A Controlled Trial of Working Memory Training for Children and Adolescents with ADHD

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1 This article was downloaded by: [Queen's College] On: 20 January 2013, At: 21:29 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Journal of Clinical Child & Adolescent Psychology Publication details, including instructions for authors and subscription information: A Controlled Trial of Working Memory Training for Children and Adolescents with ADHD Steven J. Beck a, Christine A. Hanson a, Synthia S. Puffenberger a, Kristen L. Benninger b & William B. Benninger a a Department of Psychology, Ohio State University b College of Medicine, University of Toledo Version of record first published: 06 Nov To cite this article: Steven J. Beck, Christine A. Hanson, Synthia S. Puffenberger, Kristen L. Benninger & William B. Benninger (2010): A Controlled Trial of Working Memory Training for Children and Adolescents with ADHD, Journal of Clinical Child & Adolescent Psychology, 39:6, To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

2 Journal of Clinical Child & Adolescent Psychology, 39(6), , 2010 Copyright # Taylor & Francis Group, LLC ISSN: print= online DOI: / A Controlled Trial of Working Memory Training for Children and Adolescents with ADHD Steven J. Beck, Christine A. Hanson, and Synthia S. Puffenberger Department of Psychology, Ohio State University Kristen L. Benninger College of Medicine, University of Toledo Downloaded by [Queen's College] at 21:29 20 January 2013 William B. Benninger Department of Psychology, Ohio State University This study assessed the efficacy of a 5-week, intensive working memory training program for 52 children and adolescents (ages 7 17) who had Attention-Deficit= Hyperactivity Disorder (ADHD) and other comorbid diagnoses. This study provided a treatment replication since the waitlist control group also completed training and was included in the follow-up data analyses. Parents and teachers completed paper-andpencil measures of working memory, executive functioning, and ADHD symptoms at baseline, posttreatment, and 4-month follow-up. Parent ratings indicated that participants improved on inattention, overall number of ADHD symptoms, initiation, planning=organization, and working memory. Teacher ratings approached significance at posttreatment and at 4-month follow-up on and Initiate scale. Working memory training appears promising as an intervention in improving executive functioning and ADHD symptoms. Attention-Deficit=Hyperactivity Disorder (ADHD) is a prevalent, chronic, and impairing disorder occurring in 3% to 7% of school-aged populations (Angold, Erkanli, Egger, & Costello, 2000; Jensen et al., 1999). The primary deficits seen in ADHD are those of inattention and hyperactive-impulsive behavior (American Psychiatric Association [APA], 2000). Research has also shown that children and adolescents with ADHD demonstrate deficiencies in other abilities generally considered to fall within the domain of executive functioning (Barkley, 2006). Executive functioning is a broad construct that refers to a variety of processes including attention, working memory (WM), flexibility of thought, planning, and the regulation of goal-directed behavior. One such deficit in executive functioning is WM, which is considered a potentially important mechanism in ADHD Correspondence should be addressed to Steven J. Beck, Ohio State University, Department of Psychology, 1885 Neil Avenue Mall, Columbus, OH beck.5@osu.edu (Castellanos & Tannock, 2002). WM is a system that allows one to temporarily hold information in mind long enough to use the information for some purpose (Baddley, 2000). WM is a key function that is necessary for many cognitive tasks, such as remembering instructions and completing tasks, and is implicated in such practical applications as academic learning and reasoning (Nigg, 2006). According to the influential WM model proposed by Baddeley and Hitch (1974) and extended by Baddeley, (2000), WM is broken down into three components: two storage systems (i.e., the phonological loop and the visuo-spatial sketchpad) and one control system, (i.e., the central executive). The phonological loop is conceptualized as the part of WM that is responsible for holding verbal information in mind, and the visuo-spatial sketchpad is thought to be responsible for holding nonverbal information in mind. The central executive is described as regulating WM in that it directs

3 826 BECK ET AL. attention, guides the flow of information, coordinates the execution of two or more tasks at once, and interacts with long-term memory (Baddley, 2000). A recent study found impairments in all three components of Baddley s model of WM in children with ADHD (Rapport et al., 2008). However, they found larger effect sizes for impairments of the central executive aspect of WM than the two storage systems. Another study found that WM was more impaired in adolescents and adults with ADHD compared to controls when required to overcome interference in order to maintain items in WM (Engelhardt, Nigg, Carr, & Ferreira, 2008). WM deficits in ADHD have been consistently demonstrated (Martinussen, Hayden, Hogg-Johnson, & Tannock, 2005; Westerberg, Hirvikoski, Forssberg, & Klingberg, 2004). A recent meta-analysis found verbal and visual spatial WM impairments in children and adolescents with ADHD, when compared to non-adhd children (Martinussen et al., 2005). Researchers speculate that WM is impaired in individuals with ADHD such that they are distractible and unable to hold in mind that what they are suppose to be paying attention to in the face of interference (Engelhardt et al., 2008). Thus, impairments in the central executive functioning of WM appear to be associated with ADHD symptoms (Barkley, 1996) and they may play an important role in the difficulties children and adolescents with ADHD have with complex reasoning, forgetfulness, organization, planning, and goal setting (e.g., Rickel & Brown, 2007). Given the high prevalence of ADHD and its impact on many aspects of development, considerable effort has been focused on finding treatments to alleviate symptoms. Although pharmacological management is one of the empirically supported interventions, stimulant medications typically do not ameliorate all of the problems associated with ADHD (Smith, Barkley, & Shapiro, 2006). In addition, what benefits do accrue from stimulant medication disappear after the medication is out of the system or discontinued. As such, the development of nonpharmacological treatments is important to additionally improve attention or other cognitive abilities in children and adolescents with ADHD. Attentional and other cognitive control training interventions for children with ADHD have been developed and tested, but these studies have generally used small sample sizes or no control condition. Kerns, Esco, and Thompson (1999) assessed 14 children identified as having ADHD who participated in an attention-demanding task. Half of the children received the attention training intervention, whereas the remaining 7 children were controls. Results indicated that the children who received twice-weekly, 30-min sessions over 8 weeks performed better on the attentional material and on comparable, untrained neuropsychological tasks. However, there was no significant improvement on measures of academic efficiency or on parent or teacher ratings of ADHD symptoms or related behaviors at home or school. WM training has been investigated as an intervention for children with ADHD. Holmes, Gathercole, and Dunning (2009) identified 22 children who scored low on verbal WM. Children completed either an adaptive WM training in which task difficulty was matched to the child s current memory span or a placebo to control for expectancy effects. They found that the majority of children who completed the adaptive training improved on four WM measures at posttreatment and at a 6-month follow-up. In addition, children receiving the adaptive training improved at the 6-month follow-up on mathematical reasoning. Klingberg, Forssberg, and Westerberg (2002) gave an intensive WM training to children with ADHD and normal adults. The training was also adaptive and included an algorithm to increase training difficulty as performance improved. The control group trained on a placebo treatment, which was the WM program without the algorithm, making their training less rigorous. They found at posttreatment the children who received full treatment did significantly better than the control group on measures of visuo-spatial WM, nonverbal reasoning, and response inhibition. They also displayed fewer head movements, which has been shown to correlate with behavioral ratings of hyperactivity. These results were replicated and expanded in a randomized controlled trial with 53 Swedish children ages 7 to 12 who were identified as having ADHD (Klingberg et al., 2005). The WM training included both verbal and visuo-spatial WM exercises similar to those used in the present study. Each training session took about 40 minutes. Participants completed 25 training sessions over 5 to 6 weeks, which is the same training regimen used in the present study. The study included an experimental and a placebo treatment equivalent to the one just mentioned (Klingberg et al., 2002). At posttreatment, Klingberg et al. (2005) also found significant improvements of the experimental group on measures of visuo-spatial WM, nonverbal reasoning, and response inhibition. In contrast to Klingberg et al. (2002), they did not find significant improvements on motor activity. Klingberg et al. (2005) also found significant improvements on parent-reported, but not teacher-reported, symptoms of inattention and hyperactivity at posttreatment. Additional improvements were seen between posttreatment and a 3-month follow-up on measures of visual-spatial WM and parent-rated symptoms of ADHD. Limitations of the study revolve around the sample. First, investigators did not formally diagnose the children as having ADHD and instead relied on

4 pediatricians, child psychiatrists, or educators to identify the children as presenting with ADHD symptoms. In addition, the investigators did not report comorbid diagnoses within the sample but did indicate children were excluded from the sample if they were identified as presenting with oppositional-defiant characteristics. Finally, none of the children in their study were taking stimulant medication during the WM training. Therefore, their sample was likely not representative of typical children with ADHD in the United States. Holmes et al. (2009) assessed the impact of stimulant medication and a WM training program similar to the one used by Klingberg et al. (2005) and the present study for 25 children between 8 and 11 years of age identified as having ADHD. Children who were taking stimulant medication were recruited through psychiatrists and pediatricians in the local community. All children met Diagnostic and Statistical Manual of Mental Disorders (4th ed. [DSM IV]; APA, 1994) diagnoses for ADHD, although the procedures for how this was accomplished (e.g., by a structured clinical interview) were not reported. The children were assessed using the Automated Working Memory Assessment (Alloway, 2007; Alloway, Gathercole, & Pickering, 2006), which provides multiple measures of both verbal and visual-spatial storage and WM. Children were assessed on the Automated Working Memory Assessment at pretraining off medication and then on medication, and again at post training and at a 6-month follow-up on the medication. Medication significantly improved visual-spatial memory performance, but WM training led to substantial gains on all components of WM at posttraining. Significant training gains were maintained on three of the four aspects of WM after 6 months, with gains not being maintained on verbal short-term memory. Intelligence test scores were unaffected by either intervention. The present study investigated whether a 5- to 6-week, intensive training of WM given to children and adolescents with ADHD in the United States would lead to improvements on parent and teacher ratings of working memory, other executive functions, and ADHD-related symptoms at posttraining and at a 4-month follow-up. A strength of the present study is that the children and adolescents participating in the study are more representative of a typical U.S. ADHD clinical sample in terms of co-occurring diagnoses and their current use of stimulant medication. Children and adolescents were assigned to an experimental group or a waiting list control group, with the waiting list control completing training after the experimental group had finished, providing a replication of the efficacy of the WM training. We hypothesized that at posttreatment participants would improve on measures of WM and inattention. A CONTROLLED TRIAL OF WORKING MEMORY 827 METHODS Participants Participants were 52 predominantly Caucasian (96%) children and adolescents from 7 to 17 years of age (M ¼ 11.75, 16 girls). Participants were recruited from a private school for children and adolescents with ADHD and=or learning difficulties, which is located in a large Midwestern city. Participants were included in the study based on parents rating them either in the clinical range (T > 64) on the Working Memory scale of the Behavior Rating Inventory of Executive Function (BRIEF; Gioia, Isquith, Guy, & Kenworth, 2000a) or endorsing at least six of the inattentive symptoms from the DSM IV TR (APA, 2000). Forty-six of the participants (88%) had initial BRIEF Working Memory t scores above 64, and the 6 other participants met the criteria of having six or more inattentive symptoms from the DSM IV (APA, 1994). A parent then completed a phone administered, DSM IV TR-based structured clinical interview, the Children s Interview for Psychiatric Syndromes Parent Form (P-ChIPS; Weller, Weller, Rooney, & Fristad, 1999). All participants met DSM IV TR (APA, 2000) criteria according to the P-ChIPS for ADHD, either combined type (29%) or predominately inattentive type (71%). Children and adolescents in the sample also had co-occurring conduct problem disorders (oppositional defiant disorder or conduct disorder, 46%), anxiety disorders (39%), and mood disorders (8%). Twenty-nine percent of the sample presented with one comorbid diagnosis, 17% with two, and 17% with three or more comorbid diagnoses. Sixty-one percent of the children and adolescents in the study were taking stimulant medication. Parents were requested to have their child consistently complete their daily training either while the medication was active or when the medication should have been worn off. Parents were also asked to avoid medication changes while participating in the study. However, four parents reported a change in their child s medication while they were actively completing the training (three from the experimental group and one from the waitlist control group). There were four additional participants who had medication changes while they were either serving as a control or following their completion of the intervention (three from the waitlist control group and one from the experimental group). During the experimental group intervention, 1 participant from the control group was excluded from the experimental and control group comparison analyses because parents did not complete their pretreatment measures on time. Three children in the waitlist control group dropped out of the study during their intervention period, with parents citing lack of time or motivation as

5 828 BECK ET AL. their reason for discontinuing, leaving 49 children and adolescents completing the intervention. Procedures This study was conducted in compliance with the Institutional Review Board of The Ohio State University. All parents of children that attended the private school initially received a flyer from school personnel informing them of the study. If parents were interested, they were asked to attend an information meeting describing the WM training and the duties that parents and children would be expected to perform if they decided to participate. If parents were willing to participate, they filled out consent and permission forms as well as prescreening measures. We later obtained assent from the participants. Participants were listed in alphabetical order and assigned to either the experimental or the waitlist control group in an alternating manner. One parent of each child filled out the outcome measures before treatment and 1 and 4 months after their child completed the intervention. The outcome measures were the number of DSM IV TR inattentive symptoms endorsed (APA, 2000), the BRIEF Parent Form, and the Conners Parent Rating Scale Revised: Short Form (Conners, Sitarenios, Parker, & Epstein, 1998a). The participant s teachers filled out the Conners Teacher Rating Scale Revised: Short Form (Conners, Sitarenios, Parker, & Epstein, 1998b) and the BRIEF Teacher Form before treatment and 1 month after the intervention. The teachers filled out the questionnaires 4 months after the intervention for the experimental group only, because after this point, summer vacation occurred and the children had different teachers. Teachers were blind to which condition children were assigned. Three of the research staff received training in administering the WM intervention. The research staff then trained the parents of the participants to show their children how to use the program, how to supervise and encourage their children, and how to implement an individually tailored reward system with their child during the training period. Initially, the experimental group received the WM intervention and weekly calls from the research staff, whereas the control group received nothing during this time. After the posttreatment data collection, the waitlist control group received the identical intervention. WM Training Intervention The WM training consisted of a computer-based training program that participants did in the home under the supervision of one parent. 1 The training included 1 The working memory training program used was Cogmed RM developed by Cogmed America Inc. 25 sessions completed in about 6 weeks, with each session taking approximately 30 to 40 min. Each session included 15 trials of 8 (of a possible 12) WM exercises. The exercises included verbal WM tasks, such as backwards digit span, and visuo-spatial WM tasks, most of which presented objects in a specific sequence and then had participants reproduce this sequence. If a participant took less than 30 min to complete a session, in the rest of the sessions they did 16 trials of each exercise. The training included an algorithm that continually increased or decreased the difficulty of each exercise according to the child s performance, so the participants were always working at their WM capacity. A trained research staff member viewed the results of each session, and each week called and talked with the participant and his or her parent about the quality of their sessions that week. The phone calls lasted an average of 10 min, with an emphasis on providing positive reinforcement to the child or adolescent for continuing with the training program as the training became increasingly difficult due to the algorithm. Parents were given feedback about their child s training sessions, which included information regarding which tasks appeared to be more difficult for their child or adolescent and tips for changing the sequence of tasks, which could lead to less frustration and increased improvement in their child or adolescent s performance. During the phone contact parents were encouraged to adhere to consistent training schedules. The participants also received rewards from their parents for doing the training. These rewards varied by participant, and the participant and their parent decided on them before the training began. The research staff was able to measure overall improvement from the beginning of training on one of the verbal and nonverbal WM exercises. This measure, called the Index Score, calculates the difference in performance between the average of the first three sessions of training and the session with the highest performance. Measures Structured clinical interview. We administered the P-ChIPS to determine each participant s diagnoses. The P-ChIPS is based on the DSM IV and screens for 20 Axis I disorders and psychosocial stressors. There is evidence to support its reliability and validity as a diagnostic instrument in clinical research for children and adolescents from 6 to 18 years of age (Fristad et al., 1998; Fristad, Teare, Weller, Weller, & Salmon, 1998; Teare, Fristad, Weller, Weller, & Salmon, 1998; Weller et al., 2000). The P-ChIPS correlates well with clinician diagnoses of children, with 76% agreement for ADHD (Fristad, Teare, et al., 1998). Fristad, Teare, et al. (1998) found the P-ChIPS to have an average sensitivity of 78% and an average specificity of 76%, with 100%

6 sensitivity and 44% specificity for ADHD. The two trained interviewers received training on the P-ChIPS from an experienced trainer who has conducted research on the P-ChIPS. The two trainers achieved at least 90% agreement on diagnoses with the experienced trainer before conducting the phone interviews. Measures of inattention. We administered both the parent and teacher versions of the Conners Rating Scale Revised, Short Form. The Conners measure has four scales: Oppositional, Cognitive Problems=Inattention, Hyperactivity, and an ADHD index. The measures are widely used for assessing ADHD symptoms (Conners et al., 1998a, 1998b). The Conners scales have good internal consistency, with Cronbach s alpha ranging from.83 to.95. The test retest reliabilities from 6 to 8 weeks is.62 for Oppositional,.73 for Cognitive Problems=Inattention,.85 for Hyperactivity, and.72 for the ADHD Index (Conners, 2000). Parents also completed a measure that asked them whether they endorsed each of the nine inattentive symptoms from the DSM IV TR for their child. Measures of WM. We administered the parent and teacher forms of the BRIEF (Gioia et al., 2000a). The BRIEF is an 86-item teacher and parent questionnaire, with two summary index scores, an overall general index score, and eight scales intended to capture the basic components of executive functioning. Although there are other scales on the BRIEF, the Metacognition Index (MCI) appears to best reflect the purpose of the study. The MCI includes the scales of Working Memory, Initiate, Plan=Organize, Organization of Materials, and Monitor. Reliability studies show high internal consistency, and test-retest reliability (Gioia, Isquith, Guy, & Kenworth, 2000b). Convergent validity was established with other measures of inattention, impulsivity, and learning skills in clinical ADHD populations (Gioia et al., 2000b) Data Analysis The first set of analyses compared the experimental and control groups on all outcome measures after the experimental group received treatment. These analyses were a series of 2 2 repeated measures analyses of variance with condition (experimental vs. waitlist control group) as a between-subjects factor and time (baseline vs. posttreatment) as a within-subjects factor. Effect sizes (Cohen s d) for the baseline to posttreatment change were calculated using the following formula: d ¼ (baseline to posttreatment change in experimental group baseline to posttreatment change in control group) pooled baseline standard deviation A CONTROLLED TRIAL OF WORKING MEMORY 829 Statistically significant results were then evaluated for clinical significance and reliable change following the methods described by Jacobson and Truax (1991). The next set of analyses involved determining if treatment effects were replicated by analyzing the data for the control group after they received treatment. These analyses consisted of a series of paired-samples t-tests and calculated effect sizes. A series of t tests were conducted to determine if the treatment effects were significantly different for the experimental and control groups. Clinical significance and reliable change were tested in the same manner as previously described. Last, 4-month follow-up data were analyzed. For the parent follow-up data, the experimental and control groups were first compared for outcome differences at follow-up using t tests. The experimental and control groups were then combined, unless there were significant differences between the two groups on the follow-up outcome measures, in which case the follow-up data are reported separately for each group. For the teacher data, ratings at follow-up were available only for the experimental group, because 4 months after the control group received treatment, it was a new school year, so participants had different teachers. Paired samples t- tests and effect sizes (Cohen s d) were used to evaluate changes between baseline and follow-up and changes from posttreatment to follow-up. RESULTS Based on chi-squared analyses, the experimental and waitlist control groups did not differ at baseline on their gender, medication status, ADHD type (Inattentive or Combined), presence of comorbid disorders, presence of four or more disorders, presence of internalizing disorders (Mood and Anxiety Disorders), or presence of externalizing disorders (oppositional defiant disorder or conduct disorder), with all p >.10. At baseline, the experimental and control groups also did not differ on parent reported mean age of participants, mean number of diagnoses, or mean scores on any of the baseline measures. At baseline the experimental and control groups also did not differ on teacher reported baseline measures. Age and medication status did not affect treatment outcomes. Baseline to Posttreatment Results Because there were multiple outcome measures, the Sidak-Bonferroni correction (Keppel & Wickens, 2004) was used for all analyses with a familywise alpha level of.10. This means that the alpha level is.017 for BRIEF measures,.021 for parent measures of ADHD

7 830 BECK ET AL. Downloaded by [Queen's College] at 21:29 20 January 2013 symptoms, and.026 for teacher measures of ADHD symptoms. ADHD symptoms. As hypothesized, the repeated measures analyses of variance showed an interaction between group and time for parent-rated inattention, such that after treatment the experimental group was rated lower (less inattentive) than the control group on the Conners Parent Cognitive Problems=Inattentive scale with a moderate to large effect size and on the number of DSM IV TR inattention symptom endorsed with a large effect size (see Table 1). For the Conners Parent Cognitive Problems=Inattentive scale, 48.1% of participants showed clinically significant change and 25.9% of participants showed reliable change. There was also a significant Condition Time interaction on the ADHD Index of the Conners Parent, with a moderate effect size. The Condition Time interaction approached significance for the Hyperactivity scale of the Conners Parent, with a small effect size. On the ADHD Index, 37.0% of participants showed clinically significant change and 33.3% showed reliable change. On the Hyperactivity scale, 51.9% of participants showed clinically significant change and 22.2% showed reliable change. There was no condition by time interaction for the parent-rated Oppositional scale or for any scales on the Conners Teacher Rating Scale (see Table 1). Executive functioning. As hypothesized, there was a significant Condition Time interactions on the BRIEF Parent Form on the Working Memory scale, with a large effect size (see Table 2). Clinical significance analyses revealed that 33.3% of participants showed clinically significant change and 44.4% of participants showed reliable change. There were also significant Condition Time interactions on the Parent BRIEF scales of Initiate, Plan=Organize, and the MCI, with large effect sizes. On the Initiate scale 37.0% of participants showed clinically significant change and 22.2% of participants showed reliable change. On the Plan=Organize scale 25.9% of participants showed clinically significant change and 48.1% of participants showed reliable change. On the MCI, 33.3% of participants showed clinically significant change and 33.3% of participants showed reliable change. No Group Time interactions were significant on the BRIEF Teacher Form. However, one scale, Initiate, approached significance (see Table 2). The Index score, which is an objective measure of each participants overall improvement on a verbal and nonverbal WM exercise, was significantly correlated with the experimental group s baseline to posttreatment change in parent-rated WM (r ¼.47, p ¼.01) and DSM IV TR inattentive symptoms (r ¼.54, p <.01) as well as teacher-rated Hyperactivity (r ¼.40, p ¼.04). TABLE 1 Posttreatment Comparisons between the Experimental and Control Groups for ADHD Symptoms Baseline Posttreatment Conners Parent Scales Group M SD M SD F p d ADHD Index Experimental a Control b Cognitive Problems= Inattention Experimental Control Hyperactivity Experimental Control Oppositional Experimental Control DSM IV Inattentive Scale Experimental Control Conners Teacher Scales ADHD Index Experimental Control Cognitive Problems= Inattention Experimental Control Hyperactivity Experimental Control Oppositional Experimental Control Note: The F and p values that are reported are for the group (experimental vs. control) by time (baseline vs. posttreatment) interaction. ADHD ¼ Attention-Deficit=Hyperactivity Disorder; DSM IV ¼ Diagnostic and Statistical Manual of Mental Disorders (4th ed., text revision, APA, 2000). a n ¼ 27 for the experimental group. b n ¼ 24 for the control group. p <.05. familywise alpha <.10.

8 A CONTROLLED TRIAL OF WORKING MEMORY 831 TABLE 2 Posttreatment Comparisons Between the Experimental and Control Groups for Executive Functioning Baseline Posttreatment BRIEF Parent Scales Group M SD M SD F p d Downloaded by [Queen's College] at 21:29 20 January 2013 Metacognition Index Experimental a Control b Working Memory Experimental Control Initiate Experimental Control Monitor Experimental Control Organization of Materials Experimental Control Plan=Organize Experimental Control BRIEF Teacher Scales Metacognition Index Experimental Control Working Memory Experimental Control Initiate Experimental Control Monitor Experimental Control Organization of Materials Experimental Control Plan=Organize Experimental Control Note: The F and p values that are reported are for the group (experimental vs. control) by time (baseline vs. posttreatment) interaction. BRIEF ¼ Behavior Rating Inventory of Executive Function. a n ¼ 27 for the experimental group. b n ¼ 24 for the control group. p <.05. familywise alpha <.10. Waitlist Control Group Treatment Outcome ADHD symptoms. As hypothesized, after the waitlist control group received treatment there were significant improvement in their scores from baseline to posttreatment on the Conners Parent Cognitive Problems= Inattention scale and the number of DSM IV TR inattention symptom endorsed, with moderate effect sizes (see Table 3). On the Cognitive Problems=Inattention scale 30.0% of participants showed clinically significant change and 10.0% showed reliable change. The baseline to posttreatment change approached significance for the Conners Parent ADHD Index (Table 3). According to teacher report, there were no significant improvements from baseline to posttreatment on any of the scales. However, on the Oppositional scale on the Conners Teacher there was a trend toward worse scores at posttreatment than at pretreatment (see Table 3). Executive functions. After the waitlist control received treatment, the change from baseline to posttreatment on the Parent BRIEF Working Memory scale was not significant and had a small to moderate effect size (see Table 4). On the Working Memory scale, 7.5% of participants showed clinically significant change and 20.0% showed reliable change. The baseline to posttreatment change approached significance on the Parent BRIEF scales of Initiate and Plan=Organize. According to teacher report, there were no significant improvements from baseline to posttreatment on any of the scales (see Table 4). After the control group received treatment, their Index scores were correlated with their baseline to posttreatment changes on the teacherreported BRIEF scales of Initiate (r ¼.54, p ¼.01), Plan=Organize (r ¼.44, p ¼.03), and the MCI (r ¼.47, p ¼.02). Follow-Up Outcomes ADHD symptoms. The experimental and control groups were compared on their follow-up measures and, if their treatment outcomes at follow-up did not differ significantly, the groups were combined. The experimental group improved significantly more from baseline to follow-up on the number of DSM IV TR inattention symptom endorsed, t(31) ¼ 2.71, p ¼.01.

9 832 BECK ET AL. TABLE 3 Posttreatment Outcomes on ADHD Symptoms for the Control Group after Receiving Treatment Pretreatment Posttreatment Conners Parent Scales a M SD M SD t p d ADHD Index Cognitive Problems=Inattention Hyperactivity Oppositional DSM IV TR Inattentive Scale Conners Teacher Scales b ADHD Index Cognitive Problems= Inattention Hyperactivity Oppositional Downloaded by [Queen's College] at 21:29 20 January 2013 Note: ADHD ¼ Attention-Deficit=Hyperactivity Disorder; DSM IV ¼ Diagnostic and Statistical Manual of Mental Disorders (4th ed., text revision, APA, 2000). a n ¼ 20. b n ¼ 22. p <.05. familywise alpha <.10. The experimental group improved significantly from pretreatment to follow-up, t(19) ¼ 5.25, p ¼.00, d ¼ 1.70, whereas the control group did not, t(9) ¼ 0.95, p ¼.36, d ¼ The experimental group also improved more from baseline to follow-up than the control group on the Conners Parent ADHD Index, t(31) ¼ 2.43, p ¼.02. For the experimental group, there was a significant change from baseline to follow-up on the ADHD Index, t(19) ¼ 5.07, p ¼.00, d ¼ However, for the control group there were no significant change from baseline to follow-up on the ADHD Index, t(10) ¼ 1.24, p ¼.25. The experimental group showed a trend toward improving more from baseline to follow-up than the control group on the Cognitive Problems=Inattention, F(1, 31) ¼ 5.26, p ¼.03, scale of the Conners Parent. For the experimental group, there was a significant change from baseline to follow-up on the Cognitive Problems= Inattention scale, t(19) ¼ 4.22, p ¼.00, with a large effect size (d ¼ 1.05). However, for the control group there were no significant changes from baseline to follow-up on the Cognitive=Problems Inattention scale, t(10) ¼.83, p ¼.43, and a small effect size (d ¼ 0.17). There were no significant differences between the two groups on any other follow-up measures, so the groups TABLE 4 Posttreatment Outcomes on Executive Functioning for the Control Group after Receiving Treatment Pretreatment Posttreatment BRIEF Parent Scales a M SD M SD F p d Metacognition Index Working Memory Initiate Monitor Organization of Materials Plan=Organize BRIEF Teacher Scales b Metacognition Index Working Memory Initiate Monitor Organization of Materials Plan=Organize Note: BRIEF ¼ Behavior Rating Inventory of Executive Function. a n ¼ 20. b n ¼ 22. p <.05. familywise alpha <.10.

10 TABLE 5 Changes from Pretreatment to Follow-Up on ADHD Symptoms A CONTROLLED TRIAL OF WORKING MEMORY 833 Pretreatment Follow-Up Conners Parent Scales a M SD M SD t p d ADHD Index Cognitive Problems= Inattention Hyperactivity Oppositional DSM-IV Inattentive Scale Conners Teacher Scales b ADHD Index Cognitive Problems= Inattention Hyperactivity Oppositional Downloaded by [Queen's College] at 21:29 20 January 2013 Note: The teacher follow-up only includes participants in the experimental group, because summer vacation occurred before the control group follow-up data collection. ADHD ¼ Attention-Deficit=Hyperactivity Disorder; DSM IV ¼ Diagnostic and Statistical Manual of Mental Disorders (4th ed., text revision, APA, 2000). a n ¼ 32. b n ¼ 23. p <.05. familywise alpha <.10. were combined for the remainder of the analyses. There was a significant change from baseline to follow-up on the Conners Parent Hyperactivity scale. This change approached significance for the Conners Parent Oppositional scale (Table 5). On the Conners Parent ADHD Index, between posttreatment and follow-up, participant s scores showed a trend towards decreased T scores with a small effect size, t(30) ¼ 2.41, p ¼.02, d ¼ However, teachers rated that participants showed a trend toward higher (more symptomatic) t scores at follow-up than at posttreatment on the ADHD TABLE 6 Changes from Pretreatment to Follow-Up on Executive Functioning Pretreatment Index, t(21) ¼ 2.46, p ¼.02, d ¼ The Index Score was also correlated with the combined group baseline to follow-up change in parent-rated DSM IV inattentive symptoms (r ¼.35, p ¼.04). Executive functioning. The BRIEF Parent Form Working Memory scale participants improved significantly from baseline to follow-up (see Table 6), as well as from posttreatment to follow-up, t(31) ¼ 2.59, p ¼.01, d ¼.32 There were also significant decreases in T scores from baseline to follow-up for all other Follow-Up BRIEF Parent Scales a M SD M SD t p d Metacognition Index Working Memory Initiate Monitor Organization of Materials Plan=Organize BRIEF Teacher Scales b Metacognition Index Working Memory Initiate Monitor Organization of Materials Plan=Organize Note: The teacher follow-up only includes participants in the experimental group because summer vacation occurred before the control group follow-up data collection. BRIEF ¼ Behavior Rating Inventory of Executive Function. a n ¼ 32. b n ¼ 23. p <.05. familywise alpha <.10.

11 834 BECK ET AL. scales of the parent BRIEF, with effect sizes ranging from d ¼ 0.42 to d ¼ 0.83 (Table 6). Improvement from posttreatment to follow-up approached significance for the parent BRIEF Parent Form scales of Monitor, t(31) ¼ 2.05, p ¼.05, d ¼.22, and the MCI, t(31) ¼ 2.35, p ¼.03, d ¼ Improvement from pretreatment to follow-up approached significance for the BRIEF Teacher scales of Working Memory and Initiate (see Table 6). DISCUSSION The present study tested the effectiveness of an intensive WM training using a sample of children and adolescents with ADHD and common comorbid diagnoses and with 61% of the participants in the present study taking stimulant medication. The WM training was conducted in the participant s home, which is a practical setting for this type of intervention. Previous working memory studies have been conducted in laboratory settings (e.g., Klingberg et al., 2005) or in the child s school (e.g., Holmes et al., 2009). The most robust finding in the current study was found when comparing the experimental group immediately following treatment to the waitlist control group who had not yet started training. The present study s moderate to strong effect sizes on parent ratings of ADHD symptoms (d ¼ 0.76), inattention (d ¼ 0.79), and reduction in attentive DSM IV TR symptoms (d ¼ 1.49) are similar to the effect sizes found by Klingberg et al. (2005), for parent-rated inattention (d ¼ 0.89) when the effect sizes in Klingberg et al. (2005) are calculated in the same ways as in the present study. These results indicate that WM training had a beneficial effect of reducing parent-reported inattentive behaviors and ADHD symptoms at posttreatment and at a 4-month follow-up. Similarly, after training, parents reported significant changes on measures of executive functioning at posttreatment and at follow-up. About one fourth to one half of the sample showed clinical significant changes on the measures of executive functioning and ADHD symptoms that showed statistically significant change. It is important to note that the three BRIEF scales Working Memory, Initiate, and Plan=Organize, in which parents rated improvements after treatment and at the 4-month follow-up appear to address core deficits in children and adolescents with ADHD. Specifically, the Working Memory scale measures the capacity to hold information in mind for completing a task and is important in learning academic material (Nigg, 2006). The Initiate scale pertains to beginning academic tasks or activities and involves problem-solving strategies. The Plan= Organize scale measures the child or adolescent s ability to manage current or future-oriented task demands (Gioia et al., 2000b). Teacher-reported improvements in executive functioning and ADHD symptoms in the classroom would have strengthened the finding of the current study. Although teachers in the present study were less biased compared to parents, because teachers were not aware when participants were receiving WM training, their findings approached significance only on Initiate at posttreatment and Initiate and WM at the 4-month follow-up. Because the present study used a waitlist control group that received the identical WM training soon after the experimental group completed training, we were able to replicate some of the findings observed in the experimental group. As indicated in Table 3, the waitlist control group at posttreatment showed similar parentreported improvements on the two inattentive scales and on the ADHD Index scale, but this group reported only a trend toward significance on the parent-reported Initiate and Plan=Organize scales at posttreatment and no significant changes on WM. Possible explanations for the weaker parent-reported executive functioning changes in the waitlist control group after training may be the time of the academic year when data were collected. The experimental group training ended in December, whereas the waitlist control group completed training toward the end of the school year. Perhaps academic demands changed throughout the school year, which may have affected parents sensitivity to changes in executive functioning. Changes from pretreatment to the 4-month follow-up were reported on the parent-reported ADHD symptoms and executive functioning scales. However, these effects were larger for the experimental group. One reason that the control group may have shown lesser improvement from pretreatment to follow-up is that only 48% of the control group completed follow-up measures compared to 74% of the experimental group. Klingberg et al. (2005) reported similar findings 3 months after WM training with children with ADHD features on measures of inattention and several neuropsychological tasks. These results suggest that WM and executive functioning may be improved by practice. Additional gains from posttreatment to follow-up approached significance on parent-rated ADHD symptoms, Monitoring, and the MCI, which measures the ability to cognitively manage tasks and monitor performance. Klingberg et al. (2005) posited that with the increase in WM capacity following training, individuals may be more likely to engage in tasks that have a higher WM load, such as mathematics or other demanding academic tasks. This increase in tasks involving WM could maintain gains and lead to further practice effects and further improvements on executive functioning, which may explain the additional

12 gains seen from posttreatment to follow-up. Similarly, Holmes et al. (2009) reported an improvement in mathematical reasoning 6 months after WM training in children identified low in memory skills. The present study suggests that parent reports of executive functioning and ADHD symptoms can be improved by intense and prolonged training. One possible mechanism for how WM training can lead to improvements on ADHD symptoms and executive functioning is altering brain activity. For example, Olesen, Westerberg, and Klingberg (2004) found that after similar WM training there was increased activation in the prefrontal cortex, an area that shows deficits in those with ADHD (Shaw et al., 2007). The potential effectiveness of this type of WM training can be better understood when taking into account the effortful concentration and WM workload required by participants for 5 or longer weeks of training. The built-in algorithm used in the training that allows individuals to continuously work at their WM capacity may be a key component, because training without the algorithm does not lead to substantial gains (Klingberg et al., 2005; Klingberg et al., 2002). Another possible explanation is that the intense and prolonged nature of the training may increase the use of WM strategies that compensate for weaknesses in basic processes, or of the increase in voluntary control of attention. Support for this possibility was reported by Holmes et al. (2009), who conducted posttraining interviews with children who completed training. Ten of the 15 interviewed children reported using a variety of strategies that involved enhancing attentional focus. One important shortcoming of the study is that parents were not blind to treatment and may have unintentionally been biased in their ratings due to the time they invested. Because parents were not blind to treatment conditions, expectancy effects cannot be ruled out as contributing to the present findings (Caspi & Bootzin, 2002). However, as mentioned earlier, a previous study found similar effect sizes using a placebo treatment to control for expectancy effects (Klingberg et al., 2005). Conversely, it could be argued that parents in the present study may have been more attuned to the potential WM improvements in their child or adolescent based on the daily one-on-one observations of their child or adolescent. A second shortcoming of the study is that due to the waitlist control there was no longer a control group at the 4-month follow-up that would allow for continued comparisons between those who received the WM training to those who did not. Follow-up data may have also been attenuated, because a significant portion of the sample (38%) did not return follow-up measures. Finally, only parent and teacher reports were used as outcome measures, and other more potentially objective measures of treatment effects such A CONTROLLED TRIAL OF WORKING MEMORY 835 as cognitive or neuropsychological measures of WM or executive functions were not used. Implications for Research, Policy, and Practice There appears to be accumulating evidence over the last several years that WM training has a beneficial effect on neuropsychological measures of visual-spatial and verbal memory and in the reduction of parent ratings of inattentive behaviors and ADHD symptoms for children with ADHD (Holmes et al., 2009; Klingberg et al., 2005; Klingberg et al., 2002). Results from our study also suggest that WM training may be a promising treatment in an armamentarium of interventions in addressing core ADHD deficits. Effects were maintained at a 4-month follow-up, suggesting that WM training may have longer term beneficial effects. Because other empirically supported interventions for ADHD have shown the benefits of a combination of treatments (e.g., MTA Cooperative Group, 1999), WM training should be investigated in combination with other well-established ADHD treatments, particularly those that address core ADHD deficits. In addition, the heterogeneity of the diagnosis and treatment of ADHD is currently receiving considerable attention (e.g., Nigg, 2006), and future studies could examine if children and adolescents diagnosed with different subtypes of ADHD would benefit more from WM training. Future studies on WM training need to conduct longer follow-ups with additional booster sessions to further assess the lasting benefits of training. More studies are needed to confirm the training effects on other populations, such as individuals that have experienced strokes or traumatic brain injury, and answer questions pertaining to the mechanisms underlying training induced improvements of WM. Finally, in addition to improvements in informant ratings, or laboratory and paper-and-pencil visual-spatial or verbal measures of WM, the efficacy of WM training needs to demonstrate observable, practical, and clinically meaningful behavior change in children and adolescents with ADHD. For example, can WM training help children and adolescents with WM deficits and ADHD better remember instructions, complete more academic tasks, and improve on objective academic measures? REFERENCES Alloway, T. P. (2007). Automated working memory assessment. Oxford, UK: Harcourt. Alloway, T. P., Gathercole, S. E., & Pickering, S. J. (2006). Verbal and visuo-spatial short-term and working memory in children: Are they separable? Child Development, 77, American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author.