The human brain evolved to cope with stress in a specific manner. When a predator threatened our prehistoric ancestors, that acute stress created a fight-or-flight response that included release of the hormone cortisol and other stress hormones, raising levels to circulate throughout the body and in the brain.

Those hormones accelerated heart rate and heightened mental acuity, providing the endangered human a survival advantage.

And those ancient neural pathways are still programmed into our brains today.

Luckily, for many of us times have changed and those hardwired responses to acute stress are no longer necessary to survive on a daily basis.

Unfortunately, less life-threatening types of stress still lead to the same hormone release.

When we experience chronic elevations of stress hormones, it can actually damage brain cells, impair memory, worsen mood, and increase the risk for Alzheimer’s disease.

Acute stress also shifts brain activity from the frontal lobe (the thinking part of the brain) to the amygdala (the emotional brain).

This shift allows for quick responses to threats, but subverts complex problem-solving — which is a good reason you shouldn’t make important long-term decisions while under stress.

This effect has been shown in experiments. When researchers injected the stress hormone cortisol into human volunteers, they observed temporary declines in both learning and memory.