HMM: Youngest in class twice as likely to take ADHD medication. “A likely cause of the late birth date effect is that some teachers compare the maturity of their students without due regard to their relative age, resulting in higher rates of diagnosis among younger class members. . . . The late birth date effect is not the only factor creating unease about ADHD. Multiple studies, including the WA study, have established boys are three to four times more likely to be medicated for ADHD. If, as is routinely claimed, ADHD is a neurobiological disorder, a child’s birthdate or gender should have no bearing on their chances of being diagnosed.”