It's been proven that when you're exposed to a great amount of stress, you IQ can actually drop significantly!

It's also worth mentioning that there's another type of stress, which is called hormetic stress, and this one is actually beneficial :) Some activities, that cause your body to go into hormesis include: cold exposure, exercise, intermittent fasting. Doing these on regular basics will make you literally more resilient to the negative type of stress.