Two recent studies (2010) suggest that ADHD could be potentially misdiagnosed in nearly 1 million children in the USA simply because they are the youngest in their kindergarten class.
The first study by Dr Todd Elder, assistant professor of economics at Michigan State University, looked at a sample of nearly 12,000 children from the Early Childhood Longitudinal Study Kindergarten Cohort (June 2010). His results found that “the youngest children were significantly (60%) more likely to be diagnosed with ADHD and to be prescribed behavior-modifying stimulants such as Ritalin than their older classmates”.
According to Dr Elder, “the “smoking gun” was that the diagnoses depended on the children’s age relative to classmates and the teacher’s perceptions of whether they had symptoms”. He continued to say that there was “a big difference between a five-year-old and six- year old” and urged teachers and medical practitioners to take that into account when evaluating children for ADHD.
Furthermore Elder stated that, “medicating such children inappropriately was a cause for concern not just because of the effect of long term stimulant use on their health but also because it costs a lot of money and he estimated about 320 to 500 million US dollars is being wasted on unnecessary medication of young children for ADHD, of which 80 to 90 million is funded by Medicaid”. Finally, his study estimated that the overall misdiagnosis rate in the USA is approximately 1 in 5. This suggests that around 900,000 of the 4.5 million children currently diagnosed with ADHD have been misdiagnosed.
The second study (August 2010) which included researchers from North Carolina (NC) State University, Notre Dame and the University of Minnesota concurred with conclusions from the Elder study. Dr Melinda Morrill, co-author of the study and assistant professor of economics at NC State, found that children who were born after the cutoff date for kindergarten were 25% less likely to receive a diagnosis for ADHD when compared to their “relatively young-for-grade” peers” (i.e. those born just before the cutoff date). The study concluded that misdiagnosis in five year olds was due to lack of maturity and not because of “underlying biological or medical reasons,” (Morrill).
Elder, T.E (2010): “The importance of relative standards in ADHD diagnoses: Evidence based on exact birth dates.” Journal of Health Economics, In Press, Corrected Proof, Available online 17 June 2 010 DOI:10.1016/j.jhealeco.2010.06.003
Evans, W.N, Morrill. M.S., Parente, S.T. (2010): “Measuring Inappropriate Medical Diagnosis and Remedy in Survey Data: The Case of ADHD among School-Age Children.” Journal of Health Economics, In Press, Accepted Manuscript, Available online 4 August 2010.