This article originally appeared in Science of Us.

If you are the sort of person who has a hard time just watching TV—if you’ve got to be simultaneously using your iPad or laptop or smartphone—here’s some bad news. New research shows a link between juggling multiple digital devices and a lower-than-usual amount of gray matter, the stuff that’s made up of brain cells, in the region of the brain associated with cognitive and emotional control.

More details, via the press release:

The researchers at the University of Sussex’s Sackler Centre for Consciousness used functional magnetic resonance imaging (fMRI) to look at the brain structures of 75 adults, who had all answered a questionnaire regarding their use and consumption of media devices, including mobile phones and computers, as well as television and print media.

They found that, independent of individual personality traits, people who used a higher number of media devices concurrently also had smaller grey matter density in the part of the brain known as the anterior cingulate cortex (ACC), the region notably responsible for cognitive and emotional control functions.

But a predilection for using several devices at once isn’t necessarily causing a decrease in gray matter, the authors note—this is a purely correlational finding. As Earl Miller, a neuroscientist at MIT who was not involved in this research, wrote in an email, “It could be (in fact, is possibly more likely) that the relationship is the other way around.” In other words, the people who are least content using just one device at a time may have less gray matter in the first place.

Researchers once thought that once gray matter was gone, it was gone forever, but recent findings in neuroscience show that there are some ways to build more brain cells, Miller explained. “Studies have shown that physical exercise can increases production of new brain cells in mice,” he said. “And humans studies have shown aerobic exercise helps enhance cognitive abilities.” Alas, it seems the best way to build up your brain is by leaving the couch.