The U.S. Food and Drug Administration (FDA) says it is "increasingly likely" that the stop-smoking drug Chantix can cause depression, suicidal thoughts and other psychiatric problems, the Associated Press reported Feb. 1.

People who want to use the drug to stop smoking should inform their doctor if they have a history of mental-health problems, FDA said. "Chantix may cause worsening of current psychiatric illness even if it is currently under control. It may also cause an old psychiatric illness to reoccur," the agency said.

Two weeks ago, Chantix maker Pfizer amended warnings on the drug to include information on the reported link between use of the stop-smoking drug and psychiatric problems. About four million prescriptions for Chantix have been written.