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Effectiveness of Cognitive Training for Improving Working Memory in Children with ADHD

Abstract

  • Objective: This literature review examines the effectiveness of cognitive training in improving working memory (WM) in children diagnosed with attention-deficit/hyperactivity disorder (ADHD).

  • Methods: Search strategies utilized PubMed, Scopus, PsychINFO, and Google Scholar to identify relevant studies published from 2013 onwards. Inclusion criteria necessitated computer-based cognitive training, minimum 4-week duration, minimum sample size of 25 individuals diagnosed with ADHD, and exclusion of sources with conflicts of interest. Critical appraisal utilizing the CASP tools ensured credibility.

  • Results: The synthesis of the selected articles showed a positive effect of cognitive training on WM and ADHD symptoms. Engagement levels among participants and consistency in the training structure were important factors influencing intervention success. While some studies demonstrated control for such factors, others lacked uniformity, affecting reliability.

  • Discussion: Although cognitive training enhanced aspects of WM for children with ADHD, it should not be considered a standalone treatment. Future research should investigate unexplored areas such as potential side effects. Furthermore, while this review contributes to the growing literature on cognitive training, there are limitations such as time constraints and variation in the studies selected.

  • Conclusion: Cognitive training, while promising for improving some aspects of WM in children with ADHD, should complement rather than substitute other treatment strategies. 

Keywords: Attention-deficit/hyperactivity disorder (ADHD), working memory (WM), cognitive training, executive functions (EFs), computer-based interventions

Introduction

Figure 1
Figure 1: An individual with ADHD can experience a range of symptoms relating to inattention and/or hyperactivity-impulsivity, notably including impairment of working memory. They can undergo treatment that include medication, behavioral therapy, and cognitive training.

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental condition characterized by ongoing patterns of inattention and/or hyperactivity-impulsivity that interfere with functioning or development [1]. These characteristics often impede social, interpersonal,  behavioral, and academic functioning. Within the spectrum of cognitive challenges linked to ADHD, the impairment of working memory (WM) stands out prominently. Working memory is the ability to temporarily store, manipulate, and retrieve information during cognitive tasks and is an essential executive function. Executive functions (EFs) are defined as a set of high-level cognitive processes that guide goal-directed behavior [2]. Executive functions are primarily involved in tasks such as problem-solving, planning, decision-making, and the ability to sustain attention [2]. Recently, there has been a growing interest among healthcare workers, educators, parents of children with ADHD, and researchers for ADHD interventions that target the WM deficit. The search for a promising intervention is crucial as WM is needed for children to regulate their behavior, learn, complete tasks, and interact with their peers and adults; without an intervention, consequences may persist until adulthood [1].

Current approaches for managing ADHD symptoms include medication, behavioral therapy, parent training, and cognitive therapy; all aiming to provide coping strategies [3]. However, these approaches come with limitations; for example, medication can have side effects, while family time constraints may impede consistent therapy attendance. Additionally, it is important to note that a comprehensive treatment approach must combine multiple strategies to address the range of symptoms of ADHD. Consequently, cognitive training is being explored as a possible component of the multi-modal treatment strategy. Cognitive training aims to enhance specific psychological skills through repetitive practice, frequently presented in game-like computer programs [1]. These games balance engagement, fun, and learning to assist with training compliance; some even embed performance feedback within tasks to improve performance [4,5]. The effectiveness of cognitive training programs can vary based on factors such as the duration and intensity of the training, individual differences in learning, and the transferability of skills to real-world situations.

Although there has been increasing development in cognitive training in recent years, its effectiveness on some cognitive deficits and clinical symptoms of ADHD has been questioned [6]. Hence, this systematic review aims to evaluate and synthesize some of the available evidence to address the question: is cognitive training effective for improving WM in children diagnosed with ADHD?

Methods

Search strategy

The search was conducted through PubMed, Scopus, Google Scholar, and PsychINFO. All the databases were accessed through the UC Davis Library to ensure full access to the available articles. Moreover, advanced search engines were used for all of the databases with search terms including Cognitive training, Cognitive stimulation, Working memory, Memory improvement, ADHD, Children, Attention-deficit, AD, Hyperactivity disorder, HD, and Executive functions.

Inclusion and Exclusion Criteria

Articles published from 2013 onwards were selected to ensure the inclusion of the most current literature, aiming to prevent outdated information from being incorporated. To maintain the integrity of the evidence used, Ulrich’s Periodical Directory was utilized to ensure that the selected articles were peer-reviewed. Furthermore, to be included, studies needed to involve computer-based cognitive training lasting a minimum of 4 weeks and must have included a minimum of 25 clinically-diagnosed ADHD participants. The exclusion criteria ruled out sources with a clear conflict of interest such as industry-sponsored research. Additionally, studies without a clear focus on quantitative experimental study designs were excluded. This methodology yielded four primary articles and one meta-analysis for examination, all exploring the impact of cognitive training on improving WM in children diagnosed with ADHD.

Critical Appraisal 

The selected studies underwent critical appraisal using the Critical Appraisal Skills Programme (CASP) Randomized Controlled Trial Checklist and Systematic Review Checklist [7]. The checklists focus on aspects such as randomization methods, blinding, generalizability, and biases. This process ensured the validity, reliability, and relevance of each study, enabling informed decisions based on the evidence available.

Results 

Diverse Methodologies and Outcomes

Currently, various methodologies are used to investigate the outcomes of cognitive training. Westwood et al.'s meta-analysis assessed the efficiency of computerized cognitive training interventions in children with ADHD, emphasizing randomized controlled trials (RCTs) that integrated objective measures to quantify changes in WM and inattention. Across 36 studies analyzed, cognitive training led to improvements in WM and inattention [8]. However, it didn't show positive outcomes in other neuropsychological aspects like inhibition or academic performance [8]. Interestingly, while there wasn't sustained improvement in WM after 6 months, there were indications based on the verbal and visuospatial span tasks that the effects on verbal working memory may persist over a longer duration [8]. The strength of this meta-analysis is in its large participant size, comprising a total sample of 2,234 children, and the homogeneity in study designs of the articles selected. The consistency in the study design of the 36 papers selected for the meta-analysis enhances confidence in the results.

Similar to the approach by Westwood et al. (2023), the study conducted by Bigorra et al. (2015) employed RCTs to investigate the effects of computerized working memory training (CWMT) in alleviating ADHD symptoms, enhancing performance-based measures of executive functions, and fostering learning [6]. The sample included 66 newly diagnosed children between the ages of 7 and 12 who had not received prior treatment [6]. Participants were randomly assigned to either a training or control group. Those assigned to training underwent CWMT RoboMemo, which is a set of computer-based games targeting visuospatial, auditory, and location memory [6]. Those assigned to the control group underwent MegaMemo which is a simpler version of RoboMemo without the adjustment for difficulty. Without adjusting for difficulty, the game did not generate the prolonged cognitive demand necessary for WM improvement [6]. Sessions were conducted in the children’s home, under the supervision of a family member. Each training session included 90 trials (rounds of the game) for a total duration of 45 minutes. Participants attended 5 sessions per week over a 5-week period. Improvement was measured through cognitive assessments completed by trained graduates in psychology and teacher/parental surveys. The results showed a significant reduction in inattention in daily life and improvement in performance-based measures of EF (PBMEF). The PBEF assessed academic achievement and included questionnaires regarding clinical symptoms and functional impairment [6]. CWMT demonstrated a substantial impact on addressing ADHD deficits, leading to far-transfer effects 6 months post-intervention. This primary research stands out compared to Westwood et al.'s meta-analysis due to its recruitment of newly diagnosed children without any prior treatment, effectively eliminating potential confounding variables that might have arisen from previous interventions.

Johnstone et al. (2017), also utilized RCTs in the investigation of cognitive training, with a sample composed of 85 children averaging 9.42 years old, similar to the meta-analysis and Bigorra et al.'s study [4]. Forty-four children had a professional diagnosis of ADHD based on The Diagnostic and Statistical Manual of Mental Illnesses (DSM-5) while 41 children simply displayed ADHD-like symptoms but lacked a professional diagnosis [9]. Those assigned to the training group completed a series of 25 at-home computer game sessions, each lasting 20 minutes, targeting WM. The training duration spanned 6-8 weeks with 3-4 sessions per week [9]. All participants received a pre-test and post-test evaluation by guardians and teachers assessing ADHD behavioral symptoms. Additionally, electroencephalogram (EEG) measurements were taken to assess the neurological activity of the frontal lobe. Notable changes within the frontal lobe included a reduction in delta activity and an increase in alpha activity, indicating a reduction in ADHD symptoms [4]. The study further suggested that computerized cognitive training technology can be an effective means of delivering interventions and reducing ADHD symptom severity in children [6,8,4]. One of the strengths of this study is its incorporation of both a control group and a within-comparison. Between-comparison (control group) individuals are assigned to only one experimental condition and each person provides only one score for data analysis; on the other hand, in a within-comparison, the effects of treatments are seen through the comparison of scores of the same participant observed under all the treatment conditions [10]. However, a limitation of the ADHD behavioral measures compared to Bigorra et al. (2015), is the dependence on only guardians' and teachers' responses; such surveys are susceptible to respondent bias as their expectations may alter their responses [4, 6].

Figure 2
Figure 2: Different methods with which studies used to determine whether children with ADHD benefited from computerized cognitive or working memory training. With a combination or pre- and post-assessments that included clinical, academic performance, and ADHD symptom assessments, many found improvement in working memory and attention.

Almarzouki et al. (2022) took an alternative approach to tackle the question of WM deficit by adopting an uncontrolled within-study design. Their sample comprised 29 children, averaging 10.56 years old, all of whom had received an ADHD diagnosis based on DSM-5 criteria which were confirmed through the National Institute for Children's Health Quality (NICHQ) Rating Scales before enrollment [1]. Each participant engaged in a CWMT program, involving 45-minute sessions 5 days a week for 5 consecutive weeks. The assessment of ADHD symptoms and academic performance utilized the parent and teacher Vanderbilt ADHD Diagnostic Rating Scale (VADRS) tool, conducted both before the program and after its completion [1]. Furthermore, a phone interview gauged parents' satisfaction and willingness to continue with the program. The study's findings highlighted CWMT as a promising tool for enhancing WM and improving ADHD behavioral symptoms [1]. In contrast to Johnstone et al. (2017), this study took additional steps to ensure the internal consistency and validity of the VADRS survey, effectively eliminating respondent bias [1,4]. However, the study's limitation primarily revolves around its notably smaller sample size, which restricts the statistical power and generalizability [1,6].  

Wiest GM et al. (2022) employed a within-study design, but they conducted it within a clinical setting. Their sample included 43 children with an average age of 11.7 years old, all with clinical diagnoses of ADHD and specific learning disorder (SLD). SLD is characterized by a persistent impairment in at least one of three major areas: reading, written expression, or math [11]. The cognitive training was administered via the Captain’s Log program, a suite of computer-based games that target cognitive abilities [12]. The training consisted of 20 sessions over the span of 4-8 weeks, with each session lasting 60 minutes. The pre-and post-tests analyzed verbal working memory, symbolic working memory, continuous performance tasks, and feedback sessions with the parents. These tests were conducted through the Integrated Visual and Auditory Continuous Perform Test, Second Edition (IVA-2) and the Wide Range Assessment of Learning and Memory, Second Edition (WRAML-2), decision support softwares that help clinicians test and evaluate visual and auditory attention, response control functioning, memory function, and learning [12]. The results demonstrated that attention and WM improved following computerized cognitive training. Specifically, participants’ scores in attention, inhibition, verbal WM, and visuospatial WM were significantly higher after the intervention [12]. 

Discussion

The overall findings from the primary studies suggest that cognitive training may be beneficial for improving WM in children with ADHD [1,4,6,12]. That being said, it's crucial to acknowledge that cognitive training in its current forms can not be utilized as a stand-alone treatment for core ADHD symptoms [8]. Furthermore, when interpreting the results of this review, two significant themes should be considered: the level of engagement among children and the consistency of computer game structure. 

Children’s Engagement Level
Figure 3
Figure 3: Two main potential effects on the results of the studies: children’s engagement with the activities in the study, and inconsistency between computer games.

Children's engagement with computerized cognitive training plays a pivotal role in determining experimental success. It influences the effectiveness of the training, quality of data collected, participant retention, and overall success of the study. The results from Johnstone et al. (2017) may have been influenced by the lack of control in children’s engagement [4]. As noted in their results, children's engagement and enjoyment declined due to the length of the training; this may have affected participants' motivation and not shown a comprehensive effect of cognitive training [4]. Conversely, Bigorra et al. (2015) adjusted difficulty levels dynamically, tailoring challenges to individual performance, ensuring stable engagement, and exceeding existing cognitive limits for better results [6]. Similarly, Almarzouki et al. (2022) adjusted the difficulty level based on performance in previous trials to maintain engagement throughout the sessions [1]. Wiest et al. (2022) took a different approach by incorporating active praise, short breaks, and a token economy to manage engagement and reduce task frustration [12]. These strategies show the importance of actively managing children's engagement for optimal cognitive training results.

Computer Game Consistency

Consistency in the structure of computer games across participants is essential for effective results [4]. It helps establish participant patterns and routines, enabling better progress tracking over time. Johnstone et al. (2017) maintained consistency of training sessions by ensuring that all participants received the same size computer, consistent computer-to-eye distance, audio level, and game durations [4]. Comparably, Wiest et al. (2022) maintained complete consistency throughout the study by having a trained technician present at all times who could verify that the participant understood the activities [12]. On the other hand, Almarzouki et al. (2022) lacked environmental and training consistency; participants were not provided instruction regarding computer size, audio, and noise level [1]. The discrepancies in the environment may have altered the results obtained during training sessions. The fluctuations in performances may obscure the progression of WM abilities, making it harder to draw accurate conclusions. Likewise, Bigorra et al. (2015) conducted the study in a variety of settings (e.g., in the participant’s home); each person's house represents a unique environment due to factors such as noise levels [6]. Furthermore, they conducted the training under the supervision of a family member which may introduce variability in the training environment [6]. Consistency across training environments is crucial for drawing reliable conclusions and generalizing results regarding cognitive training outcomes.

Future Directions and Limitations 

Future studies should investigate potential side effects, such as stress due to the demands of the training, along with conducting cost-benefit and opportunity-cost analyses related to cognitive training [8]. Moreover, a significant gap exists in the longitudinal analysis of cognitive training. In this review, only one study examined the effects up to a 6-month post-training period [6]. Measuring results immediately after training concludes without following up might not adequately encompass the advantages that could emerge over a prolonged duration. Thus, a more extensive longitudinal investigation to track the enduring effects into adulthood is needed to analyze the true long-term value of cognitive training interventions for children with ADHD.

The strength of this review is in the uniformity of the age range with the selected studies; all studies include participants aged between 7 and 12 years old. By targeting young children at a developmental stage during which ADHD symptoms first become evident, many of the adverse long-term consequences that typify the trajectory of ADHD may be avoided [13]. This allows for better analysis of the potential effectiveness of cognitive training interventions within the specific childhood developmental stage, further minimizing confounding variables associated with age-related differences. On the other hand, the limitation of this review is the lack of consistency in cognitive training tasks. This review analyzed a variety of cognitive training such as standard CWMT, RoboMemo, and the Captain’s Log program [1, 8, 12]. This variance in training methods may potentially impact the comparability of results, making it challenging to generalize the outcomes across all children with ADHD. Additionally, it's important to acknowledge that this review faced limitations due to constraints in both time and resources. The review was conducted by a single undergraduate researcher within an 8-week time frame. This constraint affected the depth and breadth of the review. The narrow scope and limited duration may have excluded valuable studies that provide further insights into the effectiveness of cognitive training for ADHD in children. Therefore, while this review offers valuable insights, it should be considered within the context of the review's limitations.

Conclusion

The implementation of cognitive training should be left up to healthcare workers, educators, and parents of children with ADHD given the data collected by researchers. With the current results, cognitive training should be accompanied by other interventions for maximal benefit; the current training does not target all aspects of ADHD symptoms and the longevity of the improvement remains unanswered.

Conflict of Interest

The author of this review claims no conflicts of interest.

Author's Note

This formal scientific literature review has been prepared in response to an assignment from Dr. Brendan Johnston's UWP104F class, "Writing in the Health Sciences." The focus of this review is the examination of cognitive training as a non-pharmacological intervention for enhancing ADHD outcomes in children. The rationale behind selecting this topic is to provide insight into alternative interventions for ADHD,  acknowledging the multifaceted nature of this complex disorder and the varying responses individuals exhibit to traditional medications. This review synthesizes current research findings on cognitive training, aiming to serve as a comprehensive resource for healthcare professionals, educators, and parents. The objective is to offer a nuanced understanding of how a multimodal approach, specifically incorporating cognitive training, can be instrumental in managing ADHD symptoms. By exploring alternative treatment avenues, this paper seeks to expand the discourse on effective strategies beyond conventional pharmacological interventions. I express my sincere gratitude to Dr. Johnston for guiding me through the structure and approach of this scientific review. His help has been crucial in making this work possible.

References

  1. Almarzouki, Abeer F., Alessio Bellato, Maha S. Al-Saad, and Basma Al-Jabri. 2022. “COGMED Working Memory Training in Children with Attention Deficit/Hyperactivity Disorder (ADHD): A Feasibility Study in Saudi Arabia.” Applied Neuropsychology: Child, May, 1–12. https://doi.org/10.1080/21622965.2022.2070020.
  2. Sira, C. S., and C. A. Mateer. 2014. “Executive Function.” Edited by Michael J. Aminoff and Robert B. Daroff. ScienceDirect. Oxford: Academic Press. January 1, 2014. https://www.sciencedirect.com/science/article/pii/B9780123851574011477.
  3. Centers for Disease Control and Prevention. 2022. “Treatment of ADHD.” Centers for Disease Control and Prevention. August 9, 2022. https://www.cdc.gov/ncbddd/adhd/treatment.html.
  4. Johnstone, Stuart J., Steven J. Roodenrys, Kirsten Johnson, Rebecca Bonfield, and Susan J. Bennett. 2017. “Game-Based Combined Cognitive and Neurofeedback Training Using Focus Pocus Reduces Symptom Severity in Children with Diagnosed AD/HD and Subclinical AD/HD.” International Journal of Psychophysiology 116 (June): 32–44. https://doi.org/10.1016/j.ijpsycho.2017.02.015.
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  6. Bigorra, Aitana, Maite Garolera, Silvina Guijarro, and Amaia Hervás. 2015. “Long-Term Far-Transfer Effects of Working Memory Training in Children with ADHD: A Randomized Controlled Trial.” European Child & Adolescent Psychiatry 25 (8): 853–67. https://doi.org/10.1007/s00787-015-0804-3
  7. Critical Appraisal Skills Programme. 2018. “Critical Appraisal Checklists.” Critical Appraisal Skills Programme. 2018. https://casp-uk.net/casp-tools-checklists/.
  8. Westwood, Samuel J., Valeria Parlatini, Katya Rubia, Samuele Cortese, Edmund J. S. Sonuga-Barke, T. Banaschewski, D. Baeyens, et al. 2023. “Computerized Cognitive Training in Attention-Deficit/Hyperactivity Disorder (ADHD): A Meta-Analysis of Randomized Controlled Trials with Blinded and Objective Outcomes.” Molecular Psychiatry, March. https://doi.org/10.1038/s41380-023-02000-7
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  10. “APA Dictionary of Psychology.” n.d. Dictionary.apa.org. https://dictionary.apa.org/between-subjects-design.
  11. American Psychiatric Association. 2021. “What Is Specific Learning Disorder?” Psychiatry.org. 2021. https://www.psychiatry.org/patients-families/specific-learning-disorder/what-is-specific-learning-disorder
  12. Wiest, Grahamm M., Kevin P. Rosales, Lisa Looney, Eugene H. Wong, and Dudley J. Wiest. 2022. “Utilizing Cognitive Training to Improve Working Memory, Attention, and Impulsivity in School-Aged Children with ADHD and SLD.” Brain Sciences 12 (2): 141. https://doi.org/10.3390/brainsci12020141
  13. Halperin, Jeffrey M., Anne-Claude V. Bédard, and Jocelyn T. Curchack-Lichtin. 2012. “Preventive Interventions for ADHD: A Neurodevelopmental Perspective.” Neurotherapeutics 9 (3): 531–41. https://doi.org/10.1007/s13311-012-0123-z. 

 

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