Stress not only affects physical disease but also the very structure of our brains, making us even more likely to experience a drained brain. A number of studies have been done to reveal what happens in healthy people's brains when they go through something stressful. One study demonstrated a link between a smaller hippocampus and people who had experienced long-lasting stress. Why does this matter? This part of the brain helps you remain resilient in the face of stress and is involved in mood regulation. It also helps you to monitor the safety of your environment and store dangerous images in your longterm memory so you can avoid them in the future. It does all these things as part of its duties of regulating your sympathetic and parasympathetic nervous systems. But chronic stress can confuse the hippocampus and lead to turning signals for cortisol "on" instead of "off," which can trap you in a constant state of fight, flight, or freeze.