Adult content can make it hard to maintain one’s manhood.

So says new research which found a correlation between men watching porn — and men suffering from erectile dysfunction.

“We found that there was a highly significant relationship between time spent watching porn and increasing difficulty with erectile function with a partner,” professor Gunter de Win, head researcher, said about his team’s work, which was presented this week at the annual European Association of Urology Congress.

Researchers from Belgium, Denmark and the UK based their findings on 3,267 men’s answers to an 118-question online survey about their porn, masturbation and partnered sex habits.

“We found that there was a big range of responses,” de Win said. “In our sample, men watch quite a lot of porn, on average around 70 minutes per week, normally for between 5 and 15 minutes per time, with obviously some watching very little and some watching much, much more.”

Only two-thirds of respondents rated sex with a partner to be more stimulating than porn and nearly a quarter of those under 35 reported some amount of erectile dysfunction during partner sex — a larger percentage than de Win’s team anticipated.

“This figure was higher than we expected. We found that there was a highly significant relationship between time spent watching porn and increasing difficulty with erectile function with a partner, as indicated by the erectile function and sexual health scores,” he said.

Their findings, de Win acknowledged, are based on a questionnaire and not a clinical trial, but they prove that, without a doubt, “porn conditions the way we view sex.”

In addition to complicating men’s ability to perform, porn also creates a slippery slope to more and more intense porn: Researchers found that 90% of men fast-forward to the most pornographic scenes and that, over time, 20% required increasingly extreme porn to maintain their arousal levels.

“Our next step in this research is to identify which factors lead to erectile dysfunction, and to conduct a similar study on the effects of porn on women,” de Win said. “In the meantime, we believe that doctors dealing with erectile dysfunction should also be asking about watching pornography.”