Some Antidepressants May Increase A Person's Risk Of Developing CDI

Depression medications mirtazapine and fluoxetine may increase a person’s risk of developing Clostridium difficile infection (CDI) by as much as two-fold, according to a new study published Tuesday in the journal BMC Medicine.

The idea for the study was first hatched when the researchers came across an article published by the Centers for Disease Control and Prevention (CDC) showing that patients with CDI were three times more likely to have psychoses and depression, according to Medscape Medical News.

Later, the scientists found a study conducted by a group of Canadian pharmacists that found antidepressants were strongly related to CDI; however, the study was more focused on proton pump inhibitors than antidepressants.

“Both of these observations were essentially buried as minor findings in the medical literature, but as we reviewed these studies and looked at our own data, we began to see a pattern, and so we decided to follow this trail,” lead author Mary A.M. Rogers told the medical news outlet.

Sure enough, an initial study that included nearly 17,000 showed that people with major depression had a 36 percent increased risk of developing CDI compared those without.

Moreover, widowed participants showed a 54 percent increase in their chance of developing CDi than married individuals. Those simply living alone experienced a 25 percent increase in risk.

In their second study, researchers narrowed their focus on a possible association between antidepressant medication and CDI acquired in hospitals.

This study included just over 4,000 participants and of the 12 antidepressants that were tested, only mirtazapine and fluoxetine increased the risk for CDI.

In all, patients who received the former were twice as likely to contract CDI than those who did not. Furthermore, for each dose of the medication taken, researchers found the odds of testing positive for the infection increased by 8 percent.

Those receiving fluoxetine also had a near two-fold increase in cases of CDI while the odds for testing positive increased by 6 percent for every dose received.

The reason for this, hypothesizes Rogers, has to do the bacterial makeup of the gut due to the fact that the infection occurs when there is less diversity in gut bacterial communities and, based on previous studies, scientists know that patients with depression often have different bacterial communities than those without.

While not sure why this is, Rogers says inflammation may play a role, or perhaps changes in the diet.

“The use of mirtazapine occasionally results in gastrointestinal side effects, such as increased appetite and weight gain,” she said. “This implies a change in dietary intake, which we know affects the bacterial composition of the gut. Fluoextine also at times results in gastrointestinal problems, as one systematic review showed that people who used fluoxetine were more likely to experience diarrhea, vomiting, nausea, and weight loss than those receiving other antidepressants.”