Smartphones could be used to detect depression in its users, according to a recent study.

Researchers at Northwestern University Feinberg School of Medicine in Illinois found that depression can be detected from an individual's smartphone sensor data by tracking the number of minutes they use the phone and their daily geographical locations, CNN reported.

"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," David Mohr, senior author of the study, said in a statement. "We now have an objective measure of behavior related to depression. And we're detecting it passively. Phones can provide data unobtrusively and with no effort on the part of the user."

For the study, researchers recruited 28 individuals with an average age of 28 and followed them for two weeks. They were asked to download the Purple Robot app which "collected their information," CTV News reported.

"The main reason for the development of the app is to see if we can objectively and passively identify if people are depressed," Sohrob Saeb, one of the developers of Purple Robot, told CNN.

The app identified people with depressive symptoms with 87 percent accuracy, according to researchers.

They found that people who spend more time using their phone were more likely to be depressed, The Los Angeles Times reported. The average daily usage for depressed individuals was about 68 minutes, while for non-depressed individuals it was about 17 minutes.

Based on their analysis, they also found that spending most of the time at home and most of the time in fewer locations -- as measured by GPS tracking -- also are linked to depression. And, having a less regular day-to-day schedule, such as an individual leaving their house and going to work at different times each day, for example, also is linked to depression.

"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. "When people are depressed, they tend to withdraw and don't have the motivation or energy to go out and do things."

While the phone usage data didn't identify how people were using their phones, Mohr suspects people who spent the most time on them were surfing the web or playing games, rather than talking to friends.

"People are likely, when on their phones, to avoid thinking about things that are troubling, painful feelings or difficult relationships," Mohr said. "It's an avoidance behavior we see in depression."

The findings, which are detailed in the Journal of Medical Internet Research, could ultimately lead to monitoring people at risk of depression and enabling healthcare providers to intervene more quickly.