Birth control pill can intensify jealousy experiences within intimate relationships

The use of hormonal contraceptive pills can significantly effect and intensify the experience of jealousy among female users. Evolutionary psychologist Kelly Cobey monitored the effects of pill use on both jealousy levels and female-female competition. Her research indicates that women in stable relationship experience increased jealousy levels while using the pill and that some pills generate more reactive jealousy than others. What’s more, negative effects are not limited to the female users. Male partners tend to find women more attractive when they are naturally cycling and relatively less attractive when using the pill.    

The birth control pill regulates the levels of oestrogens, progesterone and other hormones that are involved in the maintenance of the female menstrual cycle. While the pills social impact and the physical side effects have been well researched, far less is known with certainty about their psychological side effects. During a natural cycle women are largely non-fertile and only experience brief instances of fertility mid-cycle. It is at this time, that women can experience a change in their partner preference or behavior. The most likely biological mechanism behind this transition, hormone fluctuation, is suppressed by the birth control pill. This research is one of the first studies to specifically investigate correlations between birth control pill use and one possible side effect: jealousy.  

Establishing fertility

An important step in the research was the use of trans-vaginal ultrasonoraphy to establish the exact transition from non-fertility to fertility. This precise timing enabled participants in the research to answer questions about behavior and jealousy during accurate periods of the cycle. The participants were monitored while using the pill as well as while they were not using it at a time when they were both fertile and non-fertile. Male partners were also asked to monitor their behavior and relationship dynamics in order to test for effects of both the menstrual cycle and pill use on their perceptions of their relationship.

Oestrogen and jealousy

The results show that women experience increased levels of jealousy mid-cycle during fertility when not using the pill. Cobey concludes that this correlation is robust, as it is found regardless of age or relationship status in different cultures. Women who use the pill experience jealousy levels that are comparable with jealousy levels experienced during fertility in the natural cycle. Amongst the different kind of birth control pills on the market, a correlation was found between increased jealousy and the use of pills that contain higher doses of synthetic oestrogen. Particularly these pills may thus affect intimate relationships through jealousy induced changes in behavior. In general, Cobey concludes that any change in pill use pattern since the start of the relationship is likely to increase the risk of higher levels of jealousy.  

Reduced mutual attraction

A specific part of the research targeted the effects of pill use on perceptions of attractiveness within relationships. Several psychological laboratories have shown that men find women more attractive during fertility. Cobey likewise concludes from her findings that male partners find their female partners more attractive during their fertile period as compared to the non-fertile period, but she also concludes that they find them less attractive when they use birth control pills. At the same time, male self-perception, in terms of attractiveness, improves when their female partners are naturally cycling. The female partners, in contrast, report no change in self-perception of attractiveness across their cycle or as a result of pill use.  

Evolutionary side effect

Evolutionary psychology assumes that physiological characteristics, such as natural female hormone levels, are a product of natural selection and aid individuals with successful survival and reproduction. Cobey investigated a link between jealousy and female-female competitiveness, suspecting that higher levels of competition when fertile may help women to strive for better partners with whom to reproduce. The results do not support this. Participants in this research reported increased levels of jealousy when fertile. However, there was no simultaneous increase in competitiveness at this time. In fact, results suggested a reduction in competitiveness during pill use, which may be better explained by a reduction of testosterone levels. The birth control pill suppresses testosterone levels whereas a natural cycle occurs without a change in testosterone levels. Cobey concludes that variation in jealousy is more likely to be an evolutionary side effect of cyclical shifts in sexual desire rather than female-female competitive behaviour.

Social message

Cobey believes that her research is relevant for doctors and other professionals that prescribe birth control pills or otherwise give advice to women and couples in birth control related matters. “The birth control pill has proven its value as a wonderful social instrument. Because of all of its benefits, women are therefore willing to accept minor negative consequences. However, there appear to be subtle effects that can influence relationships and behavior and women are rarely briefed about such effects when they go to the doctor. I now present evidence that there are good reasons to pay attention to these effects and to study their potential impact more thoroughly.

Curriculum Vitae

Kelly Denise Cobey (Canada, 1986) graduated in Advanced Biology (evolutionary psychology) at the University of Liverpool. September 5^th 2013, she defends her PhD Thesis ‘Female Physiology Meets Psychology: Menstrual cycle and contraceptive pill effects’ at the University of Groningen Faculty of Behavioural and Social Sciences, with prof.dr.A.P.Buunk as promotor. Cobey now holds a post doc position at the University of Stirling.