And while the research team didn’t know exactly what people were doing on their phones, they suspect the depressed participants weren’t talking to friends or family but rather surfing the web and playing games.

A study published by the Northwestern University Feinberg School of Medecine used mobile phone data to identify people with symptoms of depression – with a rate of 86 per cent accuracy, apparently.

“The data showing depressed people tended not to go many places reflects the loss of motivation seen in depression”, said Mohr, who is a clinical psychologist and professor of preventive medicine at Feinberg.

Small study contends that people who use the devices more often are likelier to have the disorder.

Researchers have developed an Android app, called Purple Robot, to help store and forward data collected by most cellphones.

The data also showed that depressed people tended to visit fewer places. Researchers found that a healthy person spends on average 17 minutes per day to talk on the phone.

The research at Northwestern University in Illinois, US, studied 28 people, half with depression.

Of the 28, 50 percent were found to have no symptoms of depression, while the other 50 percent was diagnosed with mild to severe depression.

USA researchers set out to assess any links between smartphone usage, geographical location (as measured by Global Positioning System tracking on the phone) and depression. The software didn’t track what people did on their phones-just whether or not they were using it. But the authors have some ideas about why they saw phone activity rise with depression.

The scientists now wish to try and determine whether phones can be used to keep a close eye on people at risk of depression and make it easier for care providers to intervene, should need be.

The proponents of the research told their colleagues that their aim is to passively detect any signs of depression.

While the recent study could not prove if staying at home for long periods or spending too much time in the digital world caused depression, the correlation could be useful in “passively” and “unobtrusively” detecting symptoms, said Mohr.

Researchers at Northwestern are planning to follow up their study to see whether getting people to change their behaviour could improve their mood and alleviate depression. He added that when individuals suffer from depression they have a tendency to withdraw and don’t show energy or motivation to do things and go out.

For most of us our phone is like our PA – telling us where to go, when and how to get there – and its ability to second-guess us may just have reached a new level: a new study suggests our smartphones can detect whether or not we’re depressed.