Psychologists typically distinguish between two types of anxiety: trait anxiety, a persistent and lasting tendency to experience fear and worry; and state anxiety, a temporary response of fear to a threatening situation. Many forms of social media can agitate both trait and state anxiety, and perhaps none more so than Twitter, which reminds the perpetually anxious that we always have something to be anxious about and instills a sense of anxiety in even the most laid-back user. Twitter’s constant flow of new information and the fact that users tend to follow people who are more accomplished and successful than they are creates an especially potent cocktail of comparison for anxious people. "Twitter really inflames my professional anxiety," says Caitlin Cruz, a freelance journalist based in New York. "But it's also given me a lot of professional success." Cruz deleted the Twitter app from her phone a few weeks ago, which she says has made her life more bearable.

Twitter users have to contend with competing voices that yell at you as soon as you log on. You haven't written a best-selling novel yet? Here's a “30 Under 30” list of best-selling novelists! You're over 30? Here's an article about how you're a bad parent! You haven't had children yet? This bestselling author has three, and she's under 30! Twitter is a megaphone for achievements and a magnifying glass for insecurities, and when you start comparing your insecurities with another person's achievements, it's a recipe for anxiety.

"Generally speaking, the comparisons that we make on social media are more likely to be 'upward' comparisons," says Azadeh Aalai, a professor of psychology at Montgomery College in Maryland. "We're comparing ourselves to the individuals who appear to be higher status and are achieving more" than we are, which can lead to feelings of envy, discontent, and anxiety. It's also not the whole story. When I was young, my mom used to warn me against "comparing my insides to other people's outsides." Using Twitter, I am constantly comparing my insides—my anxieties, fears, and insecurities—with other people's outward selves: their accomplishments, polished selfies, and edited articles. There will always be someone who’s doing better than I am in any aspect of my life. And because I, like many people, tend to follow people I admire or who are already famous, I am constantly aware of just how much better other people are. Twitter also gives me a quick and handy way to quantify my worth: this many likes, this many retweets. I'd like to think I'm more than the sum of my followers, but there are plenty of days when I don't feel that way.

Anxiety functions by constantly reminding you to pay attention to it. And so does Twitter. Twitter draws users back for more and more and more. Smartphones are designed to provide instant gratification, and many of Twitter's features depend on our biological fear of scarcity, says Pamela Rutledge, the director of the Media Psychology Research Center. The push notifications, the little number next to our mentions, the bar that tells us how many tweets have been sent since we last refreshed the page—all of these details are designed to keep users coming back, afraid that we might have missed something vital. "Social media doesn't really promote moderation," Aalai says (in what could perhaps be the understatement of the year).