What causes sexual desire to fluctuate?

The world of sex research can be hard to keep up with. To probably no one’s surprise, so much of what we have held as scientific fact for centuries is being undermined every day, to the point where we have to throw whole concepts in the bin, and for good reason. These “facts” about sexuality are usually cultural assumptions derived from shame, not evidence. Take, for example, the hymen: a symbol of ‘virginity’ (another made up concept) that, once broken, has been pointed to as evidence of intercourse. Or the understanding that the clitoris was a tiny nub at the top of a vulva. The clitoris has appendages that straddle the vagina, and not all people with vulvas were born with hymens, while some hymens stick around until after menopause, regardless of penetrative experience. Here we are, in 2021, relearning so much of what we thought we knew! Even then, some myths persist. We’re not out of the woods of shame or poor sexuality education. 

The idea of the ‘sex drive’ is one of those questionable facts under scientific review. Emily Nagoski, researcher and author of ‘Come As You Are’, is emphatic that the sex drive does not exist. A biological drive is a mechanism our bodies have developed to keep us alive. Hunger, thirst and fatigue are examples. We won’t die without sex, so it’s not considered an essential drive. Instead, sex is thought to be an “incentive motivation system”. This refers to when an attractive external stimulus compels us to act, rather than an internal discomfort and lack. 

Nagoski argues that the idea of a sex drive has been dangerous because it makes people expect their desire to be spontaneous, available in nearly any context and emerge from within them. In reality, spontaneous desire is only one desire style. The other style many people experience is responsive desire, which is context-dependent and reacts to arousal, like feeling horny after someone grabs your butt. 

The “sex drive” has allowed doctors and therapists to pathologise people, most of them women, who don’t desire sex out of the blue. Society has spread the message that, without this innate survival need, such people must be sick. This includes 30 per cent of cis women who rarely or never experience desire for sex without external stimulus. All of them are normal. 

So, how do we explain human sexual desire? And why does it vary among people and across lifespans? Enter the dual control model of sexual response. Erick Janssen and John Bancroft developed this framework in the 1990s. They said that sexual response works much like our central nervous system. On one hand, the Sexual Excitation System accelerates our sexual response to relevant stimuli, like certain smells, sounds or images. It feeds the information back to our brain and tells it to feel turned on. 

The Sexual Inhibition System works in opposition. It puts the brakes on in response to other stimuli, like danger, telling our brain to be sexually turned off. What constitutes the exciting stimuli and inhibiting stimuli depends on the individual and their context. They also aren’t innate, but learned throughout our lives. Some people experience a more sensitive Sexual Excitation System and a less sensitive Sexual Inhibition System, meaning they are more easily turned on and less readily turned off. Others might experience the opposite, or score somewhere in the middle. Asexual people usually have less sensitive accelerators, but studies show no difference in their brakes from their sexual counterparts. And one person’s brake can be another person’s Accelerator. 

It’s all very interesting and very normal. There is so much variation between us all, within and across gender lines. Nagoski says the goal is to learn your brakes and accelerators so you can use them to your liking. You can also understand yourself better and be kinder when your body isn’t behaving as you’d like it to. 

Some examples of common stimuli affecting desire include: 


Stress can really put the brakes on sexual desire. Over fifty per cent of women report that stress, depression and anxiety decrease their interest in sex. During stress, the brain is focussed on survival, and can’t take in much more information. If you’re at a stage in your life with multiple stressors—kids, work, study, illness, relationship troubles—these can weigh heavily on your brakes, even if you have a strong excitation system. But we’re not all made the same. Nagoski writes that around 10 to 20 percent of people report that stress actually turns them on, even if it blocks pleasure. 


For survivors of sexual assault, sex itself can become the stressor. According to Nagoski, after sexual trauma, things that used to be accelerators might become brakes because they are now perceived as threats. Someone might also engage in compulsive sexual behaviour to revisit the trauma or to try to reframe it. It might take therapy to work through this. 


Sickness and medication can interfere with our body’s regular or ideal functioning. Although Nagoski is quick to note hormones are the least likely cause of low desire. 

Relationship satisfaction and security

This one seems pretty obvious. If you aren’t particularly satisfied in your sexual relationship/s, you probably won’t want to get busy. This isn’t to say all long-term monogamous relationships are sexually doomed, though. If you take the time to learn yours and your partner’s brakes and accelerators, these can be wielded accordingly.

On the darker side, relationship insecurity or instability can actually make you crave sex more. This is because sex becomes a safe haven or relief from the bad times, when the relationship is threatened. This can become a very dangerous dynamic in abusive relationships.

Body Image 

Studies have shown links between body image and all areas of sex: arousal, desire, pleasure, orgasm and sexual assertiveness, among others. Almost always, body self-criticism negatively affects sex. Science tells us that loving our bodies more will help us have better sexual experiences. 

Do you think you have a sensitive accelerator or brake? Both? Or somewhere in the middle? Have a think about what your accelerators and brakes actually are. How can you incorporate them into your life to improve your sexual wellbeing?

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