Depressed users were less likely to use filters...
The study found that users with confirmed depression usually posted bluer, darker, and more faded images. They were less likely to use filters than non-depressed users, but when they did, they favored "Inkwell" over any other, with "Crema," "Willow," and "Reyes" rounding out the top four. Conversely, non-depressed users preferred "Valencia" and posted images with warmer tones.
... and posted fewer group shots
Interestingly, depressed participants were more likely to 'Gram photos with faces in them, but usually of just one or two people -- so, more selfies or photos of individuals, and fewer shots with large groups.
Users without depression got more likes, while depressed users got more comments
The researchers also discovered that the more comments a post received, the more likely it was posted by a depressed participant. On the other hand, a higher number of likes signified it was posted by someone who wasn't depressed.
Now before you start surveying your friends' Instagram feeds looking for recurring blue-hued shots, a second analysis was done by a group of participants who were asked to rate the photos on a scale of one to five, based on how sad, happy, or likable they were. Turns out, humans were incredibly unreliable predictors -- only the computer program could properly determine the differences. The study's authors also point out that despite their findings, a person's behavior on Instagram should not be used as a test to diagnose people suffering from depression, but rather as a way to screen for individuals who might be, and prompt them to get treated earlier than they might otherwise.