I'm currently reading "Pilots Under Stress" by S.J. Sloan and C.L. Cooper. It's a very dry tome about an extensive study of pilot stress they did in the mid-eighties of 440+ British pilots. They are also authors of the pilot wives study I wrote about; which was actually an extension of the original study. Although I would love to see a repeat of this study done today, and in the US, I don't have the statistical abilities to do all of the analyzing of the data at this point.
So far my favorite quote is: "My main stressors occur on the ground; getting the damn thing into the air... once I'm in the air and totally in control of what's going on, I find that there is very little stress." This was said in relation to stresses from the management of the airline. I think that with all of the paperwork and procedures involved in flying these days, this quote probably holds true for a lot of pilots still.