When you hit a low, your Insta pics turn blue

Turns out, your blue mind can taint your online photos.

When you're feeling blue, your photos turn bluer too. And more gray and dark as well, with fewer faces shown. In other words, just like people can signal their sadness by body language and behaviour, think deep sighs and slumped shoulders, depression reveals itself in social media images.

That's the conclusion of new research showing that computers, applying machine learning, can successfully detect depressed people from clues in their Instagram photos. The computer's detection rate of 70% is more reliable than the 42% success rate of general-practice doctors diagnosing depression in-person.

"This points toward a new method for early screening of depression and other emerging mental illnesses," said co-author Chris Danforth from the University of Vermont. "This algorithm can sometimes detect depression before a clinical diagnosis is made."

The scientists asked volunteers, recruited from Amazon's Mechanical Turk, to share their Instagram feed as well as their mental health history. From 166 people, they collected 43,950 photos. The study was designed so that about half of the participants reported having been clinically depressed in the last three years.

Then they analyzed these photos, using insights from well-established psychology research, about people's preferences for brightness, color, and shading. "Pixel analysis of the photos in our dataset revealed that depressed individuals in our sample tended to post photos that were, on average, bluer, darker and grayer than those posted by healthy individuals," Danforth and Reese write in a blog post to accompany their new study. They also found that healthy individual chose Instagram filters, like Valencia, that gave their photos a warmer brighter tone. Among depressed people the most popular filter was Inkwell, making the photo black-and-white.

"In other words, people suffering from depression were more likely to favor a filter that literally drained all the colour out the images they wanted to share," the scientists write.

Faces in photos also turned out to provide signals about depression. The researchers found that depressed people were more likely than healthy people to post a photo with people's faces, but these photos had fewer faces on average than the healthy people's Instagram feeds. "Fewer faces may be an oblique indicator that depressed users interact in smaller settings," Danforth and Andrew Reece of Harvard University noted, which corresponds to other research linking depression to reduced social interaction--or it could be that depressed people take many self-portraits.

"This 'sad-selfie' hypothesis remains untested," they wrote.

"This study is not yet a diagnostic test, not by a long shot," said Danforth, "but it is a proof of concept of a new way to help people."

The results were published in journal EPJ Data Science.