Consumer smartwatches are everywhere today. They promise to track our sleep, energy, exercise, stress, and even mental health. But can they really tell us how stressed or tired we are? A new study says: maybe not.
Researchers recently tested Garmin Vivosmart 4 devices on nearly 800 university students over a three-month period. The students also answered ecological momentary assessments (EMAs) on their smartphones four times a day. Each night, they reflected on their best or worst experiences.
The results showed something surprising: the smartwatch data did not always match how students actually felt.
What the Study Found
The overlap between smartwatch readings and self-reported feelings was very small.
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Stress scores on the watch often didn’t match what students reported.
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Fatigue readings were also unreliable.
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Only sleep tracking showed modestly better accuracy.
Co-author Eiko Fried explained why. He said wrist devices mainly look at heart rate and heart rate variability (HRV). But a fast heartbeat doesn’t always mean stress.
For example:
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You could feel nervous during an exam.
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Or excited at a wedding.
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Or even happy while playing sports.
In all three cases, the watch might label you as “stressed” because your heart is beating faster.
Why It Matters
This finding is important because wearables are becoming popular tools for health and wellness. Many people rely on them daily to measure:
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Sleep quality
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Stress levels
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Energy balance
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Fitness progress
But if stress tracking is not accurate, users could misunderstand their own mental state. For example, your watch might warn you about stress while you are simply enjoying a fun conversation.
Bigger Picture: Wearables and Mental Health
This research is part of WARN-D, a larger project that wants to build an early warning system for depression. If wearables can’t reliably measure stress or fatigue, scientists need to rethink how to use them in mental health research.
As Fried told The Guardian, his own smartwatch marked him as stressed both when working out and when catching up happily with a friend. This shows that context matters, and numbers alone don’t always tell the full story.
What Users Should Know
If you use a smartwatch, here are some things to keep in mind:
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Sleep tracking is better than stress tracking – watches can give useful insights into rest.
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Don’t panic over “stress” alerts – they may simply reflect excitement or physical activity.
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Combine watch data with your own feelings – ask yourself how you really feel instead of trusting numbers alone.
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Use wearables as guides, not doctors – they are tools, not replacements for medical advice.
Final Thoughts
Smartwatches are amazing for fitness tracking, sleep insights, and motivation. But when it comes to stress and fatigue, they may not be as reliable as many people think.
Future research may create better ways to measure mental health through technology. For now, the best approach is to listen to your body and mind first, and use your watch as a helpful guide, not the final answer.
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