Key points from article :
A new study led by Eiko Fried, associate professor of clinical psychology at Leiden University, has cast doubt on the accuracy of smartwatches in tracking stress levels. Published in the Journal of Psychopathology and Clinical Science, the research followed 800 young adults over three months, asking them to report their stress, fatigue, and sleep four times daily while wearing Garmin vivosmart 4 devices. When compared with participants’ self-reported stress, the smartwatch readings showed almost no correlation — often flagging stress during moments of excitement or exercise rather than emotional strain.
The team found slightly stronger, though still weak, associations between smartwatch data and self-reported fatigue, while sleep duration tracked more reliably with how rested participants felt. In about two-thirds of cases, longer reported sleep was matched by an average two-hour increase in Garmin-recorded duration. However, the devices still offered little insight into subjective sleep quality, highlighting a gap between measurable metrics and lived experience.
Fried stressed that consumer wearables, while increasingly popular, are not medical devices and can easily misinterpret physiological signals that overlap between positive and negative emotions. Heart rate, for example, may rise in both anxiety and joy. He shared personal anecdotes of his smartwatch incorrectly flagging stress while he was happily chatting at a wedding or working out at the gym, illustrating the technology’s limitations.
Despite the shortcomings, the research is part of a broader effort to explore wearable data as an early warning system for conditions like depression. While certain patterns, such as lower activity levels, show potential as predictive markers, experts like Margarita Panayiotou from the University of Manchester caution that such data should be interpreted alongside personal context and self-reports. The study underscores that while wearable tech can offer useful clues, it is far from a definitive guide to mental wellbeing.
