1997 behavioral characteristics of dsm-iv adhd subtypes ina scholl - gaub, carlson
TRANSCRIPT
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8/12/2019 1997 Behavioral Characteristics of DSM-IV ADHD Subtypes Ina Scholl - Gaub, Carlson
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Journal
of
Abnormal Child Psychology, Vol. 25, No. 2, 1997,pp. 103-111
Behavioral
Characteristics
of
DSM-IV
ADHD
Subtypes
in a School-Based Population
Miranda
Gaub1
and Caryn L.
Carlson
1,2
Received
August 8,1995; revision received February 21,1996;
accepted
February 27,
1996
From anethnically diverse sampleof2,744 school children,221attention
deficit
hyperactivity
disorder
(ADHD) [123 (4.5%) predominantly inattentive (IA), 47
(1.7%)
predominantly hy-
peractive/impulsive
(HI), and 51(1.9%) combined type (C)] were
identified
using teacher
ratings on a
Diagnostic
andStatisticalManualofMentalDisorders(4th ed.) (DSM-IV) symptom
checklist. Subjects were compared to 221 controls on teacher ratings of behavioral, academic,
and social
functioning.
Theresults revealed relatively independent areasof impairmentfor
eachdiagnostic group.
The IA
children were impaired
in all
areas,
but
were rated
as
dis-
playing
more appropriate behavior andfewerexternalizing problems than HI or C children.
The HI
group displayed externalizing
and
social problems,
but was
rated
as no
different
than controls
in
learning
or
internalizing problems.
The C
groupdemonstrated severe
and
pervasive
difficulties across domains. These findings support
the
validity
of the
DSM-IV
ADHD subtypes;
all
ADHD groups demonstrated impairment relative
to
controls,
but
show
different patternsofbehavioral characteristics.
KEY WORDS: ADHD; ADHD subtypes; behavioral characteristics; impairment; teacher ratings; ethnic
minority.
Since its inception, attention
deficit
hyperactivity
disorder
(ADHD)
has
been known
bymany
names,
such asminimal brain dysfunction, hyperkinesis,hy-
peractivity,
and
attention
deficit disorder with
(ADD/H) or without (ADD/WO) hyperactiviry. The
changing
nomenclature reflects disagreement regard-
ingthe diagnostic necessity of the three core charac-
teristics: impulsivity, inattention, and motor excess.
Various
editionsof the
DiagnosticandStatisticalMan-
ual
of
MentalDisorders (DSM) have implemented
varioussubtyping systems which cluster the three core
characteristicsin anumberofways.Thethird edition
[DSM-III; American Psychiatric Association (APA),
1The
UniversityofTexasat Austin, Austin, Texas78712.
2Addressallcorrespondence to CarynL.Carlson, Departmentof
Psychology,
Mezes 330, The University of Texas at Austin,
Austin,Texas78712.
1 3
CWl-OttW/WOMWOSllSM)
C
1997Plenum
PublishingCorporation
1980] subtyped ADHD children usingabidimensional
approach such that a child was diagnosed as ADD/H
orADD/WO.The revised third edition (DSM-III-R;
APA,1987)
implemented a unidimensional approach
which
included children with varying degrees
of hy-
peractivity under
the
diagnostic category
of
attention
deficit hyperactivitydisorder.
The fourth
edition (DSM-
IV;
APA, 1994)
has
returned
to a
bidimensionalsystem,
clustering hyperactivity and impulsivity symptoms into
one
dimension,
and
separating
it from the
inattention
dimension. Based
on
this system,
the
DSM-IVpre-
sents an ADHD diagnosis with three subtypes:
pre-
dominantly inattentive (IA), predominantly
hyperactive/impulsive
(HI),and combinedtype(C),
Children displaying symptoms of both inatten-
tion
and
hyperactivity
(i.e.,
ADD/H
and
ADHD)
un-
der the
various
DSM
systems have
consistently
demonstrated significant
difficulties
in adjustment,
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1 4
socialfunctioning,and internalizing and externalizing
behavior
(Barkley, 1990; Hinshaw, 1994; Whalen,
1989).The
pervasiveness
of
such associated
difficul-
ties has been demonstrated primarily within clinic-
referred
samples.
Although behavior problems
associated with ADHD have been explored in popu-
lation-based samples
to a
lesserextent, they have
also
been documented
(August,
Ostrander, &
Bloomquist, 1992; Szatmari,
Offord,
& Boyle,1989).
Research
has
demonstrated that children display-
ing both inattention and hyperactivity differ from
thosewhodisplay inattentionin theabsenceofmotor
excess. This latter
form
of
ADHD,
first
formallyiden-
tified
inDSM-III
as
ADD/WO,
has
been less
widely
studied.
In a
recent review
of the
ADD/WO litera-
ture, Lahey, Carlson, and Frick (in press) concluded
that, as compared to ADD/H children, ADD/WO
children are more internalizing but less antisocial, less
rejected
by
peers,
and less
externalizing.
The
DSM-IV
C and IA
subtypes were intended
to be
congruent with past diagnoses
of
ADD/H
and
ADD/WO,
respectively. However, DSM-IV diagnos-
tic
criteria deviate somewhatfrom those
of
previous
DSMversions, interms of numbersand clustersof
symptoms.Thus,
it
remains
to be
seen whether cur-
rent DSM
criteria identify
children
similar
to those
identified
in previous research.
The HIsubtype, introduced tocaptureagroup
of
childrenwhowere perceived byclinicians in the
field trials to have a clinically significant disorder
(Lahey et al., 1994), has no previous diagnostic coun-
terpart. The
validity
of the HI subtype has been ques-
tioned by those who have suggested that these
children, who were identified primarily among pre-
schoolers
in the field
trials,
may
eventually display
inattention symptoms
and
qualify
for a C
diagnosis
(Barkley,
1997).
The
DSM-IV
field trials (Lahey et al., 1994)
found
that, among clinic-referred children, the DSM-
IV ADHD subtypes showed
different
patterns of as-
sociated impairment. C and HI groups were rated as
more globally impaired than the IA group, while C
and
IA
children
had
more academic problems than
the HI group. Teachers rated C children as less
liked
and more disliked than HI children, while IA chil-
dren
did not differ
from
the
other
twosubtypeson
like
or
dislike
scores.
Apart
from
the field
trials,
descriptive informa-
tion about the DSM-IV diagnostic subtypes is scarce.
McBurnett, Pfiffner, Swanson, Ottolini, & Tamm
(1995) used parent
and
teacher ratings
on a
DSM-
III-R diagnostic checklist of 520 child referrals to an
ADHD clinic to retrospectively classify them into
DSM-IV subtypes. A comparison of the behavioral
characteristics of the three ADHD subtypes indicated
that, consistent
with
Lahey et al. (1994), HI children
were more academically successful than C or IA chil-
dren.HI
children
did not differ from C
children
on
ratings of peer dislike, but both of these groups were
more disliked than the IAgroup. In addition, both
the HI and C groups received higher ratings than the
IA group on measures of disruptive behavior.
Twostudies examined behavioral correlates
of
the DSM-IV subtypes in nonreferred
samples
(Baumgaertel, Wolraich,
&
Dietrich, 1995; Wolraich,
Hannah, Pinnock, Baumgaertel, & Brown, inpress).
Wolraich
et al. obtained teacher ratings for
8,258
children in grades K-5 in a middle Tennessee county.
An overall ADHD prevalence
rate
of 11.4% was ob-
tained, with ratesfor LA, C, and HI of 5.4%, 3.6%,
and
2.4%, respectively. Baumgaertel
et al.
(1995)
obtained teacher
ratings
for
1,077 children
in
Grades
1 to 4 inRegensburg, Germany.An overall
prevalence rate of 17% was obtained, with rates for
IA, C, and HI of 9%, 4.8%, and 3.9%, respectively.
Consistent with the results of Lahey et al. (1994)
and
McBuraet et al. (1995), the C and HI groups
displayed behavioral problems,
while the C and LA
groups
were
associated with academic problems.
Wolraichet al. also
found
the proportion of children
displaying anxiety/depression
was
lower
for the HI
(9.2%)
than
for the C
(29.3%)
or IA
(21.9%)
groups.
The goals of the present study were to enhance
the existing literature by (1) using a large-scale,
population-based sample to prevent contamination
bypossible referral bias; (2) exploring behavioral cor-
relatesof the three
DSM-IV-diagnosed subtypes
of
ADHD;
and (3)attemptingtoevaluatethe extentto
which
the current DSM-IV system identifies subtypes
comparable
to
those identified using previous diag-
nostic systems.
METHOD
Data
for the present study were obtained under
the auspices of a larger community service program
entitled
the Schoolof the Future Project.This pro-
gram, implemented by the Hogg Foundation, pro-
vides school-based mental health services
to low
income communities. Since 1990, this program
has
Gaub and
Carlson
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ADHD
Subtypes
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Table I.
Demographic Characteristics
of
Population
Grade
Overall
Gender K 1 2 3 4 5
totals
Boys
Girls
Totals
255
263
518
19%
288
249
537
19%
261
235
496
18%
202
178
380
14%
218
184
402
15%
193
218
411
15%
1,417
52%
1,327
48%
2,744
100
been in effect in some elementary and secondary
schoolsin several Texas cities.Yearlyevaluations, in-
cluding
teacherratings, have been used to assess the
effectiveness ofservice deliveryin these schools.
Data were collected for allchildren for whom
parental consent
was
obtained (approximately
96%
of
eligible
children).
The 3% of
children
of unknown
or
other ethnicity were excluded, leaving
a
sample
of 2744children
in
nine elementary schools
who had
adequate
data available for the 1993-1994 school
year.Demographic characteristicsfor thesampleare
presented
in
Table
I. Children were predominantly
from low-socioeconomic-status (low-SES) back-
grounds.Basedonpaternal occupation, availablefor
30 of the sample, meanSESrating (using total la-
bor force comparisons) on the revised Duncan So-
cioeconomic Index (Stevens
&
Featherman, 1981)
was
23. The
ethnic composition
was 76%
Hispanic,
16%
African American, and 8% Caucasian.
Subjects
For
thecurrent study,221children, representing
8.0
of the total population, met the criteria for
ADHD
(via teacher reports)
and
were included
in
analyses. The 221 ADHD children were compared
to 221
non-ADHD subjects selected from among
nondiagnosedchildrenandmatchedforgender, age,
grade,and
ethnicity. Demographic characteristics
of
thegroups are reported inTable II.
Measures
Teacher evaluationsforeach subject consistedof
theTeacher's Report Form (TRF; Achenbach,1991),
a
teacher-completed DSM-IV-based diagnostic
checklist for
ADHD
and
oppositional
defiant
disor-
der (ODD), and three Likert-type scale questions re-
garding social functioning
[adapted
from
a
questionnaire developed by Dishion (1990) used in
the
DSM-IV
field
trials].
TRF.
The TRF (Achenbach, 1991) is a widely
used, standardized tool for the assessment ofchild-
hood functioning and impairmentinbehavioral and
emotional realms. All analyses used raw scores rather
than T-scores, since the latter are scaled
differently
for each gender.
SNAP-IV
(Swanson
Carlson, 1994). This diag-
nostic checklist
for
ADHD
and ODD
[Swanson,
No-
lan, and Pelham Checklist-IV and the DSM-IIIR
Disruptive Behavior Disorder Rating Scale (Pelham,
Gnagy,
Greenslade, & Milich, 1992)] consists of 26
questions thatclosely parallel
in
wording
the
diagnos-
tic
symptoms
forboth ADHD and ODD astheyap-
pear in the DSM-IV The instructions ask the teacher
toindicate, foreach question, whichof the following
fourchoices best describes
the
child:
not at
all, just
a
little,
quite
a
bit,
orvery
much.
Social
Functioning.
Three
questions, adapted
from Dishion (1990), were included to assess the
teacher's
perception of the child's level of social
functioning.
Teachers estimated
the
proportion
of the
child's peers that like/accepted, dislike/rejected,
and
ignoredhim/her based
on a
5-point Likert-type scale
ranging from
1(very
few/less than25 )
to 5
(almost
all/more
than
75 ).
Procedure
Data
were collected during April 1994
for the
1993-1994
school year. Subjects were excluded from
the original sample if their TRF
scores
had more
than eight unanswered items
totalor
more than
three
unanswereditems on anyscab.This sample was then
screened for those children who met DSM-IV
teacher
rating criteria
for the
three subtypes
of
ADHD. For diagnostic purposes, items endorsed as
very
muchwere tallied
as present
symptoms,
and
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Gaub andCarlson
Table II.
Group Demographic Characteristics
Hyperactive/
Demographic Combined Inattentive
impulsive
Controls
characteristic (n = 51) (n = 123) (n = 47) (n =221)
Age
[mean (SD)]
Gender
ratio (Male:Female)
Ethnicity
withingroup:Hispanic
African American
Caucasian
7.6years
(1.6)
2.8:1
70%
24%
6%
7.6
years (1.9)
2.3:1
79%
15%
6%
7.5
years (1.6)
4.1:1
57%
30%
13%
7.6
years (1.7)
2.6:1
77%
15%
8%
students
were assigned ADHD subtype diagnoses ac-
cording to DSM-IV criteria.
Toform a control group, a nondiagnosed child
wasmatched to each ADHD child. These nondiag-
nosed
controls (NC) were sought within the same
classroom
to
adjust
for
potential rater
differences.
If
a
nondiagnosed child (of the same gender and eth-
nicity)
was not in the ADHD child's classroom, a
match
was
chosen from
the
next classroom
(on an
alphabetical list) of the same grade within that
school.Onrare occasions, amatchhad to bechosen
from
a
same grade classroom
at a
different elemen-
taryschool. Approximately
94% of the
matches were
from the
same classroom,
5%
werefrom
a
different
classroom
in the
same school,
and
fewer than
1%
werefrom adifferent school.
Analyses
compared the three ADHD subtypes
and
the NC group on 19 variables
(four
TRF adjust-
ment
questions, eleven TRF behavior scales, three
sociometric questions,and ODD
symptom
rating).To
maintain a focus on diagnostic group, data for the
current study were collapsed across ethnicity and age.
Gender was not included as an independent variable
inthe current
study
since a separate report of gender
effects
is in preparation.
RESULTS
Therewere no significant differences among
ADHD subgroups in age
[F(2,
215) = .05,p = .96],
gender \yf(df = 2) = 2.0,p = .37], or ethnic group
composition[%2(4f
= 4) =
8.8,p =.07].
The
number
of children
in the
sample obtaining
the C, LA, and
HI diagnoses were
51
(1.9%),
123
(4.5%),
and 47
(1.7%),respectively.
Using a 0- to 3-point scoring system on the DSM
checklist,
the
followingscores were obtained
for the
total sample: LAsymptom total (M = 6.82, SD =
7.79),
HI
symptomtotal
(M = 4.22, SD =
6.29),
and
ODD symptom total (M= 2.94, SD = 5.35).
Behavioral Variables
One-wayanalysesofvariance (ANOVAs) were
executed
for
each
of the
nineteen dependent vari-
ables. Maineffects werefurtherevaluated using the
Tukey
(Tukey, 1972) test to explore group differ-
ences.Cell
sires,
means and standard deviations, F
andp values, andpost hoc comparisons for the be-
havior
ratings are reported in
Table
III.
On the
adjustment
variables, the three ADHD
groups were
all
rated
as
significantly more impaired
than the NC group on measures of Hard Working,
Appropriate Behavior, and Happy. Surprisingly, on
the fourth
adjustment
variable, Learning, the HI
group did not
differ
from
the NC
group, while
the
C and
LA
groups received significantly poorer ratings
than the NC and HI groups. Although more im-
paired than the NCgroup, the HI group received
higher ratings of Hard Working than the othertwo
ADHD groups, and higher ratings of Happy than the
Cgroup. However,theLAgroup obtained higherAp-
propriate Behavior ratings than the other two diag-
nosed groups.
On the three sociometric rating variables and
the TRF Social Problems scale, all three of the di-
agnosed
groups were rated
as
having poorer social
functioning than the NCgroup. The Cgroup re-
ceived higher ratingson the Peer Dislike than the
LAgroup and higher ratings on the TRF Social Prob-
lems variables than either the HI orLAgroups, which
did not
differ
significantly
from
each other oneither
variable. On the Peer Like variable, the
LA
group was
rated as liked by more peers than the C group, with
no significant
differences
betweeneitherof these two
groups
and the HI
group.
On the
Peer Ignore vari-
able,
there
were no differences among groups.
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ADHD Subtypes
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Table
DDLGroup
Comparisons
on
Behavioral Ratings
a
Significant groupdifferences based
ADHD ADHD ADHD onTukey/wrthoctests
Variable C IA HI NC F-ratio
(p C
Disliked
by
2.96 2.27 2.65 1.50 35.62*
C, ffl and IA > NQ OIA
Peers (1.34) (1.29) (1.23) (0.86)
Peers
Neutral 112 2.22 1.98 1.44 18.5s C, HI. and IA>NC
Toward (1.21) (1.17) (1.18) (0.80)
ODD
symptom 16.09 7.13 15.02 3.65 71.0*
C and
HI>IA>NC
ratiag (6.64) (7.53) (6.74) (5.92)
Hardworking 1.67 1.68 3.26 4.32 116.9* NC>HI>C
and IA
(0.97) (0.98) (1.34) (1.64)
Appropriate 1.55 2.45 1.67 4.12 67.2* NC>IA>Cand HI
Behavior (0.87) (1.48) (1.15) (1.77)
Learning 1.84 1.82 3.67 4.17 86.4* NC andHI>C and IA
(1.03) (1.08) (1.49) (1.67)
Happy
2.53 3.08 3.42 4.32 30.8* NOC,
HI, and IA;
(1.26) (1.35) (1.69) (1.54) HI>C
Withdrawn
4.46 5.82 2.45 2.27 29.3* C andIA>HIand NC
(3.65) (4.52) (2.19) (2.86)
Somatic 1.78 1.12 0.67 0.53 7.2* C>HIand NC;IA>NC
Complaints (Z97) (2.13) (1.60) (1.24)
Anxious/
8.94 5.15 5.81 3.24 18.2* C>NIandIA>NC
Depressed
(6.35) (4.93) (5.75) (4.62)
Social 9.79 6.12 6.36 2.32
56.2*
C>HI andIA>NC
Problems
(5.02) (4.62) (4.45) (3.35)
Thought 1.80 1.16 1.79 0.35 15.9* C, HI, and IA>NC
Problems (2.54) (2.01) (Z47) (1.05)
Attention 29.89 25.8 18.98 8.03 218.4* C>IA>HI>NC
Problems (4.25) (6.16) (6.85) (7.90)
Delinquency 7.43 4.83 6.59 2.04 51.2* C andHI>IA>NC
(3.87) (3.63) (4.13) (2.87)
Aggressive 31.22 14.76 31,95 8.12 88.5*
C and
HI>IA>NC
Behavior (11.12) (12.82) (10.31)
(10.72)
Internalizing 14.35 11.57 8.36 5.85 21.2* C>HI
and NC;
IA>NC
Behavior (10.98) (8.84) (8.04) (7.06)
Externalizing
38.52 19.61 37.84 10.25 89.5* C and
Hl>IA>NC
Behavior (13.42) (15.47) (13.13) (13.07
Total
Problem 93.94 64.61 75.34 27.40 121.5*
C> HI and
IA>NC
Behavior (27.00) (26.93) (27.25) (26.54)
aADHD
=
attention
deficit
hyperactivitydisorder;
C =
combined type;
IA =
predominantlyinattentive;
HI =
hyperactive/impulsive;
NC =nondiagnosedcontrols. Mean
values
forADHDC,ADHD IA,
ADHD
HI, and NCgroupsare followed bystandard deviationsinparentheses.
bp
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Gaub andCarlson
Table IV.PercentageofChildreninADHD
Subtypes Classified
asImpaireda
Impairment
C IA HI
variable
(a =51) (n = 123) (n = 47)
Social(Peer Like
or
Dislike)
82 59 53
Behavioral
(Appropriate Behavior)
90 58 80
Academic(Learning) 82 76 23
NotImpairedin any of the
three
domains 2 11 4
aADHD = attention deficit hyperactivity disorder; C = combined type; IA =
predominantlyinattentive;HI =hyperactive/impulsive.
On all TRF externalizing variables (Aggressive
Behavior, Delinquency,
and
Externalizing Behavior)
and
the ODD symptom rating, the three diagnosed
groups received higher scores than
the NC
group.
No
differences
emerged between
the C and HI
groups,
with
both
receiving
significantly
higher ratings than
the IA
group
on all
variables. Thus,
on
externalizing
variables, the C and HI children are rated as most
deviant, while
the IA
children obtain lower ratings.
The
pattern
of
group differences
for the TRF in-
ternalizing variables
was
more complex than those
in
other domains.
On all
four internalizing variables
(Withdrawn, Somatic Complaints, Anxious/De-
pressed, and Internalizing Behavior), the C and IA
groups were rated
as
significantly more impaired than
the NC group. HI children received higher ratings
than NC children only on the Anxious/Depressed
variable; on all other internalizing variables, the HI
group
was
rated
as no
different than
the NC
group.
The C group was rated as having significantly more
problems than
the HI group on allfourvariables. The
IAchildren werenot significantly
different
from the
other two diagnostic groups on Somatic Complaints
or
Internalizing.
The IA
group
was
rated
as
more
Withdrawnthan the HI group, but the groups did not
differ on the other threeinternalizing variables.
On the Thought Problems scale,the three diag-
nosed groups were rated
as
significantlymore deviant
than the NC group, with the C group rated assignifi-
cantly more impaired than the HI and IA groups,
which
did not
differ from each other.
On the
Atten-
tion Problems scale, allthree diagnosed groups re-
ceived
significantly
higher ratings than
the NC
group,
with
the C
group receiving significantly higher ratings
than the IA group. The HI group received signifi-
cantlylower ratings than either the C or the IA group.
On the Total Problem scale the C groupwas
ratedby
teachers
as
having significantly higher scores
than anyother group. No differences emerged be-
tween the HI and IA groups, both of which were
rated as
having significantly
moreproblemsthan the
NC
group.
Impairment
Criteria
To
approximate
the
impairment criteria required
by
DSM-IV, NCscoreswere used to calculate objec-
tive
criteria
on various ratingitems.A child was con-
sidered impaired if he/she scored 1SD or greater
from the NC
mean
(in the
deviant direction)
in the
following domains: academic (TRF Learning), be-
havioral (TRF Appropriate Behavior), social (Peer
Dislike
or Peer Like). Table IV shows the proportion
of
children
in
each subtype
ratedas
unpaired
in
each
domain, and the proportion who did not meet im-
pairment criteria in anydomain.
As indicated, the C group was most pervasively
impaired, with percentages
of
children rated
as im-
paired
socially, behaviorally, and academically of
82%, 90%,
and
82%, respectively. Only
one C
child
(2%) did not show impairment in any domain.
AmongLAchildren, academic impairmentwasmost
common(76%), with moderate rates of social (59%)
and behavioral (58%) impairment.Few LAchildren
(11%) were rated as nonimpaired in anyarea.Chil-
dren in the HI group were most likely to show be-
havioral impairment (80%), with moderate rates
of
social impairment (53%)
and
relatively
lowratesof
academic (23%) impairment.Very few HI children
(4%) were rated as unimpaired in any domain.
DISCUSSION
Prevalence
The present findings in this nonreferred popu-
lation indicate that prevalence ratios varied
across
the
three ADHD subtypes, with
the
following rates;
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ADHD Subtypes
1.9 for C, 4.5%for LA, and 1.7% for HI. Thepro-
portionof the population identified as C(1.9%)was
slightly lower than prevalence estimates of ADHD
using
previous
diagnostic criteria, which are generally
cited
in the 2-3% range (APA,
1987).
While the cur-
rent
findingscouldmerely reflectthe stringent crite-
riaforsymptom presence (i.e.,a very muchraring),
it ispossible
that changes
in
diagnostic criteria have
decreased
the prevalence of the C subtype. If, as sug-
gestedby the field
trials (Lahey
et
al., 1994), most
children meeting criteria
for the HI
subtype would
likely have been diagnosed byclinicians ashaving
ADHD(according
to
DSM-III
and
DSM-C
III-R
cri-
teria),the current results showing a 3.6% prevalence
of
these
two
subtypes combined (1.9%
for C and
1.7
for HI) appear consistent with previous preva-
lence
estimates.
The
rate
of IA was also higher than previous
ADD/WO
prevalence rates
of approximately 3%
(Szatmari
et al.,
1989).
This was
likely
due to the
change in diagnostic criteria resulting in more chil-
dren
qualifyingfor an LAdiagnosis; this conclusion
isconsistent with the DSM-IV field trials (Lahey et
al., 1994) findingthatthe majorityof the new cases
identified by DSM-IV were IA children.
Thehigher rates
of all three subtypesfound in
previous
population-based studies of DSM-IV crite-
ria
(Baumgaertel
et al., 1995; Wolraich et al., in
press)werelikely
due to the more lenient
cutoff
cri-
teria employed in those studies, bothof which em-
ployed
slightly
differently
phrasingforanchor points,
butcounted symptoms
as
present
if
either
of the two
mostextremeratings (i.e.,often or very
much)
were
endorsed.
Despite
some differences in relative pro-
portions of the subtypes, both previous studies and
thecurrent studyfound that
LA
wasmost prevalent,
and
HIleast prevalent, in nonreferred populations.
An interesting
difference between current re-
sults
and
those from
research using clinic-referred
samples(Laheyetal., 1994;
McBurnett
et al., 1995)
involvesthe relative
ratios
of the
three
ADHD sub-
types. In the
current study,
LA was
identified twice
as
often as C(C:IA ratio of1:2.4);conversely, both
the field trials (Lahey et al., 1994) andMcBurnett
et al.(1995) found C to be much more prevalent
than
LA
(C:IA ratios of 2.1:1 and3.5:1,respectively).
In addition, while the current study found nearly
identical ratesof
C
and
HI C: Hl
ratio
=
1.1:1),
both
previous studies (Laheyetal., 1994; McBurnett
et al., 1995) found much higher CM ratios (3.0:1
and4.3:1,respectively).Thesediscrepancies
in
preva-
1 9
lence
ratios likely reflected
the
nature
of the
samples
(population-based
vs.
clinic-referred).
Relatedly,
Wolraichet al. (in press) found that C children were
two
to four times more likely than
LA
or HI children
to be
referred
to a
clinic.
Behavioral
Characteristics
The distinctive pattern of impairment by subtype
found in the current study clearly indicates that the
DSM-IV diagnostic system distinguishes three groups
of
children that are all impaired, relative to nondi-
agnosed controls, and that can be differentiated from
each other based on differentpatternsof difficulties.
The C
subtype
was
associated with
the
most perva-
sive
pattern ofdifficulties,with severe ratingsof im-
pairment found
in all
major domains
of
functioning.
For variables includingAnxious/Depressed, Social
Problems, Attention Problems,
and
Total Problem
Behavior, the C group was rated as more unpaired
than
any of the
other groups.
As
noted earlier, this
pattern
of
pervasive deficits displayed
by C
children
is consistent with that shown in children diagnosed
using previous ADHD
criteria.
In the DSM-IVfield
trials sample, Lahey
et al.
(1994)also demonstrated
that C children experienced extensivedifficulties,and
were significantly impaired
in all
assessed areas
in-
cluding social, academic, and global functioning.
The IA
children, like
the C
children, were rated
by
teachers
as significantly
impaired
in all
major
do-
mains
of functioning. Nonetheless, the LAchildren
demonstrated areas of advantage relative to the other
two diagnosed groups. Specifically,
the LA
children
were perceived as displaying more appropriate behav-
ior and
less externalizing behavior than
C or HI
chil-
dren.
Previous research comparing ADD/WO and
ADD/H children found that ADD/WO children
showed
more internalizing behavior, but less external-
izing
and
antisocial behavior,
and
lower
ratesof
peer
rejection, than those
with
ADD/H (Lahey
et
al.,
in
press).This pattern
is
consistent with
the
present
find-
ings, with IA children receiving significantly lower
TRF ratings on Aggression, Delinquency and Exter-
nalizingscales, lower
ODD
symptomscores,lower
Peer Dislike ratings, and higher Peer Like ratings than
C children. Surprisingly, however, LA and C children
were rated as no different fromeach other (although
both received
significantly
higher
scores
than NC chil-
dren) on three internalizing variables (Withdrawn, So-
matic Complaints
and Internalizing Behavior).
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11
Furthermore, although they did differ on theAnx-
ious/Depressed rating, this difference
was in the un-
expected direction; the C children were rated as more
Anxious/Depressed than
the IA
children. This
finding
parallels those of Wolraich et al. (in
press),
who also
found cooccurring anxiety/depression to be more
common
among
C
(29.3%) than
IA
(21.9%)children.
While
this unexpected result may be attributable
to the
revised diagnostic criteria,
it
seems unlikely
that the changes would produce such a strong effect
A closer examination of past research, as reviewed
byLahey, Carlson,
and
Frick
(in
press),suggests that
the epidemiological (school-based) studies available
(Lahey,
Schaughency, Strauss, & Frame, 1984; Pel-
ham,
Atkins, Murphy,
&
White, 1981)
did not find
differences in
anxiety/depression between
the
ADD/H
and
ADD/WO subgroups. Rather, these dif-
ferences were evident primarily in studies using
clinic-referred samples
(e.g.,
Lahey, Schaughency,
Hynd,
Carlson, & Nieves,1987).There may be a re-
ferralbias operating such that those
IA
children
with
highlevelsofanxietyanddepressionaremore likely
to be referred to clinics. Thus, IA (or ADD/WO)
childrenwho are includedin clinic-referred popula-
tions may be more anxious/depressed than their
counterparts in the overall population, resultingin
this
discrepancy across studies.
The HI
group
in the
current study demonstrated
a
pattern
of
impairment that
was
quitedifferent than
that of the C and IA groups. While the HI group
received significantlypoorer ratings than the NC
group in the
socialfunctioning,externalizing, atten-
tion, andthought problems domains, theydid notdif-
fe r significantly from
NC
children
on
several
variables, including
the
Learning
and
most internal-
izingsubscales (Withdrawn, Somatic Complaints,
and
Internalizing).
In
addition,
the HI
group
was
rated
assignificantlymore hard working than
the IA and
C
groups
and
significantlyhappier than
the C
group.
Thus, consistent with existing research (Baumgaertel
et
al., 1995; Laheyetal., 1994; McBurnettet al,1995;
Wolraich et al., inpress),HI children appear to be
characterized byexternalizingand peer relationship
problems, but do not demonstrate internalizing prob-
lems
or academic impairment. Overall, the results
from this
and
other research indicate that
the new
subtypeof HI is a valid and useful addition to the
DSMdiagnostic system; HI children are significantly
impaired
in some areas of functioning, but the pat-
tern of behavioral problems is distinctly different
from that
found
among
IA and C
children.
Gaub andCarlson
The younger age of onset for HI reported in the
field trials (5.65 years) (Lahey et al., 1994) led to
speculation that, rather than representing
a
separate
ADHD subtype, younger, Hi-diagnosed children
might
eventually display inattentive symptoms
and
qualify
for C diagnoses (Barkley,
1997).
In the
McBurnettet al.(1995)sample, the HI subtype was
also significantly younger than the C or IA subtypes;
however, the mean HI age (7.25 years) was not as
young
as
that reported
in the field
trials. Further-
more,
in the
current study,
no
significant
age differ-
enceswere
found
among the C(M= 7.6 years), IA
(M = 7.6
years),
or HI
(M =
7.5
years) groups. Since
disruptive,hyperactive behavior would likely lead to
referral
at an
earlier
age than inattentive, less dis-
ruptive
behavior, the younger ages for HI children
in
studies using clinic samples (Lahey et. al, 1994;
McBurnett
et al., 1995) mayreflect referral patterns
rather than true differences across subtypes in age
of onset.Thus,
the
current
findings of
different
as-
sociated impairment
for the HI
subtype, along with
evidence that this subtype
was
found
in all age
groups, support the validity of HI as a distinct sub-
type of ADHD rather than a precursor to C.
Limitations
There
are
several limitations
of the
current study.
The
exclusive
use of
teacher ratings
on a
symptom
checklist
to
assign diagnoses
is
problematic, since nei-
ther the age of onset of symptomsnor information
regarding impairment
or
cross-situationality
was ob-
tained.In an attempt to address this limitation within
the parameters of the available data, the strictest pos-
siblecut-off scores were implementedfor theSNAP-
IV The low
proportion
of
children
(2% of C, 11% of
IA, and 4% of HI) who
were
not
rated
as
unpaired
in
any
realm suggests that
the
current study appro-
priately avoided identifying subthreshold cases. The
study
is
also limited
by its
reliance
on
teachers
for
both diagnostic and dependent variable ratings, al-
though the finding of
different
patterns ofbehavior
problems across subtypes provided evidence
of the as-
sociation
between teacher perceptions of diagnostic
symptoms
anddomain-specific
dysfunction
.
Another
limitation
of the present study is the
extent
to
which theseresults
are
generalizable
to the
overall population since the current sample consisted
primarily
of lower-SES Hispanicsubjects. However,
the consistency of the obtained pattern of results
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8/12/2019 1997 Behavioral Characteristics of DSM-IV ADHD Subtypes Ina Scholl - Gaub, Carlson
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ADHD
Subtypes
111
(particularlyregarding group differences
in
areas
of
functioning) with findings
from
previous
research
suggests that ADHD children
from
both minority
andnonminorityethnic backgrounds share common
behavioral
characteristics.
Thisand other research supports the concurrent
validity of the DSM-IV ADHD subtypes. The com-
parability of the current results and those of the
other two population-based studies (Baumgaertel et
al., 1995; Wolraich et ah, in press), which used pri-
marily
Hispanic,German, and Caucasian subjects, re-
spectively, establishes the cross-cultural congruency
of
behaviors associated withADHD. Future research
should work toward examining the etiological and
predictivevalidity of the current diagnostic system by
exploring potential subtype differences in causes,
outcomes,
and
treatment responsiveness.
ACKNOWLEDGMENTS
Thisstudywas made possible through collabora-
tion
with
the
Hogg Foundation School
of the
Future
Project (SOF).The authors thank Wayne Holtzman,
Ph.D.,
Special Consultant to the Hogg Foundation,
as well as Scott Keir,
Ph.D.,
SOF
Director
of Re-
search,
and Pam
Diamond, Ph.D.,
SOF
Senior
Re-
searchAssociate,
for their enthusiastic support. Also,
thanks
to
Anne Anderson, Joey Martin,
and
Scott
Davis
fortheir
manyhours
of
data entry.
This
research
was partially supported by an
NIMHFIRST grant, MH49827 awardedto the sec-
ond
author.
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