I am neither a pediatrician nor a specialist, but I know in my area doctors have advertised themselves as dermatologists without having had any formal derm training, and I've known internists that called themselves cardiologists as they had special interest and background in cardiology. I think you can call yourself whatever you want, especially in your case since it's a true statement you specialize in pediatric/adolescent ADHD and mood disorders. You just can't put as many acronyms after your name.

Randy
Solo FP
Iowa