Few things agitate Robert F. Kennedy junior, America’s new health secretary, more than the rate of attention-deficit hyperactivity disorder (ADHD) among American children. And for good reason: one in nine children aged 3-17 years has been diagnosed with ADHD, two to three times the rate in other Western countries. On February 13th, Mr Kennedy’s first day in office, President Donald Trump put him in charge of a special commission tasked with working out, in the next 100 days, why so many American children have ADHD and other chronic conditions.