The Efficacy of Cognitive Training Programs in Children and Adolescents
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Background: Cognitive therapies are intended to improve basic cognitive functions, whatever the cause of the deficiency may be. Children and adolescents with various cognitive deficits are treated with behavioral therapeutic and computer-supported training programs. We here report the first meta-analysis of the efficacy of such programs.
Methods: We systematically searched the Medline, Embase, PsycINFO, PSYNDEX, and ERIC databases to find pertinent publications for a meta-analysis of cognitive training programs that are used in children and adolescents to improve attention, memory, and executive performance (primary goals) as well as behavior/psychopathology, intelligence, and school performance (secondary goals). The mean differences between the treatment and control groups are given here as standard deviation (SD) scores.
Results: 1661 potentially relevant publications were found, including 22 studies that were considered in the meta-analysis, 17 of which were randomized controlled trials. The target variables were measured with more than 90 different testing techniques. The overall effects of cognitive training on attention (SD 0.18, 95% CI –0.11–0.47) and executive function (SD 0.17, 95% CI –0.12–0.46) were consistently small. A relatively strong effect was found on memory performance (0.65 SD, 95% [−0.12–1.42), albeit with marked heterogeneity (I 2 = 82%) owing to two studies. The largest effect was found in the area of behavior and psychopathology (SD 0.58, 95% CI 0.31–0.85), but this last figure is derived mainly from studies that lacked an active control group.
Conclusion: Cognitive therapies for children and adolescents have generally favorable, but probably nonspecific effects on behavior. On the other hand, the specific effects, however, were weak overall. Therapeutic benefit has been demonstrated only for certain individual types of therapy for specific indications.
Cognitive therapy and training programs focus on basic functions that underpin cognition, particularly attention, retentiveness and memory, visuospatial perception, and executive functions. Courses for children utilize cognitive behavioral therapy (CBT) (according to Meichenbaum et al. , modified from Lauth and Schlottke ) and computer-aided training programs (CTPs), e.g., Captain’s Log, Cogmed, or Rehacom (eTable 1). The aim is to ameliorate the impairment of basic functions and thus improve competence. Such training programs are used in children with the following disorders:
- Disturbances in mental development
- Severe attention disorders
- Acquired cerebral function disorders or brain injury, also status post mild craniocerebral trauma (e1, e2)
Cognitive therapy and training programs are most frequently indicated in children with attention deficit disorders or attention deficit hyperactivity disorders (ADD/ADHD), where the efficacy of solely medicinal treatment has been questioned (3). The best results in children with ADD/ADHD have been achieved by medicinal treatment in combination with intensive behavioral therapy training of the child together with the parents/guardians (4, 5). Whether such extensive, long-term programs are practicable (outside the context of studies) in normal family and school conditions is uncertain (6).
Systematic reviews of the literature on evaluation of CBT in adults with acquired brain injury (7–9) show that it is only sometimes effective, because the studies do not completely satisfy scientific criteria.
Although favorable results have been found for individual interventions, the effects remain unconfirmed because not all studies are of sufficiently high methodolocical quality (10, 11). Assessment of the effects of CBT in children with ADD/ADHD varies (12–14). One point of criticism is that transfer of, for example, acquired learning techniques and improved basic functions to school performance or the family situation has not been demonstrated convincingly (13).
The common feature of all treatment approaches in cognitive training is that they aim for favorable effects in at least one of the basic functions or their components, e.g., selective or divided attention or working memory. It thus seems desirable to achieve a synopsis of the efficacy studies to date—both CBT-based and computer-aided—in the form of a meta-analysis. Do cognitive therapies lead to improvement in functions promoting cognition, and do they enhance behavior, intelligence, and school performance?
In searching the literature for relevant publications, no limitations were imposed on the indication for cognitive training. The interventions were carried out in pediatric patients with acquired brain injury, ADD/ADHD, or specific learning disorders and for improvement of cognitive performance in healthy children and adolescents.
Interventions and goals
Child-centered treatment approaches were analyzed: CBT or CTP. In Germany, physicians can prescribe these treatments as ergotherapeutic interventions (§ 38 of the Regulations Governing the Prescription of Remedies [Heilmittelrichtlinien]: Cognitive performance training/neuropsychologically oriented therapy). The interventions are not disease-specific, but focus on various functional disturbances: disorders of attention, memory, executive functions (e.g., capacity for self-regulation of behavior and reflective problem-solving), and visuospatial perception. These were the primary outcome measures of the meta-analysis. Furthermore, secondary effects on behavior, intelligence, and school performance were investigated.
The control group was recruited from comparable patients who had received either no treatment (passive control group) or treatment with a different postulated mechanism of effect (active control group).
The treatment effects were determined immediately after conclusion of treatment. No limitations were placed on the tests used, but defined criteria with regard to construct relevance and construct representativeness had to be fulfilled. In order to be able to summarize the effect sizes, we compared the Z-score differences between intervention group and control group.
A systematic literature survey was conducted in the Medline, Embase, PsycINFO, PSYNDEX, and ERIC databases (up to 5 March 2012); publications in German or English, no restrictions on type of study or year of appearance. The abstracts of 1661 initially identified publications were inspected. Thirty-seven potentially suitable studies and 28 further publications cited therein were examined in full using the CONSORTS checklists for nonpharmacological treatment studies (38). Twenty-two studies were subjected to analysis (eFigure).
A more detailed account of the methods is available in the online supplement (eSupplement).
Twenty-two studies published between 1986 and 2012 were included in our meta-analysis (Table 1); overall, they provided data on 905 children and adolescents over the age of 5 years from nine different countries. The discontinuation rate was low in all studies, with an average of 5.6%. The cause and grade of the heterogeneous disorders was usually described clearly. The criteria for the diagnoses ADD and ADHD were based on the edition of the ICD or the Diagnostic and Statistical Manual of Mental Disorders (DSM) valid at the time. Acquired brain injuries were caused by craniocerebral trauma, HIV infection, cerebral malaria, or brain tumors.
The CTPs varied both with regard to both their methods and their goals. Details can be found in eTable 1. The duration of the training programs varied between 1 month and 6 months (in one case 12 months ). The effects were mostly measured directly after the end of the training phase. Follow-up data for periods ranging from 2.5 to 6 months were provided in six studies (18, 21–23, 26, 30). Existing medications were continued.
eTable 2 shows the test procedures and instruments used to calculate the effect strengths.
The quality of the studies was evaluated with regard of statistical and methodological aspects (Table 2). In only three studies were the participants randomized by generation of a randomization sequence and masked assignment to groups (21–23). Participants and trainers were mostly not blinded, because a wait-list control group design was often selected. A few studies, however, attempted blinding at the stage of data acquisition. All studies gave reasons for any data loss and drop-outs. In seven studies (16, 21, 23, 25, 27, 35, 37), evaluation according to intention to treat was documented.
In total, the studies employed around 90 different test procedures. The spectrum ranged all the way from ad-hoc instruments to internationally recognized, well validated and normalized methods. Both for the primary and the secondary goals, the procedures used were predominantly classified as adequate.
Overall effects and subgroup analysis
Primary outcome measures
Attention—The overall effect of cognitive training programs on attention was low (SD 0.18, 95% CI = [-0.11; 0.47]) (Table 3). Subgroup analysis showed a slight amount of heterogeneity:
- Diagnosis (ADHD/ADD, specific learning disorders, acquired brain injury, healthy): I2 = 39%
- Treatment type (CTPs versus CBT): I2 = 33%
- Study quality: I2 = 19%
- Medication (with or without methyl phenidate): I2 = 0%
- Parent counseling (with versus without): I2 = 0%
Memory—The effect strength for memory was greater, but with a 95% confidence interval that included null and unfavorable effects (SD 0.65, 95% CI = [-0.12; 1.42]). The relatively high point estimators were essentially explained by two studies (25, 28) that were also responsible for the high heterogeneity (I2 = 82%). While the study by Lepach (28) exhibited methodological weaknesses (no blinded randomization, imprecise description of blinding at the stage of data acquisition and of ITT evaluation), one of the two studies by Klingberg (25), with a small number of cases, broadly fulfilled the usual criteria for methodological quality. In both studies by Klingberg (25, 26) the intervention selected (working memory training) was unusual. The remaining studies showed no effect on memory (SD 0.06, 95% CI = [-0.33; 0.46]), regardless of diagnosis, study quality, type of treatment, or medication.
Executive functions—The effect strengths of cognitive training for executive functions were consistently low (SD 0.17, 95% CI = [-0.12; 0.46]).
Secondary outcome measures
Behavior/psychopathology—The greatest effects were reported in the area of behavior/psychopathology (SD 0.58, 95% CI = [0.31; 0.85]). Testing for possible nonspecific effects revealed stronger effects (I2 = 71%) in studies with a passive control group (N = 11) (SD 0.80, 95% CI = [0.39; 1.21]) than in those with an active control group (N = 11) (SD 0.25, 95% CI = [-0.19; 0.68]).
Intelligence—The overall effect was slight. The only study to show effects whose confidence interval did not include null was that by Lauth (37), in which children with learning difficulties underwent specific training in learning competence.
School performance—Here too, the effects were slight. The overall positive effect is explained purely by the Lauth study (37), the only one to investigate patients with specific learning disorders.
The treatment effects of studies with active and passive control groups were also compared for these secondary outcome measures. The differences were small (school performance: I2 = 31%; intelligence: I2 = 0%).
ADHD subgroup analysis
Subgroup analysis was performed only for patients with ADHD. Our reason for this was the fact that most of the studies were carried out in children with ADHD, coupled with the high level of public interest in this disorder. The pattern was almost identical:
- Slight effects on attention (SD 0.38, 95% CI = [-0.13; 0.90]) and executive functions (SD 0.23, 95% CI = [-0.11; 0.58])
- Moderate effect on memory (SD 0.51, 95% CI = [-0.16; 1.17])
The effects on memory were restricted to training programs using the learning program RoboMemo to improve working memory. Favorable effects on behavior were also found in children with ADHD (SD 0.57, 95% CI = [0.18; 0.97]), albeit only in studies with a passive control group. No effects were found for the remaining secondary outcome measures (intelligence: SD 0.15, 95% CI = [-0.44; 0.74]); school performance: (SD -0.08, 95% CI = [-0.81; 0.65]).
Five studies (18, 21–23, 26) provided data on treatment effects not just straight after the intervention but also from follow-up visits 2.5 to 5 months thereafter. The pooled treatment effect on executive functions was greater immediately after treatment than later (treatment difference SD 0.21, 95% CI = [-0.07; 0.50]), but this was not the case for behavior/psychopathology (treatment difference SD 0.04, 95% CI = [-0.22; 0.30]).
The primary aim of cognitive training programs is the improvement of specific cognitive functions such as attention, memory, and executive functions. The effects on attention—consistently across all studies—were slight; the 95% confidence intervals of the pooled effect included superiority of the control group. The overall effect on memory was greater, albeit with pronounced heterogeneity. No effect was observed in the majority of investigations, but in three studies (33, 34, 36) an effect was discernible, possibly explained by the particular characteristics of the training programs involved. With regard to the secondary outcome measures there were overall moderately favorable effects on behavior, but these may not be specific to cognitive behavioral therapy.
A few individual studies on the efficacy of cognitive training programs showed “significant” improvement of certain parameters. The principal strength of a meta-analysis is systematic evaluation and quantification of all available studies on the given topic: in this case, the effect strengths of various tests were standardized, using their respective standard deviations, and rendered comparable. Although earlier reviews were also based on systematic research (10, 11, 13, 39), the observed effects could not be compared or summarized quantitatively.
For the clinician, the results with regard to the primary outcome measures were sobering. One single study (35) showed a clear-cut effect on attention; all others revealed minimal effects or no effect at all. This study had a distinctive patient population and type of treatment: children with attention disorders following severe head injury underwent 6 months of training of all aspects of cognition with the CTP Rehacom. Its statistical power is limited by its lack of randomization. Three studies (25, 26, 28) found distinct effects on memory. These studies varied in the quality of their methods. The study by Lepach (28) lacked well-defined randomization and it was unclear whether the results were determined in a blinded fashion or whether there was an ITT analysis, so the validity of the findings is questionable. The first study by Klingberg (25) showed strong effects and the 95% confidence interval did not include null effects; the quality of the study was limited solely by uncertainty with regard to randomization. When the authors attempted to confirm their results in a larger study of equally high quality (sole weakness: lack of ITT evaluation), the effect was smaller and its 95% confidence interval included null effects (26). The distinguishing feature of the two Klingberg studies was training of working memory with the CTP RoboMemo. This particular treatment thus seems potentially effective. This is confirmed by a study by Thorell et al. that used the same training instrument in healthy individuals (31) and was also of high quality apart from the lack of ITT evaluation. With regard to executive functions, most studies, with the exception of the above-mentioned study by Klingberg (25), showed only slight effects or none at all.
Favorable impact on the secondary measures (behavior, school performance, intelligence) would be of particular clinical relevance. The favorable overall effect of cognitive therapy on behavior reflected the results in studies with a passive control group (no treatment); this effect was not found in studies with an active control group. It therefore seems likely that the favorable effect on behavior represented a nonspecific effect of attention in the form of treatment. No consistently favorable effects were demonstrated on the other secondary measures (school performance and intelligence). Only one study (37) showed positive effects on both intelligence and school performance.
These effects may reflect the fact that in this study—which displayed several methodological deficiencies—patients with a clearly defined learning disorder underwent targeted training in learning competence.
A potential limitation of this meta-analysis lies in the heterogeneity of the underlying diseases, treatments, and intensity and duration of the interventions and tests employed. Earlier systematic reviews, in contrast, often focused on defined underlying diseases (10, 11, 13). Inclusion of a broad spectrum of underlying diseases seems justified, however, because the interventions analyzed do not treat the underlying disease but are intended to ameliorate specific functional deficits. These specific functions represent the primary outcome measures of our meta-analysis. This is confirmed by the subgroup analysis of children with ADHD, which showed a pattern identical with that of the overall analysis including all underlying diseases. Application of uniform criteria for various test procedures enabled comparison of their quantitative results. Potentially differing effects of specific treatments can be identified in forest plots. Indeed, individual specific treatments seem to be probably more effective than the other procedures used.
One conspicuous finding was the low discontinuation rate for all treatments. This indicates high acceptance of CBT or CTP lasting several weeks. Therefore, repeated courses of training seem appropriate if there are discernible favorable effects on the outcome measures.
Cognitive training in its various forms represents one potential element of a comprehensive program of treatment with involvement of parents/guardians and consideration of the patients’ general circumstances. This meta-analysis showed favorable but probably nonspecific effects on behavior, a secondary outcome measure. The effects on the specific primary measures were only slight; the 95% confidence intervals included null and negative effects. Only for particular individual training programs and treatment indications were specific effects demonstrated. Painstaking neuropsychological evaluation is required to identify patients who fulfill these specific indications.
Conflict of interest statement
The authors declare that no conflict of interest exists.
Manuscript received on 15 January 2013, revised version accepted on
30 April 2013.
Translated from the original German by David Roseveare.
Prof. Dr. med. Rüdiger von Kries
Institut für sozaile Pädiatrie und Jugendmedizin
81377 München, Germany
@For eReferences please refer to:
eSupplement, eBox, eFigure, eTables:
The Institute of Social Paediatrics and Adolescent Medicine, Ludwig-Maximilians-Universität, Munich:
University of Education of Ludwigsburg, Faculty of Special Pedagogy: Prof. Dr. Dipl. Renner
Altötting: B. Sc. Ergotherapeut (FH) Lichtenauer
The Institute of Social Paediatrics and Adolescent Medicine, Ludwig-Maximilians-Universität, Munich:
Prof. Dr. med. von Kries
|1.||Meichenbaum DH, Goodman J: Training impulsive children to talk to themselves: a means of developing self-control. J Abnorm Psychol 1971; 77: 115–26. CrossRef MEDLINE|
|2.||Lauth GW, Schlottke PF: Training mit aufmerksamkeitsgestörten Kindern. Weinheim: Beltz; 2002. PubMed Central|
|3.||Bundesärztekammer: Stellungnahme zur Aufmerksamkeitsdefizit-/Hyperaktivitätsstörung (ADHS). Dtsch Arztebl 2005; 102(51–52): A-3609–16. VOLLTEXT|
|4.||Conners CK, Epstein JN, March JS, et al.: Multimodal treatment of ADHD in the MTA: an alternative outcome analysis. J Am Acad Child Adolesc Psychiatry. 2001; 40: 159–67. CrossRef MEDLINE|
|5.||The MTA Cooperative Group: A 14-month randomized clinical trial of treatment strategies for attention-deficit/hyperactivity disorder. Multimodal Treatment Study of Children with ADHD. Arch Gen Psychiatry 1999; 56: 1073–86. CrossRef MEDLINE|
|6.||Döpfner M, Breuer D, Schürmann S, Metternich TW, Rademacher C, Lehmkuhl G: Effectiveness of an adaptive multimodal treatment in children with Attention-Deficit Hyperactivity Disorder—global outcome. Eur Child Adolesc Psychiatry 2004; 13 Suppl 1: 117–29. CrossRef MEDLINE|
|7.||Rohling ML, Faust ME, Beverly B, Demakis G: Effectiveness of cognitive rehabilitation following acquired brain injury: a meta-analytic re-examination of Cicerone et al.’s (2000, 2005) systematic reviews. Neuropsychology 2009; 23: 20–39. CrossRef MEDLINE|
|8.||Sturm W: Evidenzbasierte Verfahren in der neuropsychologischen Rehabilitation: Therapie von Aufmerksamkeitsstörungen. Neuro Rehabil. 2010; 16: 55–62.|
|9.||G-BA: Stellungnahme zur ambulanten Neuropsychologischen Therapie. www.g-ba.de/downloads/40-268-1791; 2011. Last accessed on 18 June 2013.|
|10.||Slomine B, Locascio G: Cognitive rehabilitation for children with acquired brain injury. Dev Disabil Res Rev 2009; 15: 133–43. CrossRef MEDLINE|
|11.||Ross KA, Dorris L, McMillan T: A systematic review of psychological interventions to alleviate cognitive and psychosocial problems in children with acquired brain injury. Dev Med Child Neurol 2011; 53: 692–701. CrossRef MEDLINE|
|12.||Buch SR, Diener C, Sparfeldt JR: Kognitive Förderung. Psychologische Förder- und Interventionsprogramme für das Kindes- und Jugendalter. Heidelberg: Springer; 2009.|
|13.||Toplak ME, Connors L, Shuster J, Knezevic B, Parks S: Review of cognitive, cognitive-behavioral, and neural-based interventions for Attention-Deficit/Hyperactivity Disorder (ADHD). Clin Psychol Rev 2008; 28: 801–23. CrossRef MEDLINE|
|14.||Domsch H, Lohaus A: Psychologische Förder- und Interventionsprogramme für das Kindes- und Jugendalter. Heidelberg: Springer; 2009. MEDLINE|
|15.||Banaschewski T, Rothenberger A. Eine Evaluation des sensomotorischen Trainings bei Kindern mit ADHS. Motorik 2006; 29: 57–64.|
|16.||Bangirana P, Giordani B, John CC, Page C, Opoka RO, Boivin MJ: Immediate neuropsychological and behavioral benefits of computerized cognitive rehabilitation in Ugandan pediatric cerebral malaria survivors. J Dev Behav Pediatr. 2009; 30: 310–8. CrossRef MEDLINE PubMed Central|
|17.||Boivin MJ, Busman RA, Parikh SM, et al.: A pilot study of the neuropsychological benefits of computerized cognitive rehabilitation in Ugandan children with HIV. Neuropsychology 2010; 24: 667–73. CrossRef MEDLINE|
|18.||Brown RT, Borden KA, Wynne ME, Schleser R, Clingerman SR: Methylphenidate and cognitive therapy with ADD children: a methodological reconsideration. J Abnorm Child Psychol 1986; 14: 481–97. CrossRef MEDLINE|
|19.||Butler RW, Copeland DR, Fairclough DL, et al.: A multicenter, randomized clinical trial of a cognitive remediation program for childhood survivors of a pediatric malignancy. J Consult Clin Psychol 2008; 76: 367–78. CrossRef MEDLINE PubMed Central|
|20.||Chenault BM: Effects of prior attention training and a composition curriculum with attention bridges for students with dyslexia and/or dysgraphia. [Washington]: University of Washington; 2004.|
|21.||Fehlings DL, Roberts W, Humphries T, Dawe G: Attention deficit hyperactivity disorder: does cognitive behavioral therapy improve home behavior? J Dev Behav Pediatr 1991; 12: 223–8. CrossRef MEDLINE|
|22.||Jaeggi SM, Buschkuehl M, Jonides J, Shah P: Short- and long-term benefits of cognitive training. Proc Natl Acad Sci U.S.A. 2011; 108: 10081–6. CrossRef MEDLINE PubMed Central|
|23.||Kausch T: Evaluation Kognitiv-behavioraler Interventionsmethoden zur Behandlung von aufmerksamkeitsdefizit- und hyperaktivitätsgestörten Kindern: Messung Einzel- und Additiveffekten. Tübingen: Universität Tübingen; 2002. Dissertation.|
|24.||Döpfner M, Schürmann S, Frölich J: Therapieprogramm für Kinder mit hyperkinetischem und oppositionellem Problemverhalten:THOP. (2nd revised edition). Weinheim: Psychologie Verlags Union; 1998.|
|25.||Klingberg T, Forssberg H, Westerberg H: Training of working memory in children with ADHD. J Clin Exp Neuropsychol 2002; 24: 781–91. CrossRef MEDLINE|
|26.||Klingberg T, Fernell E, Olesen PJ, et al.: Computerized training of working memory in children with ADHD—a randomized, controlled trial. J Am Acad Child Adolesc Psychiatry 2005; 44: 177–86. CrossRef MEDLINE|
|27.||Kozulin A, Lebeer J, Madella-Noja A, et al.: Cognitive modifiability of children with developmental disabilities: a multicentre study using Feuerstein’s Instrumental Enrichment—Basic program. Res Dev Disabil 2010; 31: 551–9. CrossRef MEDLINE|
|28.||Lepach AC, Petermann F: Wirksamkeit neuropsychologischer Therapie bei Kindern mit Merkfähigkeitsstörungen. Kindheit und Entwicklung 2009; 18: 105–10. CrossRef|
|29.||Lomas KM: Computer-assisted cognitive training with elementary school-age children diagnosed with attention-deficit/hyperactivity disorder and mild/moderate comorbidity: A short-term prospective study on attention, planning and behavior. Washington: Howard University; 2002. Dissertation.|
|30.||Sonntag W: Der Einfluss des Klauerschen Denktrainings auf mathematisches Denken und Lernen von lernbehinderten Sonderschülern. ZfPP 2004; 18: 101–11.|
|31.||Thorell LB, Lindqvist S, Bergman Nutley S, Bohlin G, Klingberg T: Training and transfer effects of executive functions in preschool children. Dev Sci 2009; 12: 106–13. CrossRef MEDLINE|
|32.||Tucha O, Tucha L, Kaumann G, et al.: Training of attention functions in children with attention deficit hyperactivity disorder. Atten Defic Hyperact Disord 2011; 3: 271–83. CrossRef MEDLINE PubMed Central|
|33.||Braun J, Weyhreter H, Köhnlein O, Storck M, Bode H: Kognitives Training: Ein Programm zur Förderung von Vorschulkindern mit intellektuellen Defiziten. Psychologie in Erziehung und Unterricht; 47: 10–7.|
|34.||Dreisörner Thomas: Wirksamkeit verhaltenstherapeutischer Gruppenprogramme bei Kindern mit Aufmerksamkeitsdefizit- und Hyperaktivitätsstörungen (ADHS). Kindheit und Entwicklung 2006; 15: 255–66. CrossRef|
|35.||Galbiati S, Recla M, Pastore V, et al.: Attention remediation following traumatic brain injury in childhood and adolescence. Neuropsychology 2009; 23: 40–9. CrossRef MEDLINE|
|36.||Lauth GW, Naumann K, Roggenkämper A, Heine A: Verhaltensmedizinische Indikation und Evaluation einer kognitiv-behavioralen Therapie mit aufmerksamkeitsgestörten/hyperaktiven Kindern. Z Kinder- Jugendpsychiat 1996; 24: 164–75.|
|37.||Lauth GW, Husein S, Spieß R: Lernkompetenztraining bei leistungsschwachen Grundschülern. Kindheit und Entwicklung. 2006; 15: 229–38. CrossRef|
|38.||Boutron I, Moher D, Altman DG, Schulz KF, Ravaud P: Methods and processes of the CONSORT Group: example of an extension for trials assessing nonpharmacologic treatments. Ann Intern Med 2008; 148: W60–6. CrossRef MEDLINE|
|39.||Abikoff H: Cognitive training in ADHD children: less to it than meets the eye. J Learn Disabil 1991; 24: 205–9. CrossRef MEDLINE|
|e1.||Yeates KO, Taylor HG: Neurobehavioural outcomes of mild head injury in children and adolescents. Pediatr Rehabil 2005; 8: 5–16. MEDLINE|
|e2.||Crowe LM, Catroppa C, Babl FE, Anderson V: Intellectual, behavioral, and social outcomes of accidental traumatic brain injury in early childhood. Pediatrics 2012; 129: e262–8. CrossRef MEDLINE|
|e3.||Park BS, Allen DN, Barney SJ, Ringdahl EN, Mayfield J: Structure of attention in children with traumatic brain injury. Appl Neuropsychol. 2009; 16: 1–10. CrossRef MEDLINE|
|e4.||Barkley RA: Behavioral inhibition, sustained attention, and executive functions: constructing a unifying theory of ADHD. Psychol Bull 1997; 121: 65–94. CrossRef MEDLINE|
|e5.||Ylvisaker M, Turkstra L, Coehlo C, et al.: Behavioural interventions for children and adults with behaviour disorders after TBI: a systematic review of the evidence. Brain Inj 2007; 21: 769–805. CrossRef MEDLINE|
|e6.||Ylvisaker M, Adelson PD, Braga LW, et al.: Rehabilitation and ongoing support after pediatric TBI: twenty years of progress. J Head Trauma Rehabil 2005; 20: 95–109. CrossRef MEDLINE|
|e7.||Borenstein M, Hedges LV, Higgins JPT, Rothstein HR: Introduction to Meta-Analysis. Chichester, West Sussex, United Kingdom: John Wiley & Sons; 2009.|
|e8.||Cohen J: Statistical Power Analysis for the Behavioral Sciences. New York: Academic Press; 1969.|
|e9.||Hedges L: Distribution therory for Glass’s estimator of effect size and related estimators. Journal of Educational Statistics. 1981; 6: 107–28.|
|e10.||Kline RB: Beyond significance testing: Reforming data analysis methods in behavioural research. Washington: American Psychological Association 2004.|