To what extent are ADHD medications insufficiently used to address properly diagnosed ADHD? To what extent are they misused by persons who are either undiagnosed or improperly diagnosed?
In search of answers, an international team of researchers from Brazil, the United Kingdom, and the United States conducted a systematic review of the peer-reviewed literature and a meta-analysis of studies from four continents – South America, North America, Europe, and Australia.

The benchmarks set for proper ADHD diagnosis were any of the following:
·        Criteria established in the Diagnostic and Statistical Manual of Mental Disorders (DSM)or the International Statistical Classification of Diseases and Related Health Problems (ICD), confirmed by validated diagnostic instruments or clinical interviews.
·        Use of validated ADHD symptom scales with pre-specified thresholds.
·        Participants or caregivers affirming ADHD diagnosis by a physician.

Medications reviewed were those recommended by the majority of the international guidelines– both stimulant(methylphenidate, dexmethylphenidate, amphetamines), and non-stimulant (atomoxetine).
The team excluded studies relying on the insurance health system and third-party reimbursement datasets because the focus was on rates of ADHD medication use in the entire population rather than among individuals searching for treatment.
A meta-analysis of18 studies with a total of 3,311 children and adolescents properly diagnosed with ADHD in seven countries on four continents (Canada, United States, Australia, Brazil, Netherlands, England, Venezuela) found an overall pharmacological treatment rate of only 19%. There was considerable variation, with the highest treatment rates in the United States (frequently over 40%) and the lowest treatment rates in Brazil, Venezuela, and Canada (under 10%). There was no sign of publication bias.
A second meta-analysis pooled 14 studies with a total of 29,559 children and adolescents without a proper diagnosis of ADHD in five countries on four continents (United States, Canada, Venezuela, Australia, Netherlands). Roughly 1% were using ADHD medications. Again, there was considerable variation, with the highest rates of medication misuse being reported in the United States and Venezuela (3-7%). Again, there was no sign of publication bias.
The authors cautioned, “it is important to note that even though the data collected constitute the most comprehensive evidence available in the literature and response/completion rates observed are acceptable, it does not constitute a world representative sample.” Also, the predominance of samples from prosperous countries “most certainly inflates the treatment rates due to the exclusion of a large proportion of the world population with significant financial, cultural, and health access barriers to ADHD treatment.”
They concluded, “Despite these limitations, our meta-analysis provides evidence for substantial undertreatment of children and adolescents affected by ADHD in different countries. This is a relevant public health issue worldwide since ADHD under treatment is associated with known negative outcomes in education, healthcare, and productivity systems. At the same time, we found evidence of overtreatment/misuse in individuals without a formal ADHD diagnosis. This practice might expose individuals to undesirable side effects of medications, increased risk of medication misuse, and unmeasured costs for the health care system.”