Jessica McCabe, creator of the YouTube channel “How to A.D.H.D.,” is not a doctor or medical professional. At 38, she’s had a variety of professions including stand-up comedian, actor and restaurant server. Through all those years, she has been learning about attention deficit hyperactivity disorder, which she was diagnosed with at the age of 12. Explaining that information is something she has done on her YouTube channel since 2016.