Antidepressant medication linked with increased risk of superbug infection

Certain types of antidepressants may put people at an increased risk for developing a deadly superbug infection, a new study suggested.

Researchers from the University of Michigan revealed that individuals who suffer from depression and those taking antidepressants such as mirtazapine and fluoxetine had a much higher chance of contracting Clostridium difficile infection (CDI) – a life threatening infection that can cause severe diarrhea and inflammation of the colon.

One of the most common infections acquired by patients at hospitals, C. difficile has been occurring with more and more frequency, resulting in the deaths of 14,000 individuals in the United States each year, according to the Centers for Disease Control Prevention.

The rise of CDIs is often attributed to the overuse of antibiotics in health care facilities.  While these medications destroy harmful bacteria responsible for illness, they also destroy protective bacteria in the gastrointestinal (GI) tract – leaving individuals vulnerable to C. difficile bacteria lurking on foods, surfaces and objects contaminated by infected feces.

“People knew (C. diff) was associated with hygiene factors, so it’s important to wash your hands and keep things clean (when in the hospital),” lead author Dr. Mary Rogers, research director of the patient safety and enhancement program at the University of Michigan in Ann Arbor, told “But I was also given the charge of looking at other patient-related factors so that maybe we could predict and prevent transmission.”

Previous research had implicated other medications in the increase of CDIs, so Rogers and her team decided to investigate the potential relationship between widely-used antidepressants and C. difficile.

First, scientists compared C. difficile infections in people with and without depression, even looking at those who simply reported depressive symptoms.

“What popped out was that people who have a diagnosis of major depression or depressive disorder – and also people who had reported feeling sad or having emotional, nervous psychiatric problems – were more likely to have Clostridium difficile infection,” Rogers said.

Those with major depression had a 36 percent higher chance of having a CDI than those without depression.  Older, more socially isolated individuals were also at a greater risk for infection: Widowed Americans had a 54 percent increased risk of CDI than their married counterparts, and living alone increased risk by 25 percent.

In the second portion of the study, Rogers and her team looked more specifically at the relationship between antidepressant medications and CDIs.  While most of the 12 antidepressant medications tested did not affect an individual’s CDI risk, mirtazapine (also called Remeron) and fluoxetine (also called Prozac and Sarafem) were associated with a doubled chance of contracting the infection.

Rogers said the findings shouldn’t deter people from taking prescribed antidepressant medication, but the association does call for more research into this connection.  The team theorized that antidepressants might destroy beneficial GI bacteria, similar to how antibiotics operate.

“The link with the antidepressants, we were thinking they too affected the GI system in some way,” Rogers added. “Fluoxetine can result in diarrhea, and sometimes those anti-depressants affect the GI system too, so possibility their affecting the healthy bacteria in the gut.  That might influence whether you’re at risk of C. diff infection.”

Rogers also noted that dietary alterations might affect the bacteria in a person’s GI tract, making them more prone to CDI.  This could potentially explain why depressed and socially isolated individuals have a higher risk of contract C. difficile, as appetite changes are a common symptom of depression.

“There’s a kind of a nexus between the brain and the gut that people don’t think about very much,” Rogers said. “But I think it’s more important than it might first appear that what happens in your gut might sometimes affect problems with brain function and different mental conditions you have – and visa versa.  It’s an interesting area of research, and we’re hoping we can look into it a bit more.”

The research was published in BioMed Central’s open access journal BMC Medicine.