The frontal cortex doesn't even fully develop until age 25, which is wild!

We live well enough to have the luxury to get ourselves sick with purely social, psychological stress.

As long as experiencing your optimal level of good stress doesn't damage others, it's hard to objectively define where normal enjoyment of stimulation becomes adrenaline junkiehood.

Hormones influencing the sensitivity of the person to environmental stimuli.

...I might continue to believe that there is no god even if it were proved that there is. A religious friend of mine once remarked that the concept of god is useful, because you can berate god during the bad times. But it is clear to me that I don't need to believe there is a god in order to berate him.

On an incredibly simplistic level, you can think of depression as occurring when your cortex thinks an abstract thought and manages to convince the rest of the brain that this is as real as a physical stressor.

If a rat is a good model for your emotional life, you're in big trouble.