Attention deficit hyperactivity disorder (ADHD) is characterized by inattentiveness, restlessness, and impulsive behavior. It is one of the most common neurodevelopmental disorders in childhood [1].

Being inattentive, overactive, preoccupied, forgetful, impatient, easily frustrated, overly talkative, and easily distracted are common issues observed. These problems disrupt daily activities and negatively impact academic performance. Often, ADHD is not diagnosed until the behaviors cause problems in school. Many children with mild symptoms go undiagnosed, impeding their optimal personality development. As these children mature into adults, they may develop behavioral and emotional disturbances, including depression, mood swings, anger issues, addictions, and relationship problems in both their personal lives and at work.

ADHD is primarily diagnosed through clinical methods, which include behavior rating scales, clinical interviews, physical examinations, and neuropsychological evaluations. There are several standardized behavior rating scales that effectively identify children with ADHD.

The global prevalence of ADHD is 7.6% among children aged 3 to 12 years and 5.6% among teenagers aged 12 to 18 years [2]. In India, the prevalence of ADHD, based on school and hospital-based population studies, ranges from 4.7% to 29.2% [3]. Given its vast geographical expanse, India has seen numerous studies aimed at assessing the prevalence of ADHD in children. However, these studies are often confined to specific geographic areas and show significant variations in prevalence rates. In a school-based study from the South Indian state of Tamil Nadu, the prevalence of ADHD among children aged 8 to 11 years was found to be 8.8% [4]. In another city within the same state, the prevalence among children aged 6 to 11 years was reported at 11.32% [5]. From Dehradun in North India, another study reported an ADHD prevalence of 11.8% [6]. In contrast, the prevalence of ADHD in primary school children was reported at 5.7% in Belagavi, South India [7], and 2.3% in another study from a different city in the same state [8].

Ghosh et al. [9] observed a 12.6% prevalence of ADHD among primary school children in Assam, North-East India. The variation in prevalence across different regions and nations may be attributed to several factors, including poor awareness, a greater tolerance for developmental deviations in certain cultures, stigma associated with seeking treatment, availability of resources, variability in assessment tools, and inconsistencies in research methodology.

There is limited literature on the prevalence of ADHD in the Telugu-speaking states of South India, highlighting a need to understand its magnitude in our region. This study aimed to determine the prevalence of ADHD among primary school children, examine the socio-demographic profiles of these children, and identify the subtypes of ADHD present in our community. Additionally, the study sought to raise awareness among schoolteachers about ADHD in children and to train them in the use of screening tools for early diagnosis.

This descriptive cross-sectional study was carried out by the Department of Pediatric Neurology at a medical college in Hyderabad, South India, from October 2018 to October 2019. This study was approved by the Institution Review Board of Shadan Institute of Medical Sciences, Hyderabad. Written informed consent was obtained from all patients. A school located near the medical college and hospital was chosen for the study after receiving approval from the school principal. All children enrolled in primary school, from first to fifth grade, were eligible to participate. Children under 5 years of age or over 12 years old, those with pre-existing neurological conditions such as cerebral palsy, epilepsy, deafness, or visual impairments, and children whose parents did not consent were excluded from the study.

The Modified Kuppuswamy’s Socioeconomic Status Scale, 2019 (consumer price index [CPI]-328), was utilized to assess the socioeconomic status of the family, as depicted in Table 1. This scale comprises three parameters: education, occupation, and income. The total score, which ranges from 3 to 29, categorizes families into five distinct groups: upper class, upper middle class, lower middle class, upper lower class, and lower socioeconomic class. The income scale is periodically adjusted in accordance with changes in the CPI [10].

The Vanderbilt Assessment Scale, teachers’ version [11], which is a rating scale based on the Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnostic criteria for ADHD, was utilized. This scale comprises 43 questions divided into two main components: symptom assessment and performance impairment. The symptom assessment component is designed to identify symptoms of both inattentive ADHD (items 1-9) and hyperactive ADHD (items 10-18). For a child to meet the diagnostic criteria, they must exhibit at least six positive responses to either the inattentive or hyperactive core symptoms, or both, and must achieve a score of 4 or 5 on any of the performance items (36-43). A positive response is defined as a score of 2 or 3, indicating “often” or “very often.”

In primary school, each grade is divided into five sections, with class sizes ranging from 28 to 35 students. A total of 25 teachers received training on how to use the Vanderbilt Assessment Scale Teacher’s version across two sessions held at the school. The first session employed multimedia aids in English, Hindi, and Telugu to educate the teachers about ADHD and its impact on children's academic performance, quality of life, and broader societal implications. In the second session, the teachers learned how to complete the Vanderbilt Assessment Scale, Teacher's version.

The class teacher for each grade from first to fifth assessed the students who met the inclusion criteria using the Teacher’s version of the Vanderbilt Assessment Scale. This assessment took place at the convenience of the teachers over a period of 2 to 3 months. During this period, frequent school visits were conducted to address any concerns and to assist the class teachers in evaluating the students and completing the questionnaire. Once the questionnaires were completed, they were analyzed, and students who screened positive were recommended to consult with a pediatric neurologist and child psychologist, along with their parents, for a detailed evaluation and final confirmation of the diagnosis. Based on the evaluations, further management including behavioral modification therapy and medication was recommended as necessary, with regular follow-up.

Data were analyzed using a Microsoft Excel sheet and SPSS software version 21.0 (IBM Corp., Armonk, NY, USA). Frequencies and percentages were calculated for qualitative data, while means and standard deviations were computed for quantitative measures. The chi-squared test was employed to analyze categorical variables. A P value of <0.05 was considered statistically significant.

The school had more than 2,000 children enrolled across grades ranging from kindergarten to 10th grade. Of these, 756 primary school students were deemed eligible for the study. Three students had migraines, seven had epilepsy, two had spastic diplegia (cerebral palsy), and 44 students declined to participate. Consequently, 56 children were excluded from the study (Fig. 1). Demographic data for the excluded students are not available.

Seven hundred students participated in the study, comprising 389 boys (55.5%) and 311 girls (44.5%), as shown in Table 2. Sixty-seven students (9.57%) screened positive for ADHD, including 51 boys (76.11%) and 16 girls (23.9%), as presented in Table 2. The mean age of children diagnosed with ADHD was 8.91 years, compared to 8.65 years for those without the condition. The prevalence of ADHD was highest in the 5-year-old age group (14.28%), followed by the 10- and 11-year-old groups (12.1%).

The most common subtype of ADHD was combined (52.3%), followed by attention deficit (29.8%) and hyperactive-impulsive (17.9%). All subtypes were more prevalent in boys than in girls. The majority of the study population belonged to the upper lower (35.4%) and lower (50%) economic strata, with ADHD being more prevalent in the lower socioeconomic group (10.8%) (Table 3). However, this difference was not statistically significant (P=0.686).

According to a recent review by Kuppili et al. [3] on ADHD in India, the prevalence range of ADHD was found to be 4.7% to 29.2%, which aligns with the 9.57% prevalence rate observed in our study. A meta-analysis on the burden of ADHD among Indian children indicated a pooled prevalence of 7.5% in school-based settings [12], similar to global prevalence rates. In studies conducted in Dehradun, North India, and Coimbatore using the Vanderbilt ADHD Diagnostic Teacher Rating Scale and Conner’s Rating Scale respectively, prevalence rates of 11.8% [6] and 11.3% [5] were reported, both slightly higher than our findings. The prevalence of ADHD in a school-based study from Assam, North India, was noted to be 12.6% [9]. Epidemiological studies reporting higher prevalence rates should be considered as providing screening prevalence estimates, as they may include many false positives, according to Kurtzke [13]. This could partially explain the variations observed in different studies. Another study in Kancheepuram, South India, focusing on children aged 4 and 10 years using Conner’s rating scale, reported an overall prevalence rate of 8.8% [4]. In contrast, two studies in Bengaluru City, South India, reported lower prevalence rates of 1.3% [14] and 2.3% [8], despite also using Conner’s rating scale for diagnosing ADHD. ADHD prevalence estimates are higher in the Middle East and North America compared to African and Asian countries [15]. Significant heterogeneity was found across studies, with one notable factor being the "setting" of the study. Higher prevalence rates were observed in school-based studies compared to community studies, likely due to the influence of teachers' assessments of children's behavior in diagnosing ADHD. The studies also exhibited clinical heterogeneity due to the use of a variety of screening and diagnostic tools, as well as differences in the age ranges of the participants [12].

Children with ADHD were also stratified based on their age. In this study, the prevalence of ADHD was highest among 10-year-old, similar to findings in Bengaluru, where the highest prevalence was observed among children aged 11 to 12 years [14], and in Dehradun, where it was higher among those aged 8 to 10 years [6]. Similarly, a study in Coimbatore reported the maximum prevalence in children aged 9 and 10 years [5]. This consistent age pattern may be due to the increased demands for attention at school and home as children grow older. In a study conducted in Kancheepuram, the highest prevalence of ADHD was seen among 8-year-old, although the study only included children ranging from 8 to 11 years [4]. In Assam, ADHD was predominantly found in children aged 7 and 8 years [9]. Despite these findings, there is no consistent evidence across studies to pinpoint the most prevalent age group for the diagnosis of ADHD. However, most studies, including ours, have reported a higher prevalence in the age groups of 9 to 10 years.

ADHD is predominantly observed in males, with a reported sex ratio of approximately 2:1 in children. In our study, the prevalence of ADHD was higher in boys (13.11%, n=51) than in girls (5.14%, n=16), resulting in a ratio of 3.2:1. This finding aligns with a study conducted in Germany, which reported that boys were three times more likely to have ADHD than girls [16]. Similarly, a study from Spain found a sex ratio of 2.8:1, which is close to our results [15]. Various studies from India have also reported a comparable sex ratio of around 3:1 [5,6,8]. However, some studies have noted even higher ratios of 5:1 [9], while others have reported lower ratios, down to 1.6:1 [14]. The predominance of ADHD in boys may be attributed to the effects of sex hormones such as testosterone during the intrauterine period. These hormones are thought to act on the dopaminergic neural system in the prefrontal cortex and striatum, influencing the severity and clinical manifestations of ADHD [17]. Additionally, recent research suggests that sex chromosome genes (X- and Y-linked genes) and stress hormones could also play a role in the sex differences observed in ADHD through molecular mechanisms [18]. Moreover it is possible that girls are under-diagnosed and under-identified due predominance of inattentive symptoms and fewer hyperactive/impulsive symptoms, and fewer disruptive behavior causing less trouble to family and at school.

Our study revealed that the combined subtype of ADHD was the most prevalent at 52.2%, followed by the attention deficit subtype at 29.8% and the hyperactive-impulsive subtype at 17.9%. These findings align with research from Assam and Bangalore, where the combined subtype was also commonly observed [9,14]. In contrast, a study by Mannapur et al. [8] in Bangalore identified the hyperactive-impulsive subtype as the most frequent, although it involved a small sample size (only 23 students). Meanwhile, research conducted in Dehradun found the inattentive subtype to be most prevalent [6]. A recent global meta-analysis reported that each subtype constituted approximately one-third of the cases [2].

Environmental factors, including vehicular pollution and lead exposure, have been implicated in associations with ADHD. Other relevant factors that increase the risk of developing ADHD include parental alcohol consumption, lack of breastfeeding, being the firstborn, a history of pregnancy or delivery complications, ongoing parental discord, and parental psychiatric illness or aggression [19].

The prevalence of ADHD decreased with improvements in socioeconomic status. The highest prevalence was observed in the lower socioeconomic group at 10.8%, followed by the upper lower at 8.8%, lower middle at 8.1%, upper middle at 4.5%, and upper at 0%. However, the chi-squared test did not reveal this trend to be statistically significant. These findings align with those of Venkata and Panicker [5] who noted a higher prevalence of ADHD in the lower socioeconomic stratum compared to the middle socioeconomic class. A potential correlation exists between socioeconomic deprivation and the risk of ADHD, which may be influenced by factors such as maternal smoking during pregnancy, parental discord, and parental mental health issues.

The strengths of this study include its large sample size and the comprehensive training provided to schoolteachers on using screening tools to identify ADHD in children. However, the study has several limitations. Firstly, the sample was drawn from a school-based setting, which limits the generalizability to community settings. Additionally, the study focused on children from schools primarily serving middle and low socioeconomic groups, without a comparative analysis of students from affluent schools. This lack of diversity among the participants makes it difficult to generalize the findings across the entire country. Another limitation is the use of the Vanderbilt Assessment Scale, Teacher’s version, which has a sensitivity of 69% and a specificity of 84% for predicting ADHD. This suggests that some children with potential ADHD features may have been overlooked. Further investigation into environmental factors, exposure to chemicals, dietary habits, maternal status during pregnancy, and social factors could have provided additional insights.

In conclusion, over the past few years, there has been an increasing focus on various aspects of etiology and clinical interest, leading to a rise in ADHD research within Indian contexts. This study has yielded crucial epidemiological data that helps us understand the prevalence of ADHD in our South Indian community. We recommend screening all children for ADHD as they enter primary school. Additionally, it is essential that schoolteachers receive training in ADHD screening to promptly identify and support vulnerable children, ensuring timely referrals. Further qualitative research is necessary to explore carer burden, parental awareness, and attitudes. Such studies are vital to address issues significant to families and to conduct thorough research that deepens our understanding of the disorder.