Researchers from the University of Michigan Depression Centre tested the drug's ability to help depression patients achieve total relief from their symptoms.
During the study 2,876 men and women who had a clear diagnosis of major depression, were given citalopram over a number of weeks, with the doses increasing over time.
The researchers found that women were 33 percent more likely to achieve a full remission of their depression, despite the fact that they were more severely depressed than the men when the study began.
The study shows that gender differences have important implications to the way the medication affects women compared with men.
"Other studies have suggested that there are differences between men and women in response to different antidepressants, but the evidence has been conflicting," said study's lead author Elizabeth Young, M.D., a professor and associate chair of psychiatry at the U-M Medical School and member of the Depression Center.
"This study is large enough, and we were able to control for enough complicating factors, that we feel confident there is a true difference. These results have clear implications for the clinical treatment of depression," she added.
Young and her colleagues, including Susan Kornstein, M.D., of Virginia Commonwealth University, and John Rush, M.D., formerly of the University of Texas Southwestern Medical Center at Dallas, conducted the analysis of data from men and women between the ages of 18 and 75, many of whom were being treated by primary care physicians and not psychiatrists.
All of the patients had been experiencing depression for years, with the average length of experience around 12 years.