The persistence of a gender difference in response to the drug — even after the researchers accounted for many complicating factors — suggests that there’s a real biological difference in the way the medication affects women compared with men.
The reasons for that difference are still unclear, but further studies are now examining hormonal variations that may play a role.
The study involved citalopram, a commonly used antidepressant that is available both as a generic drug and under the brand name Celexa.
Researchers from the University of Michigan Depression Center and their colleagues from around the country tested the drug’s ability to help depression patients achieve remission, or total relief from their symptoms, in a multi-year study called STAR*D.
The gender differences emerged from a detailed analysis of data from 2,876 men and women who had a clear diagnosis of major depression, and took citalopram over a number of weeks, with the doses increasing over time.
In the end, women were 33 percent more likely to achieve a full remission of their depression, despite the fact that women in the study were more severely depressed than the men when the study began.
The study showed no differences between men and women in side effects, the amount of time that patients stuck to taking the drug, or the amount of time it took for them to achieve remission of their symptoms.
The new findings, which represent the largest and most rigorous analysis ever of gender differences in response to an antidepressant, are published online in the Journal of Psychiatric Research.
Elizabeth Young, M.D., a professor and associate chair of psychiatry at the U-M Medical School and member of the Depression Center, is the study’s lead author.
“Other studies have suggested that there are differences between men and women in response to different antidepressants, but the evidence has been conflicting,” she says.
“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.”
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.
The study was funded by the National Institute of Mental Health.
Source: University of Michigan