Editorial: Youngest Kids in Class and Their Long-term Outcomes

In this issue of the JAACAP, Kuntsi et al.⁷ reports from the Swedish national registers to analyze the outcomes of almost 300,000 individuals who were relatively young or relatively old in class (ie, born in the 2 months before and after the national cut-off for school entrance in Sweden). Four events were measured between 15 and 23 years of age: low educational achievement, a conviction of any crime, substance use disorder, and depression. As predicted, young relative age was a risk factor for ADHD (with an odds ratio of 1.7), which in turn was a risk factor for all 4 outcomes considered (with odds ratios of 3.5-5.2). The novelty of their analyses, however, was to evaluate the additive effects of relative young age beyond ADHD on negative long-term outcomes. For the first time, Kuntsi et al.⁷ demonstrated that children with ADHD who are the youngest in their class are at increased risk for lower educational achievement and receiving a diagnosis of substance use disorder when compared to children with ADHD who are the oldest in their class.