By: Elizabeth Palermo, LiveScience Staff Writer
Published: 06/10/2015 02:38 AM EDT on LiveScience

Women with low libido could soon get a “little pill” of their own that aims to improve their sex life. Last week, an expert panel voted to recommend that the Food and Drug Administration (FDA) approve a drug called flibanserin, which is touted as boosting women’s desire for sex. If the FDA decides the drug is safe and effective, it could soon find its way into bedrooms across the United States.

Unlike Viagra, which causes more blood to flow to a man’s penis, flibanserin doesn’t just aim to improve a woman’s physical readiness for sex. Instead, the drug purportedly works by amping up the brain’s levels of dopamine and serotonin — two chemicals known to induce sex-related feelings, such as motivation, appetite and desire.

However, sexual desire is complicated, and some experts aren’t sure that a pill is really the cure for an ailing female mojo.

“I’m skeptical [about flibanserin] as both a professional and as a woman,” said Dr. Elizabeth Kavaler, a urologist at Lenox Hill Hospital in New York City. “The libido in both men and women is very complex, and it’s not going to be remedied with a pill.” [5 Myths About Women’s Bodies]

There are lots of things that can quell a woman’s desire to have sex, Kavaler told Live Science. These range from psychological factors, such as her self-esteem and mental health, to physical factors, such as her hormone levels and how well she’s sleeping, Kavaler said.

In fact, researchers have conducted dozens of studies exploring the many reasons why a woman might not feel like having sex. Here are five reasons that women may not be in the mood:

1. She’s in pain.

Several studies have explored the relationship between sex and pain in women. One study, published in 2009 in The Journal of Sexual Medicine, looked at women with dyspareunia — a condition that results in recurrent genital pain during intercourse and that’s estimated to affect 8 to 21 percent of women worldwide, according to the World Health Organization (WHO).

The study found that women with dyspareunia have thoughts about pain that can be easily activated, said Lea Thaler, a researcher at the University of Nevada, Las Vegas who led the study. Shortly after that study’s publication, Thaler told Live Science in an interview that women with the condition tend to be “hypervigilant about” (or constantly on the lookout for) pain during sex.

Although Thaler’s study didn’t focus on how this increased vigilance about pain may affect a woman’s desire to have sex, other studies have explored the relationship between pain and libido. A 2014 study published in The Journal of Neuroscience found that female mice that are in pain are less motivated to have sex than female mice that are not in pain. The study also found that the same thing is not true for male mice, which were willing to copulate even when in pain. [The 10 Most Surprising Sex Statistics]

The findings of this study could provide clues about how libido works in women, according to the researchers, who told Live Science that their findings could help scientists understand why women with chronic pain often experience a decreased desire to have sex.

2. She’s on the pill.

Women who use hormonal contraceptives, such as the pill or the patch, are more likely to have a decreased sex drive than women who don’t use hormonal contraceptives, according to a study published in 2010 in the Journal of Sexual Medicine.

The link between hormonal contraceptives and low libido needs to be explored further, said the authors, who noted that their findings are preliminary. Specifically, the researchers said they would like to study the effects of different dosages of estrogen and synthetic progestins (two types of hormones commonly used in contraceptives) on female sexual function.

In 2013, researchers with the European Society of Contraception and Reproductive Health conducted a systematic review of the literature surrounding the link between sexual desire and the use of combined oral contraceptives (which contain both estrogen and synthetic progestins). They reviewed 36 studies and found that, among the hormonal contraceptive users, 85 percent reported an increase in libido or no change in libido when taking these contraceptives, while 15 percent reported a decrease in libido. The researchers also found that women who reported a decrease in libido were taking contraceptives containing a lower dose of estrogen hormones.

3. She’d rather masturbate.

Although testosterone is the hormone most often associated with virility in men, this chemical may actually decrease a woman’s desire to have sex (at least with other people), according to a study published in 2012 in the journal Archives of Sexual Behavior. The study, which found a link between higher levels of testosterone and decreased sex drive in women, also found that high-testosterone women were more likely to masturbate than low-testosterone women. [6 (Other) Great Things Sex Can Do For You]

Interestingly, the researchers found that men’s levels of testosterone did not affect sexual desire. The average man reported more sexual desire than the average woman, the researchers found,

4. She’s just not that into you (anymore).

Women’s desire may fade as a relationship goes on, according to a study published in 2012 in the Journal of Sex & Marital Therapy. Researchers polled 170 heterosexual men and women who had been in relationships for between one and nine months. They found that although most participants reported feeling satisfied with their relationships and sex lives, women reported lower levels of desire related to the length of their relationships.

Specifically, the researchers found that for each additional month women were in a relationship with their partner, their sexual desire decreased by a small amount — 0.02 points on the Female Sexual Function Index (a self-reporting tool that helps scientists study female sexual arousal, pain, satisfaction and orgasm). This finding did not hold true for men, whose sexual desire remained steady over time.

“When an individual has had sex with their partner over the course of many, many years, it takes creativity and openness to keep things fresh and exciting, Sarah Murray, one of the sex researchers who conducted the study at the University of Guelph in Ontario, Canada, told Live Science. “Making time to be together and keep one’s sex life as an important part of one’s relationship is very important, and putting in effort and keeping things fun and interesting are crucial components.”

5. She has a headache.

Women who get frequent headaches or migraines are more likely to have dysfunctional sex lives than women without these health issues, according to a study published in 2012 in the Journal of Sexual Medicine. The study, which looked at 100 women being treated for headaches, found that 91 percent of the patients’ scores on a questionnaire showed they had sex problems beyond what would be considered within the normal range.

Among these problems was low sex drive. About 17 percent of the women surveyed said they weren’t interested in having sex, and another 20 percent of study participants said they not only had a low sex drive, but were also distressed about their lack of desire.

There are many possible reasons why headaches and low sex drive may be linked. Research shows that any type of chronic pain affects desire and arousal, and also that people with headaches often have mood disorders such as depression and anxiety, both of which have been shown to affect sex drive and sexual satisfaction. The medications taken to treat headaches, depression or anxiety can also interfere with a woman’s desire to slip between the sheets.

Follow Elizabeth Palermo @techEpalermo. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

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