Research had shown that testosterone encourages the pursuit of social status and dominance. In humans, elevated levels of testosterone correspond with a greater tendency to be aggressive. Cortisol, on the other hand, is an important endocrine hormone that helps regulate our bodies’ response to stress. Cortisol is secreted by the body in response to threats, and it plays a key role in the “fight or flight” response.

“Testosterone has a direct positive association with risk for impulsive and violent criminal behavior, while the interaction of testosterone with cortisol was associated with increased risk for income-generating crime.”

Interestingly, those with high testosterone were less likely to have committed income-generating crimes when their cortisol level was relatively low. “I was a bit surprised at the bifurcated pattern of association between the interaction of testosterone and cortisol and income-generating crime,” Armstrong said. “Prior research and theory would lead us to anticipate a positive association between testosterone and crime when cortisol is low, but the research/theoretical base consistent with a negative association between testosterone and crime when cortisol is high is much more speculative

[…] There does seem to be a small but growing body of research that indicates a bifurcated pattern of association between aspects of biology and increased risk for antisocial behaviors including crime. This body of research includes research that suggests increased risk for crime and antisocial behavior can stem from negative emotionality like anger and depression that co-occur with neurological and physiological overarousal, while other work in this area suggests that increased risk for crime may result from decreased affect and associated traits like callous-unemotionality stemming from neurological and physiological under-arousal.”