CHICAGO (Reuters) - Highly publicized government warnings that antidepressants could cause suicidal thoughts in adolescents may have scared off parents and doctors alike, meaning fewer depressed children are being diagnosed, U.S. psychiatrists say.The warnings, starting in 2003, were followed by the biggest one-year spike in suicide rates in 15 years among U.S. children and young adults, according to figures released last week by the U.S. Centers for Disease Control and Prevention.