Immediate effects ofmethylphenidate oncognitive attentionskills of children withattention-deficit–hyperactivity disorder

Jane Hood* MSc, Consultant Paediatric Neuropsychologist;Gillian Baird MB BChir FRCPCH, ConsultantNeurodevelopmental Paediatrician, Newcomen Centre,Guy’s Hospital;Peter M Rankin DClinPsychol, Consultant PaediatricNeuropsychologist, Neuropsychology Department, GreatOrmond Street Children’s Hospital and DevelopmentalCognitive Neuroscience Unit, Institute of Child Health;Elizabeth Isaacs PhD, Senior Research Fellow, MRCChildhood Nutrition Research Centre, Institute of ChildHealth, University College London, London, UK.

*Correspondence to first author at Newcomen Centre,Guy’s Hospital, St Thomas Street, London SE1 9RT, UK.E-mail: jane.hood@gstt.sthames.nhs.uk

This study investigated the immediate effects of stimulantmedication (methylphenidate) on cognitive attention processesin children with attention-deficit–hyperactivity disorder(ADHD). Thirteen males and two females (mean age 9y 5mo,SD 18.3mo) with a diagnosis of ADHD and who were to beprescribed methylphenidate were assessed twice on one day withthe Test of Everyday Attention for Children, aneuropsychological battery designed to tap different aspects ofcognitive attention. Between assessments, the children wereadministered methylphenidate (10mg). Each child had at leastaverage intelligence (IQ 80 or over, as measured by theWechsler Intelligence Scale for Children – III UK) and was onno other medication. A group of 16 children, who were matchedfor age, sex, and intelligence, also performed the cognitive teststwice on the same day to control for practice effects of testing.At the first assessment, children with ADHD demonstratedsignificant impairments in several aspects of cognitive attentionin comparison with the control group, particularly sustainedattention. After administration of methylphenidate for thechildren with ADHD, they showed significant improvements intheir performance on measures of cognitive attention comparedto controls. The immediate effects of methylphenidate and thesignificance of measuring cognitive aspects of attention as wellas behavioural measures are discussed.

Increasing numbers of children are being diagnosed withattention-deficit–hyperactivity disorder (ADHD), a diagnosismade on the basis of the presence of observable behavioursas described in the Diagnostic and Statistical Manual of MentalDisorders, 4th edition (DSM-IV; American Psychiatric Asso-ciation 1994). Current estimates indicate that 3 to 5% of theAmerican population have ADHD, defined according to thesecriteria (Shaffer et al. 1996, Goldman 1998), with similar pro-portions within the UK population of primary-school age(Taylor 1999). DSM-IV diagnostic criteria specify a number ofproblems with attention, hyperactivity, and impulsivity. Thedegree and pervasiveness of these problems are determinedthrough the use of parental interview, observation of thechild, and the completion of questionnaires, such as theConners Rating scale (Conners 1997), at home and school.

Optimal treatment for children with ADHD is multimodaland involves a combination of behavioural/educational man-agement strategies and drug therapy, such as methylphenidate(Ritalin). The aim of this study was to examine whethermethylphenidate could be shown to be effective in improv-ing cognitive attention with the use of an objective measure.

Methylphenidate is a short-acting psychostimulant med-ication with a duration of action of 1 to 4 hours and a half-lifeof 2 to 3 hours. Its effectiveness is determined in terms of thechanges in behaviour that led to the diagnosis. Its mechanismof action is not entirely understood but it is considered to acton and improve functioning in the frontostriatal regions ofthe brain. It is believed to affect neurotransmitters withinthese regions, particularly the uptake and release of dopamine(Himelstein et al. 2000, Volkow et al. 2001). ADHD may resultfrom low dopamine levels in the brain as a consequence ofan excess of dopamine transporters. Dopamine is a neuro-transmitter that is associated with motivation and reward,and its presence in the brain during inherently unmotivat-ing tasks allows interest in the task to be maintained andperformance to be improved (Volkow et al. 2001). The actionof methylphenidate is to maintain adequate levels ofdopamine, enabling children with ADHD to keep a higherdegree of control over their attention. In particular, it hasbeen shown to be effective on the oppositional and overac-tive elements of behaviour seen in some children with ADHD(Klorman et al. 1988, Zeiner et al. 1999, Connor et al. 2000).Coghill (2002) has reviewed the psychopharmacological treat-ment for children.

The behavioural difficulties associated with ADHD areoften managed with psychotherapeutic approaches, despitean absence of studies with positive outcomes (Brown andIevers 1999). A large-scale Multi-modal Treatment Study ofChildren with ADHD (MTA), conducted by the MTA Co-oper-ative group (1999), demonstrated that the most effectivetreatment for ADHD was closely managed pharmacotherapy.There have been several challenges to these findings (e.g.Owens et al. 2003, Tutty et al. 2003), but well-titrated medicaltreatment for ADHD remains the treatment of choice.

There are now several research studies investigating thecognitive profiles of children with ADHD. Neuropsychologicalmeasures, in particular, challenge the established view of thetraditional triad of impairment (inattention, hyperactivity, andimpulsivity) by considering children’s difficulties in terms ofcognitive attention and executive functioning deficits (seeGioia et al. 2002, Lawrence et al. 2002). Monitoring the effect ofmedication on the performance of children with ADHD on

408 Developmental Medicine & Child Neurology 2005, 47: 408–414

See end of paper for list of abbreviations.

Effects of Methylphenidate Medication on Children with ADHD Jane Hood et al. 409

neuropsychological measures has shown evidence ofimprovement on tasks of executive functioning, such as spa-tial working memory, set-shifting, cognitive flexibility, andplanning ability (Douglas et al. 1995, Aman et al. 1998, Kemptonet al. 1999, Mehta et al. 2004).

Despite extensive studies into the effects of medication onbehaviour in ADHD, there are few investigations measuringits effects on cognitive attention in clinical management. Studiesthat have attempted to measure cognitive attention have reliedon experimental measures, for example the Maudsley Attentionand Response task battery (Rubia et al. 2001), which are notwidely available and lack the normative and ecological data tobe routinely administered in clinical practice. However, clini-cal measures are increasingly becoming available commercial-ly for the paediatric population, e.g. Test of Variables ofAttention (TOVA; McCarney and Greenberg 1990), A develop-mental Neuropsychological Assessment (NEPSY; Korkman etal. 1998), and Test of Everyday Attention for Children (TEA-Ch;Manly et al. 1999).

With the increasing availability of such measures, the resultsfrom some studies implicate the effectiveness of neuropsycho-logical tests in monitoring medication on cognitive attention.For example, Aggarwal and Lillystone (2000) used the TOVA, acontinuous performance test, to assess variables such as impul-sivity and inattention before treatment. The children weretreated with stimulant medication for 12 months and thenretested without medication. They found that scores for impul-sivity were significantly improved, although other measures,such as inattention, were unaffected. These findings have beenfurther supported by a study looking at the immediate effect ofmethylphenidate treatment (Bedard et al. 2003), althoughthese authors concluded that the specific difficulties for chil-dren with ADHD and the effect of the medication was broaderthan a problem of inhibition. Berman et al. (1999) indicatedthat the effect of methylphenidate is to improve self-regulatorybehaviour and to enable children to adapt their attentionaccording to the demands of the task, for example to slowdown their response speed as task demands increase.

Cognitive attention is not a unitary brain process; rather,neuropsychological studies of adults (Robertson et al. 1996,Mirsky et al. 1999) suggest that distinct neuroanatomical net-works perform specific attentional operations and that theseare vulnerable to selective damage. Accordingly, characteriz-ing and monitoring attentional disorders may be most appro-priately performed by a variety of tasks that differentiallychallenge these systems. The TEA-Ch (Manly et al. 1999) wasdeveloped to tap the dissociable aspects of cognitive attentionmeasured in neuropsychological studies, including selective,sustained, switching, and dual attention. The multi-compo-nent approach of the TEA-Ch has been supported by struc-tural equation modelling of the normative dataset for childrenaged 6 to 16 years. Therefore, unlike unidimensional mea-sures of attention, the TEA-Ch is more sensitive to highlight-ing specific cognitive strengths and weaknesses within a domainof attentional skills.

Manly and colleagues (2001) used the TEA-Ch to investigatethe performance of 24 males diagnosed with ADHD. TheADHD group showed significant deficits on measures of sus-tained attention when compared with a control group (n=15),matched for age and Vocabulary subtest scores. However, it wasnoted that the ADHD group had very low Vocabulary scores(mean score 4th to 6th centile) and were not prescribed stimu-

lant medication. A larger-scale study was conducted by Heatonand colleagues (2001) with children of average ability (meanFull Scale IQ 92, SD 13). They concluded that the ADHD group(n=63) performed significantly below the control group(n=23) on measures of sustained attention and attentionalcontrol. However, using the more stringent degrees of signifi-cance applied by Manly et al. (2001; controlling for multiplecomparisons) they would also show significant differencesonly on measures of sustained attention. A post-hoc analysis oftheir results revealed that 25 participants in the ADHD samplewere taking stimulant medication at the time of testing and 35were not. The two subgroups showed no significant differ-ences on any measure of the TEA-Ch.

A small-scale, clinic-based study was undertaken to investi-gate the cognitive attention skills in children with ADHD, and,in particular, to monitor the immediate effects of methyl-phenidate on individuals’ cognitive attention.

MethodPARTICIPANTS

Group with ADHD

This group was a consecutive sample taken from the popula-tion of children currently attending the ADHD medication clin-ic at Guy’s Hospital (Newcomen Centre). The children attendthe clinics from the south-eastern region of the UK and all chil-dren within the 7 to 11 year’ age band with a primary diagnosisof ADHD were included. Exclusion criteria were: learning dif-ficulties (IQ below 80, after assessment by the first author),other psychiatric diagnoses (apart from conduct disorder oroppositional defiant disorder) and the prescription of medica-tion other than methylphenidate. Neurodevelopmental diag-noses were made by the second author and were based onmultidisciplinary assessment, with all children meeting the cri-teria of ADHD according to DSM-IV. Three of the children weretaking methylphenidate for the first time. The remaining 12children, who were already taking methylphenidate routinely,did not take their medication before attending the clinic and sowere unmedicated for at least 12 hours before testing. All par-ticipants were taking methylphenidate as their only medica-tion and all except one had been taking the medication for lessthan a year. A total of 15 children (13 males, two females) wereincluded in the study. Mean age of the ADHD group was 114months (SD 18.3; range 7y 2mo to 11y 9mo) and their meanFull Scale IQ was 110 (SD 15.4; range 85 to 137).

Control group

A total of 16 children (14 males, two females) between theages of 7 and 11 years were recruited from two local schools inLondon, UK. The control group was matched for age and intel-ligence with the ADHD group (mean age 116mo, SD 16.2;range 7y 6mo to 11y 5mo; mean Full Scale IQ 106, SD 12.4,range 80 to 124). There was no significant difference betweenthe mean Verbal IQs or Performance IQs when the ADHD andcontrol groups were compared. Children in the control groupwere selected by their teachers on the basis of having nobehavioural or learning difficulty and having academic achiev-ement within the average range.

All participants gave informed consent to take part in thisstudy. The study was approved by the ethics committee ofGuy’s and St Thomas’ NHS Trust.

*US usage: mental retardation.

MEASURES

Wechsler Intelligence Scale for Children, UK (WISC-III UK),

short form

Four WISC-III UK (Wechsler 1992) subtests were given toprovide a measure of intellectual ability. This short formcomprised two verbal subtests (Similarities and Vocabulary)to give a Verbal IQ estimate, and two performance subtests(Picture Completion and Block Design) to give a PerformanceIQ estimate. IQ scores were computed in accordance withthe procedure described by Sattler (1992) to account for sub-test reliability. All three IQ scores have a mean of 100 (SD 15).(See Appendix I for subtest descriptions.)

The TEA-Ch

The TEA-Ch is designed to tap different attentional processesand has two versions (A and B) of each subtest to facilitaterepeat administration.

The first four subtests of the TEA-Ch, considered to be thecore subtests (Sky Search, Score!, Creature Counting, SkySearch DT), were administered to provide measures of selec-tive, sustained, dual, and switching attention. Three additionalsubtests (Walk, Don’t Walk; Same World; and Opposite World)were included to provide a measure of disinhibition/impul-sivity. These tests produce 10 separate scores for analysis andare described fully in Appendix II. The TEA-Ch subtests yieldage-corrected Scaled Scores with a mean of 10 and an aver-age range of 7 to 13. There is no overall attention index of thechild’s performance on this battery of tests.

PROCEDURE

The first author assessed all children on the neuropsychologicalmeasures. The ADHD group was assessed within the clinic ina quiet room that was free from distractions. They were firstassessed on version A of the TEA-Ch in the morning, when theyhad not taken any prescribed medication that day. Their parentsadministered their usual medication (10mg) and they werethen reassessed on version B of the TEA-Ch after a period ofbetween 60 and 90 minutes to allow the medication to takeeffect. The WISC-III assessment was conducted during the sec-ond session, when the children had taken their medication.

Participants in the control group were seen in theirschools, and children were tested in a quiet room that wasfree from distractions. There was a gap of between 90 and 120minutes between administrations of versions A and B of the

TEA-Ch. The four subtests of the WISC-III were administeredduring the second session.

STATISTICAL ANALYSES

A series of independent-sample t-tests was used to comparethe performance of the two groups at each time point. Repeated-measures analyses were then used to determine whetherthere were any significant interactions between the experi-mental variables. Where there were found to be significantinteractions, the nature of these was investigated with theuse of repeated-measures t-tests.

ResultsMean scores and standard deviations for the two groups attimes 1 and 2 are presented in Table I.

Scores of the control group and the ADHD group at times1 and 2 were compared using t-tests. Given the small numberof participants in each group, relative to the number of sub-tests used, only those subtests achieving significance atp<0.005 (Bonferroni correction) were considered to be themost reliable indicators of a significant difference betweenthe groups at each time point.

Using this level of significance, the scores for the ADHDgroup at time 1 were significantly below those of the controlgroup for the Score! (p=0.001) and Sky Search DT subtests(p=0.004). If the less stringent level of significance of p<0.05is used, the scores for Sky Search Targets (p=0.016), CreatureCounting Total (p=0.012) and Walk, Don’t Walk (p=0.010)also reached significance.

Because stimuli similar to those used in the Score! subtestcomprise a subcomponent of the Sky Search DT subtest, itwas considered possible that scores for these two subtestsreflect the same basic attentional weakness in the ADHDgroup. Therefore the performances of the two groups on SkySearch DT at time 1 were compared, covarying for Score!.This analysis showed no significant difference between thegroups (F=0.73, p=0.401) on Sky Search DT if their differentabilities on Score! are taken into account.

When the scores of the control group and the ADHD groupwere compared at time 2, the ADHD group was significantlybelow the control group on only one measure: CreatureCounting total (p=0.004).

A repeated-measures analysis of variance (ANOVA) was per-formed for each measure, with group (ADHD and controls) as

410 Developmental Medicine & Child Neurology 2005, 47: 408–414

Table I: Scores for two groups at times 1 and 2 on subtests of TEA-Ch

Subtest Score at time 1 p Score at time 2 p

ADHD Controls ADHD Controls

Sky Search Targets 8.9 (3.0) 11.4 (2.3) 0.016 10.1 (3.4) 9.8 (2.6) 0.816Sky Search Time per Target 8.7 (3.7) 9.6 (2.4) 0.432 11.1 (2.6) 11.4 (2.7) 0.802Sky Search Attention Score 7.9 (3.3) 9.3 (2.5) 0.197 10.1 (2.4) 10.6 (2.8) 0.654Score! 6.7 (3.8) 10.9 (2.6) 0.001 9.9 (3.6) 11.0 (2.6) 0.320Creature Counting Total 7.2 (2.2) 9.9 (3.3) 0.012 10.5 (1.7) 12.4 (1.7) 0.004Creature Counting Time 8.7 (3.3) 9.9 (1.6) 0.230 9.8 (3.3) 10.2 (1.9) 0.222Sky Search DT 4.7 (3.6) 8.3 (2.9) 0.004 7.6 (2.9) 7.7 (2.9) 0.887Walk, Don’t Walk 4.9 (3.4) 8.3 (3.4) 0.010 8.9 (3.9) 9.8 (3.9) 0.507Same World 8.8 (3.9) 10.7 (3.0) 0.089 11.1 (2.9) 11.0 (3.3) 0.951Opposite World 8.4 (3.2) 9.9 (2.3) 0.147 10.9 (3.1) 10.4 (3.3) 0.724

Results are presented as mean (SD). TEA-Ch, Test of Everyday Attention for Children (Manley et al. 1999).

the between-participants variable and time (1 and 2) as theparticipants variable, to determine whether the effect of timewas the same for both groups. These analyses also indicatedwhether there was a significant interaction between groupand time for each measure. The latter is important in deter-mining whether the difference from time 1 to time 2 in thescores of the ADHD group is additional to any practice effect.

TIME

There was a significant effect of time for the following mea-sures: Sky Search Time per Target (p<0.001); Sky SearchAttention Score (p=0.001); Score! (p=0.016); Creature Coun-ting Total (p<0.001); Walk, Don’t Walk (p<0.001); Same World(p=0.001); and Opposite World (p=0.001). For all these mea-sures, test performance was better at time 2 than at time 1 forboth groups.

INTERACTION

The interaction terms for the following measures were signifi-cant: Sky Search Targets (p=0.047); Score! (p=0.02); SkySearch DT (p=0.007); Walk, Don’t Walk (p=0.032); SameWorld (p=0.011); and Opposite World (p=0.027). Significantinteractions for each subtest were determined using t-tests.

For Score!, Walk, Don’t Walk, Same World, and OppositeWorld there were significant time and interaction effects; t-tests indicated that the ADHD group improved significantlyon each measure (p values at least 0.005), whereas the con-trol group did not. The improvements in scores from time 1to time 2 for the ADHD group were therefore unlikely to havebeen due to a practice effect.

The subtests Sky Search Targets and Sky Search DT showedno time or group effect but did show a significant interactioneffect. Despite there being a significant interaction effect forSky Search Targets, neither group’s score increased signifi-cantly from time 1 to time 2. However, there was a significantdifference between the groups at time 1 that did not exist attime 2. This is presumably because Sky Search Targets was oneof the few tests in which the control group scores decreasedfrom time 1 to time 2 but the ADHD group improved, althoughneither change was statistically significant. For Sky Search DT,the score of the ADHD group increased significantly from time1 to time 2 (p=0.007), whereas the control group’s did not.The mean score for the control group also decreased slightlyfrom time 1 to time 2, although not significantly.

Subtests showing no significant interaction between thefactors time and group were Sky Search Time per Target, SkySearch Attention, and Creature Counting Total. However,they did show a main effect of time, indicating that improve-ments in the test results for both groups are likely to havebeen due to practice alone.

DiscussionThis investigation was undertaken to consider whether same-day repeat administration of the TEA-Ch would be useful formeasuring the immediate effect of stimulant medication onthe cognitive attention of children diagnosed with ADHD.

When the ADHD group’s cognitive attention scores werecompared with those of the control group at time 1, the ADHDgroup was found to perform significantly below the controlgroup on two subtests of the TEA-Ch (p<0.005, using Bonferronicorrection): Score! and Sky Search DT (measures of sustainedattention). If a less stringent statistical criterion is used (p<0.05),

scores for the Sky Search Targets, Creature Counting Total,and Walk, Don’t Walk subtests were also significantly lower forthe ADHD group than for the control group at time 1. Lowscores on these subtests indicate that the ADHD group showedparticular difficulties with tests of visual search, divided atten-tion, and response inhibition. These findings also suggest thatthe two subtests Score! and Sky Search DT, which showed thelargest difference between the groups, might be useful for dif-ferentiating between children with ADHD and those without.

When Manly et al. (2001) compared 24 males with ADHD(with low Vocabulary scores and no stimulant medication)with 15 controls, they found that Walk, Don’t Walk and ScoreDT (a subtest not administered in this study) showed themost significant differences. Heaton and colleagues (2001)replicated these results with 63 children with average intelli-gence and ADHD compared with 23 controls. According tothe structural equation data produced by Manly et al., thesetwo subtests measure the same underlying cognitive con-struct as the two most significant tests in this study (Score!and Sky Search DT), which is sustained attention. Therefore,although the ADHD group in this study had higher levels ofverbal intellectual ability, a similar cognitive profile wasobserved for attention deficits.

A further analysis of the relation between the ADHD and con-trol groups’ performances on Score! and Sky Search DT at time1 was conducted to determine the extent to which performanceon Sky Search DT was affected by poor sustained auditory atten-tion skills, as measured by the Score! subtest. This revealed thatthere were no significant differences between the groups on SkySearch DT (when performance on Score! was used as a covari-ant), indicating that performance on Sky Search DT is likely toreflect the participants’ sustained auditory attention ability.

When the groups were retested on the TEA-Ch at time 2, theADHD group’s scores were within the normal range, indicatingthat the effect of the methylphenidate was to bring the cogni-tive attention skills of the ADHD group up to normal levels.

The main aim of this study was to determine whether theTEA-Ch is a useful measure for examining the immediate effectof methylphenidate on the cognitive attention difficulties ofchildren diagnosed with ADHD. To do this, any practice effectfrom same-day testing with the TEA-Ch had to be ruled out.The results described above show that several tests did have asignificant practice effect for both the control and ADHD groups.However, the subtests that showed a significant improvement,in addition to any practice effect, were Score!, Walk, Don’tWalk, Same World, and Opposite World. On these subtests,the ADHD group showed an improvement in scores signifi-cantly greater than that shown by the control group and thatis therefore attributable to the effects of the medicationtaken by the group with ADHD.

In clinical use, the effects of medication are not monitoredin terms of their effect on cognitive attention but rather by theireffects on observed behaviour. It was considered important toinvestigate the effect of medication on cognitive attention skillsto determine, especially for those children in whom there is lit-tle or no observed improvement in behaviour, whether themedication might be improving their ability to concentrate inclass and sustain their attention to learning activities. For thegroup with ADHD in the clinic sample, all reported that theyfound it easier to concentrate in class and, therefore, to com-plete work when they had taken their medication, even whentheir behaviour was still unpredictable. For those who re-

Effects of Methylphenidate Medication on Children with ADHD Jane Hood et al. 411

ported recent Standardized Attainment Test scores (half thesample), all were achieving at or above the average level.

The importance of following up those children for whomthere is a positive effect on cognitive attention is highlighted bya recent review of the research on interventions for ADHD,conducted by Purdie and colleagues (2002). They found onlyeight studies looking at the effects of school-based interven-tions for children, and few of these considered cognitive or aca-demic outcomes. They found that school-based interventionshad a greater effect on cognitive outcomes than medical inter-vention and that medication was more effective in treating thebehavioural difficulties of children with ADHD, although thereliability of these findings is limited by the small sample size.Further work is needed to determine whether the combinationof classroom-based intervention and well-controlled medica-tion would produce the optimum result for children.

The effects of medication on children’s cognitive attention,as opposed to purely behavioural benefits, may have beenunderestimated until now. Children with ADHD tend to under-perform at school when their academic attainments are com-pared with their intellectual ability (Zentall 1993). Lindsay andcolleagues (1999) provide an example of the effect of medica-tion on improved academic performance. They review thebeneficial effects of methylphenidate on mathematical perfor-mance and link this to improvements in executive functionskills and working memory. If children with ADHD are experi-encing behavioural difficulties in school and are underper-forming academically, an additional benefit of treating themwith stimulant medication might be to improve their academicperformance. The results of this study suggest that improvedacademic performance might not be purely a consequence ofreduced behavioural difficulties but also a direct effect ofimproved cognitive attention on academic learning.

Therefore, in situations where parents do not report anychange in observed behaviour, formal measures of cognitiveattention skills, repeated with and without medication, canprovide evidence of more subtle effects that might influencethe child’s success or otherwise in academic tasks.

Limitations and future directionsThe ADHD group included a small number of children whowere taking methylphenidate for the first time as well as thosewho had been taking it before the study. It might be that there issome difference between the effectiveness of methylphenidatewhen it is first administered and its effect when taken over anumber of months or years. Similarly, for those children whonormally take methylphenidate but did not on the day of test-ing, there might be some rebound effect that has not beendetermined or controlled for. The effect of taking medicationcould also be controlled for in future studies with the use of aplacebo. Ideally, another control group would have beenincluded, composed of children with a diagnosis of ADHD whorepeated the test twice without methylphenidate, but with aplacebo on second administration, i.e. a randomized, double-blind control trial. However, this was not considered appropri-ate for this study, as the participants in the ADHD group wereall part of a clinical population attending for treatment.

This study included a small number of females (two ineach of the ADHD and control groups). The normative valuesfor the TEA-Ch are different for males and females becausethere were found to be significant differences in the way inwhich the two groups performed at different ages. It is not

possible to comment, from this sample size, on whetherthere was any difference in the effect of the medicationbetween females and males in the ADHD group.

Given the nature of the problems with attention and moti-vation within the ADHD group, it seems likely that the ADHDgroup would be more likely to experience boredom and fatigueon second administration, especially when they have strug-gled with the first trial. This would suggest that the effect ofthe methylphenidate on attention and motivation might begreater than demonstrated by this experiment. A placebo trialwould also allow this possibility to be explored.

It is important to be able to relate the findings of repeatadministration to information supplied by the standard par-ent and teacher behavioural questionnaires. This would helpto determine whether specific improvements on cognitiveattention could be linked to behavioural observations. It isbeyond the scope of this paper to identify whether improve-ments on cognitive testing lead directly to improved academicperformance, and it would be useful to compare the children’srate of progress on academic attainments, such as literacyand numeracy, to determine whether the improvements inattention and executive functioning can be seen to have adirect effect on rate of academic learning.

ConclusionConsistent with previous research (Heaton et al. 2001, Manlyet al. 2001) this study used the TEA-Ch to demonstrate that chil-dren with ADHD have significant cognitive attention impair-ments when compared with a control group of childrenwithout ADHD, particularly on tasks of sustained attention.The findings also show the significant immediate benefits ofmedication for the cognitive attention skills of children withADHD. Impairments in cognitive attention are likely to haveimplications for children’s learning, despite their normal intel-lectual ability. This has been shown to be so in studies byZentall (1993) and Lindsay et al. (1999) cited above. A recentstudy by Wilding (2003) showed that the difficulties faced bychildren with attention difficulties (although without a formaldiagnosis of ADHD in this example) increase with task com-plexity. Educational underachievement within the ADHD pop-ulation has usually been thought of as a consequence ofbehavioural difficulties or lower intellectual ability, but thesefindings support the view that, in the context of average IQ,their underachievement is perhaps a consequence of cognitiveattention difficulties, in addition to behavioural difficulties.The effects that stimulant medication has on children’s learn-ing and behaviour should therefore be carefully monitored.

DOI: 10.1017/S0012162205000794

Accepted for publication 28th June 2004.

Acknowledgements

We thank the pupils of Invicta Primary School, Greenwich, London,and Charles Dickens Primary School, Southwark, London, for theircontribution to this study.

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Appendix I

WECHSLER INTELLIGENCE SCALE FOR CHILDREN III UK:DESCRIPTION OF SUBTESTS

Similarities: a series of orally presented word pairs, for which thechild has to explain the similarity between the objects or theconcepts they represent.Vocabulary: a series of words presented orally that child has to define.

Similarities and Vocabulary subtests are used to give an estimateof Verbal IQ.Picture Completion: a set of pictures of common objects and scenes,all with an important part missing that the child has to identify.Block Design: child is given three-dimensional blocks composed oftwo colours, which are used to reproduce a two-dimensionalabstract pattern.

The Picture Completion and Block Design subtests are used togive an estimate of Performance IQ.

List of abbreviations

ADHD Attention-deficit–hyperactivity disorderTEA-CH Test of Everyday Attention for Children

414 Developmental Medicine & Child Neurology 2005, 47: 408–414

Appendix II

TEST OF EVERYDAY ATTENTION FOR CHILDREN: DESCRIPTION OF SUBTESTS

Sky Search: this test measures selective attention. It requires the childto search for targets on a complex but organized visual array. This isa timed test and the child has to indicate when they think they havelocated all the targets. Measures of the child’s speed and accuracyare taken. Three scores are produced from this subtest: Sky SearchTargets, Sky Search Time per Target and Sky Search Attention.Score!: this test measures sustained attention. It requires the childto listen to a tape that plays sequences of tones with variableintervals between tones. The child has to count the number of tonessilently, up to a maximum of 15. No feedback on the success of theirperformance is given and there is little to engage their attention asthe task quickly becomes monotonous. This subtest produces asingle score: Score!.

Creature Counting: this test measures attentional control orswitching attention. It requires the child to count pictures of creaturesin a burrow. Arrows are interspersed between the creatures and whenthe child reaches an arrow, they must switch the direction of theircounting according to the direction of the arrow. For example, if theyhave been counting upwards (2, 3, 4) and they come across an arrowpointing down, the next number they say should be 3 and they shouldcontinue counting down until another arrow is reached. The child hasto complete each section as accurately and quickly as possible andthey are scored for speed, accuracy and the number of correctdirectional switches made. This subtest produces two scores: CreatureCounting Total and Creature Counting Time.

Sky Search DT: this test measures sustained attention and the child’s

dual-task ability, namely the ability to attend to two things at once.In this test the child is required to repeat the Sky Search subtestwhile simultaneously performing the Score! Subtest. This testproduces a single score: Sky Search DT.

Walk, Don’t Walk: this test measures sustained attention and thechild’s ability to inhibit a trained response. The child is required tolisten to a tape that plays two different sounds: one sound indicatesthat it is safe to move forward along a printed path on a sheet andthe other that it is not safe to move forward. While listening to thetape, dots are placed in consecutive ‘stepping-stone’ squares on thepath. They must mark the next square only if they hear a safe ‘go’tone and not if they hear the ‘no-go’ sound. The tones are played atregular intervals within each of 20 games but the inter-tone intervalis reduced as the child progresses through the games. This testproduces a single score: Walk, Don’t Walk.

Same World: this subtest measures response speed. The child has toread lists of numbers, 1 and 2, that alternate in an irregular fashion,as quickly as possible. This test provides a single score: Same World.

Opposite World: this test measures attentional control. The childhas to read a similar list of numbers to that presented in Same Worldexcept that they have to say 2 when they see a 1 and vice versa. Theyare stopped to correct themselves if they make a mistake and theirtotal time for each array is recorded. This test produces a singlescore: Opposite World.

SSBP 9th International Symposium

Treatment of Behavioural Problems in

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