When Brown looked closely, though, she saw something else: trauma. Hyper-vigilance and dissociation, for example, could be mistaken for inattention. Impulsivity might be brought on by a stress response in overdrive.

“Despite our best efforts in referring them to behavioral therapy and starting them on stimulants, it was hard to get the symptoms under control,” she said of treating her patients according to guidelines for ADHD. “I began hypothesizing that perhaps a lot of what we were seeing was more externalizing behavior as a result of family dysfunction or other traumatic experience.”