The study took advantage of a mobile school-based mental health screening program run by the university’s medical unit in 2022. Rather than recruiting families into a clinic, the researchers brought the assessment to the classroom, relying on teacher-completed ratings on the Thai version of the Swanson, Nolan, and Pelham Version IV scale, widely known as the SNAP-IV. This instrument, originally developed to measure ADHD symptoms against diagnostic criteria, asks teachers to rate how frequently a child displays behaviors such as failing to finish tasks, being easily distracted, fidgeting, interrupting others, arguing with adults, or deliberately annoying peers. Because teachers observe children over many hours in structured settings, their ratings are considered a valuable and practical proxy for identifying children whose behavior falls into the clinically significant range.

The retrospective chart review covered 540 primary school students who participated in the screening program. The headline result was unexpected in its proportions. Clinically significant symptom levels were most prevalent for oppositional and defiant behavior, affecting 38 percent of the children screened, with a 95 percent confidence interval of 34 to 42 percent. Hyperactivity and impulsivity came next, at 15 percent, and inattention was identified in 8 percent of students. For context, global prevalence estimates for diagnosed ADHD in children typically hover around 5 to 8 percent, and ODD estimates generally fall between 2 and 10 percent, although teacher-rated symptom screening tends to capture broader groups than formal clinical diagnosis. Even allowing for that methodological difference, the sheer weight of oppositional symptoms in this sample stands out.

Geography proved to be one of the most powerful variables in the dataset. When the researchers broke the results down by province, they found that prevalence varied significantly across geographic areas, and one province in particular, Nan, in northern Thailand near the border, recorded the highest proportions across every symptom domain. In Nan, clinically significant inattention was observed in 16.8 percent of students, hyperactivity and impulsivity in 23.5 percent, and oppositional or defiant behavior in a remarkable 71.4 percent of screened children. All of these geographic differences were statistically significant, with P values below 0.001, meaning the probability that such variation arose by chance alone is extremely small. The pattern suggests that children in certain border communities carry a substantially elevated behavioral symptom burden compared with their peers elsewhere in the screening catchment.

The study also examined how symptom prevalence and severity differed by sex and grade level, and here the picture became more nuanced. Sex-related and grade-related differences in the distribution of symptom severity varied across the different symptom domains rather than following a single uniform pattern. This is consistent with a well-established body of child psychiatry research showing that boys are more often flagged for hyperactivity and externalizing behaviors, while inattention can present more quietly and be missed in classroom settings, and that the expression of ADHD symptoms tends to evolve as children move through primary school. The authors note that these demographic patterns in symptom-severity distributions differed across domains, underscoring that a single screening threshold applied uniformly may not capture every child who needs help.

Methodologically, the team used chi-square tests and Fisher’s exact tests to compare proportions across provinces, sexes, and grade levels, standard statistical tools for categorical data of this kind. The screening instrument itself has a long pedigree. The SNAP-IV scale was built around the symptom lists of the Diagnostic and Statistical Manual of Mental Disorders, tracing its structure from the DSM-III through the DSM-IV, the DSM-IV Text Revision, and into the DSM-5 era, and it remains one of the most widely used teacher and parent rating scales in ADHD research worldwide. The Thai version used here allows locally validated cutoffs to be applied to teacher ratings, converting everyday classroom observations into standardized scores that flag clinically significant symptom levels. The researchers followed STROBE reporting guidelines for observational studies, and the work received ethical approval from the Institutional Review Board of Srinakharinwirot University, with written informed consent obtained from parents or legal guardians and all data anonymized before analysis.

Why might oppositional and defiant symptoms be so elevated in these border regions? The study itself is descriptive and does not test causal explanations, but the broader literature on child mental health in marginalized settings offers plausible context. Border and remote rural communities in Thailand often face compounded adversity: poverty, limited educational resources, family separation due to labor migration, reduced access to health services, and in some areas the stresses associated with ethnic minority status and cross-border instability. Chronic environmental stress in childhood is strongly associated with externalizing behaviors, and where developmental screening and early intervention are scarce, behavioral difficulties can accumulate unrecognized for years. A teacher in a resource-strained classroom may also rate disruptive behavior more severely when support systems are thin, although the study design cannot disentangle such reporting effects from true differences in symptom burden.

The practical significance of the work lies in what it reveals about service gaps rather than in diagnosis itself. A screening program of this kind does not assign clinical diagnoses; it identifies children whose symptom scores cross thresholds that warrant fuller evaluation. In urban Thai settings, a child flagged by teacher ratings might be referred to a child psychiatrist within weeks. In a border province, the nearest specialist may be many hours away, and families may lack the resources to travel. The authors frame their findings as descriptive epidemiological evidence intended to inform future research, school-based screening programs, referral pathways, and service planning for the early identification and support of children with behavioral difficulties. In other words, the numbers are meant to give health planners a map of where the need is concentrated so that limited specialist capacity can be deployed where it will matter most.

The mobile medical unit model at the heart of the study deserves attention in its own right. By embedding screening within routine school visits, the program reached children who would almost certainly never appear in a clinic-based study, which is precisely the population that most epidemiological datasets miss. This is a recurring problem in global child mental health research: prevalence figures are disproportionately drawn from urban, clinic-adjacent populations, while children in remote and low-resource settings remain statistically invisible. The 540 students in this sample represent a small but meaningful corrective, and the authors are explicit that unequal access to child mental health screening and early intervention remains a major public health challenge in geographically marginalized settings.

There are, of course, limits to what a single retrospective screening review can establish. The data come from teacher ratings at one point in time in 2022, without the multi-informant assessment, clinical interview, and functional impairment evaluation that formal diagnosis requires. The sample, while valuable, is not a nationally representative survey, and the very high oppositional symptom figure in Nan province invites further investigation into local conditions, rating practices, and referral history before firm conclusions are drawn. Still, the study’s core contribution is difficult to dispute: it documents, with standardized instruments and clear statistics, that clinically significant behavioral symptoms are common among primary school children in Thailand’s border regions, that they cluster unevenly across geography, and that school-based screening is a feasible vehicle for finding them. As health systems worldwide grapple with post-pandemic rises in child behavioral and emotional problems, this Thai border-region dataset is a reminder that the children most in need of early identification often live farthest from the clinics designed to provide it.

Subject of Research: Prevalence of ADHD and oppositional defiant disorder symptoms among primary school students in Thailand's border regions

Article Title: Prevalence of clinically significant attention-deficit/hyperactivity disorder and oppositional defiant disorder symptoms and their behavioral characteristics among primary school students in Thailand’s border regions: evidence from a school-based screening program

Article References: Eiamudomkan, M., Khuancharee, K., Narkwichean, A., Muangnoi, P., Charoenthamruksa, C., Wannaiampikul, S., & Tanunyutthawongse, C. (2026). Prevalence of clinically significant attention-deficit/hyperactivity disorder and oppositional defiant disorder symptoms and their behavioral characteristics among primary school students in Thailand’s border regions: evidence from a school-based screening program. BMC Psychiatry. https://doi.org/10.1186/s12888-026-08724-4

Image Credits: AI Generated

DOI: 10.1186/s12888-026-08724-4

Keywords: ADHD, oppositional defiant disorder, school-based screening, child mental health, Thailand, border regions, SNAP-IV, pediatrics, psychiatry, health disparities, teacher ratings, epidemiology