Variable ratio reinforcement
Likes, messages, and new posts arrive unpredictably, creating a powerful reward schedule similar to the one used by slot machines. Pull-to-refresh is structurally close to pulling a lever.
Digital & Society
The studies are in. The results are not what the optimists or the pessimists expected. In 2018, Stanford and NYU researchers paid about 2,000 Facebook users to deactivate their accounts for four weeks, then compared them with a control group. The findings were mixed in exactly the way real life tends to be: people felt slightly better, used their time differently, and became less exposed to political information. Quitting social media produces measurable effects on wellbeing, mood, polarization, information access, and time use. Not all of them are what you would expect.
Quick answer
Social media abstinence studies generally find reduced anxiety and depression symptoms, improved subjective wellbeing, less FOMO, better sleep, less political exposure, and more available time. The tradeoff is reduced access to social information and weaker connection with distant acquaintances. The Stanford/NYU Facebook study found deactivation made people slightly happier but also significantly less politically informed.

The short answer
Social media abstinence studies generally find reduced anxiety and depression symptoms, improved subjective wellbeing, less FOMO, better sleep, less political exposure, and more available time.
Variable ratio reinforcement
Likes, messages, and new posts arrive unpredictably, creating a powerful reward schedule similar to the one used by slot machines.
Curiosity twist
The Stanford/NYU Facebook study found deactivation made people slightly happier but also significantly less politically informed.
Common mistake
Rising social media use proves that social media directly caused rising adolescent depression.
Next tiny mystery

Digital & Society
Another big-question explanation in the same collection.

Body & Brain
Another big-question explanation in the same collection.

Body & Brain
Another big-question explanation in the same collection.