New research provides evidence that heightened levels of testosterone and cortisol are associated with a increased risk of impulsive and violent criminal behavior. The new findings have been published in the scientific journal Hormones and Behavior.
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.
The effects of both of these hormones are believed to play a role in criminal behaviors, but research into this area is still in a nascent stage. In their new study, lead author Todd Armstrong (@crimvids) and his colleagues sought to better understand the direct and interactive effects of testosterone and cortisol in relation to criminal activity.
“A more comprehensive understanding of the role of individual differences in risk for criminal behavior including biological differences may support the development of individualized prevention and treatment efforts,” explained Armstrong, a professor of criminology at the University of Nebraska Omaha. “However, this research base is emergent, and we have much to learn before we begin to use our understanding of the role of individual differences in risk for criminal behavior to inform prevention and treatment.”
The researchers recruited a sample of undergraduate students as part of a larger study on criminal behavior. Their final sample included 552 participants, who were 66.5% female and averaged 20.34 years of age. The participants completed a 38-item survey in which they reported past year occurrences of a broad range of criminal activities.
To assess testosterone and cortisol levels, the researchers collected two saliva samples from each participant. The first sample was taken shortly after the participant arrived at the laboratory. The second sample was taken about 15 minutes after the participant had completed an experimentally-verified stress induction task. During the task, the participants were told they had two minutes to prepare a two-minute speech regarding their faults and weaknesses. They were informed that the speech would be recorded and analyzed. They then delivered the speech, and were instructed to stop if they exceeded the two-minute time limit.
The researchers found that those with relatively high testosterone and cortisol were more likely to have engaged in impulsive and violent crime. Those with high testosterone were also more likely to have committed income-generating crimes, but only when cortisol was low. The latter finding “is consistent with the dual hormone hypothesis that holds that the positive effects of testosterone on status relevant behaviors is particularly strong at lower levels of cortisol,” the researchers said.
“Hormones are associated with variation in risk for criminal behavior and the nature of this association differs across criminal behavior type,” Armstrong told PsyPost. “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.”
“However, 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.”
As with any study, the new research includes some limitations. Changes in hormone levels from pre- to post-stressor were unrelated to criminal behavior. But the stressor (the threat of negative social evaluation) may not have been relevant to the criminal behaviors being studied. Additionally, the use of college students could limit the ability to generalize the findings to other populations.
“The results of the specific study need to be replicated in a sample at high risk for criminal behavior and with longitudinal data,” Armstrong said. “More generally we need to begin to consider how markers of biological risk for criminal behavior interact to shape serious and enduring patterns of criminal behavior.”
Despite the limitations, the findings provide important preliminary insights into the relationship between hormones and criminal activity.
“This type of research is seriously underfunded at the federal level,” Armstrong added. “We’ve had to do the scholarly equivalent of holding a bake sale to fund our research and a lot of people have made major sacrifices to develop the data that the study is based on. If you know anybody interested in supporting this kind of thing, please have them email me. Analyzing hormones is not cheap, it is worthwhile though. There is no doubt that a better understanding of the role of individual differences in risk for criminal behavior will support better prevention and treatment efforts.”
The study, “Testosterone, cortisol, and criminal behavior in men and women“, was authored by Todd A. Armstrong, Danielle L. Boisvert, Jessica Wells, Richard H. Lewis, Eric M. Cooke, Matthias Woeckener, Nicholas Kavish, Nicholas Vietto, and James M. Harper.
