Lots of prior research has established a correlation, or association, between social media use and depression. Ours is the first study to establish an actual causal relationship between using more social media, and feeling more depressed. We improved on prior research in a number of ways. First, the study was experimental. Second, we got objective data on how much people were using social media, rather than relying on self-report, or how much people believed (or were willing to admit) that they were using it. Third, we included three of the major platforms that folks in this age group use, Facebook, Snapchat and Instagram. Fourth, we did a week of baseline data collection before asking half the people to change their behavior. This allowed us to account for the effects of self-monitoring. Finally, we set realistic goals for use (10 minutes per platform per day) rather than requiring complete abstinence, which is probably unrealistic for millennials. We found that over three weeks, participants who were randomly assigned to limit their use showed significant declines in depression and loneliness compared the people who kept using as normal. Lots of our subjects shared that participating in the study made them realize how much time they had been spending on social media and how much happier and more productive they were when they limited their use. What readers should take away is that social media may be fine in moderation, but you shouldn’t spend much more than a half hour per day passively scrolling and comparing yourself to other people. It’s much better to use that time engaging in activities that make you feel good about yourself and strengthen social bonds with people in person. So put down your phone, get your work done and go out to dinner with friends.