WASHINGTON — The Federal Aviation Administration yesterday banned pilots and air traffic controllers from using a popular anti-smoking drug after a study found that it had apparently contributed to auto accidents and other mishaps that posed risks to both users and others.

The drug, marketed as Chantix, has been hailed as an innovative treatment to help smokers quit. But a study by a medical safety group linked it to a variety of serious side effects, including loss of consciousness and seizures, and prompted the FAA to act.

The aviation agency had approved the drug last summer, before federal safety regulators began investigating reports of serious psychiatric problems, including suicidal behavior, sharp shifts in mood, and vivid nighttime episodes some patients call “Chantix dreams.”

A new warning came from a report by the Institute for Safe Medication Practices, based on an analysis of “adverse events” reports submitted to the Food and Drug Administration.

“We have immediate safety concerns about the use of (Chantix) among persons operating aircraft, trains, buses, and other vehicles, or in other settings where a lapse in alertness or motor control could lead to massive, serious injury,” the study said.