Here’s a long-form interview between a sex researcher and a urologist (MD) about how porn really effects us; both on an individual level; and in aggregate as a society. https://www.youtube.com/watch?v=cEqe5dHuQYE

TLDR: Porn is a bit of an over-stimulation on the brain, but the scale of the effect is similar to caffeine or nicotine. Far less impactful than that of any hard drug like cocaine or heroine. And unlike a chemical stimulant, it’s impossible to overdoes. Some people have excessive reactions to watching porn and having it readily available, so things like porn addiction are real and shouldn’t be dismissed. But the frequency of this is low (far lower than nicotine, gambling, or alcohol as comparison points) and the severity of such addictions are often minor (addicts skip other social interactions, but are unlikely to go into debt or lose jobs except in the most extreme cases).

There is no strong evidence that early exposure to porn via the internet has significant adverse effects. There are worse effects from exposure to violent content (including violent porn) than pornography in general.

This makes sense as from an evolutionary standpoint seeing other naked humans is expected. It’s only recently (in evolutionary time frames) that we’d not expect children to see other naked humans regularly or be unexposed to sex at all until an adult age. From a biological standpoint it makes perfect sense that our brain can handle seeing other people engaged in sexual activity.