The more time a person spends on their smartphone, the more likely they are depressed, a new study suggests.

According to the findings, the average daily usage for a person who is depressed is 68 minutes, while for people are who are not depressed, it is 17 minutes.

US researchers set out to assess any links between smartphone usage, geographical location (as measured by GPS tracking on the phone) and depression. They analysed the phone usage and GPS locations of 28 people over a two-week period.

The participants were also assessed for depression using a standardised questionnaire. Half were found to have signs of depression, ranging from mild to severe.

The study found that the more time people spent on their phones, the more likely they were depressed. It also found that people who spent most of their time at home, or in fewer locations overall, were more likely to be depressed as well.

The researchers also noted that people with an irregular schedule, e.g. those who went to work at different times each day, were more likely to be depressed.

Using this data, the researchers were able to accurately identify almost 90% of those with depressive symptoms.

"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 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," commented the study's senior author, David Mohr, of Northwestern University in Chicago.

The study showed that depressed people generally did not go to many places, perhaps reflecting a loss of motivation that is commonly seen in depression, the researchers noted.

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

While the study did not look into what people were doing on their phones, Mr Mohr believes that those who spent long periods of time on their phones were probably playing games or surfing the net, 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. It's an avoidance behavior we see in depression," he said.

Details of these findings are published in the Journal of Medical Internet Research.

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