MONTREAL, May 28 (UPI) -- A drug may reduce the brain's ability to recall negative emotions, challenging the theory that memories cannot be modified, researchers in Canada say.

Lead author Marie-France Marin, a doctoral student at Louis-H. Lafontaine Hospital and the University of Montreal, and Dr. Sonia Lupien, director of the Center for Studies on Human Stress at Louis-H. Lafontaine Hospital and professor at the University of Montreal, say recalling painful memories while taking metyrapone lessens the brain's ability to re-record the negative emotions associated with bad memories.


"Metyrapone is a drug that significantly decreases the levels of cortisol, a stress hormone that is involved in memory recall," Marin says in a statement.

The study involved 33 men learning a story composed of neutral and negative events. Three days later, they were divided into three groups -- one received a single dose of metyrapone, the second received two doses, while the third were given a placebo.

The study participants were asked to remember the story, and their memory performance was evaluated four days later.

"We found that the men in the group who received two doses of metyrapone were impaired when retrieving the negative events of the story, while they showed no impairment recalling the neutral parts of the story," Marin says in a statement.

The findings are published online in the Journal of Clinical Endocrinology & Metabolism.