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A groundbreaking study from the Salk Institute highlights a potential new role for antidepressants in immune defense.
Antidepressants like Prozac (fluoxetine) are widely prescribed to treat mental health disorders, but new research suggests they could also help protect against severe infections and life-threatening sepsis. Scientists at the Salk Institute have discovered how these drugs regulate the immune system, providing insights that may lead to new life-saving treatments and better preparedness for future pandemics. The study was published in Science Advances on February 14, 2025.
The findings align with previous research showing that users of selective serotonin reuptake inhibitors (SSRIs) like Prozac experienced less severe COVID-19 infections and were at a lower risk of developing long COVID. Additionally, earlier studies indicated that fluoxetine effectively protected mice against sepsis—a dangerous immune overreaction to infection that can cause multi-organ failure or death.
Fluoxetine’s Role in Infection Defense
Salk researchers sought to understand the biological mechanisms behind fluoxetine’s ability to boost the immune response. Their experiments showed that mice pretreated with fluoxetine were protected from sepsis, organ damage, and death following bacterial infections.
The team found that fluoxetine has antimicrobial properties that help reduce bacterial growth, leading to less severe infections. Additionally, fluoxetine increased levels of IL-10, an anti-inflammatory molecule, which helped prevent sepsis-induced metabolic disturbances and protected vital organs. Importantly, these protective effects were found to be independent of fluoxetine’s influence on serotonin levels, a key factor in its mental health benefits.
Professor Janelle Ayres, lead researcher and holder of the Salk Institute Legacy Chair, explained the significance of these findings: “Most medications we have in our toolbox kill pathogens, but we were thrilled to find that fluoxetine can also protect tissues and organs. It’s essentially playing both offense and defense, which is ideal.”
Potential Implications for Human Health
The study’s findings pave the way for future clinical trials to explore fluoxetine’s potential in treating sepsis and other infections in humans. The researchers plan to investigate appropriate dosing regimens and assess whether other SSRIs may have similar effects.
“Fluoxetine, one of the most prescribed drugs in the U.S., is showing dual protective and defensive effects,” said Ayres. “Finding such properties in an already-approved drug is an exciting step toward developing new solutions for life-threatening infections.”
The study was co-authored by Robert Gallant, Karina Sanchez, Emeline Joulia, and Christian Metallo from the Salk Institute, along with Jessica Snyder from the University of Washington.
Disclaimer:
While these findings are promising, further research and clinical trials are needed to determine the safety and effectiveness of fluoxetine and other SSRIs in treating infections and sepsis in humans. Patients should not use antidepressants for infection treatment without consulting their healthcare provider.
