Case Scenario

An eight-year-old boy presents to your office for his annual well-child examination. His grandmother is his legal guardian and is concerned because he has difficulty finishing his homework and gets distracted easily by noises at home. His second-grade teacher informed the grandmother that the patient performs significantly below grade-level expectations. His medical history is notable for prematurity (28 weeks of gestation) and grade 2 intraventricular hemorrhages. His grandmother asks you to prescribe a chewable long-acting stimulant such as the one his cousin takes to improve his school performance. You provide Vanderbilt assessment forms (https://www.nichq.org/sites/default/files/resource-file/NICHQ-Vanderbilt-Assessment-Scales.pdf) for the patient’s grandmother and teachers to complete.

Clinical Commentary

EPIDEMIOLOGY

Rates of attention-deficit/hyperactivity disorder (ADHD) have increased over the past several decades (Figure 1).¹ A nationwide, population-based, cross-sectional survey found that ADHD rates increased by 67%, from 6.1% in 1997 to 1998 (when the survey first included questions on ADHD) to 10.2% in 2015 to 2016.² Similar increases have been observed in other Westernized countries.^3,4 During this period, there was a concordant increase in the use of stimulants.^1,5 In contrast to the increase in ADHD diagnoses, the frequency and severity of ADHD symptoms have stayed relatively constant.^3,6 It is unknown if the increase in ADHD diagnoses and the use of stimulants represent changing neurobiology, improved detection, expanding definitions of disease, the impact of pharmaceutical marketing,⁷ or other factors.

DEFINITIONS OF DISEASE

There is evidence that ADHD is “dimensional,” meaning that hyperactivity, inattentiveness, and impulsiveness exist on a continuum with normal behavior.⁸ The cutoffs that define abnormal are subject to interpretation and change. Each subsequent version of the Diagnostic and Statistical Manual of Mental Disorders (DSM) has expanded the definition of ADHD.⁹ In 2013, the DSM-5 lowered the percentage of criteria needed for diagnosing ADHD in older adolescents and increased the age by which behaviors must have first appeared (from seven to 12 years).¹⁰ Proponents of the new criteria contend that these changes were made out of concern for the previous underdiagnosis of ADHD; however, critics point to the high proportion (78%) of the DSM-5 ADHD Working Group members with financial conflicts of interest that may have influenced the expansion.¹¹

The significant variation in stimulant prescriptions across states suggests that factors beyond underlying neurobiology may dictate diagnosis and treatment. In Hawaii, 1 in 100 children is prescribed stimulants, whereas the rate is nearly 1 in 7 in Alabama.¹² Geographic variations may be due to differences in clinician characteristics, such as knowledge, training, or attitudes, or differences in parental expectations or interpretations of child behavior. Clinician subjectivity may also play a role. In a case vignette study, clinicians were twice as likely to diagnose ADHD in a child described as male compared with a child described as female with the same behavior.¹³

CHILDREN YOUNG FOR THEIR GRADE

There are significantly higher rates of ADHD in children who are young for their school grade.^14,15 One study found that ADHD is more than twice as likely to be diagnosed in the youngest month compared with the oldest month of age eligibility.¹⁴ These findings suggest that comparisons across children in the same grade play a role in the diagnosis of ADHD and that relative immaturity can be misdiagnosed as ADHD.

RACIAL DISPARITIES

Although older studies found that ADHD is more common in self-identified White children,^16,17 more recent studies have shown that Black children are equally if not more likely to be diagnosed with ADHD.^18,19 It is unclear what is leading to these temporal trends. Biases and variable interpretations of behavior may play a role because questionnaires used to diagnose ADHD rely on parental and teacher reports of a child’s behavior.^20–22