This is one of the most challenging topics we've tackled to date. Not just because of the subject matter, but because very few things are studied as widely in behavioural science as pornography, and enormous quantities of research exist to back up almost any perspective imaginable. Nonetheless, we've given it a go.

To start with, it’s worth getting a sense of how mainstream pornography use really is. This isn’t as straightforward as you might think: not everyone agrees about what constitutes pornography.

Some surveys include media like written erotica, and some are limited to videos or images. Surveying adults without disaggregating data by age or sex tends to skew results significantly. Some surveys ask about lifetime consumption (“Have you ever seen pornographic material?”); some focus on habits (“How many times a month/week/day do you view pornography?”)

This means that estimates of how many adults actually use porn vary from about 30% to about 98%. 

Below, we’ve visualised some data from a particularly large Spanish study (totalling 8040 individuals). Unusually for this subject, children were included: the survey has an age range from 12 to 85 years old.

The group was split into five discrete life stages as follows:

• ‍<18: children and adolescents‍
• 18-25: young adults‍
• 26-40: adults‍
• 41-60: older adults‍
• >60: elderly

The study found overall porn consumption in about 95% of adult men, and 80% of adult women.
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To begin with, researchers asked all participants whether or not they’d ever searched for pornography. The proportion of those from each life stage who said "yes" is displayed in the line graph above, and on the leftmost columns below.

All those who said yes were then asked which genres of pornography they searched for. The most popular answers are shown in the other columns below.
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The verdict is in: almost all adults consume pornography. So what effect is this having on our minds, bodies, and relationships? 

This is one of the most controversial issues in behavioural science. Some research finds that exposure to pornography (and particularly violent pornography) is associated with increased acceptance of violence towards women, belief in rape myths, and dangerous sexual behaviour including sexual assault.

But other analysis finds that the effects of violent pornography itself are negligible, and that once confounding variables such as individual character differences are controlled for, any causal relationship between pornography and sexual violence disappears.

These points are not mutually exclusive, however. It could be the case that violent people are naturally drawn towards violent pornography, which confirms and increases their tendencies towards misogyny or sexual aggression.

What we do know is that men who are more promiscuous, and more hostile towards women, are more likely to consume violent pornography. Those who use it frequently are also more likely to report having been sexually violent. Likelihood of committing rape is strongly associated with all pornography use, but espeically violent and sexually violent pornography – although even “soft porn” was found to be associated with both sexual force and non-violent coercive behaviour. At least five independent studies have produced the same results.

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Of course, none of this is proof of causation. Given that almost all men use pornography, it's possible that those who claimed not to (or claimed to do so less frequently) were also likely to mislead interviewers about their treatment of women. Conversely, those who were candid about the type and extent of pornography they used might have been more likely to be candid about their misogynistic attitudes or behaviour.

A number of experiments in the 80s and 90s found that exposure to adverts depicting women as sex objects influenced how likely men were to hold attitudes that supported sexual violence against women, such as believing that women enjoy being victims of sexual aggression.

But many of these studies were done in laboratory conditions, and generalising from lab results to real-world effects is not always straightforward. There are other reasons to be cautious, too: most studies in this area differ widely in their methodologies and, as we saw above, in what they count as pornography or even sexual aggression.

On the latter, researchers have found that anywhere between 2% and 90% of pornography contains sexual aggression. This unhelpfully broad range is the result of mixed definitions: "sexual aggression" is sometimes defined narrowly enough to exclude all but the most violently forceful acts, and sometimes defined broadly enough to encompass almost any heterosexual content. And because it’s such a contentious subject, researcher bias is impossible to exclude.

Given these difficulties, it’s no surprise that scientists can’t agree on whether pornography is getting more or less violent with time. Violence is certainly more controversial (i.e. both liked and disliked by viewers than non-violent pornography), but according to one relatively comprehensive review, about 13% of the most-viewed videos on a major pornography outlet contained visible violence. About 1.4% of the most popular videos also contained non-consensual aggression. 

We do know that ’trends’ in pornography tend to create trends in real-life bedrooms. Sexual choking has recently come under discussion, and it’s a good example of this phenomenon: consuming more pornography means exposure to more depictions of sexual choking, which predicts a higher likelihood of choking sexual partners due to believing that choking is safe, pleasurable, and doesn’t require consent.

Several other, similarly aggressive sexual behaviours follow the same pattern. Qualitative research also finds that sexually aggressive norms lead to some women feeling forced to submit to unwanted sexual behaviours. Similar patterns exist for gay men.

Within heterosexual relationships, however, the effect of pornography on men and women is different. Men consume pornography far more frequently than women, and consider it to be more realistic than women do, but its effect on women’s attitudes is particularly striking. Both men and women who use pornography tend to report that it has positive effects on them. But the data from at least 50 studies suggests that this reporting is at best only part of the picture, and at worst inaccurate.

Women who use pornography tend to have lower self-esteem related to their bodies, as well as partners who are more critical of their bodies. They also tend to feel increased pressure to imitate acts seen in pornography (whilst having less sex overall). Men who use pornography report symmetrical effects: they are more critical of their partners’ bodies, and less interested in actual sex.

Both men and women who are exposed to high levels of “provocative social media” (i.e. soft porn, usually in the form of static images on social networks) see lower rates of satisfaction with the love they receive in their sexual relationships. Women also see lower sexual satisfaction overall, as do men who consume a significant amount of sexually objectifying material. They become more likely to objectify their own partners (and women become more likely to objectify themselves, which as we've seen results in low self-esteem). That leads to lower sexual satisfaction for both members of the relationship. Men in particular can also become disappointed with their partners’ lack of ability (or desire) to perform the sex acts they’re used to watching actors conduct in pornography.

So, is the news all bad? 

Perhaps not. Pornography has often been hypothesised to contribute to erectile dysfunction in men, but evidence suggests that most of the time this isn’t the case (or, rather, it only does so for very frequent users of pornography, and in those instances it’s possible that a third variable – such as low self-esteem or fear of sexual failure – is responsible for both problems).

It also seems likely that sexual dissatisfaction and sexual health problems are more the result of very frequent pornography use (i.e. three or more times a week) than use of pornography altogether.

And in women, pornography use doesn’t predict negative sexual outcomes as reliably as other variables, such as demographic and relationship factors.

The context of pornography use may also affect its results. Both men and women who feel pressured into using porn by their partners report high levels of sexual insecurity, and difficulty accessing sexual pleasure as a result. Voluntary use alone, however, can have the opposite effect (up to a point, as we’ve seen). The good news is that people tend to be reasonably self-aware about whether or not their consumption is leading them towards negative thoughts or behaviours.

So there are certainly reasons to be optimistic about at least some effects of pornography, particularly when explored from inside healthy and mutually supportive relationships – but all good things in moderation.