More Americans are using the hemp (or marijuana) extract on their kids, but experts aren’t sold on its efficacy...“When you’re desperate, you want options,” said John Mitchell, clinician at Duke ADHD Clinic in Durham, N.C. “I’m a parent myself. I get it.” But, he cautioned, for now the enthusiasm is running ahead of the science. “I’m very hesitant to say anything promising about it. It’s an open question.”