Study suggests long-term relationships reduce men’s testosterone

New research has found further support that an elevated level of testosterone in men is linked to motivation to find new mating partners.

In a study published earlier this year in Evolutionary Psychology, Dr. Daniel Farrelly, of the University of Sunderland and the University of Worcester, and his colleagues show that salivary levels of testosterone are reduced in undergraduate men who report being in a long-term relationship (greater than one year), compared to single men and men in new relationships.

Previous work has suggested that testosterone is an important physiological motivator in men to find new sexual partners. It is known that married men and men in long-term committed relationships typically have lower levels of testosterone than single men, and that fathers have especially reduced levels of testosterone. Furthermore, men who are in polyamorous relationships or are interested in extra-pair sexual activity also exhibit elevated testosterone.

Thus far, however, studies have relied on participants’ self-categorization of their relationship commitment into broad categories such as “in a relationship” or “casually dating.” This new study avoids such tricky labels by asking men directly how long they have been in their current relationship.

Researchers collected salivary testosterone samples from 76 heterosexual men between the ages of 18 and 39. Men that had been in a relationship for greater than one year had lower levels of testosterone than both single men and men who were in more recent relationships.

The researchers report that there were no significant effects of current relationship satisfaction or the frequency of seeing one’s partner. Unlike previous research in this area, this study found no differences in testosterone based on one’s current or a previous-relationship history of engaging in sex with a person other than one’s partner, or one’s potential willingness to do so. There were also no effects of age. Among men in long-term relationships, there were no further differences in levels of testosterone based on the length of the relationship.

Reduced testosterone is thought to promote relationship building and caring for children instead of pursuing mates. From an evolutionary perspective, this behavioral shift is important to ensure that after a man secures a mate and produces offspring, his offspring are provided with adequate care. The researchers point out that, “men in new relationships are still in a physiological state that aids competition with other men for access to potential mates.”

Future studies will address the causal relationship between testosterone and the psychological state of mate pursuit. Currently it could be the case that men with naturally higher levels of testosterone are more likely to breakup with their partners, or that men with naturally lower levels are more likely to commit to longer relationships. Longer-term studies will have to sample men over time as their relationship status changes to see how levels of testosterone respond.