Frustration, aggression, and murder.

"… 51 male murderers and their 51 nearest-age brothers were investigated with respect to frustration in infancy, childhood, and adolescence… . The central hypothesis was: There is a significant positive relationship between the amount of frustration experienced by persons in infancy, childhood, and adolescence… and whether or not they later commit murder… . The results showed that] significantly more murderers than control brothers scored high on the Indices of Physical, Psychological, and General Frustration." (PsycINFO Database Record (c) 2010 APA, all rights reserved)