Why do you check Facebook so much? Or email? Or your Twitter feed? It’s not because they bring us joy, but because they reduce anxiety, according to journalist Sharon Begley.

Begley is author of the book Can’t Just Stop: An Investigation of Compulsions, and she dives deep into the science and psychology of compulsive behavior.

Begley defines compulsive behavior as repeated, chronic action that happens because of anxiety. We engage in compulsive behaviors like checking our phones, obsessively shopping, and even exercising to excess, because every time we perform those actions, our anxiety lessens. Begley is quick to point out that OCD and compulsive behaviors are not the same thing.

“The difference between an eccentricity … and a mental disorder is that if it is causing you distress or impairment, then it’s a mental disorder,” Begley said. “Just because you have a compulsive behavior, does not mean that your brain is broken. In fact, it can mean the opposite, that you are reacting to, that you are coping with, the events in your life in a helpful way.”

Basically, if something takes the edge off your anxiety, it’s not an entirely bad thing. And anxiety itself isn’t evil or terrible. There’s an evolutionary reason for it.

“We are wired to be anxious because ... those of our ancestors or predecessors who did not have a good antenna for what should make them anxious, they did not become our ancestors because they left no descendents,”said Begley. In other words, there’s a link between an anxiety-reducing check of Twitter and checking the savanna for hungry predators.

But even though we’re not fleeing from tigers on a daily basis (unless your life is way more interesting than mine), anxiety may have gone up in our modern era. App creators are using psychological tricks to keep us engaged, and we’re exposed to a huge amount of worrying news on a daily basis. Begley sees this as an “age of anxiety,” so it makes sense that we’re engaged in more and more compulsive behaviors.