I appreciated Robert L. Ehrlich Jr.'s thoughtful letter to his son about marijuana ("A letter to my son on marijuana," Feb. 16). In our communities, our first response is to "warn" youth. As a certified prevention specialist, I can tell you we understand youthful brains more now. We realize despite our best messages, modeling and intentions, a young person is often unable to seriously consider any long-term consequences of their actions. Our time could more often be spent informing parents, coaches, teachers, anyone who works with youth about the health and mental health consequences of marijuana use. Research clearly shows when a population perceives a substance isn't harmful, the levels of use go up. [continues 68 words]