In his latest post, blogger Neuroskeptic critiques a recent challenge to the "immaturity hypothesis" and points to what may be a common misdiagnosis of ADHD in younger children, who seem relatively immature to their older classmates in the same grade. Earlier this year, a Canadian study of ADHD rates in almost a million children found that children born later in the year were more likely to be diagnosed with ADHD.
LinkThis is strong support for the "immaturity hypothesis" - the idea that some children get a diagnosis of ADHD because they're younger than their classmates at school, and their relative immaturity is wrongly ascribed to an illness.