Prevalence of ADHD
The prevalence of ADHD is approximately 7-8% in children and adolescents worldwide, with an estimated 2.5% prevalence in adults. 1
Childhood and Adolescent Prevalence
Global estimates indicate ADHD affects 7.2% of children worldwide based on meta-analytic data, though community-based samples report somewhat higher rates ranging from 8.7% to 15.5%. 1
In the United States, 9.4% of children aged 2-17 years have ever received an ADHD diagnosis, with current ADHD affecting 8.4% of this age group (representing 5.4 million children). 1
The best estimate for school-aged children is 5-10%, though published prevalence estimates range widely from 2% to 18% depending on diagnostic methods, informant choice, and case definitions used. 2, 3, 4
Preschool-aged children (2-5 years) have a prevalence of 2.4%, which is lower than school-aged children, likely reflecting both developmental factors and diagnostic challenges in this age group. 1
Adult Prevalence
Adult ADHD prevalence is estimated at 2.5%, though up to 70% of individuals with childhood-onset ADHD continue experiencing impairing symptoms into adulthood even if they no longer meet full diagnostic criteria. 1, 5
Between 1-6% of the general adult population continues to manifest appreciable ADHD symptoms, representing one- to two-thirds of the 3-10% of children originally diagnosed with ADHD. 6
Gender Disparities
Boys are more than twice as likely as girls to receive an ADHD diagnosis, primarily because hyperactive and disruptive behaviors (more common in boys) are more easily observable than inattentive symptoms (more common in girls). 1, 7
Girls with ADHD are more likely to present with predominantly inattentive symptoms and comorbid internalizing conditions (anxiety, depression), making their ADHD easier to miss and contributing to underdiagnosis in females. 7
Important Clinical Context
At least an additional 5% of children have substantial difficulties with overactivity, inattention, and impulsivity that fall just below the diagnostic threshold for full ADHD criteria, meaning the total burden of ADHD-type difficulties exceeds the formal diagnostic prevalence. 3
ADHD remains relatively under-recognized and underdiagnosed in most countries, particularly in girls and older children, meaning actual prevalence likely exceeds administrative (clinically diagnosed) prevalence. 3
The median age of diagnosis is 7 years, with approximately one-third diagnosed before age 6, and more than half of children are first diagnosed by primary care clinicians. 1, 8
Common Pitfalls
Prevalence estimates vary dramatically (2-18%) based on methodology, including who is asked (parent vs. teacher), how information is combined, and which diagnostic criteria are applied, so understanding the source of prevalence data is critical. 2, 4
Administrative prevalence (clinically diagnosed cases) underestimates true community prevalence because many children, especially girls with inattentive presentations, remain undiagnosed despite meeting criteria. 3
Failing to account for the high rate of subthreshold symptoms (an additional 5% beyond the 5-10% meeting full criteria) underestimates the total public health burden of ADHD-related impairment. 3