to children showing large numbers of
inattentive symptoms but relatively few hyperactive-impulsive symptoms. The
exact opposite is true for children with the hyperactive-impulsive subtype,
while children with the combined subtype display high numbers of both types of
symptoms.
A seventh group was comprised of children who never met symptomatic criteria
for ADHD. They served as a comparison group.
Once these groups were identified, children with each subtype of ADHD whose
symptoms emerged either before or after the age of 7 were compared to one
another, and to children without ADHD symptoms. Children were compared on a
variety of different dimensions, including: the number of settings in which
they were currently struggling, the presence
of other psychiatric problems in addition to ADHD symptoms, if they
had required mental health services during the past 3 months, and the degree
to which their symptoms were adversely affecting their parents.
If the age at which ADHD symptoms first emerge is important for making valid
diagnoses of ADHD, then one would expect children in the early vs. late-onset
groups to differ on these factors. However, if there were no differences
between children in the early vs. late-onset group, the utility of including
age of onset in the diagnostic criteria would be questionable.
Results
The authors first examined whether there were differences between ADHD
subtypes in the age when parents reported the emergence of symptoms. For each
subtype of ADHD, a substantial proportion of parents reported that their
child’s symptoms had always been present and were unable to identify a
specific year when they first emerged. This is consistent with the widely
held belief that ADHD is typically evident in early childhood. Differences in
the age of onset between the subtypes were also evident, with 26% of parents
of inattentive youth reporting symptom onset after age 7, compared to only
13% for the combined subtype and 8% for the hyperactive-impulsive subtype.
(Because symptom onset before age 7 was reported for over 90% of children
with the hyperactive-impulsive subtype, comparison of early vs. late-onset
groups was not possible.)
For the inattentive subtype, both early and late-onset children were more
likely than comparison children to be impaired in 2 or more settings, to have
used a greater number of services during the past 3 months, and to have behavioral
and/or emotional problems that parents perceived as creating difficulty in
their own lives. Early-onset children were more likely than comparison
children to display strong oppositional behavior while late-onset children
were more likely to be depressed. When early vs. late-onset inattentive
children were compared to one another, they did not differ on any measure of
co morbidity, impairment, or impact on parental functioning.
For the combined subtype, children in the early and late-onset groups were
more likely than comparison children to be impaired in multiple settings, and
to have used a greater number of services during the past 3 months.
Early-onset children were also more likely to be diagnosed with conduct
disorder (CD), oppositional defiant disorder (ODD), or an anxiety disorder,
and their parents reported that their children’s problems caused more
difficulty for their own functioning. When the early vs. late-onset groups
were directly compared, the early-onset group was at an increased risk for
both ODD and CD, and also appeared more likely to be depressed. They were
also more likely to be receiving services and to have a greater number of
negative impacts on their parents’ functioning.
Summary And Conclusions
The results of this study suggest that the age-of-onset criteria have
different clinical implications depending on the ADHD subtype. For youth with
the inattentive subtype of ADHD, symptom onset after age 7 occurs about one
quarter of the time, and there does not appear to be any difference between
early and late-onset groups in a number of meaningful clinical outcomes. In
addition, children with the inattentive subtype of ADHD were clearly
struggling relative to non-ADHD comparison children regardless of whether
their symptoms emerged early or late. There is thus little support in these
data for the requirement of an onset of symptoms prior to the age of 7 for
the inattentive subtype of ADHD. In fact, one could plausibly argue from
these data that such a requirement would be likely to increase the number of
incorrect diagnoses by precluding a diagnosis of children with ADHD who
really do have the condition.
However, a very different picture emerged for children with the combined
subtype of ADHD. Among these children, those with an early onset of symptoms
differed from those in the late-onset group on a number of dimensions and
clearly had worse clinical outcomes. Thus, even though children in the
late-onset group were struggling relative to comparison children, they were
not as impaired as those whose symptoms began earlier in life. This pattern
of findings suggests that the age-of-onset criteria is meaningful for the
combined subtype and argues against dropping it as some have suggested. Doing
so would result in the identification of a much more heterogeneous group of
children as having the combined subtype of ADHD.
In regards to the clinical implications of these results, it appears that
clinicians should be cautious about ruling out a diagnosis of ADHD for an
inattentive child just because that child’s symptoms were not evident until
later in life. This could result in a child’s inattentive symptoms being
incorrectly attributed to some other condition such as a mood or anxiety
disorder, and prevent the child from getting appropriate treatment. Although
there are instances where a child’s inattentive symptoms reflect the impact
of such conditions rather than ADHD, and clinicians always need to be
vigilant about this possibility, it is the practice of ruling out ADHD as a
diagnosis for inattentive children with a late onset of symptoms that is potentially
problematic. (Note: In the current diagnostic system, it would still be
possible to diagnose such children as "ADHD, not otherwise
specified".)
Parents should be aware that the emergence of significant attention problems
in older children does occur and may reflect ADHD for which appropriate
treatment is required. Sometimes such symptoms do not become evident until
children have moved further along in school when the academic and organizational
demands increase substantially from the early elementary grades. Suddenly, a
bright child who has always done well is struggling, and these problems can
be wrongly attributed to laziness, lack of motivation, or an emotional
problem like depression. When a parent is told that their child couldn’t have
ADHD because they never showed such struggles before, attributions are likely
to be made and the consequences can be quite harmful.
For a child who begins showing inattentive and hyperactive-impulsive symptoms
consistent with the combined subtype diagnosis at a later age, results from
this study suggest that caution in making an ADHD diagnosis is appropriate.
Children with a late onset of combined symptoms seem to differ from those
with earlier symptom onset, raising the possibility that their symptoms occur
for reasons other than ADHD.
Therefore, when a child begins to show such symptoms at an older age, parents
should raise questions if their child’s health care provider initiates
traditional treatment for ADHD without first considering other explanations
for their child’s symptoms.
As the authors acknowledge, there are limitations to the current study that
preclude any definitive answer to the question of whether requiring
age-of-onset criteria for diagnosing ADHD is appropriate, and additional work
in this area is required. For example, it would be key to learn whether
children with early vs. late-onset combined-type symptoms showed different
patterns of response to stimulant medication treatment, different long-term
outcomes, and different patterns of results on neuropsychological tests. The
same would be true for children with early vs. late-onset inattentive
symptoms. These kinds of data would help address this question more
definitively, and would be enormously helpful in refining current diagnostic
guidelines. Hopefully such information will become available shortly.
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