The connection between the birth control pill and sexual desire has been complicated from the start.

The pill is known for having ushered in a sexual revolution, and yet for some, the cocktail of hormones that prevents pregnancy can also dampen libido.

“For a minority of women, oral contraceptive pills can cause very significant sexual dysfunction,” said Dr Andrew Goldstein, a gynecologist and former president of the International Society for the Study of Women’s Sexual Health.

A decade ago, researchers analysed 36 studies on the side effects of the combined hormonal birth control pill (containing both estrogen and progestin). They found that 15 per cent of the 13,700 women studied reported that their libido had decreased during the time they were on the pill. In the years since, only a few studies have examined why this might be, and they haven’t resulted in a clear consensus — particularly when it comes to different versions of the pill, which contain varying doses of hormones.

But what is clear is that the pill lowers users’ circulating testosterone levels, which researchers think is the crucial link to sexual desire.

Decreased libido isn’t acknowledged in the pill’s safety leaflets, nor are many primary care doctors or gynecologists aware it can be an issue, Goldstein said — so when women do mention it to healthcare providers, they’re often told “it can’t be the pill”.

Declining desire

A loss of sexual desire can manifest in a variety of ways, said Dr Lauren Streicher, clinical professor of obstetrics and gynecology at Northwestern University. Anecdotally, Streicher has found that some women might feel changes to their libido within weeks of starting the pill, while studies have found that, for others, it can take months or years for a shift to happen. For some, it might start off with the loss of the spontaneous desire for sex and then evolve into a lack of arousal in response to stimuli, she said.

One 2016 study randomly assigned 340 women the contraceptive pill or a placebo over three months to measure how it affected sexual function overall. The researchers measured blood levels of certain hormones and used a survey to determine how many sexual encounters participants had, as well as whether factors such as desire, arousal, orgasm, pleasure and self-image had changed. Although the pill didn’t affect overall sexual function, which was measured by totaling the score from survey results, the study found that it did negatively affect desire, arousal and pleasure.

Dryness and pain

The pill has also been linked to reduced lubrication, which can make sex painful and affect libido that way, Goldstein said.

And some people on the pill develop a condition called hormonally mediated vestibulodynia, in which the tissues at the opening to the vagina become dry, painful and “very pale”, Streicher said. A 2002 study found that those who used oral contraceptives had a higher likelihood of developing these physical symptoms than those who didn’t use the pill, though the overall risk remains low.

“If somebody has vestibulodynia, they’re going to lose their libido,” Streicher said, adding, “If your vagina hurts like crazy, then your brain is going to say ‘I don’t want to do this.’ "

The likely culprit

Combined contraceptive pills reduce the amount of testosterone in the bloodstream in two ways, Goldstein said: they suppress the production of testosterone and increase the production of a protein that attaches to testosterone in the bloodstream and renders it inactive. Low free testosterone is thought to be a cause of low libido, reduced lubrication and vestibulodynia.

Genetic differences mean that some people need more free testosterone than others to activate their hormone receptors — so a drop in testosterone might have a noticeable impact for them.

“The pill may have some effects for some people and not for others,” said Dr Caroline Moreau, associate professor in the Department of Population, Family and Reproductive Health at the Johns Hopkins Bloomberg School of Public Health. “Understanding who is more sensitive and who are the people who might develop adverse side effects is something that we’re missing for now.” She added that it’s difficult to directly connect biological markers, such as testosterone levels, to sexual function, which can be impacted by stress, relationship dynamics or other circumstances.

Solutions within reach

For the subset of women who have these negative experiences on the pill, the effects are reversible, Streicher said. While people’s needs vary, the first step is often to explore alternative birth control options, particularly non-hormonal ones, such as the copper intrauterine device.

Women who experience a loss in libido might get their desire back almost immediately after switching to another form of birth control, she said. “People will go off the pill and within a matter of weeks, they’ll say, ‘I’m so much better now.’”

They will also, over time, produce lubrication again, Goldstein said.

And for those with vestibulodynia, testosterone and estrogen creams can help revive tissue in the vaginal area, Streicher said.

“It’s very rare for a physician who sees complex patients to be able to say ‘I can make you better,’” she added, but when it comes to the effects of the birth control pill on sexual desire, “we can help”.

This article originally appeared in The New York Times.

Written by: Alisha Haridasani Gupta

Illustration by: Holly Stapleton

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