Watching pornography may be linked to reduced activity in certain areas of the brain, according to a recent study Reuters reported.

German researchers found that men who watch a lot of porn tend to have less volume and activity in regions of the brain linked to rewards and motivation. However, researchers did not determine whether watching porn leads to the decreased volume and activity, or if people born with certain brain characteristics watch more porn.

"Unfortunately we cannot answer this question based on the results of the present study," Simone Kühn, the study's lead author from the Max Planck Institute for Human Development in Berlin, told Reuters.

However, the study provides evidence linking pornography consumption to reductions in brain size and brain activity in response to sexual stimuli.

For the study, researchers recruited 64 healthy men between the ages of 21 and 45 years and asked them questions about their porn-watching habits. They also took images of the men's brain to measure their volume and to see how their brains reacted to pornographic pictures, Reuters reported.

"We found that the volume of the so-called striatum, a brain region that has been associated with reward processing and motivated behavior was smaller the more pornography consumption the participants reported," Kühn said. "Moreover we found that another brain region, that is also part of the striatum that is active when people see sexual stimuli, shows less activation the more pornography participants consumed."

Researchers also found that the connection between the striatum and prefrontal cortex, which is the outer layer of the brain associated with behavior and decision making, worsened with increased porn watching.

However, Kühn said other behaviors, such as driving a taxi, are linked to changes to brain size and functioning.

"Basically everything that people do very frequently can shape their brain structure and function," she said.