Facebook addicts, not the casual user, but the hardcore, checks-every-few-minutes kind of users, tend to have a smaller “nucleus accumbens.” That’s the “reward center” of a brain. The study was done over a course of 5 weeks, and was made up of 46 male students, and 39 female students.
The researchers tracked the amount of time each user spent on Facebook, the number of times they “Checked-In” somewhere, and overall use of the app on the phone. Then, the brains of each student were scanned using an MRI machine. In a nutshell, the results of the study determined that people who more frequently checked the app had “smaller gray matter volumes of the nucleus accumbens.”
It doesn’t say whether or not the actual use of Facebook shrinks the brain, or if people who already have a smaller reward center tend to use the app more, but they have discovered a link. They’re saying it really reveals the dark side of social networks, especially when paired to other studies that link a higher number of likes with a lower amount of self-reported happiness.