Fascinating article in Science magazine this month:

mice

There is a molecule in the brain of mice that seems to correlate with how they respond to bullying. Remove the molecule and depressed mice who have been bullied and become withdrawn, now take the bullying in stride and do not hesitate to enter territory in which they have been routinely bullied.

They also treated the withdrawn mice with antidepressants and got a similar response -- they ventured out again and were much less likely to withdraw when bullied.

I can offer anecdotal evidence in my own life. I suffer from social anxiety disorder and depression, and some antidepressants have a very definite effect on my ability to function socially. The medicine changes the impact of events on my psyche.

I wonder if people who "have no fear" are missing this molecule - the normal messages that tell most of us that some endeavor is too risky don't take with them. How amazing to think such small differences could create vastly different personalities, and to think that social confidence could be so directly affected by such seemingly small changes. Perhaps this will lead to better medications in the future.