Among several points quite interesting but not so surprising (for me), here’s a thought I’d actually never considered:

Previous MRI studies have shown that during social situations, specific areas in the brains of loners experience especially lively blood flow, indicating a sort of overstimulation, which explains why they find parties so wearying. […] This added sensitivity, she speculates, could mean that people who are reserved have an ability to respond quickly to situations — such as coming to your aid in a moment of need — or show unusual empathy to a friend, due to their strong emotional antennae.

For some reason the first thing that comes to mind now is the Charmed episode where one of the Ps goes insane or depressive or whatever because she absorbed an empath’s capabilities and human beings aren’t made to withstand that kind of stress.