Islamabad: Smartphones could provide a useful way of telling when people are depressed, according to new research.

Tracking the number of minutes a phone is used, and its location, can provide clues about the user's state of mind, a study suggests.

The more time someone spends on his or her phone, the greater the chance they are depressed, the researchers claim.

The average daily usage for depressed individuals was found to be around 68 minutes, compared with 17 minutes for happier souls.

The more time someone spends on his or her phone, the greater the chance they are depressed, it's claimed

People who spend most of their time at home or in fewer locations - as measured by GPS tracking via their phone - are also more likely to show signs of depression, it is claimed.

Using mobile phone data, the US team was able to identify people with depressive symptoms with 87 per cent accuracy.

Lead researcher Professor David Mohr, of Northwestern University Feinberg School of Medicine, said: 'The significance of this is we can detect if a person has depressive symptoms and the severity of those symptoms without asking them any questions.

'We now have an objective measure of behaviour related to depression. And we're detecting it passively.

'Phones can provide data unobtrusively and with no effort on the part of the user.'

Smartphones could in future be used to monitor people at risk of depression, enabling health professionals to provide help more quickly when necessary, said the scientists.

The findings are reported in the Journal of Medical Internet Research.

For the study, the researchers recorded the phone usage of 28 men and women over a period of two weeks and tracked their locations every five minutes.

The phone data turned out to be a more reliable way of detecting depression than asking participants questions about how sad they were feeling on a scale of one to 10.

'The data showing depressed people tended not to go many places reflects the loss of motivation seen in depression,' Professor Mohr added.

People who are depressed tend to spend more time at home or in fewer locations - which can be measured by smartphones' GPS tracking. Phones data could provide a useful way of diagnosing depression, doctors said