Attention-deficit/hyperactivity disorder (ADHD) is a condition that occurs in children during the developmental period with symptoms being manifested at home and school with characteristics such as impulsivity, inattention, and hyperactivity . ADHD syndrome has been categorized into three types, namely: the combination type, the predominantly inattentive type, and the predominantly hyperactive/impulsive type. The severity of the symptoms ranges from mild, moderate, and severe (American Psychiatric Association, 2013) . The Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) mentions that people with ADHD have a history of inattention and/or hyperactivityimpulsivity, which makes it difficult for them to work and develop skills . According to the DSM-5, individuals with ADHD under the age of 16 should exhibit six or more symptoms of inattention and hyperactivity-impulsivity, while adolescents and adults aged 17 and above should exhibit five or more of the symptoms, with the symptoms having been present for at least six months, which becomes inadequate for their developmental stage. Although some of the abovementioned behaviors are sometimes considered as characteristic features of typically developing children as well, when exhibited inappropriately in varied settings, it is reflected as a psychiatric disorder .
Children with ADHD tend to be noisy and violate rules with their disruptive behaviors, resulting in greater difficulties with off-task behaviors, thereby bringing them at risk for social refusal . They tend to exhibit signs of hyperactivity and inattention, coexisting with a reduced level of communication skills . Pronounced deficits in phonological and syntactic structures have been noted in children with ADHD , which is crucial for literacy development . Apart from these linguistic components, studies have reported language problems in ADHD characterized by pragmatic deficits . These pragmatic impairments associated with ADHD may include children having: 1) reduced verbal output and further disfluencies when faced with activities that include preparation and coordination of verbal responses, such as storytelling or giving directions; 2) timing issues when it comes to starting a discussion, taking turns and keeping or changing topics during a conversation; and 3) excessive verbal output during spontaneous interactions, task changes, and play conditions .
Different interventional approaches have been suggested for the treatment of individuals with ADHD, which may include behavioral, pharmacological, psychotherapeutic, physical exercise, and education-based approaches . Pelham et al.  emphasized the role of behavioral interventions for ADHD, which included parents and teachers administered, combined, and direct intervention programs with the affected individuals. Parents become primary educators in their children’s lives, with the power to mold their attitudes. As a result, it is important to provide parents with the support they need by addressing their child’s problem habits and offering solutions for modifying or enhancing the behaviors that interfere with their daily activities. Rather than focusing on the symptoms of ADHD, a behavioral approach focuses on functional impairments . Some of the key organizational skills required for children with ADHD have been noted to be in the area of strategy and skill preparation .
School-home note intervention is a frequently used method to enhance classroom behavior and task-relevant behavior in middle-aged and elementary school children . Using methods such as these have resulted in a significant enhancement in classroom behaviors such as paying attention, performing homework, talking with the teacher’s permission, maintaining seating, as well as executing quality and quantity classwork . As children with ADHD face challenges in academic settings, it becomes difficult for them to perform well in classroom settings, with frequent display of symptoms of inattention, disruptive behaviors, poor sitting behaviors and an inability to control their impulses. The visual activity schedule (VAS) intervention program is a frequently used method to teach multiple skills involving on-task, use of schedules, transition behaviors, social initiation, independent play skills, classroom skills, and academic skills . An activity schedule can include pictures, drawings, photographs, or a set of images that cue a person to engage in a sequence of doing things that helps one to complete their activity or assignment without the need for assistance. A child’s academic and social skills depend on their ability to remain on tasks with minimal distractions. Such skills allow children to gain the required input, complete tasks or assignments, and be active during discussions that are held in a classroom . VASs have been used to reduce the latency to initiate a new activity , reduce temper tantrums during transitions , and to enhance and maintain multiple social skills . The implementation of VAS intervention programs such as providing smallgroup directions have been used in general classrooms and/ or educational settings , aiding in the enhancement of academic skills and the degree of interaction between peers, thereby reducing disruptive behaviors in classrooms . This interventional approach is commonly used among children with autism spectrum disorder (ASD)  and intellectual disabilities . Children diagnosed with ADHD exhibit difficulties in these skills, leading to disruptive behaviors in the classroom. The efficacy of using the VAS in children with ADHD has been studied minimally compared to that in children with ASD. Consequently, the current systematic review aimed to evaluate the efficacy of using the VAS in children with ADHD between the ages of 5 and 12 years.
The review protocol for the current study was registered in the International Prospective Register of Systematic Review (PROSPERO). The registered protocol can be found at: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=212844.
The databases used for the present systematic review included the PubMed and Scopus databases. A search strategy was used for each of the databases with two keywords pertaining to the population (“attention deficit hyperactivity disorder,” “ADHD”); seven keywords in relation to the intervention (“VAS,” “visual activity schedule,” “picture prompts,” “visual schedule,” “visual cues,” “work system,” “visual reminders”); and five keywords pertaining to the outcome (“on task behavior,” “on schedule behavior,” “independent skills,” “social skills,” “problem behaviors”) [14,22-26], with the Boolean operators such as “AND,” “OR,” and “NOT.”
The initial search was performed on October 16, 2020, and the search terms were determined based on two criteria. First, the outcomes or skills that improved with the use of VAS were identified from eight research articles [14,22-28] with outcomes being considered as the key words. Second, most of the possible alternative words were used as keywords in the search to avoid missing any relevant articles. The search was restricted to peer-reviewed English language studies published between 2010 and 2020. We also manually searched for the following journals: 1) Journal of Emotional and Behavioral Disorders; 2) Journal of Behavioral Neurology; 3) Journal of Psychology & Psychotherapy; 4) Journal of Health & Medical Research; and 5) Journal of Special Education and Technology to identify any potential articles that could have been missed.
A three-phase selection process was considered for the final inclusion of the studies. It was initiated by compiling the studies obtained from the search of the two databases using the Mendeley desktop reference management system. In the second phase, the duplicates were removed, and using the COVIDENCE manager (https://www.covidence.org/) the two reviewers independently screened the titles and abstracts according to the inclusion and exclusion criteria set a priori. The inclusion criteria were: 1) children diagnosed with ADHD in the age range of 5 and 12 years; 2) English language peerreviewed observational studies or randomized controlled trials (RCTs) published between 2010 and 2020; 3) either single case research studies or group design studies; 4) studies with at least one participant diagnosed with ADHD; and 5) studies from PubMed and Scopus databases. The exclusion criteria were as follows: 1) children diagnosed with other disabilities such as ASD and intellectual disabilities; 2) children with neurodevelopmental disorders; 3) thesis/dissertations from institutional repositories; 4) narrative review articles, case reports, or editorials; and 5) studies with adolescents with ADHD (over 12 years of age).
The full length review was performed only after we identified all relevant articles, including the manual search. In cases of uncertainty over whether an abstract met the inclusion criterion, the authors obtained the full-text article and independently evaluated each paper to incorporate it. In the event of a disagreement, the researchers arrived at a consensus by reevaluating the inclusion criterion and recorded the reasons for excluding these studies. Finally, we recorded our decisionmaking process using a Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) chart .
The two reviewers independently extracted the data from the full-length articles that met our criteria using a specifically devised data extraction form. A third reviewer checked both of the reviewers’ data extractions. The following data were extracted for the current systematic review: 1) research design; 2) participant gender and age; 3) settings; 4) targeted skills; 5) dependent variables/measures; 6) schedule type and mode of presentation; 7) materials used; 8) strategies used; and 9) results/outcomes .
The quality of the two single case studies [25,26] was assessed using relevant quality indicators . The quality assessment scale, a yes/no rated system, was used to evaluate if the described criteria were met. A total of 20 indicators were used to assess the quality of the reviewed studies. Two independent reviews assessed the quality of each study using the quality indicators , and responses were verified by a third reviewer. One of the studies by Hart et al. , followed a crosssectional case design, and the quality (selection, comparability, and outcome) of the study was assessed using the Newcastle Ottawa scale . The quality of the fourth study by Pfiffner et al.  followed a randomized clinical trial which was assessed using the validated revised Cochrane risk-ofbias tool for randomized trials (RoB 2) .
Initially, 964 articles were identified across the two databases. Among them, 444 were found to be duplicates and were removed based on the title and abstract. The existing 525 articles were screened, and 489 were found to be irrelevant based on the prior set of the inclusion and exclusion criteria set by the researchers. A total of 57 articles met the eligibility criteria, of which 53 articles were excluded after full length review. Finally, four articles were found to be relevant to the study and met the inclusion criteria. The PRISMA chart of the systematic review is shown in Fig. 1.
The study characteristics of the four included articles have been shown in Table 1.
Among the four studies, 237 children were diagnosed with ADHD, with 38.81% being female and 61.18% being male. All participants in the four studies were between 5 and 12 years of age. Two studies reported recruiting 58%  and 76%  of male participants. The 199 participants included in one of the studies  included children between 7 and 11 years of age, diagnosed with ADHD-Inattentive Type (AD-HD-I); and in another study , the 33 participants included children between 7 and 12 years of age who were diagnosed with ADHD. Among the two single case studies, one of them  reported two male participants of 7 and 9 years of age, respectively, while the other  reported three male participants (a child with moderate intellectual disability, a child with ADHD, and a child with global delay) with the ADHD participant aged 5.8 years.
All four selected studies had at least one child with ADHD who participated in the study. In one of the single case studies , the risk of ADHD in the two participants was rated using Conner’s Teacher Rating Scales-Revised, Short and Conner’s Parent Rating Scales-Revised, Short . In another study , there was no mention of the scale/tool used to diagnose the participant as ADHD. Since the use of a standard diagnostic system was not part of the study selection criteria for the current systematic review, this study  was therefore considered for the review, primarily because it met all other criteria pertaining to the use of VAS as an intervention for children with ADHD.
In a RCT study , the participants were diagnosed with ADHD-I using the Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children and Wechsler Intelligence Scale for Children and for ADHD-I, all of the patients met the full DSM-IV requirements. In a study by Hart et al. , the researchers used parent and teacher rating scales, such as the Disruptive Behavior Rating Scale  and IOWA Conners Rating Scale  to determine ADHD symptoms.
All four studies conducted the intervention program in different settings and/or environments [25-27,31]. Two single case studies [25,26] conducted the treatment in the participant’s classroom. A RCT study  conducted an intervention at the University of California San Francisco and the University of California, Berkeley. The intervention included group meetings with parents and children in clinics, the school premises, and over the phone, while the teacher consultations were conducted at the school and occasionally over the phone. Hart et al.  conducted a study relating to a summer treatment program in an academic learning center. Cirelli et al.  mentioned the layout of the classroom, which included 20 desks for students, one desk for teachers and a horseshoe-shaped table. However, none of the other studies [25,27,31] reported the same.
The quality of the two single case studies [25,26] was assessed using single-case study quality indicators . The quality of the study was determined by taking the ratio of the total number of agreements by the total number of indicators, and then multiplying by 100. One of the single case studies  received a quality appraisal of 95%, while the study by Stephenson  met a 90% quality standard, as shown in Table 2. The ratings obtained for the cross-sectional study  for each section (selection, comparability, and outcome) were 4, 1, and 3, respectively, indicating good quality, as shown in Table 3. For the RCT study , the quality was determined by taking the ratio of the total number of “yes” (5) and the total indicators (19), then multiplying by 100. The result revealed a score of 26.3%, suggesting the study was of low quality, as shown in Table 4.
The current systematic review included four peer-reviewed articles (two single case studies, one cross-sectional study, and one RCT study). All four studies attempted to focus on ADHD participants, with the single case studies [25,26] having a smaller number of participants which enabled them to provide more attention to the chosen participants. This was possible in the RCT  and the cross-sectional study  because of the large number of children who participated. One of the parameters set for the study selection criteria was to have at least one participant diagnosed with ADHD, which was met by all four studies that were finally included in this systematic review. However, in the study by Stephenson , although one of the participants was diagnosed with ADHD, there was no mention of the diagnostic system used for the same. However, as the use of a standard diagnostic system was not part of the study selection criteria for the current systematic review, this study  was considered for the review, primarily because it met all other criteria pertaining to the use of VAS as an intervention for children with ADHD. The recruitment of participants  and the study settings  largely contributed to the efficacy of the study. The recruitment process was well-documented in the RCT and the crosssectional study, but not in the two single case studies. Similarly, the study settings in the two single case studies were mentioned clearly, since it was conducted in a school and classroom setting; however, there was no such clarification in the RCT and cross-sectional study. As the single case studies [25,26] were conducted in the classroom, the examiners were able to concentrate on classroom and academic skills that the participants could easily generalize . In a crosssectional study , academic testing was used as part of the recruiting procedures to assess the participants’ eligibility for the study, which was not addressed in other studies, however, it is generally considered as an ideal method for recruiting participants for research studies .
Prior to the treatment sessions, the screening protocol was discussed in terms of interviews with both parents and teachers ; however, the diagnostic procedures were mentioned in the cross-sectional study but not in the two single case studies. In all four studies [25-27,31], the chosen participants were assessed on a variety of skills. Two of the single case studies centered on classroom skills, while the RCT focused on everyday living skills. Hart et al.  targeted task behavior, which was observed over two periods. Despite the fact that the four studies focused on a wide range of skills, all of the targeted skills were significant in improving abilities and decreasing problem behaviors. In terms of the practices and materials used, each of the four studies took a different approach towards intervention. The materials used in the three studies [25-27] differed based on the type of intervention program. Pfiffner et al.  did not report the materials used in the session, even though the intervention had been mentioned. A variety of strategies, including verbal, gestural, as well as gestural and verbal prompts, were used in the schedule- based intervention program in one of the single case studies, while both verbal and physical prompts were used in another study . Physical prompts were discovered to have a significant impact on eliciting the responses, which was not mentioned in RCTs  or cross-sectional studies . During any treatment program, the duration of the session played a significant role. The duration mentioned in all four studies was different, and depended on how sufficiently they had used the strategies, tasks, and materials for the participants. In the study conducted by Cirelli et al. , the students were required to complete worksheets and place them in a work folder, which took a longer time (25–30 minutes) than the participants in the Stephenson  study who were expected to complete basic activities (counting tasks, letter identification, and numbering) using an iPad, which took a shorter time (5–10 minutes). The Child Life and Attention Skills Treatment (CLAS) program used in the study by Pfiffner et al.  lasted longer as it focused on the training of parents, teachers, and children with ADHD. In addition, the intervention program used here included parent-focused treatment and treatment as usual. Therefore, the amount of time needed to achieve the desired level of satisfaction was longer. The details of the program duration are listed in Table 6. In the study by Hart et al. , the authors provided an intervention program (10 minutes each) under three different conditions (whole group, small group, and independent seatwork), which also resulted in a longer duration of VAS intervention. In each of the studies, the duration of the VAS intervention program depended on the participants involved, task complexity, and materials used in the study. This indicates that VAS intervention programs that target training of stakeholders can be longer in duration and spread over a number of sessions, whereas programs directly targeting the ADHD students may be considered to be shorter in duration.
There were more than two team members conducting the therapy session, one of them could easily record the session, while the other concentrated on taking sessions, ensuring that there were no interruptions. It was important to evaluate the treatment program’s efficacy or consistency to determine whether the intervention program was appropriate for treating the patients. In one of the single case studies  as well as in the RCT , the inter-observer reliability was rated. Simultaneously, procedural integrity, treatment fidelity, observational reliability, and procedural reliability were all critical in determining the effectiveness of the treatment program . To prevent bias, all of these measures were included in the study [25-27]. The parents expressed high levels of satisfaction with the CLAS program as they learned more about ADHD and how to train their children with it ; however, there was no mention of social validity in another study . Two of the studies [25,26] assessed the acceptability of the treatment among teachers, patients, and peers, and found it to be satisfactory. The results of all four studies were measured differently depending on the type of intervention implemented. On-task and on-schedule performance were assessed on a percentage basis in one of the single case studies , while the progress in each step or session was examined in the other. The results of the RCT  were obtained by administering rating scales to the participants. The level of significance was measured in a cross-sectional study for all three conditions.
It was also crucial to conduct a post-intervention review to determine whether there were any deviations from the participant’s baseline. The RCT  used various rating scales to perform a post-intervention review to see how far the participants had progressed or how different they were from their baseline phase. Various rating scales were used to assess the quality of the four studies [25-27,31]. The RCT  was of low quality, while the other three studies [25-27] were of high quality. Provided that all indicators had been similarly assessed, the efficiency of all four studies could have been ascertained uniformly.
The use of VAS in children with ADHD is a promising intervention that provides teachers and parents with adequate guidelines to execute the intervention program in different settings. Using VAS also seeks to improve the most impacted areas such as academic, social and independent classroom skills, on-task and on-schedule behavior, and literacy skills. The use of scheduled-based activities are found to have a significant effect on ADHD children, as per the reviewed studies [25-27,31]. The results of the current study will help provide practitioners with guidelines for preparing scientifically planned interventions for children with ADHD. However, the generalizability of the findings of the current systematic review towards a wider age group is questionable. Moreover, the four studies that were evaluated in this systematic review followed three different study designs, resulting in the efficacy of the intervention program being debatable. Future research could address these issues, as well as determine the efficacy of other intervention programs in children and individuals with ADHD.
The authors wish to thank Mr. Rahul K for acting as the third reviewer during the ‘data extraction and management’ and ‘quality assessment’ process.
Data sharing not applicable to this article as no datasets were generated or analyzed during the study.
The authors have no potential conflicts of interest to disclose.
Conceptualization: Sudhin Karuppali. Data curation: Naveena Thomas. Formal analysis: all authors. Methodology: Naveena Thomas. Supervision: Sudhin Karuppali. Writing—original draft: Naveena Thomas. Writing— review & editing: Sudhin Karuppali.