People who frequently check Facebook on their smartphone tend to have less gray matter in a reward-related area of the brain, according to new research.

“Smartphones, Facebook – in short the digital world – is a major part of our lives,” the study’s corresponding author, Christian Montag of Ulm University, told PsyPost. “A better neuroscientific understanding of digital usage is of importance to also understand how our brains react and are shaped by digital societies.”

The study was published online April 22 in the peer-reviewed journal Behavioural Brain Research.

The researchers recruited 46 men and 39 women, and used magnetic resonance imaging (MRI) scans to examine the structure of their brain. Then, the researchers installed an app on the participants’ phones to record how long they spent on Facebook and how often they checked Facebook every day for five weeks.

Montag and his colleagues were particularly interested in the nucleus accumbens, a small structure located deep in the center of the brain. The nucleus accumbens is a core region of the mesocorticolimbic dopaminergic system, which plays an important role in addiction.

The researchers found that participants who opened the Facebook app more frequently and those who stayed on Facebook longer tended to have reduced gray matter volume in the nucleus accumbens.

“We were able to demonstrate that the nucleus accumbens, a central region of the SEEKING system — others call it the reward system — plays an important role in understanding Facebook usage on smartphones,” Montag said. “In short, the lower the gray matter volume in this area, the higher Facebook usage/frequency could be observed.”

“Indeed, frequency of Facebook checking can be compared to an energetic SEEKING activity,” the researchers wrote in the study, “whereas the users of the smartphones are checking their Facebook account in expectation of ‘Likes’, nice comments, etc.”

Does less gray matter in the nucleus accumbens lead to more Facebook use or does using Facebook lead to less gray matter? Because the study was cross-sectional, the researchers could not determine cause and effect.

“We do not know from the present data if low volumes in this area are a cause or consequence of Facebook usage. Therefore longitudinal studies are needed,” Montag explained to PsyPost.

“The present study investigated health young participants with ‘normal’ smartphone usage. Future research will show if excessive usage (which we did not investigate) could represent a behavioral addiction.”

The study, “Facebook usage on smartphones and gray matter volume of the nucleus accumbens“, was also co-authored by Alexander Markowetz, Konrad Blaszkiewicz, Ionut Andone, Bernd Lachmann, Rayna Sariyska, Boris Trendafilov, Mark Eibes, Julia Kolb, Martin Reuter Bernd Weber and Sebastian Markett.