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Researchers have developed a patch capable of detecting anxiety markers in sweat— a technological breakthrough that could transform how we monitor our mental health: silently, but continuously.

Sweat, often dismissed as a mere bodily nuisance or a simple thermal response, is now emerging as a new frontier for connected medicine. It contains far more than just water and salt, it holds valuable biochemical clues about our internal state. Among them, cortisol, often called the “stress hormone,” is drawing particular attention. Its concentration rises when the body is under chronic stress or anxiety, making it a reliable marker of these mental states.

Researchers from the Swiss Federal Institute of Technology in Lausanne (EPFL), in partnership with the startup Xsensio, have recently developed a patch capable of continuously measuring cortisol levels in sweat. This device, both flexible, discreet and non-invasive, simply attaches to the skin. It includes a microfluidic membrane that absorbs sweat and a sensor that reacts to the presence of cortisol through an electrochemical signal. The collected data can then be transmitted to a smartphone, allowing for precise, real-time monitoring.

This advancement, praised by the scientific community, could revolutionize the tracking of anxiety disorders and chronic stress, especially in environments where speaking out is rare, difficult or stigmatized. The idea of passive and silent monitoring, without blood tests, questionnaires or invasive apps, appeals to both doctors and patients. It paves the way for more personalized therapies and more refined prevention. While anxiety remains invisible, its biological signs no longer are.

When the Body Speaks Without a Word

This technology is part of a growing trend in connected medicine: understanding emotional or mental states through biometric sensors embedded in everyday objects. In California, researchers at Northwestern University have also developed an ultra-thin sensor capable of detecting stress levels via sweat. This sensor could be integrated into smartwatches or skin patches, opening the door to continuous emotional state mapping throughout the day.

The stakes are not just scientific, they are also ethical and social. In a world increasingly pressured by performance demands, mental health is quietly eroding. According to the World Health Organization, anxiety disorders affect nearly 264 million people worldwide, a figure likely underestimated. Stress-related conditions, such as burnout, depression and generalized anxiety disorders, are on the rise, often without individuals fully realizing it.

That’s where these technologies come into play. Rather than waiting for a crisis, they offer upstream monitoring, as close to the body as possible, in its subtlest signals. By gathering objective data on stress levels, they can complement psychological and psychiatric approaches, which too often focus on speech, storytelling or visible signs. They also restore a sense of autonomy to the patient, who can learn to anticipate anxiety episodes, recognize their tolerance thresholds and adjust their pace.

But these devices also raise fundamental questions. Can we truly quantify an emotion? What does it mean to “objectify” an internal state? And above all, who owns this data? EPFL researchers emphasize the need to protect users’ privacy by ensuring encryption and non-transferability of information. But in a world where personal data is currency, the line between care and surveillance can quickly blur.

Some experts also remind us that cortisol, while an important indicator, is not absolute proof of anxiety. It varies depending on the time of day, diet, physical activity and hormonal cycles. A cortisol spike does not necessarily mean an anxiety episode. That’s why these patches shouldn’t be seen as emotional oracles, but as tools within a broader healthcare ecosystem. Their power lies in creating a personalized stress map, not in delivering instant diagnoses.

The future, in any case, is already underway. Applications are starting to integrate these sensors into everyday objects, such as watches, t-shirts and headphones. The patch envisioned by Xsensio could become a standard tool for monitoring high-risk professions—healthcare workers, firefighters, teachers, managers—as well as adolescents, who have seen a sharp rise in anxiety disorders since the pandemic.

As mental health becomes a major issue of the 21^st century, the sweat we once tried to hide is finally becoming visible, audible and readable.