Effect of methylphenidate on Stroop Color-Word task performance in children with attention deficit hyperactivity disorder.
ABSTRACT Attention deficit hyperactivity disorder (ADHD) is a neuropsychiatric syndrome common in the pediatric population. It is associated with multiple nonspecific deficits on neuropsychological tests of executive function, and a beneficial response to pharmacotherapy with methylphenidate (MPH) and other psychostimulants. The Stroop Color-Word task is used empirically as an aid in diagnosis and treatment monitoring of ADHD; however, data on the sensitivity of the Stroop interference score to the effects of MPH are limited. To address this issue, we studied Stroop performance in a cohort of 18 MPH-treated prepubescent boys with ADHD and six healthy controls on and off MPH treatment conditions. MPH significantly improved performance in both groups, with the ADHD participants consistently displaying worse scores than those of controls both on and off MPH. These results suggest that though the diagnostic value of the Stroop task in ADHD remains controversial, it has heuristic value for monitoring clinical responses to MPH treatment. More research is needed to ascertain the clinical significance of our findings and to replicate this relatively small effect in a larger cohort, to determine whether MPH effects on Stroop performance are specific to ADHD symptoms or they generalize to other forms of symptomatology.
- SourceAvailable from: Laurent Querne[Show abstract] [Hide abstract]
ABSTRACT: Operant conditioning of the electroencephalographic rhythm (EEG biofeedback) is argued to be an effective method for treating children with ADHD. This study was designed to evaluate whether this method, compared to methylphenidate, achieves an equally effective outcome. Participants were 39 children aged between 7 -12 years. Thirteen children with attention-deficit/hyperactivity disorder (ADHD) were trained to enhance the amplitude of the beta1 activity (15 -18 Hz) and decrease the amplitude of the theta activity (4 -8 Hz), and 13 of which were treated with methylphenidate alone. Thirteen healthy children did not receive intervention. Several behavioral, neuropsychological and experimental tests were administered before and after intervention. While behavioral measures were improved by both types of method, methylphenidate was significantly more effective than EEG biofeedback. Response inhibition was improved only by EEG biofeedback. Both EEG biofeedback and methylphenidate were associated with improvements on the variability and accuracy measures of computerized tests. Intellectual ability increased also by both methods. Although averaged effect size for methylphenidate seems to be greater than for EEG biofeedback, the difference was not significant. In conjunction with other studies, these findings demonstrate that EEG biofeedback can significantly improve several be-havioral and cognitive functions in children with ADHD, and it might be an alternative treatment for non-responders or incomplete responders to medication as well as for those their parents favor a non-pharmacological treatment.
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ABSTRACT: Long-acting medications have been developed and approved for use in the treatment of attention-deficit hyperactivity disorder (ADHD). These compounds are intended to optimize and maintain symptoms control throughout the day. We tested prolonged effects of osmotic-release oral system methylphenidate on both attention and inhibition, in the late afternoon. A double-blind, randomized, placebo-controlled study was conducted in 36 boys (7-12 years) with ADHD and 40 typically developing children. The ADHD children received an individualized dose of placebo or osmotic-release oral system methylphenidate. They were tested about 8 hours after taking with 2 continuous performance tests (continuous performance test–X [CPT-X] and continuous performance test–AX [CPT-AX]) and a counting Stroop. A positive effect of osmotic-release oral system methylphenidate was present in CPT-AX with faster and less variable reaction times under osmotic-release oral system methylphenidate than under placebo, and no difference with typically developing children. In the counting Stroop, we found a decreased interference with osmotic-release oral system methylphenidate but no difference between children with ADHD under placebo and typically developing children.Journal of Child Neurology 10/2014; · 1.67 Impact Factor
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ABSTRACT: Methamphetamine (MA) dependence is associated with cognitive deficits. Methylphenidate (MPH) has been shown to improve inhibitory control in healthy and cocaine-dependent subjects. This study aimed to understand the neurophysiological effects before and after acute MPH administration in active MA-dependent and control subjects. Fifteen MA-dependent and 18 control subjects aged 18-46 years were scanned using functional magnetic resonance imaging before and after either a single oral dose of MPH (18 mg) or placebo while performing a color-word Stroop task. Baseline accuracy was lower (p = 0.026) and response time (RT) was longer (p < 0.0001) for the incongruent compared to congruent condition, demonstrating the task probed cognitive control. Increased activation of the dorsolateral prefrontal cortex (DLPFC) and parietal cortex during the incongruent and Stroop effect conditions, respectively was observed in MA-dependent compared to control subjects (p < 0.05), suggesting the need to recruit neural resources within these regions for conflict resolution. Post- compared to pre-MPH treatment, increased RT and DLPFC activation for the Stroop effect were observed in MA-dependent subjects (p < 0.05). In comparison to MPH-treated controls and placebo-treated MA-dependent subjects, MPH-treated MA-dependent subjects showed decreased activation of parietal and occipital regions during the incongruent and Stroop effect conditions (p < 0.05). These findings suggest that in MA-dependent subjects, MPH facilitated increased recruitment of the DLPFC for Stroop conflict resolution, and a decreased need for recruitment of neural resources in parietal and occipital regions compared to the other groups, while maintaining a comparable level of task performance to that achieved pre-drug administration. Due to the small sample size, the results from this study are preliminary; however, they inform us about the effects of MPH on the neural correlates of cognitive control in active MA-dependent subjects.Frontiers in Psychiatry 07/2014; 5:20.
Effect of methylphenidate on Stroop Color–Word task
performance in children with attention
deficit hyperactivity disorder
Daniel D. Langlebena,*, John Monterossod, Igor Elmanb, Brian Asha,
Gary Krikorianc, Glenn Austinc,F
aDepartment of Psychiatry, University of Pennsylvania School of Medicine, 3900 Chestnut Street, Philadelphia, PA 19104, United States
bMcLean Hospital, Harvard University School of Medicine, 115 Mill Street, Belmont, MA 02478, United States
cThe Community/Academia Coalition, Mountain View, CA, United States
dDepartment of Psychology, University of California-Los Angeles, 1285 Franz Hall, Box 951563, Los Angeles, CA 90095-1563, United States
Received 25 March 2005; received in revised form 8 September 2005; accepted 18 September 2005
Dedicated to the memory of Glenn Austin
Attention deficit hyperactivity disorder (ADHD) is a neuropsychiatric syndrome common in the pediatric population. It is
associated with multiple nonspecific deficits on neuropsychological tests of executive function, and a beneficial response to
pharmacotherapy with methylphenidate (MPH) and other psychostimulants. The Stroop Color–Word task is used empirically as
an aid in diagnosis and treatment monitoring of ADHD; however, data on the sensitivity of the Stroop interference score to the
effects of MPH are limited. To address this issue, we studied Stroop performance in a cohort of 18 MPH-treated prepubescent
boys with ADHD and six healthy controls on and off MPH treatment conditions. MPH significantly improved performance in
both groups, with the ADHD participants consistently displaying worse scores than those of controls both on and off MPH.
These results suggest that though the diagnostic value of the Stroop task in ADHD remains controversial, it has heuristic value
for monitoring clinical responses to MPH treatment. More research is needed to ascertain the clinical significance of our
findings and to replicate this relatively small effect in a larger cohort, to determine whether MPH effects on Stroop performance
are specific to ADHD symptoms or they generalize to other forms of symptomatology.
D 2005 Elsevier Ireland Ltd. All rights reserved.
Keywords: Methylphenidate; Interference; Response inhibition; Attention deficit hyperactivity disorder
0165-1781/$ - see front matter D 2005 Elsevier Ireland Ltd. All rights reserved.
* Corresponding author. TRC, 3900 Chestnut Street, Philadelphia, PA 19104, United States. Tel.: +1 215 222 3200x196; fax: +1 215 386
E-mail address: email@example.com (D.D. Langleben).
Psychiatry Research 141 (2006) 315–320
Attention deficit hyperactivity disorder (ADHD)
is characterized by locomotor hyperactivity, impul-
sivity and inattention (American Psychiatric Associ-
ation, 1994). Due to the lack of established
psychometric or biological markers, ADHD diagno-
sis is dependent upon clinical history, physical
examination, and observation. The accuracy of both
the diagnosis and the treatment follow-up in ADHD
is limited by the lack of pathognomonic psychomet-
ric and biological markers and the high incidence of
psychiatric co-morbidity. Moreover, symptoms of
ADHD are highly context dependent, further com-
plicating treatment follow-up. The primary ADHD
symptoms have been attributed to a core deficit in
response inhibition (Barkley, 1997a,b), as evidenced
by deficits in performance of tasks requiring
intermittent withholding of response (Aron and
Poldrack, 2005); however, the deficits that children
with ADHD exhibit on other neuropsychological
tasks suggest broader core psychopathology (Rapport
et al., 2001; Nigg, 2005).
In addition to the deficits in behavioral response
inhibition, ADHD has been associated with deficits
on a variety of neuropsychological tasks broadly
described as measures of bexecutive functioningQ
(Barkley, 1997a,b; Shallice et al., 2002; Nigg,
2005). One of the classic tasks of this type is the
Stroop Color–Word task, and the associated Stroop
effect (Stroop, 1935; Rapport et al., 2001; Reeve
and Schandler, 2001; van Mourik et al., 2005). The
Stroop binterferenceQ effect is the decrease in the
speed of reading words that are incongruent with
the color of the ink in which they are printed and
the word’s meaning (e.g. the word bredQ written in
blue), relatively to the bcolor-matchedQ words and
shapes (Stroop, 1935; Golden, 1976; van Mourik et
al., 2005). The neuropsychological mechanisms
underlying this effect are not fully understood
(Kipp, 2005). Traditionally, the theoretical justifica-
tion for Stroop’s diagnostic validity in ADHD was
based on the association between cognitive
binterferenceQ and behavioral response inhibition.
The putative basic neural mechanism mediating the
Stroop effect both in ADHD and in health was
response competition between the relatively auto-
matic word reading and the less habitual color
naming; some have been experimentally demon-
strated (Peterson et al., 1999; Nigg, 2005; van Veen
and Carter, 2005). An influential rationale for the
increased Stroop effect in ADHD is a deficit in
attentional modulation of the distributed parallel
pathways processing word and color stimuli (Cohen
et al., 1990; Carter et al., 1995; Peterson et al.,
1999). The sensitivity of the Stroop effect to
untreated ADHD (Reeve and Schandler, 2001;
Shallice et al., 2002; van Mourik et al., 2005) has
not been uniform, yet the Stroop task is widely
used empirically as an aid in clinical diagnosis
(Golden, 1976; Seidman et al., 1997; Katz et al.,
1998; Bedard et al., 2002; Nigg et al., 2002;
Rucklidge and Tannock, 2002; Schmitz et al.,
2002; Shallice et al., 2002).
One of the more consistent features of ADHD is
the behavioral response to methylphenidate (MPH)
and other psychostimulants (Solanto, 1998; MTA,
2004). The difference in the acute response to
MPH between ADHD and health is quantitative
rather than qualitative (Rapoport et al., 1978;
Weingartner et al., 1980); ethical considerations
preclude controlled studies of chronic MPH admin-
istration to healthy subjects. Although current
hypotheses of ADHD predict that MPH should
reduce the Stroop interference effect in ADHD,
experimental data of MPH’s effect on Stroop
performance in children with ADHD are inconclu-
sive, with at least one recent placebo-controlled
study reporting improved inhibitory but not inter-
ference control in children with ADHD (Scheres et
al., 2003). A recent meta-analysis of Stroop
performance in ADHD deemed the number of
studies on the effect of MPH insufficient for
analysis (van Mourik et al., 2005). Thus, though
the specificity of the Stroop effect to ADHD has
been challenged, it may have clinical value as a
treatment follow-up instrument, if shown to be
sensitive to stimulant therapy in ADHD, especially
in comparison with healthy controls.
The purpose of the present study was to test the
effect of MPH on Stroop performance in prepubes-
cent boys with ADHD. We hypothesized that: 1)
MPH would reduce the Stroop interference effect in
the ADHD cohort and 2) children with ADHD
would demonstrate a larger MPH effect than the
D.D. Langleben et al. / Psychiatry Research 141 (2006) 315–320
The study protocol was approved by the Stanford
University Hospital institutional review board. All
parents gave written informed consent and the
children assented to participate. Eighteen prepubes-
cent boys (mean age=10.2 years; range=8.1–12.9,
S.D.=1.3) with ADHD, who demonstrated a favor-
able clinical response to an average of 12 weeks
(range=8–16) of MPH therapy, were included in the
study. All participants were of Caucasian origin. The
ADHD diagnosis was confirmed by a multidisciplin-
ary team using clinical history, the Conners Teachers
scale, the parents’ and teachers’ Swanson, Nolan, and
Pelham scale (SNAP), and the Wechsler Intelligence
Scale for Children, Third Edition (WISC) (Conners,
1989; Wechsler, 1991; Swanson, 1992). Exclusion
criteria were a T-scoreb2 S.D. on the Conners scale
above the population mean (mean=50, S.D.=10);
treatment with medications other than MPH; verbal
IQb 85; history of head trauma, premature birth, or
chronic medical or psychiatric disorder other than
ADHD. Six demographically matched healthy boys
(mean age=10.8 years; range=7.4–12.2, S.D. 1.7),
participated as controls. Their verbal IQ (WISC III)
was slightly higher (125.7F4.1 vs. 114.4F13.8),
albeit not significantly (Pb0.07, two-tailed t-test).
The Stroop Color and Word Testn (Stoelting Co., 620
White Lane, Wood Dale, IL 60191, 1994) was
performed twice: bon-MPHQ and boff-MPH.Q In the
ADHD cohort, the off-MPH condition was achieved
by withholding MPH for 36 h and in the controls by
testing at least 1 week before or after the single test
MPH dose. For the bon-MPHQ condition, the morning
of the session, ADHD participants received their usual
prescribed dose of 10 to 30 mg of MPH, and the
controls received a single 10-mg dose of MPH. The
on- and off-MPH sessions were conducted 1 to 3
weeks apart, counterbalanced so that approximately
half of the participants were tested off-MPH first. The
Stroop binterference scoreQ (IntS) was derived by
correcting the raw Color–Word (CWS) score by the
age-adjusted Word (WS), Color (CS) scores, which
reflect the baseline reading and color recognition
(Golden, 1976; van Mourik et al., 2005). A higher IntS
indicates less interference. The investigator
performing the Stroop task was blind to the medica-
tion state and diagnosis of the participants.
One-way ANOVAwith group (ADHD and control)
as the between-subjects factor and treatment condition
(on- and off-MPH) as the within-subject factor
revealed that following MPH administration, there
was an overall increase (improvement) in the IntS
(treatment effect: F=8.68, df=1.22; P=0.007). In
addition, we observed a group difference, with ADHD
subjects performing worse than controls across both
treatment conditions (group effect: F=6.27, df=1,22,
P=0.019). There was no significant interaction
between group and treatment condition (F=0.99,
df=1,22, P=0.329) (Fig. 1).
A post hoc paired t-test detected MPH-induced
significant increases in the IntS for ADHD partic-
ipants (48.57F4.07 vs. 50.71F4.84; t =2.37,
df=1,34, P=0.028), but not for healthy controls
(52.33F5.72 vs. 56.67F6.28; t=1.60, df=1.10,
P=0.172). The latter results did not reach statistical
significance, perhaps by Type II error resulting from
the small sample size.
Secondary analyses were conducted on each of the
three subscores used to derive the IntS (i.e. the WS,
CS, and CWS). Each of these variables were modeled
using repeated measures ANOVA, with group (ADHD
and control) as the between-subjects factor and
treatment condition (on- and off-MPH) as the within-
subject factor. For WS, MPH administration resulted
in a significant effect of medication (F(1,25)=4.32,
P=0.048) and of group (F(1,25)=6.89, P=0.015).
Similarly, For CS, we the medication (F(1,25)=9.53,
P=0.005) and the group (F(1,25)=8.86, P=0.006)
Fig. 1. Stroop interference effect in ADHD (n=18) and controls
(n=6) on and off methylphenidate.
D.D. Langleben et al. / Psychiatry Research 141 (2006) 315–320
effects were similarly significant. Lastly, for CWS, we
observed a highly significant effect of medication
(F(1,25)=23.27, Pb 0.001) and group (F(1,25)=
We found a statistically significant yet modest
(approximately 4%) improvement in Stroop response
interference scores of children with ADHD after
administration of MPH. Inquiry into behavioral
correlates of these findings (e.g. classroom perfor-
mance) will help assess the clinical potential of these
findings. Our findings are consistent with prior reports
of an increased interference effect and associated
neurophysiological abnormalities in ADHD (Bush et
al., 1999; Shallice et al., 2002) and with the putative
neuropsychological mechanism of action of MPH
through enhancement of stimulus salience (Volkow et
al., 2005). Our results contrast with two prior studies
in children with ADHD (Bedard et al., 2002; Scheres
et al., 2003) that did not show an improvement in
interference score with MPH, though in Bedard et al.
the color and word scores improved significantly.
Methodological differences (fixed vs. varied dosing)
and the absence of a healthy control group in both
prior studies complicate the comparisons between
studies and call for further elucidation of the effects of
MPH on the Stroop interference effect.
The main effect of group on Stroop data supports
the hypothesis that ADHD is associated with a
deficiency in resistance to interference that is
improved by MPH (van Mourik et al., 2005). This
indicates that the Stroop task could be a useful
adjunct clinical measure of response to MPH and
possibly other stimulant pharmacotherapies. This
conclusion is in agreement with previous reports
showing that although it may not be specific for
ADHD (Katz et al., 1998), performance on the Stroop
task is a robust predictor of hyperactive/impulsive
ADHD symptoms (Rucklidge and Tannock, 2002)
and is sensitive to stimulant effects (Everett et al.,
1991; Weingartner et al., 1980). Our findings support
the hypothesis that the therapeutic action of MPH is
to enhance the salience of the relevant stimuli,
essentially increasing the bsignal-to-noiseQ ratio of
the distributed parallel systems processing sensory
inputs (Volkow et al., 2005). This mechanism could
account for the reduced interference we see in the
control group after MPH. In our sample, the effect of
MPH was more robust in the color than the word
score. Although this is not a reliable indication of the
effect size, the observation is consistent with prior
studies and supports the notion that color naming
may be less bautomaticQ than word reading (Scheres
et al., 2004; Nigg, 2005). These data do not add to the
debate on the diagnostic specificity of the Stroop task
or provide an indication of the expected effect size of
MPH on the Stroop performance.
Our study has a number of limitations. A male-
only cohort was studied due to the difficulty involved
in recruiting girls from a clinic-referred population
(Barkley, 1997a,b; Ernst, 1999). Therefore, our results
may not apply to females with ADHD. The duration
of the drug discontinuation was aimed at exceeding
five MPH half-lives to render our subjects free of the
clinical effects of MPH, while trying to avoid
potential clinical impact of treatment discontinuation
(Kimko et al., 1999). Although most clinical data
argue against tolerance to the clinical effects of MPH,
the existence of sensitization and tolerance with d-
amphetamine and cocaine, which share many phar-
macological properties with MPH, indicates that this
issue requires further investigation (Mendelson et al.,
1998; Swanson et al., 1999; Volkow et al., 1999;
Scheres et al., 2003). The MPH administration
schedule in our study was also constrained by the
inability to administer chronic MPH to the normal
controls. The off-MPH condition in the ADHD group
was 36 h after 8 to 12 weeks of MPH therapy, while in
the controls it was 36 h after a single MPH dose.
Therefore, the schedules of MPH administration in the
two groups are only comparable under the assumption
that there is no MPH effect beyond 36 h. An
additional potential confound is related to a possibility
of performance expectation bias that could have
resulted due to the absence of a placebo pill in this
study. To offset this issue, the investigators, the
participants and their parents were kept blind to the
study hypothesis and the investigators were blind to
the subjects’ MPH status. Although these argue
against non-specific anticipatory effects as a basis
for decreased performance on this task, future studies
employing a true placebo condition may be warranted
to fully rectify this issue. Finally, the small sample
D.D. Langleben et al. / Psychiatry Research 141 (2006) 315–320
size limits the interpretability of the negative findings
in the control group. The small number of normal
controls was caused by the difficulty to recruit
participants for a protocol involving administration
of a psychostimulant to healthy children.
In conclusion, we demonstrated that MPH
improves performance on one of the common tests
of executive function. Although the small number of
controls precluded a conclusive test of the potentially
discriminating effects of MPH on the Stroop interfer-
ence effect, our findings suggest that improvements
were comparable in the ADHD and control groups
and, hence, not specifically related to the diagnosis.
However, even in the absence of diagnostic specific-
ity, our results suggest that the Stroop task may be a
useful tool for the clinical monitoring of MPH
response in children with ADHD.
This study was supported by grants from the El
Camino District Hospital Board and the National
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