In late 2023, while taking a break at a conference in Baltimore, I shared a New York Times chart, based on detailed census records, with a colleague from the Centers for Disease Control and Prevention (CDC). The data showed a sharp rise, since 2020, in Americans reporting serious difficulty remembering, concentrating or making decisions, which are among the symptoms of attention deficit hyperactivity disorder (ADHD). Moments earlier, my colleague had presented a graph with a nearly identical curve – this one tracking the steep increase in adult stimulant prescriptions since 2020. By 2023, CDC data had confirmed that a record 7.8 per cent of American adults reported an ADHD diagnosis. Google searches for ‘ADHD’ surged, and TikTok videos tagged #ADHD had racked up more than 20 billion views. At the very most, we could be experiencing an adult ADHD epidemic in the United States. At the very least, ADHD was now suddenly very fashionable to the public. Yet, a third explanation is also possible – for better or worse, the ADHD diagnostic category might be becoming more inclusive.