The global prevalence of ADHD in children and adolescents: a systematic review and meta-analysis

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most frequent neurodevelopmental disorders in childhood and adolescence, which is typically first, diagnosed in childhood and often persists into adulthood. It is one of the most prevalent causes of children being sent to psychology and psychiatric clinics [1, 2]. Children with ADHD may struggle to focus, lack self-control and impulsive behaviors, or exhibit excessive activity [1‐3]. Hyperactivity, one of the main symptoms of ADHD, can lead to a child’s psychological and social incompatibility at home, school, and community [2]. The fundamental aspect of Attention Deficit Hyperactivity Disorder ADHD, according to the Fifth Diagnostic and Statistical Manual of Mental Disorders (DSM5), is a set of behaviors that disturb social status. Increased motor activity in inappropriate contexts, excessive wobbling, finger play, and talkativeness are examples of these social circumstances, which can interfere with personal and educational life [3].

Attention deficit disorder affects children differently depending on their age and gender, and it is more common in boys than in girls [2]. The initial signs of hyperactivity are frequently hard to detect until a child reaches the age of four, and it is most evident in elementary school. In early adolescence, the condition normally follows a predictable pattern. Yet, studies demonstrate that the main characteristics of ADHD change with age, so regardless of classification, ADHD seems to reduce in adulthood. Throughout this age range, hyperactivity in particular, though still present, is less evident (Ramtekkar et al. 2010). As a result, a thorough history is required for the diagnosis of ADHD which then leads to the identification of specific symptoms [5].

Symptoms of ADHD are frequent in school-aged children and can last far into adulthood. In general, ADHD is usually characterized by impulsivity, attention deficit, and hyperactivity. A person with inattention may have trouble remaining on task, maintaining focus, and maintaining organization. A hyperactive person may appear to move around frequently or fidget excessively. An impulsive person may behave without thinking or struggle with self-control. [2‐6]. Patients may be unable to pay close attention to detail or may be careless when performing tasks such as schoolwork, job, or other activities.

As previously mentioned, boys are more likely to manifest ADHD symptoms [6] with three times more likely to receive an ADHD diagnosis than girls [9]. Based on a study by Rucklidge, there are significant differences in how the condition reveals in boys and girls. Boys with ADHD usually show externalized symptoms, such as running and impulsivity. Girls with ADHD, on the other hand, typically show internalized symptoms [9]. These symptoms include inattentiveness and low self-esteem. Boys also tend to be more physically aggressive and externalize their frustrations, while girls tend to be more verbally aggressive and turn their pain and anger inward, putting them at an increased risk for depression, anxiety, and eating disorders [9].ADHD in children is caused by several factors, including genetics and environment, premature birth, preeclampsia, hypertension, overweight, and obesity in pregnant women, as well as maternal smoking exposure [7, 8]. Family history studies have also shown that drug abuse plays a significant role in the development of ADHD [9] Identifying whether a child has ADHD is a multi-step process. There is no single test that can detect ADHD. To diagnose ADHD a checklist for rating the symptoms is provided and a history of the child from parents, teachers, and sometimes, the child is taken [3‐9].

Guardiola et al. carried out a study in which they assessed the prevalence of ADHD in 484 pupils using two criteria: DSM-IV and neuropsychological criteria. The results showed that the incidence of ADHD using the DSM-IV criterion and the neuropsychological criterion were 18% and 3.5%, respectively [10]. Shabani et al. conducted another research wherein 428 elementary pupils were studied. According to the findings of this study, 4.9% of students (or 21 persons) have ADHD [11].

According to a survey conducted by Adonna et al., 8.7% of Nigerian students aged 7 to 12 had ADHD. In addition, the prevalence of attention-deficit subtypes was determined to be 4.9%, hyperactivity/impulsivity subtype 1.2%, and hyperactivity and attention deficit subtype 2.6% in this study [12]. According to research by Mahala et al., 18.1% of Tunisian youngsters suffer from ADHD [13]. ADHD was identified as the most common disorder among teenagers in another study by Oes Borg et al., which looked into the prevalence of chronic diseases among adolescents with mental disabilities aged 18 − 12 [14].

Another study on the prevalence of ADHD was undertaken by Maulov et al. A total of 210 Lebanese teenagers between the ages of 11 and 17 were studied. 10.2% of persons have ADHD, according to the findings of this study [15].

There are several inconsistencies across research on the prevalence of ADHD in children and adolescents, which are influenced by a variety of factors including diagnostic criteria variances. As a result, this study was conducted to determine the prevalence of ADHD in children and adolescents based on various diagnostic criteria and age groups.

This research looked at the prevalence of ADHD in children and adolescents by a systematic review and meta-analysis of cross-sectional data. The technique for carrying out the various stages of this study following the criteria of Guideline [16] was created and implemented.

In general, the criteria for selecting documents in systematic review and meta-analysis are within the framework of PICOS (Population, Intervention, Comparison, Outcomes, Study) [17]. In this study, the eligibility criteria are based on these conditions. Population: All people under the age of 18 were examined in this study. Exposure: Affected children and adolescents. Outcomes: Because of the differences in diagnostic criteria for ADHD and the prevalence of ADHD in different age and gender subgroups, the prevalence of ADHD was evaluated using DSM-V, DSM-IV, DSM IV-TR, and ICD10 criteria. Type of study: Cross-sectional observational studies were utilized to establish the disease’s prevalence. Other observational studies and methodologies, such as interventional review, were left out of the analysis.

The authors reviewed four electronic bibliographic databases, including PubMed, Scopus, WOS, and science direct, as well as any electronic publications printed before October 2020. Mesh terms and keywords used in review studies and previously published studies were utilized to choose the relevant keywords, which were chosen by one of the authors (MSH) and confirmed by the first and second authors. All keywords were selected in English. The search strategy in this study was designed using the terms “prevalence OR outbreak OR Global prevalence AND ADHD OR ADDH OR “Attention Deficit Hyperactivity Disorder”.

After using Endnote software to remove duplicate articles, an author (MSH) examined the study’s title and abstract. Excluded studies were those that did not meet the entry and exit criteria. The whole text of the paper was then examined by two writers (MSH and HGH) based on inclusion and exclusion criteria. These experiments were carried out independently and by blinding. Any comments given to affirm or reject the research were re-examined after the reviews were completed at this step. In the case of a disagreement, the study was confirmed using the third author’s (MM) reviews. If the full text of the study was not available, an email or research gate request was submitted to the paper’s lead author.

In this study, the STROBE checklist [17] was used as a tool to measure methodological quality in observational studies. According to the various criteria of this checklist, the title, abstract, introduction, method, and results of observational studies with a minimum score of 0 and a maximum score of 32 were considered separately. Studies with a score less than 16 were considered at high risk for bias. However, none of the studies were omitted due to low-quality or high risk of bias, and all studies were analyzed.

Information gathering was performed by two authors (MSH and HGH). This data was gathered using the methodology and findings of preliminary research. A form was created to extract information such as the first author’s name, year of publication, country, population examined by gender, diagnostic criteria, and diagnostic instruments. Data were extracted by (MSH) and reviewed by (MM).

Based on the I² test results (98.6) and the heterogeneity of the chosen research, a stochastic effects model was utilized to combine studies and estimate overall prevalence. Study heterogeneity can be caused by differences in sample size, sampling error, research year, and study location. The funnel diagram and Egger test at a significance level of 0.05 revealed that there was no publication bias in the distribution of data in the current investigation (P = 0.107). (Fig. 1).

ADHD prevalence was found to be 7.6% (95% confidence interval: 6.1–9.4%) in 53 studies with a total sample size of 96,904 participants who looked at children under the age of 12. The shape of the Forrest plot depicts the overall prevalence in the studies under consideration, with the midpoint of each line segment representing the prevalence in each study and the shape of a rhombus indicating population prevalence for the entire research (Fig. 2).

Based on the results of Table 2 and the methods of diagnosing hyperactivity in children under the age of 12, the DSM-IV‌ diagnostic criterion of ADHD prevalence was 7.7% (95% confidence interval: 6-9.9%).

Other criteria used to determine the prevalence of ADHD in children were DSM-IV-TR, DSM-III, DSM-V, DSM-IV, and ICD10, which were: 8.3% (95% confidence interval: 4.9–13.9%); 10.1% (95%confidence interval: 9-11.3%); 11.3% (95% confidence interval: 5.3–22.2%); and 4.4% (95%confidence interval: 2.4–8.2%), respectively (Table 2).

The prevalence of ADHD was also studied in Table 3. According to the findings of 24 studies on ADHD in children under the age of 12, the prevalence of the Inattentive subtype was 33.2% (95% confidence interval: 27.6–39.3%), Hyperactive impulsive subtype was 30.3% (95% confidence interval: 23.8.37.7%), and Combined ADHD was 31.4% (95% confidence interval: 24.6.39.1%) (Table 3).

A random-effects model was used to integrate the studies and estimate the shared prevalence based on the test results (I²: 97.8) and the heterogeneity of the selected research. Differences in sample size, sampling error, year, or study location can all contribute to the study heterogeneity The possibility of bias in the dissemination of data was determined using a funnel diagram and the Egger test at a significance level of 0.05 in the current study (P = 0.774). (Fig. 3).

In 25 studies involving teenagers aged 12 to 18, the prevalence of ADHD was determined to be 5.6% (95% confidence interval: 4-7.8%). The total prevalence in the studies examined is depicted in the Forrest plot, with the midpoint of each segment showing the prevalence in each study and the rhombus shape indicating the general population prevalence (Fig. 4).

Using the DSM-IV diagnostic criterion and based on the results of Table 4 and the methods of detecting hyperactivity in children aged 12–18 years, the ADHD prevalence was 7.1% (95% confidence interval: 4.9–10.1%). Other criteria used to determine the prevalence of ADHD in children included DSM-IV-TR, DSM-V, DSM-IV, and ICD10 which reported to be: 7.5% (95% confidence interval: 1.7–15.2%), 12.7% (95% confidence interval: 6.7–19.1%), and 1.7% (95% confidence interval: 1.1–4.5%), respectively (Table 4).

Table 5 looked at the prevalence of different kinds of ADHD. According to the findings of five studies involving children aged 12 to 18, the prevalence of Inattentive Subtype was 37.3% (95% confidence interval: 30–45.4%), Hyperactive-Impulsive Subtype was 23.1% (95% confidence interval: 13.2- 38.2%), and Combined ADHD was 31.1% (95% confidence interval: 15.6 -42.3%) (Table 5).

One of the limitations of this study is the high heterogeneity of studies in terms of age group. Since the purpose of this study was to measure the prevalence of children and adolescents separately, studies that report the prevalence of ADHD in children and adolescents combined were removed. Furthermore, because this study only looked at cross-sectional papers, it was impossible to track the participants and measure their symptoms over time.