Serotonin is best known for its role in mood, sleep, and emotional wellbeing, but growing evidence suggests it may also influence how heart valves age and become damaged. New research indicates that altered serotonin signaling—particularly when activity of the serotonin transporter is reduced—may accelerate changes in heart valves that are already vulnerable to disease.
Researchers from Columbia University, Children’s Hospital of Philadelphia, the University of Pennsylvania, and the Valley Hospital Heart Institute have led a series of studies investigating this connection. Their findings, supported by major U.S. research funding agencies, have prompted researchers to further explore how antidepressant medications, genetics, and serotonin biology may interact in heart valve disease.
Understanding Mitral Valve Disease
The mitral valve separates the heart’s left atrium from the left ventricle and normally closes tightly with every heartbeat to prevent blood from flowing backward. In degenerative mitral regurgitation, the valve gradually becomes thickened, distorted, or weakened, allowing blood to leak in the opposite direction and forcing the heart to work harder to maintain normal circulation.
Many people with early degenerative mitral regurgitation experience few or no symptoms. As the condition progresses, however, they may develop fatigue, shortness of breath, irregular heart rhythms such as atrial fibrillation, and eventually heart failure. Although medications can help manage symptoms, they cannot reverse structural damage to the valve, making surgery the primary treatment when leakage becomes severe.
Current clinical guidelines recommend surgery based largely on symptoms, heart function, and imaging findings. The new research suggests that biological and genetic factors related to serotonin signaling may also help explain why disease progression varies between individuals.
How Serotonin and SSRIs Are Connected
Serotonin communicates with cells by binding to specific receptors on their surface. After transmitting its signal, serotonin is normally removed through a protein called the serotonin transporter, or SERT, which carries serotonin back into cells in a process known as reuptake.
Selective serotonin reuptake inhibitors (SSRIs), commonly prescribed to treat depression and anxiety, work by reducing the activity of SERT. This allows serotonin to remain available for longer, enhancing its effects within the brain. Medications such as fluoxetine and sertraline belong to this widely used class of antidepressants.
Because SSRIs intentionally reduce SERT activity, researchers questioned whether the same biological mechanism might also affect heart valve cells, particularly in people whose valves are already undergoing degenerative changes. Importantly, the concern focused on valves with existing disease rather than healthy heart valves.
Findings From Patients and Laboratory Studies
The research team analyzed medical records from more than 9,000 people who underwent mitral valve repair or replacement for degenerative mitral regurgitation. They also examined approximately 100 valve tissue samples to investigate molecular changes related to serotonin signaling.
Patients taking SSRIs underwent mitral valve surgery at younger ages, on average, than patients who were not using these medications. However, the researchers emphasize that this association does not establish that antidepressants caused faster disease progression, as other medical and lifestyle factors may also have contributed.
To further investigate the biological mechanisms, the team conducted laboratory and animal studies. Mice genetically engineered to lack the SERT gene developed thicker mitral valves, while healthy mice receiving high doses of SSRIs also showed abnormal valve thickening. These findings supported the possibility that reduced SERT activity may influence valve remodeling under certain conditions.
Genetic Variants May Influence Risk
The researchers also examined a genetic region known as 5-HTTLPR, which helps regulate SERT activity. Different versions of this genetic sequence influence how much serotonin transporter is produced by cells.
Among patients with degenerative mitral regurgitation, those carrying two copies of a specific long variant underwent valve surgery more frequently than individuals with other genetic profiles. Laboratory experiments also showed that valve cells carrying this genetic variant responded more strongly to serotonin stimulation by producing greater amounts of collagen, a structural protein that can contribute to tissue thickening and stiffness.
These cells also appeared more responsive to fluoxetine, suggesting that a combination of genetic susceptibility, reduced transporter activity, and increased serotonin signaling might accelerate structural changes in already damaged valves.
Could Genetic Testing Become Useful?
Based on these findings, the researchers proposed that testing for 5-HTTLPR variants might eventually help identify patients with degenerative mitral regurgitation who are at greater risk of faster disease progression, particularly if they require SSRI treatment. Such testing could potentially be performed using blood samples or cheek swabs.
In theory, identifying higher-risk individuals could allow cardiologists to monitor disease progression more closely or consider surgical intervention earlier. However, researchers emphasize that this approach has not been incorporated into current clinical guidelines.
Additional randomized clinical trials and long-term studies will be necessary to determine whether genetic testing improves patient outcomes beyond existing approaches based on symptoms and cardiac imaging.
What Current Evidence Shows—and What It Does Not
Importantly, the researchers did not find evidence that typical SSRI treatment damages healthy mitral valves. In valve tissue obtained from donors without existing valve disease, reduced SERT activity alone did not appear sufficient to initiate degeneration.
Instead, the current evidence suggests that altered serotonin signaling may become clinically relevant primarily when valve tissue has already undergone structural damage. Under these circumstances, genetic factors and reduced SERT activity may increase the tissue’s sensitivity to serotonin.
Researchers and clinicians stress that patients should not discontinue antidepressant medications based on these findings alone. For most individuals, SSRIs remain safe, effective treatments, and untreated depression or anxiety can also have significant consequences for overall health.
New Research Expands the Picture
Since the initial publication of these findings in 2023, additional studies have further explored serotonin’s possible role in heart valve remodeling. Much of this work has been conducted in laboratory models and animals, meaning its direct relevance to patient care remains uncertain.
A 2024 study found that reduced SERT activity increased susceptibility to fibrotic changes not only in heart valves but also within the muscle of the left ventricle. The researchers identified the serotonin receptor HTR2B as a potentially important driver of this tissue remodeling.
Valve cells appeared particularly responsive to serotonin stimulation, raising the possibility that therapies targeting specific serotonin receptors might eventually protect heart valves while preserving serotonin’s beneficial functions elsewhere in the body.
Serotonin May Also Affect the Aortic Valve
Researchers have also begun investigating serotonin’s role in aortic valve disease. A 2025 clinical study involving 38 patients with severe aortic stenosis found higher blood levels of serotonin and one of its primary breakdown products compared with matched control participants.
Aortic stenosis develops when the valve controlling blood flow from the heart becomes progressively thickened and narrowed, making it increasingly difficult for the heart to pump blood throughout the body. Although the findings suggest serotonin signaling may contribute to this process in some individuals, the study’s relatively small size and single-time-point design mean it cannot determine whether elevated serotonin causes disease progression or simply reflects other cardiovascular changes.
Experimental Drug Targets Show Early Promise
In early 2026, researchers reported additional evidence linking reduced SERT activity to fibrosis in the aortic valve. Studying valve tissue from 66 patients undergoing surgery for severe aortic stenosis, they observed reduced SERT expression together with increased serotonin receptor activity compared with healthy donor tissue.
Using a mouse model, the researchers tested an experimental drug that blocks the HTR2B receptor. In animals with early fibrotic changes, the treatment appeared to preserve valve structure and improve measures of blood flow.
Experiments using human valve cells produced similar findings, suggesting that reduced SERT activity may amplify harmful responses to serotonin. However, the HTR2B blocker remains an experimental compound, and serotonin-targeted therapies for heart valve disease are still far from clinical use.
Meta-Analysis Suggests an Association
A systematic review and meta-analysis published in 2026 combined data from clinical studies investigating medications that modify SERT activity, including SSRIs and related drugs. Overall, exposure to these medications was associated with increased odds of heart valve disease, with a reported odds ratio of 2.76.
The researchers emphasize that an odds ratio reflects a statistical association rather than proving cause and effect or predicting an individual patient’s risk. The review also highlighted several important limitations, including relatively small study populations, differences in medication types and dosages, and incomplete information about participants’ underlying cardiovascular health.
The authors concluded that larger, prospective clinical studies will be necessary before changes to medical practice can be recommended.
What These Findings Mean for Patients
Taken together, current evidence strengthens the possibility that altered serotonin signaling contributes to fibrosis and structural remodeling in heart valves. This may partly explain why some patients with degenerative valve disease experience more rapid progression than others despite having similar clinical characteristics.
For now, experts emphasize that people with heart valve disease should continue following established medical recommendations, including regular cardiology assessments, imaging to monitor valve function, and surgery when clinically indicated. Any concerns about antidepressant medications should be discussed with both cardiologists and mental health professionals rather than leading to changes in treatment without medical guidance.
Future research will need to follow patients over longer periods, compare different antidepressant medications and dosages, and determine whether incorporating SERT-related genetic testing or serotonin-targeted therapies can safely improve outcomes. Until then, serotonin’s emerging role in heart valve disease remains an intriguing area of investigation that requires further clinical confirmation.
