"Casual sex makes you depressed and anxious," the Mail Online reports today.
The headline writers have presented a statistical link as proof that one thing (casual sex) causes another (depression). While an association between the two has been observed, it is not possible to say, based on this study, that casual sex causes mental distress, or whether feeling down leads to more casual sex.
The news story is based on research into the sexual behaviour and mental wellbeing of almost 4,000 heterosexual US college students.
The problem is that in this type of study – a cross-sectional study – people are asked to provide information at one particular point in time. This tells us very little about the complex interplay between young people’s sexual behaviour and their psychological health. It is impossible to tell from a cross-sectional study whether there is a cause and effect relationship.
Drawing firm conclusions from this study is also difficult because it did not take into account the many other factors that might have influenced these students’ mental health.
The study was carried out by researchers from a number of US universities including California State University. There is no information about external funding.
The Mail Online’s reporting on this study is mixed. Its headline: “Casual sex makes you depressed and anxious” is not supported by the study. However, it concedes in the ‘blurb’, just below the headline, that “It's unclear whether existing mental health problems cause young adults to engage in riskier behaviours”.
This was a cross-sectional study that looked at the association between casual sex and psychological health. Cross-sectional studies provide a snapshot of participants at a particular point in time. Because they look at all data at the same time, they cannot demonstrate cause and effect, which means they can’t show if one thing leads to another. However, cross-sectional studies can be useful for showing up patterns or possible associations in the data, which may justify further study.
The researchers point out that many young adults frequently have casual sex. Prevalence rates are estimated to range from 14% of young adults to 64%. They also say that casual sex can be defined in many ways including non-committed sexual relationships between friends ("friends with benefits") and sexual encounters with strangers ("hook-ups"). In this study they define casual sex as having intercourse with a partner who has been known for less than a week.
They also say that in studies looking at mental health and casual sex the results have so far been mixed. Some but not all research suggests an association between sex with a stranger and low self-esteem.
Other research has suggested there may be gender differences in attitudes to casual sexual behaviour, and that women are more likely to report feelings of regret and guilt after casual sex.
The authors’ hypothesis was that casual sex would be positively associated with psychological distress and negatively associated with psychological wellbeing. They also believed that these effects would be stronger for women than men.
The researchers recruited a multi-ethnic sample of 3,907 single, heterosexual college students aged 18 to 35, from 30 universities across the US. Students took part in the study via the internet. For taking part, the students were awarded a partial or full “course credit” (a way of counting the time or effort students spend on their studies) from their university.
In the study, the students were asked to recall how often within the previous 30 days they had had sex with someone they had known for less then a week. Their answers were reported on a five-point Likert scale as follows:
Because only 11% of participants reported any casual sex in the month before, researchers decided to combine the results to analyse the results as yes or no answers, rather than trying to quantify the effects of the amount of casual sex the students had.
Participants also answered validated questionnaires about four aspects of psychological wellbeing. The aspects of wellbeing assessed were:
They also completed questionnaires on three forms of psychological distress:
The researchers created a statistical model from the results.
The researchers found that:
The researchers’ modelling showed that, contrary to the researchers’ hypothesis, the associations were the same for men and women.
The researchers say that for college students, engaging in casual sex may increase the risk of poorer psychological wellbeing and higher levels of distress. They suggest that college counsellors may wish to consider the broader health implications of casual sexual behaviour and, in their efforts to promote positive sexual development, may wish to “underscore the benefits of committed relationships”.
Importantly, this cross-sectional study cannot show that casual sex – defined here as sex with someone known for less than a week – causes mental health problems.
As the authors themselves point out, it is possible that someone with psychological problems may be more likely to engage in casual sex.
Arguably, a cohort study, where students were followed over the course of many years and regularly interviewed about their sexual activities and mental health, would have been more useful (if a lot more expensive to carry out).
The study had a number of other limitations:
The possibility that regular casual sex may have a detrimental effect on psychological health is worth recognising, as is the fact that poorer psychological health may make someone more likely to engage in casual sex. However, there is likely to be a complex interplay between casual sex and mental health, influenced by many factors, rather than an easily defined cause and effect relationship.