Fear not: Smart watches may not always be so smart after all

They're supposed to monitor you throughout the working day and help make sure that life is not getting on top of you.

- Rachel Hall

But a new study has concluded that smart watches can't accurately measure your stress levels - and may think you're overworked when really you're just overexcited.

Researchers found almost no relationship between the stress levels reported by the smart watch and those that participants said they experienced.

The levels of fatigue recorded did however have a slight association with feelings of fatigue experienced.

Eiko Fried, an author of the study, said the correlation between the smart watch and self-reported stress scores was "basically zero".

He added: "This is no surprise to us given that the watch measures heart rate, and heart rate doesn't have that much to do with the emotion you're experiencing - it also goes up for sexual arousal or joyful experiences."

He noted that his Garmin watch had previously told him he was stressed when he was working out in the gym, or excitedly talking to a friend he hadn't seen for a while at a wedding.

"The findings raise important questions about what wearable data can or can't tell us about mental states," said Fried. "Be careful and don't live by your smart watch - these are consumer, not medical devices."