From sabotaging sex to axing attraction, new research is showing that the birth control pill can have impacts you never imagined. Dr Sarah Hill is a renowned evolutionary social psychologist who focuses on women and health. She is also the author of How the Pill Changes Everything: Your Brain on Birth Control.
The Psychological Impact of Hormonal Birth Control (HBC)
- Dr. Sarah Hill's interest in researching HBC stems from her personal experience of feeling a profound "waking up" approximately three months after discontinuing it, noting increased energy, libido, interest in men, and engagement in activities like downloading new music.
- Her mission is to empower women by providing scientific insights into how hormones, particularly HBC, influence their self-perception, relationships, and societal roles, emphasising that this conversation is relevant for everyone – women, their partners, and those who love women.
- HBC has been crucial for women's political and economic independence through recent history, enabling greater planning for education and careers by ensuring they can finish programmes without interruption due to pregnancy.
Natural Hormonal Cycles and Their Influence
- Women's natural ovulatory cycles involve predictable fluctuations of ovarian hormones, primarily estrogen (estradiol) and progesterone, which profoundly impact brain structure, function, mood, and behaviour. The brain is a plastic organism that changes its structure and function throughout the cycle.
- During the periovulatory phase (typically days 9-14/15 of a 28-day cycle), high estrogen levels lead to increased sexual desire, more frequent sexual behaviour, and a heightened preference for masculine cues (e.g., masculinised male faces, voices, testosterone scent) in potential partners, as the body prepares for conception. This phase is generally associated with feeling sexy and energetic.
- Conversely, during the luteal phase (after ovulation), progesterone dominance is associated with decreased sexual interest, increased sleepiness, hunger, and sometimes moodiness, as the body shifts its focus to potential embryo implantation.
- It is a misconception that women are more "hormonal" than men; everyone's behaviour and mood are influenced by hormones. Men's testosterone levels also fluctuate dynamically and unpredictably throughout the day and in response to various environmental and social cues (e.g., time of day, relationship status, presence of attractive women, competitive events, even the presence of weapons).
- The idea that sex differences are purely culturally imprinted is considered disempowering for women, suggesting they are passive products of patriarchy rather than having an evolved "female nature" shaped by inherited evolution and wisdom from successful ancestors.
Direct Psychological and Physiological Impacts of HBC on Women
- HBC works by preventing ovulation. It achieves this by providing a continuous, daily dose of synthetic progesterone (progestin) and often low levels of synthetic estrogen, which suppresses the brain's signals to the ovaries. This effectively flattens natural hormone fluctuations and keeps the body's own estrogen levels low.
- Decreased Libido and Sexual Desire: A very common side effect reported by women on HBC. This is attributed to suppressed natural estrogen levels, which typically fuel the female sexual response, and an increase in Sex Hormone Binding Globulin (SHBG) produced by the liver, which binds up free testosterone, making it inactive. Women on HBC can have free testosterone levels approximately 60% lower than naturally cycling peers, further contributing to reduced libido. While women on HBC still have sexual desire, it tends to be lower and more constant, lacking the natural peaks experienced by naturally cycling women.
- Altered Mate Preferences: Research indicates that women on HBC exhibit a decreased preference for masculinity in men (e.g., less masculinised male faces) compared to when they are naturally cycling. This shift may lead women to prioritise "tangible" qualities like financial stability, provision, and emotional stability over physical "sexiness" when choosing a partner. Studies have shown that women who chose partners while on HBC reported more satisfaction with their partners' financial resources, whereas naturally cycling women reported more satisfaction with the sexual aspects of their relationships.
- Increased Risk of Mental Health Issues: HBC use is linked to an increased risk of anxiety and depression. This risk is particularly pronounced in adolescent women (19 and younger), sometimes tripling that of adult women, potentially due to the developing adolescent brain's sensitivity to sex hormones. Studies also suggest a long-term risk of developing major depressive disorder later in life if HBC was used during adolescence, even after discontinuation. Additionally, an increased risk of suicide and suicide attempts has been linked to HBC, especially for young women.
- Blunted Stress Response: Women on HBC often exhibit a blunted or absent cortisol response to stress, a pattern also observed in individuals who have experienced PTSD or trauma. Cortisol is vital for regulating, managing, and coping with stress. This blunted response can lead to dysregulated emotional responses, contributing to the increased risk of anxiety and depression seen in women using HBC.
- Impact on Physical Fitness: HBC can influence a woman's ability to put on muscle mass and affects nutrition and fitness goals. Studies show that women on HBC gain less muscle mass and have lower testosterone and AMPk levels during exercise compared to naturally cycling women, as testosterone is a key stimulator of muscle growth.
- Changes in Perceived Attractiveness: HBC can subtly alter how women are perceived by others, including their scent and overall desirability to partners, as men are unconsciously cued into estrogen levels associated with natural fertility. Research suggests men generally find women more attractive when they are naturally cycling at high fertility compared to when they are on HBC.
- Potential for Sexual Orientation Nudges: Some bisexual women have reported shifts in their sexual preferences, feeling more heterosexual or lesbian, when on or off the pill, suggesting a hormonal influence on sexual orientation. Similar shifts might occur during other periods of hormonal disruption, such as menopause (e.g., late-in-life lesbians).
HBC's Broader Societal and Relational Implications
- Mating Crisis: While HBC has positively contributed to women's educational and career achievements, women's continued "hypergamous" preference for partners with equal or greater resources/education creates a "mating crisis". As women statistically surpass men in educational attainment and financial resources, it becomes more difficult for them to find partners who meet their standards, leading many highly educated women to opt out of long-term relationships and marriage altogether. This preference is rooted in an inherited evolutionary psychology where women historically relied on men for provisioning and protection, especially during pregnancy and child-rearing.
- Impact on Men's Motivation and Testosterone: There is a documented decline in men's testosterone levels over several decades. One intriguing hypothesis (though currently unproven) suggests that the widespread use of HBC by women, by suppressing natural ovulation and associated estrogen cues, might contribute to this decline, as men's testosterone can be sensitive to cues of female fertility. Lower testosterone can lead to decreased achievement motivation in men. Additionally, increased male caregiving roles in modern society might also contribute to lower testosterone levels. Historically, men were motivated to achieve status and resources to attract women. HBC, by allowing casual sex without pregnancy worries, arguably reduced the "price" of sex for women, potentially leading to lower standards for male partners and reinforcing "shiftlessness" in men who find they can gain sexual access with minimal effort.
- Relationship Stability: If a woman chooses her partner while on HBC, discontinuing it can lead to changes in relationship satisfaction and sexual attraction. A longitudinal study found that women partnered with attractive men experienced an increase in sexual desire and attraction after going off HBC, while those partnered with less attractive men reported a decrease in relationship satisfaction and sexual desire. These changes are often subtle "nudges" rather than dramatic transformations, but for individuals on the "tails" of attraction, the shift can be significant.
- Gendered Competition and Double Standards: Women often compete intensely with other attractive women for male partners, particularly in environments with asymmetrical sex ratios (e.g., college campuses with more women than men). This competition can lead to women being more willing to engage in casual sex to secure a partner, even if they desire long-term relationships. Women often derogate their competitors by making negative remarks about their attractiveness. Physical attractiveness is a stronger predictor of a woman's upward social mobility than her education level or socioeconomic status of origin. Men's mate preferences heavily prioritise physical attractiveness and youth, whereas women tend to prioritise cues of status, wisdom, and resource acquisition (which often increase with age). Powerful women often face a "double standard," being perceived more negatively (e.g., "cold," "bossy") than powerful men, despite confidence being generally attractive.
- "Daddy Issues" Explained: Research indicates that women whose fathers were not invested or were absent during childhood tend to experience earlier puberty and more precocious or unrestricted sexual development, including an earlier age of first sexual activity and a greater number of sexual partners, compared to women who grow up with investing fathers.
The Future of Birth Control
- Current hormonal contraception is considered "far from perfect" due to its significant psychological burden and side effects, and there is a cultural misconception that the issue of birth control is solved. Many women report significant side effects but tolerate them because the alternative (pregnancy) is deemed a greater cost.
- There is a critical need for new, non-hormonal contraceptive options that do not disrupt natural hormone production in either sex. Early research into non-hormonal male contraception (e.g., blocking a specific vitamin A derivative essential for sperm production in mice) shows potential but is a long way from human application.
- A male hormonal pill is unlikely to gain widespread acceptance because men are generally less motivated to endure side effects, given that they do not bear the direct costs of pregnancy, and women would be less likely to trust men to consistently use it, especially in casual relationships.
- The reluctance to critique HBC openly stems from its immense importance to women's independence and the fear that any negative discussion could threaten its availability, particularly in the current social and political climate.
- Informed decision-making for women regarding HBC should weigh individual risks and benefits. For teenagers, non-hormonal options like the copper IUD are suggested as preferable to avoid potential long-term impacts on brain development, if appropriate for their situation.