The first hormonal contraceptive (‘the pill’) was approved by the US Food and Drug Administration in 1960.
Hormonal contraceptives have become one of the most prescribed medications in the world, used daily by more than 100 million people worldwide.
These drugs prevent pregnancy by injecting synthetic hormones into the bloodstream. Synthetic hormones prevent the body’s own hormones from stimulating ovulation, so no egg is released, fertilization cannot occur, and pregnancy is prevented.
Research has shown that naturally occurring hormones have a strong influence on the behavior of humans and other animals. But less is known about the behavioral effects of synthetic hormones — like those on the pill.
Some hormones affected by the pill are linked to competitive behavior. We wanted to learn more about how hormonal contraceptives change this behavior, so we reviewed all the research we could find on hormonal contraceptives and competitive behavior.
Hormones and competition
Competition is part of life. We compete for a variety of resources, such as money, food, friends, and associates, to meet our needs and improve our chances of survival and flourishing.
These resources can also be intangible things, such as social status, which give us access to more tangible objects. For example, a high-status person may have better opportunities for education and employment.
Hormonal contraceptives directly affect three hormones linked to competitive behavior: testosterone, progesterone, and a type of estrogen called estradiol.
To understand the role of hormonal contraceptives in competition, we reviewed 46 studies, totaling 16,290 participants. This was all available published research that included a measure of competition.
Status and motivation
One finding from our review was that hormonal contraceptives may affect women’s motivation and ability to achieve high status.
One study shows the effect of low achievement motivation.
Another study shows poor performance on tasks that require persistence. This is related because people often achieve high status by demonstrating skill or mastery.
The pill can also affect competition around mating. Recent research shows that women who cycle naturally feel more sexually desirable and attractive mid-cycle, but hormonal contraceptive users do not.
This suggests that hormonal contraceptives reduce fertility-induced increases in feelings of desirability that motivate sexual behavior.
We did not find strong evidence that hormonal contraceptive users differed from nonusers in the types of men they were attracted to. There was also a lack of evidence that users behaved differently when competing for financial resources compared to non-users.
Interestingly, the effect of hormonal contraceptives on mating and status-based competition depended on the relationship status of the participants. For example, one study found that hormonal contraceptive use reduced self-reported competitiveness for women in relationships but not single women.
This means that synthetic hormones may affect single and partnered women differently. On the other hand, there may be other differences influencing these behaviors among single and partnered women.
Small effect sizes and methodological limitations
It is important to note that differences in behavior between those who used hormonal contraceptives and those who did not were generally small.
Another finding from our review was that much of the existing research on the effects of hormonal contraceptives suffers from significant methodological limitations.
Only one of the studies we reviewed used randomized controlled trials, the gold standard for determining the effect of a particular drug or treatment.
Many of the studies we reviewed also did not account for other differences between hormonal contraceptive users and nonusers, such as age. These are factors that may explain behavioral differences independent of hormones and hormonal contraceptives.
Small sample sizes in most research make it difficult to generalize to the wider population. Non-white women in particular were vastly underrepresented in this research.
Many studies also did not report the types of hormonal contraceptives people were using. This makes it impossible to determine whether all forms of contraception are associated with similar outcomes.
Because of these limitations, the findings of our review are only preliminary.
Where to go from here?
Despite 60 years of widespread use, the effects of hormonal contraceptives are still poorly understood. They are also used for many purposes other than birth control, such as reducing premenstrual symptoms, correcting hormone imbalances, or reducing the symptoms of acne and endometriosis.
Access to reliable contraception has enormous benefits for individuals and society. This is associated with increased female participation in higher education, a reduced gender gap in wages and a reduction in female poverty.
To ensure that women can make informed decisions about their bodies, we need reliable and robust evidence about the full effects of hormonal contraceptives.
To paraphrase American filmmaker Sind Agha, we have the right to birth control, but we also have the right to good birth control. It’s going to take a lot of research.
Lindsie Arthur, PhD Candidate, Melbourne School of Psychological Sciences, University of Melbourne; Kathleen Casto, Assistant Professor of Psychology, New College of Florida, and Khandis R. Blake, Lecturer in Psychology, University of Melbourne
This article is republished from The Conversation under a Creative Commons license. Read the original article.