Does your phone know if you're depressed?

People who spend more time at home or on their phones are more likely to be depressed – but it is unclear if one causes the other.

Information from your smartphone may be able to predict symptoms of depression, a new study found.

Researchers from Northwestern University tracked participants’ movements and the amount of time they used their smartphones daily. Though no cause was determined, the study found that those who spent more time on their phones and more time in a single location were more likely to exhibit depressive symptoms, such as sadness, hopelessness, disturbances in sleep and appetite, or difficulty concentrating.

"People are likely, when on their phones, to avoid thinking about things that are troubling, painful feelings, or difficult relationships," said senior author David Mohr in a Northwestern University press release. "It’s an avoidance behavior we see in depression."

Using cell phone data, researchers could identify those with depressive symptoms with 87 percent accuracy. Cell phone use averaged 68 minutes a day in participants who were diagnosed as depressed, and only 17 minutes a day in those who were not.

The study did not track how people were using their phones – only when, and for how long – but Professor Mohr speculated that people with depression were more likely to be playing games and surfing the Web than talking to friends.

But the study’s limitations prevented the researchers from identifying a causal relationship. Data were analyzed from only 28 participants, and the study relied on self-reported symptoms as the control against which phone data was measured.

In other words, the study could not prove that using your phone more often causes depression, or vice versa, or whether both are caused by something else.

Other research has also investigated the relationship between devices and depression. A 2014 paper published in the Journal of Social and Clinical Psychology cited two studies linking Facebook use and depression.

The evidence suggested that "people feel depressed after spending a great deal of time on Facebook because they feel badly when comparing themselves to others," reported the researchers.

It’s no secret that online personas present a heavily edited, Photoshopped version of reality – and losing that perspective can be disastrous for one’s self esteem.

"For obvious reasons, people do not advertise their negative traits on their social profiles, nor do they [post] unflattering pictures," a PsychCentral blogger wrote last year. "We are often fooled into believing other people’s lives are much better than our own.”

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.

Sohrob Saeb, lead author on the study, pointed out that their research can help people avoid behaviors linked to depression.

"We will see if we can reduce symptoms of depression by encouraging people to visit more locations throughout the day, have a more regular routine, spend more time in a variety of places, or reduce mobile phone use," said Dr. Saeb.