New research raises concerns that Attention-Deficit/Hyperactivity Disorder (ADHD) is being overdiagnosed in some countries, including the United States. The study, published in the Journal of Cross-Cultural Psychology, examined parental reporting of ADHD symptoms in four different countries.

ADHD, which is often treated with prescription medication, is one of the most commonly diagnosed behavioral disorders in children. The disorder has a worldwide prevalence estimate of about 5% — but the prevalence of ADHD is significantly higher in countries like the United States and Australia.

“My research focuses on the impact of socio-cultural factors on neurodevelopmental disorders,” said study author Beatriz MacDonald, an assistant professor at the University of New Mexico Health Sciences Center and a clinical neuropsychologist at University of New Mexico Hospital.

“As an international researcher and clinician, I often hear the statement that ADHD is overdiagnosed in the United States; therefore, we wanted to examine if this was the case. Were higher rates of ADHD in the United States in comparison to other countries the result of a cultural difference in the perception of symptoms, an actual etiological difference between countries, or some combination of the two explanations?”

For their study, the researchers examined data from the International Longitudinal Twins Study, which included 974 pairs of twins from the United States, Australia, Norway, and Sweden, who were followed from preschool-age into early school age. The study included parental ratings of the 18 symptoms of ADHD, as well as several tests that measured various aspects of cognitive ability.

At the end of preschool, 10% of the American children and 11% of the Australian children met the criteria for ADHD based on their parents’ reports — but only 4% of the Scandinavian children did. However, the researchers found that the children from Norway and Sweden performed the worst on the cognitive tests, despite having the lowest ADHD severity ratings.

“Although ADHD is a behavioral diagnosis, a comprehensive assessment is necessary to ensure that the child meets the diagnostic criteria of ADHD,” MacDonald told PsyPost.

“Parental reporting of symptoms is only one component of an assessment. It is recommended that an assessment include a clinical interview with caregivers, collateral information, standardized questionnaires, objective measures of attention, and assessing other cognitive domains.”

“Inattentive, hyperactive or impulsive behaviors are also seen in children with other psychiatric disorders, such as anxiety or posttraumatic stress disorder, so ruling out other diagnoses is necessary. When conceptualizing a case, a culturally informed model takes all these factors into consideration,” MacDonald said.

But the study — like all research — includes some caveats.

“The study used the ADHD diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-R), which is an older version. The next step would be replicating the study using the new DSM-5 criteria to diagnose ADHD, which has been described as having a more lenient threshold in certain age groups,” MacDonald said.

“It is imperative to know if the DSM-5 changes have an impact in the use of parental reporting of ADHD symptoms, which is a necessary component in making a clinical diagnosis. Another question to explore is if mental health stigma may also influence the over- or under-reporting tendency of behavioral and emotional symptoms between countries. The denial of mental health problems and the reluctance to access services is often the result of stigma.”

“I completed this study while I was a doctoral graduate student at the University of Denver under the research mentorship of Dr. Bruce F. Pennington. The Principal Investigators (PIs)/researchers, Drs. Richard K. Olson, Stefan Samuelsson, and Brian Byrne, developed this International Longitudinal Twin Study and followed participants from preschool to the end of 4th grade,” MacDonald added.

The study, “Cross-Country Differences in Parental Reporting of Symptoms of ADHD“, was authored by Beatriz MacDonald, Bruce F. Pennington, Erik G. Willcutt, Julia Dmitrieva, Stefan Samuelsson, Brian Byrne, and Richard K. Olson.