Your pain tolerance may vary depending on the structure of your brain, a new study finds. While most painful sensations are temporary, at least 20% of the global population suffers from chronic pain, and global pain management costs are expected to reach $60 million by 2015. Finding what makes injuries and illness more debilitating for some than others is a vital step in creating better treatments.

According to research in the journal Pain, the intensity of pain perception can be related to differences in the amount of gray matter—the tissue that processes information—in certain areas of the brain.

“Subjects with higher pain intensity ratings had less gray matter in brain regions that contribute to internal thoughts and control of attention,” Nichole Emerson, one of the study’s authors, said in a press release.

Two of these brain areas—the posterior cingulate cortex and the precuneus—are part of the network of brain regions associated with day dreams and free-flowing thoughts. A higher baseline of activity in these parts of the brain, the researchers said, could compete with pain perception. In other words, a higher level of background noise in the brain might keep the sensation of pain from breaking through.

A third area found to have more gray matter in high-pain tolerance individuals, the posterior parietal cortex, plays a role in attention and focus. This could be another aspect of pain insensitivity: Those who are easily able to think of something other than the pain are simply better at bearing it.

A previous study found that differences in white matter—which is mostly made up of the connective tissue between neurons and regions of the brain—can have an effect on pain as well. But while gray matter seems to affect pain’s intensity, white matter can control how long it lasts. Differences in the connective tissues of the brain, the researchers found, made acute pain more likely to become chronic.