Antidepressants appear to double the risk of suicidal thoughts and actions in children who take them, US regulators said in a study outlining the methodology used for a 2004 report that led to warnings on drugs including Eli Lilly & Co.'s Prozac and GlaxoSmithKline's Paxil.

The Food and Drug Administration first presented the findings, detailed yesterday in the Archives of General Psychiatry, to an advisory panel in September 2004. The agency followed with a requirement that makers of antidepressants warn patients and doctors. The warning led to a 20 percent drop in antidepressant prescriptions for children between March 2004 and June 2005, according to Psychiatric News, the newspaper of the American Psychiatric Association.