By: Rachael Rettner Published: 01/26/2015 10:52 AM EST on LiveScience Although a number of states have legalized marijuana for medical or recreational reasons in recent years, a leading group of U.S. pediatricians says it opposes such legalization, over concerns that these laws could be harmful to children. However, the group says that in some cases, some of the chemical compounds contained in marijuana could be used to treat children with debilitating diseases.