Worrying about teen drinking and drug use has kept many a parent up at night. With marijuana becoming increasingly available and legal in some parts of the country, the question has taken on new urgency: If teens are going to experiment, which is safer, booze or pot? "The first answer always has to be neither," Dr. Aaron Carroll, a professor of pediatrics at Indiana University School of Medicine, told CBS News. But then he acknowledges they're not exactly equivalent -- and he considers alcohol much more dangerous. Carroll wrote a provocative piece for the New York Times exploring what's known...