Hormone control: How the pill changes your behaviour

Hormone control: How the pill changes your behaviour

Sharon Ní Chonchúir talks to US psychologist Sarah Hill, who says the pill can affect your behaviour, sense of smell and choice of partner.

Have you ever been on the pill? Considering it’s one of the most reliable forms of contraception, many women are likely to answer this question with a yes. Yet how much do we know about the contraceptive pill? Do we understand its full effects on our bodies?

According to a ground-breaking new book by psychologist Dr Sarah Hill, science is only now beginning to ask these questions. She lays out the answers in How the Pill Changes Everything: Your Brain on Birth Control.

It begins with Hill’s own experience of taking the pill. She started in her late teens and continued for more than a decade. “Like most women I know, I’ve spent a good portion of my adult life taking for granted the fact I don’t need to worry about getting pregnant from sex,” she says. “That’s been a total game-changer for women.”

It meant she could focus on her studies, graduate with a PhD, and choose when to get pregnant. It wasn’t until she stopped taking the pill aged 31 that she realised it might have had other unexpected effects too.

“Over time, I started listing to more music, paying more attention to my appearance and exercising more,” she says.

One night, on the way home from dinner with my husband, I told him I felt vibrant and alive in a way I hadn’t felt since I’d been a teenager

She didn’t connect this feeling to coming off the pill until she heard about a study at an academic conference. This 2014 study found that being on the pill seems to influence the types of men women get involved with, their satisfaction with their partner, and even their likelihood of getting divorced.

This led Hill down a rabbit hole of research, the results of which she details in her book. “It’s mind-blowing,” she says. “Studies show the pill could have a hand in who we’re attracted to and even in how we respond to stress. This illustrates just how wide-ranging its effects can be and proves to me that we’re in the dark ages when it comes to understanding what the pill does to the female body.”

There are two things you have to understand before you can comprehend the potential impact of the pill. “Firstly, hormones are not specific,” she says. “They broadcast a message to the whole body, making sure there is a co-ordinated response to the matter in hand.”

This means the pill — a synthesised hormone — has the desired effect of preventing pregnancy, but has many other effects too.

Hormone control: How the pill changes your behaviour

Secondly, she points to how the female fertility cycle works. If you’re not on the pill, it splits into two halves, pre-ovulation and post-ovulation. The oestrogen hormone dominates in the first half and the progesterone hormone dominates in the second.

When you’re on the pill, levels of these hormones stay constant, with progesterone dominating throughout. The body gets the message that ovulation is not necessary, which prevents pregnancy. But what other messages is it getting too?

Mr Right — for now

Let’s go back to the study looking at the type of man women are attracted to when they’re on the pill. In the lead-up to ovulation, the surge of oestrogen means women are more likely to be attracted to tall, symmetrical men with deep voices.

These qualities indicate health and testosterone, which are more likely to result in successful pregnancies. In the latter half of their cycle, progesterone changes women’s focus and they are more likely to choose men for their ability to provide.

In pill-taking women, progesterone dominates the entire cycle. As a result, they exhibit an unwavering preference for men with less masculine faces and voices.

What does this mean for couples who met up while the woman was taking the pill? Will she dislike her partner when she stops taking it?

Research has tried to answer this question. Of the 2,000 mothers interviewed in a 2011 study about their relationships, half had met their partners while on the pill and half hadn’t. Those who hadn’t generally found their other halves sexier and reported having better sex lives than those who had.

If you find this too depressing, the same study found that women who chose their partners while on the pill were more satisfied with their partner’s financial providing and intelligence, and were significantly less likely to divorce.

Scent of a man

A diminished sense of smell could be one of the factors influencing pill-taking women’s choice of partner. In one study, researchers measured women’s sensitivity to six scents. Three — peppermint, rose, lemon — didn’t have much to do with sex, while three others — musk and two forms of testosterone – are believed to play a key role in women selecting a partner.

Pill-taking women were just as sensitive to peppermint, rose, and lemon as naturally cycling women. But when it came to the other scents, they didn’t even detect them until they were intensified to very strong levels.

Taking the pill may also affect how sexy you feel and, as a result, how much effort you put into your appearance. Studies have shown show that the five days before ovulation are marked by an increase in sexual desire, which drives women to wear more makeup and sexier clothing. Women on the pill don’t experience this desire, and consequently, display less interest in clothes and beauty products.

“Sex is so much more than just sex,” says Hill.

It’s shopping and makeup, exercising and creativity and a whole bunch of things you probably haven’t considered. Because sex is at the heart of so many things we do, the pill may change more than just your activities in the bedroom

It can even have an impact on your response to stress. Stress causes humans to produce a hormone called cortisol. That is, all humans except for pill-taking women.

You might think this was a boon for these women. The pill could reduce their stress levels.

Hormone control: How the pill changes your behaviour

Not so, according to Hill. “They still feel stressed, although the biochemistry of what’s happening in their bodies is different,” she says.

“In real life, this could mean women on the pill see a monotone version of life, which might account for some of them reporting low mood.”

The lack of cortisol might also hinder women’s ability to learn and remember information. Hill’s own studies have found that women on the pill performed worse than naturally cycling women on a difficult exam and were quicker to give up on unsolvable word puzzles.

On reflection

Had she known what she knows now, Hill would have taken more care in making considered her decision to take the pill more carefully. “I might have tried something non-hormonal like a copper IUD,” she says. “If I hadn’t tolerated that, at least I would have been more strategic about how I used the pill. I wouldn’t have used it non-stop when I wasn’t having regular sex.”

She will know better when it comes to advising her now 11-year-old daughter. “One of the things I’ve learned while researching this book is that the pill can have a huge impact on mental health, with women on hormonal contraceptives being 50% more likely to be diagnosed with depression and young women aged between 15 and 19 being at the highest risk of all,” she says.

“At such a formative age, I would urge my daughter to try a non-hormonal option first.”

In the meantime, Hill hopes that her book will help women and their doctors become more informed about the pill and what it does to women’s bodies.

“The pill has given women life-changing opportunities, but we need to be aware of the price we’re paying for those opportunities,” she says.

“We need to be sure the trade-off is worth it for us.”

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