Here’s another reason to get strolling outside: It’s good for your brain.

Researchers at the Max Planck Institute for Human Development followed six adults over six to eight months, tracking their daily behaviors while taking 40 to 50 MRI scans of each of their brains. The result: Outdoor activity positively impacts brain structure.

The researchers found that time spent outdoors is associated with more gray matter in parts of the prefrontal cortex that oversee cognitive control, regulation, and planning. “Our results show that our brain structure and mood improve when we spend time outdoors. This most likely also affects concentration, working memory, and the psyche as a whole,” says lead author Simone Kühn, a psychologist and neuroscientist at the institute. The benefit remains even when controlling for variables like sunshine, exercise, and fluid intake.

Adults spend 80-90% of their time indoors.

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