People generally think men engage in riskier behavior than women, with testosterone, often called the "male hormone," pushing them to take risks. That myth has cracked. At least the notion that testosterone affects economic behavior has turned out not to be true.
A joint research team from the Stockholm School of Economics (SSE) in Sweden and Nipissing University in Canada said on Oct. 15 (local time) that "in a large clinical trial, there was no difference in economic decisions between men who received testosterone injections and men who received a placebo."
In other words, having strong male hormones does not make someone engage in reckless investing or overextend in an auction to avoid losing. The findings were published on Sept. 23 in the Proceedings of the National Academy of Sciences (PNAS).
From 2018 to 2023, the researchers recruited 1,000 men ages 18 to 45 in three regions of Canada. This sample size is 10 to 20 times larger than prior related studies.
Participants were randomly assigned to receive an 11 mg testosterone injection or to inhale a placebo through the nose. Neither the researchers nor the participants knew who received which treatment. After allowing time for the hormone to act in the body, the participants made a series of economic choices. The researchers examined how much risk participants would take, how fair or generous they were to others, and what choices they made in competitive situations.
For example, in a "risk choice task" where participants chose between a lottery option with potential losses and a sure amount, risk aversion was assessed. Then, fairness, generosity, and altruism were measured through the "ultimatum game," where participants split money with a counterpart who could accept or reject the offer; the "trust game," which involves sending and receiving money based on trust; the "dictator game," where one decides how much to allocate to another; and a "donation game," where a set amount is donated to a charity. Finally, competitiveness was evaluated with a "competition task," in which participants solved math problems under time pressure and chose between individual compensation and competitive compensation.
In the test results, none of the evaluation items showed a statistically significant difference between the testosterone and placebo groups. In other words, testosterone did not have a material effect on economic judgment. Anna Dreber, a co-corresponding author and professor of economics at the Stockholm School of Economics, said, "Most earlier studies, based on small samples, claimed that testosterone affects risk-taking or competitive behavior, but this large-scale study did not confirm such effects."
Co-author Magnus Johannesson, a professor at the Stockholm School of Economics, said, "This study shows how important large samples and preregistered study designs are," adding, "Results seen in small-scale experiments often disappear when they are reexamined under more rigorous conditions."
The researchers explained that because this experiment examined only short-term changes in testosterone, the results could differ with long-term effects or with different doses and administration methods. They also noted that women were not included, so future research is needed on sex differences and long-term effects.
References
PNAS (2025), DOI: https://10.1073/pnas.2508519122