Hofman, S.G., Moscovitch, D.A., Litz, B.T., Kim, H.J., Davis, L.L. & Pizzagalli, D.A. (2005). The worried mind: autonomic and prefrontal activation during worrying. Emotion, 5(4), 464-75.
SUNY Downstate Medical Center (2012, April 12). Excessive worrying may have co-evolved with intelligence. ScienceDaily. Retrieved May 9, 2012, from http://www.sciencedaily.com /releases/2012/04/120412153018.htm