Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder with an estimated worldwide prevalence of approximately 5% [1]. In Japan, the prevalence estimates range from 2.5% [2] to 10% [3]. The disorder is associated with numerous functional impairments and poor long-term outcomes [4,5] and negatively affects parents’ emotional well-being, parenting practices, and the parent-child relationship [6]. Effective interventions for children with ADHD and their families are therefore a high priority [7].

Current clinical guidelines recommend a multimodal treatment approach for ADHD that incorporates both pharmacological and nonpharmacological treatment options [8-10]. Parenting interventions are an example of a recommended nonpharmacological treatment option with proven efficacy in numerous clinical trials [11,12]. Recommended interventions generally provide parents with behavioral strategies aimed at increasing the frequency of appropriate behavior while reducing the frequency of unwanted behavior in children. The needs of families of children with ADHD have received less attention, with only a few studies directly targeting parental well-being [13,14].

Parent-training interventions are becoming more widely accepted in Japan with increased implementation, especially in community settings. Although efforts have been made to develop programs to address the needs of families of children with a range of neurodevelopmental disorders [15], the availability of interventions specifically designed for ADHD remains limited.

To our knowledge, none of the behavior programs currently being implemented in Japan includes specific elements to address parental coping or emotional well-being. In addition, nothing is known about the cost-effectiveness of behavioral interventions for ADHD in Japan.

For Japanese families, the 8-session group-based New Forest Parenting Programme (NFPP) has been front-loaded with 5 additional sessions designed to increase mother’s understanding of ADHD and to address their psychological well-being and readiness to complete the NFPP program. These sessions were added on the recommendation of participants in our pilot and proof-of-concept studies [16] to provide additional support for mothers. Culturally, Japanese mothers are held responsible for their child’s behavior and struggle to request support for themselves and their children. These 5 sessions included auxiliary psychoeducation about ADHD and culturally tailored stress management training, cognitive restructuring, strategies for effective communication, and problem-solving skills, adapted from the 9-week parent stress management program [14].

The NFPP has been specifically developed for the treatment of ADHD. In addition to behavioral strategies to manage oppositional and defiant behavior, it includes games and activities targeting purported neuropsychological deficits underlying some of the symptoms of ADHD [17], designed to enhance the child’s cognition and self-regulation [18]. Numerous randomized controlled trials (RCTs) have shown that the receipt of NFPP is associated with a reduction in ADHD symptoms and improvements in parental well-being [18-21]. With the support of the program developers, the NFPP sessions were specifically adapted for use with Japanese families [16].

A recent pilot RCT of Well Parent Japan (WPJ) [22] demonstrated that participation in the program was associated with several positive outcomes compared with the wait-list control group; that is, significant reductions in parenting stress, higher levels of parenting self-esteem and use of more effective parenting strategies, reduced child aggression, internalizing problems, and a trend toward reduced inattention. Mothers who participated in WPJ also responded less negatively toward their children. WPJ appears to be an efficacious psychosocial intervention for ADHD in Japan, with the group format and the session content well tolerated.

This study aims to extend the results from the pilot RCT [22] to a larger multicenter pragmatic trial to assess the effectiveness and cost-effectiveness of WPJ compared with treatment as usual (TAU) in child and adolescent mental health care services in Japanese hospitals. WPJ will be compared against TAU at the end of the intervention and again after 3 months (short-term follow-up).

The primary objective is to compare the effectiveness of WPJ against TAU on maternal parent domain parenting stress, that is perceived stress in the parent-child dyad arising from characteristics of the parent, measured with the Parent Stress Index [23,24]. Parent domain stress was selected as the primary outcome measure given WPJ’s strong focus on the emotional well-being of participating mothers. Secondary objectives include comparison of the effectiveness of WPJ against TAU in improving child behavior, parental well-being, and parenting practices and to explore the cost-effectiveness of WPJ.

A multisite pragmatic RCT comparing the effectiveness and cost-effectiveness of WPJ (treatment arm) with TAU (control arm). Both arms will be tested at baseline, immediately after the intervention arm completes WPJ at week 14, and at 3 months follow-up; that is, week 26. The study is being carried out through Japanese child and adolescent mental health care services at three different hospital sites in Japan (Fukui, Fukuoka, and Okinawa). Table 1 lists the schedule of parent self-report, teacher, and objective assessments at each time point, whereas Figure 1 summarizes the study design and flow of participants through the trial.

The study was retrospectively registered with the International Standard Randomised Controlled Trial Number after the first of 3 waves of participant recruitment (trial registration number: ISRCTN66978270). Registration delay was an unintended consequence of ill health of one of the principal investigators, which disrupted study preparation. This oversight was identified after the first wave of participant recruitment and the trial was subsequently registered. Ethical approval for the trial, as described in the protocol, was obtained at all intervention sites before participant recruitment.

Parent domain parenting stress score at week 14 is the primary outcome measure and informed our sample size calculation. On the basis of the results of our pilot RCT [22], to detect a 0.5 standardized effect size at week 14 using 80% power at a 2-tailed .005 significance level, assuming the correlation between the baseline and follow-up measures is 0.35, 112 participants were required. After adjusting for a 15% attrition rate, the target sample size was inflated to 132.

Physicians at the 3 hospital study sites confirmed the eligibility of the mothers of their patients with ADHD to participate in the study. They briefly explained WPJ and the requirements for research participation. Interested mothers were referred to the research site administrator for a detailed verbal and written explanation of the study procedures, including randomization to WPJ or TAU and the need to access the child’s medical records. Those who agreed to participate provided written consent for their own participation and their child’s participation. Written consent from teachers was obtained by mail. Children’s informed consent was obtained at the first laboratory assessment session.

Baseline outcome measures were obtained from mothers and teachers, including the Revised Five-Minute Speech Sample (R-FMSS) and the parent-child interaction task, before randomization to the study arm (Table 1 provides the full list of baseline measures). Teachers remained blind to family treatment group allocation. When sufficient participants were recruited at a site (a minimum of 12), they were randomized to the study arm, that is, block randomization at each site, using a computer random number generator operated by DD.

All participants were assigned an ID number at each site. Raw data were stored in locked storage at the collection sites. Only anonymized data were shared with researchers at the primary research site (Okinawa Institute of Science and Technology [OIST]) for database entry and analyses.

All the participants are assigned an ID number at the trial site when they consent to participate in the study. This number is used on all questionnaires. Each site will maintain a list allowing them to link names and ID numbers.

Data collection at each clinical site is supported by a dedicated research assistant with oversight and support from the trial team at OIST. Anonymized questionnaire data will be scanned, password-protected, and saved in a shared Dropbox with the researchers at OIST. Video and audio recordings will be password-protected and saved in the same shared Dropbox. The OIST trial team will transfer the data from the shared Dropbox folder to secure electronic storage at OIST as soon as it is received. The OIST team will not have access to the data linking lists from any site. Data entry into a password-protected electronic database will be carried out by the trial staff at OIST.

Raw data (possibly containing names) will be maintained in secure storage at each site for 10 years after study completion. Access to these data is limited to the site principal investigator and dedicated research assistant. Once all data analyses are complete and manuscripts are prepared, OIST-maintained electronic password-locked files will be wiped. OIST will retain the anonymous password-protected data for 10 years after manuscript publication. GT will be responsible for the supervision of stored data.

Data analysis will be carried out by the trial statistician using an anonymized electronic database (see the Statistical Analysis section). Although there are no plans to make the data publicly available, requests for access to the data will be considered on a case-by-case basis, subject to Japanese law.

Therapists are asked to record and report any potential adverse events using a standard template, and the importance of adverse events is highlighted during supervision sessions. Any adverse events are required to be reported to the approving ethics committees. In addition, all adverse events will be reported to the independent data and ethics monitor and will be evaluated, recorded, and discussed in the final paper.

Although there are no plans to make the data publicly available, requests for access to the data will be considered on a case-by-case basis, subject to Japanese law.

The study has been approved by the OIST Graduate School Human Subject Research Review Committee (reference number: HSR-2019-014) following receipt of approval at each study site: University of Fukui Hospital (reference number: 20170085), Kurume University Hospital (reference number: 19052), and National Hospital Organization Ryukyu Hospital (reference number: 31-5).

This trial addresses the need to investigate the effect of nonpharmacological treatments for children with ADHD in everyday clinical practice in Japan. This trial combines 2 evidence-based interventions for families of children with ADHD within a hybrid program that has been developed and piloted to provide a culturally adapted and appropriately delivered behavioral intervention for families of children with ADHD in Japan. Combining support for families of children with ADHD with behavioral strategies that aim to target and alter the developmental trajectory of ADHD has implications for researchers and clinicians beyond Japan. The results will be reported at national and international conferences, published in peer-reviewed journals, disseminated to Japanese health care professionals, and communicated digitally to Japanese and international ADHD advocacy groups.

This is the first trial of WPJ based on the recruitment of children referred directly to routine clinical services in Japan. It is also the first pragmatic trial that combines the NFPP with specific and direct intervention support for parents of children with ADHD. In this sense, this multisite randomized trial tests the effectiveness of WPJ with children and families in a clinical setting for which the intervention is ultimately intended with very few exclusion criteria. It also compares WPJ directly with the usual clinical care offered for children diagnosed with ADHD in Japan. We also seek to assess and compare the cost-effectiveness of WPJ with that of TAU in Japan.

The stigma associated with ADHD in Japan and unfamiliarity with group-based interventions for ADHD posed challenges to recruitment. The COVID-19 pandemic continues to affect the trial, with local and national lockdowns and restrictions affecting recruitment and disrupting the process of delivering the intervention. The decision to provide supervision via web-based platforms ensured that this aspect of the study has not been disrupted by the COVID-19 pandemic. In principle, the group delivery model is a challenge for parents of children with ADHD, who often perform better with individual therapy, where a bespoke response can address the heterogeneity of the child’s ADHD. However, in the proof-of-concept study, a group model was requested by Japanese mothers [16]. Culturally, it was felt that an individual approach might not be appropriate, which was supported by the pilot RCT that demonstrated considerable levels of efficacy against a wait-list control group [22] using a group-based mode of delivery. Establishing the cost-effectiveness of the intervention has also been challenging, as the academic discipline of health economics is not well-established in Japan. In addition, the process for calculating society and family borne costs, such as health care use in Japan, is complex, where health care costs are based on a point system that does not easily lend itself to economic evaluation. The COVID-19 pandemic has likely influenced family health service use, with families limiting their use of, and visits to, health care providers. We assume similar effects across the 2 study arms.

In recruiting through hospital clinics, the study does not include self-referred families in the community, possibly reducing the generalizability of the findings. Having clinic doctors (in Japan, the diagnosis of ADHD is limited to medical doctors; thus, referrals to the research were made by those responsible for the diagnosis of ADHD in the children) identify eligible families may have resulted in the referral of those dealing with more severe or comorbid ADHD, or mothers deemed most in need or most likely to benefit from participation in WPJ. Nonetheless, this is consistent with the aim of the research; that is, to evaluate WPJ within the Japanese child and adolescent mental health care system with a view toward future implementation of the intervention within this system. As a pragmatic trial, study site differences will be evaluated; however, we do not control for the effects of group leader skills on treatment outcomes. All group leaders are provided with the same training and are supervised by SS, which should help minimize differences in program delivery. The registration of the protocol was retrospective, and participant recruitment is now complete. No changes were made in the study protocol.