Pornography is now only an internet search away, and is becoming ever more immersive. How is it changing people’s behaviour, relationships and desires?

Few things are truly universal. But while people across the world speak different languages, eat different foods and even feel different emotions, millions across the world watch porn. Despite being so widely consumed, porn is maligned as the source of society’s ills. It’s even been labelled a public health hazard by politicians in Utah.

Porn has transformed over the past few decades, due to the availability of the internet and faster web connections. It is also becoming more immersive than ever before. Take virtual reality. Earlier this year, researchers from Newcastle University in the UK pointed out that VR changes the experience of porn from detached observer to protagonist. They warned that this has the potential to blur the line between reality and fantasy, perhaps damaging relationships and encouraging harmful behaviour.

But what does the evidence actually say about how porn may or may not be affecting people? Can research provide any answers? The truth is that it is a difficult question for scientists to study. The nature of porn dictates that researchers must either rely on people self-reporting their porn habits, or show it to them in laboratory settings that are unnatural. (And no doubt, slightly awkward, too.)

That said, there is a growing body of literature that can provide hints. BBC Future reviewed what researchers have concluded so far:

SEXUAL VIOLENCE

The fundamental question surrounding porn – which resurfaces every time a violent crime involves the perpetrator’s porn use – is whether it has the power to encourage, normalise or even trigger acts of rape and sexual violence.

This possibility has been explored for decades. In the 1970s, for example, Berl Kutchinsky, a professor of criminology at the University of Copenhagen, measured sex crimes in Denmark, Sweden and Germany as they legalised porn in the late 60s and early 70s. He found no correlation between a rise in crime and decriminalisation – and in fact, some types of sex crime fell during this period, including rape and child molestation.

In 1995, a meta-analysis of 24 studies, involving more than 4,000 participants, measured the average correlation between porn use and the beliefs people hold around rape and sexual assault. The studies all used the “rape myth” scale, which measures a person’s beliefs by asking them to rate how much they agree with statements including: “A woman who goes to the home or apartment of a man on their first date implies that she is willing to have sex”.

Those who watched porn accepted more rape myths compared to a control group, but only in the experimental studies. Non-experimental studies – which relied on participants reporting information – showed no correlation. So, the findings were somewhat inconclusive.

However, in recent years, porn has been accused of becoming increasingly violent. A veteran porn star said in a recent documentary about porn that, in the 1990s, it constituted “making love on a bed,” and having “lovey dovey sex”. But in 2010, researchers analysed more than 300 porn scenes and found that 88% contained physical aggression. Most of the perpetrators were male, and their targets female, and the latter’s most common response to aggression was to show pleasure or respond neutrally.   

So what does the more recent research say? One review of more than 80 studies in 2009 concluded that evidence of a causal link between porn use and violence is slim, and any findings proving a connection are often exaggerated by the media and politicians. “It is time to discard the hypothesis that pornography contributes to increased sexual assault behaviour,” wrote the authors.

Neil Malamuth at the University of California, Los Angeles has carried out numerous studies examining porn and sexual violence, including one involving 300 men, and concluded that men who are already sexually aggressive and consume a lot of sexually aggressive pornography are more likely to commit a sexually aggressive act. But he argues that porn isn’t the cause of sexual violence. In 2013, he told BBC Radio 4 that porn consumption can be compared to alcohol, suggesting that it isn’t inherently dangerous, but can be for those who have other risk factors. 

BRAIN AND BODY

Watching porn could shrink a part of the brain linked to pleasure, according to a study from 2014. Researchers at the Max Planck Institute in Berlin looked at the brains of more than 60 men while they looked at pornographic images, and quizzed them on their porn-watching habits.

The found that the striatum, a part of the brain that makes up the reward system, was smaller in those who watched a lot of porn – meaning they might require more graphic material to get aroused. But the researchers couldn't conclude if respondents with smaller striatums were driven to watch more porn, or if their frequent porn-watching had caused it to shrink – although they “assume” the latter is the case. 

Further down the body, erectile dysfunction is often blamed on desensitisation cause by watching porn – but there is a lack of research to support this. In fact, watching porn could actually help sexual arousal, according to researchers from UCLA and Concordia University, who found that men who watched the most porn report feeling more sexually aroused when shown porn in the lab.

RELATIONSHIPS

“My friend wanted his girlfriend to dress like a porn star and do what a porn star would do. Porn is so easily accessible. You see guys watching it in the classroom on their phones; on the bus.”

This quote, from a 17-year-old, featured in the UK government’s recent inquiry into sexual harassment and sexual violence in schools. But while porn has been blamed for its effect on relationships – particularly between young people, research has tended to focus on adults. And the findings are conflicting.

Watching porn makes men lose interest in their partners, came the warnings after a study by Douglas Kenrick in 1989. The study was “hugely influential” in psychology, according to Rhonda Balzarini, a PhD student at the University of Western Ontario. However, in November last year she carried out similar trials, using 10 times as many participants  – 150 heterosexual females and 400 heterosexual males over three separate studies – and disputed its findings.  

She showed male and female participants nude magazine centrefolds of the opposite sex, as well as clothed photographs, and abstract art, and found no difference in how much men and women reported that they loved, or were attracted to, their partners afterwards.

Although, Balzarini concedes, the results between the two studies may differ because the original study was conducted in 1989, when the abundance and content of porn was very different to what it is now.

Contrary to this, a study published in May this year found that starting to watch porn can sometimes be a predictor of divorce. Drawing on three sets of data between 2006 and 2014, researchers found the likelihood of divorce was doubled for Americans who began watching porn. Those who said they watched porn two to three times a month had the highest likelihood of separating. The study doesn’t, however, resolve whether starting to watch porn is a cause of divorce or a symptom of an already unhappy relationship. And, importantly, the study also found that people with a very high viewing of porn – at least one a day – were less likely to divorce than those who never watched it. 

SEX LIFE

Porn has long been accused of getting between couples’ sex lives. This might be because of the type of porn consumed, according to research that found men who watched more porn were less satisfied with their sex lives. But the opposite was true for women.

Researchers suggest this could be because woman are more likely to watch porn with their partner, instead of alone; and men typically watch less consensual sex acts when watching alone. Another study found that those who watched porn with their partners reported feeling more dedicated and sexually satisfied in their relationship compared to those who watched it alone.

ADDICTION

Of the many negative effects porn is said to cause, addiction is usually high on the list.

One study from the University of Cambridge likened porn addiction to drug addiction, after finding that they both trigger the brain in a similar way.

Straight, male participants – half with compulsive sexual behaviour (CSB) and half without – were asked to rate sexual and non-sexual video clips while they underwent fMRIs. CSB, often referred to as sexual addiction, involves an obsession with sexual thoughts, urges or behaviours that can cause a person distress, and negatively affect their job, relationships and other areas of their life.

It emerged that three regions in the brain found to be more active in those with CSB are also activated when drug addicts are shown drug stimuli.

Those with CSB reported higher levels of desire towards sexually explicit videos, but didn’t necessarily like them anymore. This dissociation between desire and liking is consistent with a theory underlying drug addiction, called incentive motivation, where addicts seek their addiction because they want it, rather than because they enjoy it.  

But the researchers concluded that, while they found that the brains of those with CSB mirrored that of drug addicts, that doesn’t necessarily prove that porn is addictive.

The UK National Health Service likens sex addiction to drug addiction – and states the disorder can include having a porn habit that feels out of control. But although porn can be a component in sex addiction, whether porn itself can cause an addiction is yet to be proven.

SEXUAL BEHAVIOUR

Porn has been found to make people more open minded and comfortable about sex, but one study found it could make people a little too comfortable.  

Homosexual men who watch more sexually explicit porn where condoms aren’t used are less likely to use protection themselves, according to a survey of 265 men. If the porn they watched did feature condoms, they were more likely to use them, too.

Condoms aren’t too popular in the porn industry, where actors are regularly checked for STIs instead. California rejected a proposition last year that would have required porn actors to wear a condom in all their sex scenes, despite exponents arguing it was necessary to reduce the spread of STIs between actors. Critics said it would have driven the porn industry out of the state.

Porn has also been linked to sexual promiscuity, with some evidence suggesting that watching porn is associated with a sevenfold increase in the likelihood having casual sex. But this was only found to be the case for people who are unhappy.  

An analysis on data from 2002 to 2004 indicated that those who watched more porn had more sexual partners and more affairs, and were more likely to pay for sex. Like many other studies on the subject, however, it’s unclear whether porn caused these behaviours, or was sought out because of pre-existing factors underlying them.

ATTITUDES TOWARDS WOMEN

Porn has long been blamed for fuelling sexist attitudes and setting unrealistic sexual expectations. Research has provided contradictory results, but one study delved deeper. Researchers from the University of Copenhagen and University of California in Los Angeles asked 200 adults about their porn consumption and assessed their personality in terms of agreeableness, which is one of the “big five” personality traits that indicates how altruistic, helpful, trusting and sociable a person is.

After the participants watch porn in the lab, researchers found that increased porn consumption was associated with negative attitudes towards women, including stereotypes and hostility – but only in men who had low agreeableness, which is one of the five personality traits of the “big five” test.

CONCLUSIONS?

Watching porn has been linked to a multitude of problems for individuals and wider society – but for every study maligning it, another clears its name. Often, evidence is mixed, and the research methods and sample sizes of studies have their limitations.

Will the future of ever-more immersive porn may bring with it more risks? It’s too early to say.

The question of cause and effect comes up a lot with research into porn: does porn attract more people with sexually aggressive tendencies, those who are in unhappy relationships, those with smaller reward systems in their brain and those with sexual addiction – or does it cause these things? It’s a tricky area to research – but until the answers are more definitive, the evidence so far suggests that the likelihood that porn has a negative effect very much depends on the individual consuming it.

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