1% of people don’t have sex. New research shows it may be partly genetic

Sex is important. Romantic, typically sexual, partnerships are often among the most central relationships in individuals’ lives, providing a host of personal, health, social and economic benefits.

But what about people who don’t have sex?

In a new study, my colleagues and I looked at the differences between mature adults who had never had sex and those who had. We found sexlessness is associated with a range of genetic, environmental, physical and mental factors – but much still remains unclear.

Life without sex

Some people – often described as “asexual” – simply don’t desire sex.

However, those who do but are unable to find suitable and willing partners may be vulnerable to poor mental health and loneliness, social embarrassment, and economic disadvantages (for example due to not cohabiting with a partner). People involved in online “incel” (involuntary celibate) cultures may even be at risk of radicalisation.

So it is important to understand more about people who don’t have sex.

Knowing the characteristics associated with sexlessness would help to understand its causes and consequences. It may even inform strategies to remove barriers to people finding fulfilling partnerships.

To find out more, we studied about 400,000 UK residents aged between 39 and 73, and a further 13,500 Australian residents aged between 18 and 89. Around 1% of both men and women had not had sex.

Our team – led by Laura Wesseldijk, Abdel Abdellaoui and Karin Verweij from Amsterdam UMC, and me – examined associations between sexlessness and genes, the social environment, and various physical, cognitive, personality and mental health traits.

Sex ratios and income inequality

We found sexless men tended to live in regions of the UK with relatively fewer women.

In both men and women, sexlessness was more common in regions with higher income inequality.

These new findings align with those of an earlier study of “incel” posts on social media. It found they were more likely to originate from regions of the United States with relatively fewer women and higher income inequality.

Wellbeing and other factors

We also looked for characteristics that were more common among people who had never had sex.

Sexless individuals tended to feel more nervous and lonely and less happy, and had fewer visits from friends and family. They were also less likely to have someone to confide in or to believe that life is meaningful.

These findings confirm the entanglement of sex and wellbeing.

People who had never had sex tended to use drugs and alcohol less, be more educated, and to have started wearing glasses from a younger age.

Men with lower grip strength and arm muscle mass (proxies for general upper body strength) were less likely to have had sex. There were no such correlations among women.

Familiar stereotypes

The overall pattern we observe among sexless people – intelligent, academically successful, with less physical strength and more social isolation – aligns with existing stereotypes of lower romantic success, especially in adolescence.

Our participants were middle-aged adults, or older.

However, wearing glasses at an early age, and other stereotypically “nerdy” features, may disrupt adolescent dating experiences. This in turn may affect one’s romantic confidence into adulthood.

No gene for sexlessness

We also had genetic data about all participants. This meant we were able to analyse whether genetic differences were associated with having had or not had sex.

Using what’s called a genome-wide association analysis, we found genes accounted for 15% of the variation in whether or not individuals had had sex.

However, there were no individual genes with large effects. Rather, there were many genes, each with tiny effects.

Links to intelligence, introversion and other traits

Our genetic analyses also let us detect genetic correlations with any other traits that have been genetically analysed, even if in separate studies. A genetic correlation indicates the genes associated with one trait are also associated with another trait.

In this way, we found an array of interesting links between sexlessness and other traits.

In particular, there was a strong genetic correlation not only with education but also measured intelligence. There were also correlations with higher income and socioeconomic status.

Sexlessness was also positively genetically correlated with introversion, autism spectrum disorder and anorexia. However, it was negatively genetically correlated with drug and alcohol disorders and also depression, anxiety and ADHD.

Cause and effect is hard to discern

Our results paint a complex picture. One major aspect of uncertainty is what causes underlie the pattern of associations we found.

For example, not having had sex may cause unhappiness. But unhappiness may also make it more difficult to find a partner, or a third factor could cause both unhappiness and difficulty finding a partner.

Another aspect of uncertainty is that the participants only reported whether or not they had had sex, not whether they had ever desired sex. Many sexless individuals in the sample may be asexual.

However, some of our results are difficult to explain via asexuality – for example, the link with the local ratio of men to women, and the negative association with male strength. Our results likely reflect a mixture of voluntary and involuntary sexlessness.

A step forward

Our study represents a large step forward in understanding sexlessness. However, more nuanced assessment of desire and sexuality will be key to better characterising how sexlessness relates to the interplay between genes, local environments, sexuality and culture.

Studies of more people using more advanced methods may also be able to tease apart cause and consequence.

There should be no value judgement on individuals who do not have sex, whether voluntarily or otherwise. By studying this trait, we only aim for a deeper understanding, which generally benefits all concerned.