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Journal of Memory Disorders and Rehabilitation
Cite this article: Eme R (2017) A Review of the Most Recent Longitudinal Studies of ADHD. J Mem Disord Rehabil 2(1): 1004.
*Corresponding author
Robert Eme, Department of Psychology, Illinois School
of Professional Psychology at Argosy University,
Schaumburg Campus, USA, Email:
Submitted: 20 February 2017
Accepted: 18 March 2017
Published: 21 March 2017
Copyright
© 2017 Eme
OPEN ACCESS
Review Article
A Review of the Most Recent
Longitudinal Studies of ADHD
Robert Eme*
Department of Psychology, Illinois School of Professional Psychology at Argosy
University, USA
Abstract
This review examined the ndings from the six most recent longitudinal studies
of ADHD with a goal of answering the question of what the future likely holds for an
individual with childhood ADHD. When the ndings from these studies were combined
with those of prior longitudinal studies, the two most important answers to emerge
were as follows. First, approximately two-thirds of children with childhood ADHD will
continue to be moderately or severely impaired in young adulthood. Second, the two
most robust predictors of this outcome are severity of ADHD and co morbid conduct
problems.
INTRODUCTION
Among the most pressing questions that parents of children
with ADHD, and the clinicians involved, have is what the future
this future [1]. The answer to these questions is provided by
long-term longitudinal studies of individuals who have received
a diagnosis of ADHD during childhood and then followed for
varying lengths of time. The purpose of this article is to provide
answers to these questions by reviewing the most recent
longitudinal studies of children with ADHD. The article will begin
prominent prior longitudinal studies. It is will then proceed to
review six of the most recent studies that were not included in
the prior reviews with a special focus on how these studies have
advanced our knowledge of what the future likely holds for the
child with ADHD.
Prior longitudinal studies
prior longitudinal studies of ADHD are as follows [2-4]. First,
regarding the characteristics of the subjects, most of the children
with ADHD were white, middle class boys who were typically
facilities rather than being true community samples. In addition
to the obvious demographic limitation of the samples, it is also
important to note that clinical samples of children with ADHD
usually include more severe cases than community samples and
thus are more likely to report higher persistence rates as well as
increased co morbidity with other disorders [3].
There is a relatively high rate of persistence of ADHD from
childhood to adolescence (50-80%) and into adulthood
(35-65%).
Symptoms of hyperactivity (and perhaps impulsivity)
decline more steeply with age than do symptoms of
inattention.
Children with ADHD are at increased risk for virtually
every outcome domain that has been studied including,
but not limited to
Conduct Disorder, Substance Abuse Disorder.
Academic impairment, driving problems, social
impairment, risky sexual behavior, occupational
functioning as adults, criminality.
ADHD severity and co morbid conduct disorder in
childhood are the two most important predictors for
persistence into adulthood as well as adverse outcomes
in adulthood.
There were few if any gender differences in outcome.
Recent longitudinal studies of ADHD
The review will be roughly ordered in terms of the
chronological baseline for the start of the study. Particular
attention will be paid to how the studies have added to the
knowledge base established by the prior longitudinal studies and
thus advance our knowledge on what the future likely holds for
individuals with a history of childhood ADHD.
Prediction of adolescent outcomes among children
diagnosed with ADHD at 4-6 years of age
A study by Lahey and colleagues [5] addressed the
problem that little is known about the stability and long-term
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consequence of ADHD when it is diagnosed in early childhood.
Participants were 125 children (107 boys) recruited from
various mental health settings who were diagnosed with ADHD
at 4-6 years and followed prospectively through age 18 years.
the children improved over time, they still continued to exhibit
more symptoms, functional impairment, and risky behavior
through adolescence than demographically matched healthy
comparison children. Indeed, only approximately 10% of the
diagnosis of ADHD in early childhood, thereby validating the
recommendation of professional groups such as the American
Academy of Pediatrics who are calling for recognition and
numbers of inattention and hyperactivity-impulsivity symptoms
and higher number of concurrent symptoms (oppositional,
conduct disorder, anxiety, and depression) measured at baseline
predicted higher future levels of the same dimension of symptoms.
In addition, higher baseline levels of inattention, oppositional,
conduct disorder, and anxiety symptoms predicted greater
future functional impairment. Lastly, the authors concluded that
although the study demonstrated that future outcomes in general
could be predicted, the predictors were not accurate enough to
allow prediction on an individual basis of which children would
or would not improve.
Early development of co morbidity between ADHD
and oppositional defiant disorder
A study by Harvey, Breaux, and Lugo-Candelas [6] sought
to advance the understanding of how to explain the substantial
(ODD) that develops during the preschool years such that
between one third and one half of children who are diagnosed
with one disorder are also co morbid for the other disorder.
Participants were 199 children (107 boys) who were recruited
from the community for a longitudinal study of preschoolers
with behavior problems. Parental reports of ADHD and ODD
symptoms were collected annually from ages 3 to 6 and a family
history interview was administered at age 3. The results provided
strong support for a developmental precursor’s model to explain
the co morbidity. Namely, ADHD was a strong predictor for the
This progression from ADHD to ODD is best explained by the
ADHD symptoms of behavioral and emotional impulsivity which
greatly increase the risk for coercive, oppositional interchanges
estimated that a typical child with ADHD has an astonishing half
a million of these negative interchanges each year [10].
Developmental trajectories of ADHD symptoms from
grade 3 through 12
symptoms were explored in a sample of 413 children (66% male)
as high risk because of elevated kindergarten conduct problems
[11]. Symptoms of inattention and hyperactivity-impulsivity
were modeled using parent reports collected in Grades 3, 6, 9,
levels of inattention and hyperactivity (71% of sample), (2)
initially high but then declining symptoms (16% of sample), and
(3) continuously high symptoms that featured hyperactivity in
childhood and early adolescence and inattention in adolescence
(13% of sample). By late adolescence, children in the high class
with higher rates of arrests, school dropout, and unemployment,
whereas children in the declining class did not differ from those
in the low trajectory class. This study supports the notion that
for some children, but not for others. Children who are more
hyperactive or aggressive, or whose parents are inconsistent
or ineffective with discipline, are more likely to have clinically
activities and worse graduation and employment rates in late
adolescence. In conclusion, the most important contribution of
from prior studies that severity of ADHD in childhood predicts
persistence of ADHD into adolescence as well as increased risk
for adverse outcomes in multiple domains.
Adult outcomes 16 years after childhood ADHD: MTA
results
The Multimodal Treat Study (MTA) which has conducted
several follow-ups of 579 children (465 males) diagnosed with
combined type ADHD at ages 7-9 is the largest study to date
with the most representative, generalizable clinical sample of
children with ADHD [1]. In the most recent follow-up study,
Roy and colleagues [12], examined rates and predictors of
ADHD persistence versus desistence in 453 of the participants
from the MTA trial based on a 16-year follow up at a mean age
of 25 years. Regarding persistence, 50% of the participants
had persistent ADHD based upon DSM-5 criteria. Regarding
predictors, the study found that the most important predictors of
adult ADHD persistence were initial severity of ADHD symptoms,
increasing but not initial co morbidities (after controlling ADHD
severity), and parental mental health problems. Childhood
IQ, socioeconomic status, parent education, and parent-child
relationships showed no association with adult ADHD symptom
studies, Roy and colleagues [12] reported that their negative
status and parental income are discrepant from prior studies
association between parent-child relationships and persistence
second study by Hechtman and colleagues [13] was built on the
differences between those with persistent versus desistent ADHD
and a local normative comparison group (LNCG). Three patterns
persistent ADHD group fared the worst on functional outcomes
income, receiving public assistance, and risky sexual behavior
compared to the LNCG. Second, the desistent group had outcomes
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that were in between the persistent group and the LNCG. Third,
on emotional outcomes (emotional lability, neuroticism, anxiety
disorder, mood disorder) and substance use outcomes, the LNGC
group and the symptom-desistent group did not differ, but both
fared better than the symptom-persistent group. Fourth, there
or alcohol use disorder. In sum, although degrees of impairment
varied by domain, persistent ADHD was associated with the
greatest functional problems.
Prediction of young adult outcome for women with
childhood ADHD
A study by Owens and Hinshaw [4] investigated whether
earlier conduct problems, operational zed as symptoms of ODD
and conduct disorder (CD), which predict adult outcomes for
males with childhood ADHD also predict adult outcomes for
females with childhood ADHD. Participants were 140 females
in the Berkeley Girls with ADHD Longitudinal Study who were
recruited from various community and mental health settings
Data was collected at three times points when the females were
on average aged 9.6 years, 14.3 years, and 19.6 years. The study
found that among girls with ADHD, after controlling for severity
of childhood ADHD, IQ, and demographic factors, childhood and
adolescent conduct problems predicted overall functioning,
internalizing problems, and externalizing problems during young
for explaining how these early conduct problems predicted adult
risk for school failure and disciplinary problems during
adolescence which in turn increased risk of failure to adapt to
the demands of young adulthood. In the second pathway early
conduct problems increased risk for internalizing problems
and peer rejection during adolescence which in turn predicted
internalizing problems in young adulthood.
earlier conduct problems are as robust a predictor of young adult
outcomes for females as they are for males. It also adds to the
differences in either the future for children with childhood
ADHD or predictors of that future, with the possible exception
that females may be a higher risk for internalizing disorders and
males at higher risk for externalizing disorders [4].
Progression in impairment in adolescents with ADHD
though the transition out of high school
Despite declining symptoms levels, children with ADHD show
increasingly impaired functioning as they transition into high
school most probably because of increased academic workloads
and greater demands for independent and organized work [14].
A study by Howard and colleagues [14] using the previously
discussed MTA sample [13] sought to extend the investigation
of impairments increasing with age to adolescents through and
after leaving high school as they transitioned to adulthood. The
study found that on average the impairments of adolescents
with childhood ADHD increased through high school and after
the transition out of high school in contrast to those of LNCG
adolescents for whom impairments stabilized or declined after
high school. However, these impairments were stabilized after
leaving high school for those adolescents with ADHD who
attended college. Also, adolescents with childhood ADHD who
had more involved parenting had less impairment overall,
and those with both histories of involved parenting and who
attended college were least impaired overall as young adults.
In sum, on average adolescents with childhood ADHD became
slightly more impaired through high school, and impairments
continued to increase but at a slower rate after the transition out
of high school. The progression in impairments was mitigated by
involved parenting and college attendance.
CONCLUSION
First, as a bit of an aside, it should be noted that contrary to
the continuing erroneous opinion of some, the reviewed studies
served to further establish the validity of ADHD as a real disorder,
“as if 20,000 or more earlier studies had not” [2].
To the question of what does the future likely hold for a
person with childhood ADHD, the results of recent longitudinal
studies in combination with the prior studies suggest the
following answers? First, with regard to persistence, a distinction
must be made between ADHD symptoms and ADHD-related
impairments. With regard to persistence of symptoms, the best
answer would appear to be that approximately 50% of children
levels of ADHD symptomatology into young adulthood. With
overall adult outcomes of children with ADHD fall roughly into
impaired, and severely impaired [15]. Second, although ADHD
symptoms may decline with age, ADHD-related impairments
are less likely to do so and indeed may even increase [2]. Two
possible reasons have been advanced to explain why decline in
symptoms may not be accompanied by decline in impairments.
severity, the individual with ADHD remains at a relatively high
level of deviancy compared to the non-ADHD [2] Thus, since
the individual with ADHD remains at this relatively high level of
deviancy, they remain at the same level of risk for impairment or
even increased risk of impairment with age because of increasing
demands e.g., for independent academic or occupational
achievement [14]. The second reason why the decline in
symptoms may not be accompanied by decline in impairments is
that the decline in symptoms may be illusory. Namely, there is a
growing consensus that because the DSM-5 list of 18 symptoms
preadolescent presentations of ADHD, they are developmentally
insensitive to manifestations of ADHD at older ages [7,14,15].
DSM-5 has attempted to address this issue by listing some
expressions of the core 18 symptoms that might be more typical
beyond preadolescence, but much work remains to be done
in this regard. In short then, ADHD-related impairments may
continue or even increase because ADHD symptoms, if assessed
by developmentally appropriate criteria, are not decreasing and
With regard to the predictors of future outcomes in ADHD, the
recent studies have provided additional convincing support
in establishing severity of ADHD and co morbidity with other
disorders (especially conduct problems) as the most reliable,
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robust predictors. In addition, outcome is also determined,
as it is for virtually all disorders, by environmental demands,
compensatory skills of the individual and environmental
supports or lack thereof. Lastly, the omission of treatment of
ADHD as a predictor of long term outcome in the reviewed
studies needs to be addressed is some detail. This omission is
especially surprising since hundreds of controlled studies of
stimulant treatment for individuals with ADHD (mostly children)
have reported success rates approximating 80% over the short
term with rates for placebo being dramatically lower (i.e., 13%)
[16-18]. Indeed, “There is no medication for any mental health
condition that approaches this differential. Sometimes the effects
of stimulants are “night and day” [17]. The most probable reason
for this omission is a design problem in longitudinal studies
which make the consideration of treatment moot. Research
that attempts to study the long term predictive of outcome of
treatment for ADHD is faced with an intractable design problem
of bias once the randomization trial has ended and individuals
in the treatment and control groups self-select into various
“Disentangling this bias adequately would require a randomized
clinical trial with good adherence and retention for several
years…However, maintaining adherences to assigned treatment
over long periods of time may not be possible.” This bias helps
studies that treatment for ADHD is a predictor of persistence,
not desistence [3]! Namely, since it is the most severe cases of
ADHD that are selected for treatment [3], treatment is in effect
a proxy for severity a robust predictor of persistence. Similarly,
although 14 months of state of the art treatment in the MTA study
resulted in highly positive short-term outcomes, subsequent self-
selected extended use of medication after the trial ended found
no effect on outcome in adulthood [3]. Again, this may be because
those who elected to continue treatment with medication into
adulthood had more severe ADHD than those who chose to
discontinue treatment.
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Eme R (2017) A Review of the Most Recent Longitudinal Studies of ADHD. J Mem Disord Rehabil 2(1): 1004.
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