Attention-deficit/hyperactivity disorder severity, diagnosis, & later academic achievement in a national sample.

Although 11% (6.4 million) American children are diagnosed with attention deficit/hyperactivity disorder (ADHD), the role of ADHD severity in shaping the association between ADHD diagnosis and academic achievement is not understood. Using a nationally-representative sample of 7830 U.S. kindergartners from the Early Childhood Longitudinal Study-Kindergarten Cohort, we use regression and propensity score matching to compare diagnosed (N = 350) and undiagnosed children who are cognitively, behaviorally, and demographically similar. Diagnosed children with less severe ADHD-related behaviors on average scored lower in reading (-0.30 SD) and math (-0.22 SD) than their undiagnosed peers - a difference two times larger than that between diagnosed and undiagnosed children with more severe ADHD-related behaviors. Pharmacological treatment did not attenuate most of this "diagnostic labeling effect" among children with less severe ADHD-related behaviors. Negative factors associated with an ADHD diagnosis may outweigh potential benefits for achievement among children with less severe ADHD-related behaviors, even those receiving treatment.