How you Instagram might reveal more about you than just what you did last weekend. One study found that certain Instagram photos can predict the markers of depression, as New York Magazine's Select All reports. And it's not the first study to link social media use and mental illness.

The study, in EPJ Data Science, looked at almost 44,000 posts from 166 people (71 of them depressed) using color analysis, metadata, and face detection software. (While less than 200 people isn’t a big enough number to really cement these findings, they at least analyzed a whole lot of brunch pics.) They found machine learning could successfully distinguish between the behavior of people diagnosed with depression and those with a clean bill of mental health by looking at the Instagram filter type of photos, the setting, whether or not there were people, color, brightness, and how many “likes” and comments it got. They also looked at how often people used the app and how often they posted.

The researchers’ Instagram model worked the majority of the time to correctly identify depression, even in posts made before the researchers diagnosed the person’s mental health status. Compare that to general practitioners' rates for correctly diagnosing depressed patients, which studies have found hover around 42 percent.

Depressed people tended to post darker photos, often using Instagram’s black-and-white Inkwell filter. They received more comments, but fewer likes on their posts. They tended to post photos of faces, but typically fewer faces than non-depressed users (social isolation is often linked to depression). By contrast, healthy people loved Valencia, which lightens images, and tended to get more likes.

Loving a black-and-white photo doesn't necessarily mean you're depressed. Maybe you’re just trying out your best Ansel Adams impression. But given the outsized role social media plays in modern life, it might be able to provide doctors with insights into patients' inner thoughts and feelings that they might not otherwise be privy to.

Other studies, too, have found that technology use can provide a window into people's souls, mental health and all. Research has found that unhappy people use their smartphones to cope with negative feelings, linking increased phone usage to anxiety and depression. A 2015 study found that smartphones could predict depression by tracking how often and where people moved.

In some cases, though, social media seems to play an active role in making people unhappy, rather than simply revealing their existing unhappiness. A 2017 study of 5000 people found that the more time people spent using Facebook, the worse their sense of well-being. (And that's even before you start talking about reading the news.) Other surveys have found that for teenagers, Instagram and Snapchat usage are associated with low self-esteem, bullying, and more.

But even if obsessively Instagram is making you unhappy in the first place, how you use social media could be an important factor for doctors to consider when evaluating mental health. It's hard to open up to people about depressive thoughts, especially if it's a medical professional you only see once a year. You might tell your doctor you feel fine, but be more honest about your inner darkness on Instagram—whether you realize it or not. So although you probably don’t want to hand over your social media history to your medical providers on a regular basis, it could provide a useful way to screen patients who aren't able to fully convey their mental health issues.