Listed by the World Health Organization (WHO) as an essential medicine, birth control pills (or oral contraceptives) allow women the opportunity to control their sexual and reproductive health, and have played an important role in the liberation of women. Approximately 55 million women in the USA use oral contraception, but they do so with the knowledge that there are a number of associated side effects, including altered moods. Sometimes these effects are severe enough for some women to cease the use of the pill completely.
A new study, published in Nature’s Scientific Reports, has pointed to a potential cause of these emotional changes, and it’s to do with the pill’s impact on levels of the so-called love hormone – oxytocin.
“Oxytocin is a hormone found naturally in the body and is secreted during social cues and bonding, reinforcing social behaviour,” Associate Professor Michael Winterdahl of Aarhus University, Denmark, and corresponding author of the study, said in a statement.
“Our study presents, for the first time, evidence for changes in the levels of oxytocin in response to birth control, providing a mechanism by which some women experience altered mood.”
By analyzing blood samples of 185 young women (average age 21.2 years) from the USA, the researchers determined that those on birth control pills had a significantly higher level of the hormone than non-users. Although oxytocin has previously been shown to reduce anxiety, a sustained presence of the hormone could have negative effects on a woman’s emotional life.
“A constantly elevated level of oxytocin may mean that it is not secreted in the same dynamic way as under normal conditions,” Winterdahl explained. “It is precisely these dynamics that are important to our emotional lives. This may explain why feelings such as closeness, attachment and love appear to be altered in some women who use birth control pills.”
One way to think about it, Winterdahl told IFLScience in an email, is that initially "if you are very high in oxytocin... you are not going to feel the "buzz" from the release of a small amount of oxytocin." This can lead to a stabilization of mood and a decrease in interest and pleasure known as “blunted positive affect.” For those who experience wild mood swings this can be a good thing but "over time being deprived of positive social feedback can possibly contribute to the development of depression," Winterdahl added.
Interestingly, in accompanying psychometric measures to Winterdahl's research, the women on birth control pills had a higher satisfaction with life score than those who were not. As discussed in the study, this could be a result of a complex interplay between relationship status, sexual activity, as well as the use of the pill. Indeed, women taking oral contraceptives in other studies had an increased relative risk of depression compared to non-users.
Whilst future research will need to look into the variation of oxytocin levels between different types of birth control pills, and in longer-term use, this new knowledge may help explain why some women experience mood alterations when taking oral contraceptives.