Testosterone levels influence whether men become engaged in a committed, monogamous relationship or not, according to research published in the journal Adaptive Human Behavior and Physiology.

Previous research has found that men with one long-term partner tend to have lower testosterone levels than single men or men with multiple partners. However, the direction of this relationship was unclear. Did monogamous relationships lead to lower testosterone or were men with lower testosterone more likely to be monogamous?

The new longitudinal study of 79 male first-year college students suggests that both options may be in play. Testosterone levels predicted relationship status a month later, but the researchers also found some evidence that testosterone responded to changes in relationship status. In particular, transitioning from a committed to non-committed relationship status predicted an increase in testosterone.

PsyPost interviewed the study’s corresponding author, Sari M. van Anders of the University of Michigan, Ann Arbor. Read her responses below:

PsyPost: Why were you interested in this topic?

Van Anders: Although most research on hormones investigates how hormones affect behaviors, we are particularly interested in how behaviors can affect hormones. The steroid hormone testosterone is linked to human sexuality and relationships in both men and women. Previous research has shown links between relationship status and testosterone in men, specifically that monogamously – or monoamorously – partnered men have lower testosterone than single men. However, research had not determined directionality of these links, i.e. whether testosterone levels predict relationship status or whether relationship status predicts testosterone. This study attempts to help clarify the direction of these links.

What should the average person take away from your study?

Our study provides longitudinal evidence that, in men, testosterone levels predict relationship status, and relationship status predicts testosterone levels. Our results showed that single and casually partnered men had significantly higher testosterone than men in committed relationships, supporting previous research. In addition, we found that low testosterone levels predict a committed relationship status later on.

However, not all relationship transitions were similarly linked to testosterone. We found evidence that high testosterone levels early on did not predict later relationship status transitions from committed to single or casually partnered. Instead, transition from committed to single or casually partnered predicted high testosterone later on.

Are there any major caveats? What questions still need to be addressed?

Like every study, ours has important caveats. One is that generalizability is limited since our sample was first year college students whose relationships we classified as “casual”, “committed”, or single. Results might differ in older men and those with different types of relationship configurations and experiences. Future research could investigate links between relationship status and testosterone with more nuance in relationship type. Additionally, our sample contained a small number of relationship transitions, so future research is needed to clarify how specific types of relationship transitions are linked to testosterone.

Is there anything else you would like to add?

Testosterone is most often tied to men, maleness, and masculinity in our culture but we also do research on testosterone in women. Indeed, there is a companion paper on relationship status and testosterone in women.

The study, “Pair Bonding and Testosterone in Men: Longitudinal Evidence for Trait and Dynamic Associations,” was also co-authored by Emily R. Dibble and Katherine L. Goldey.