I will anecdotally observe anal sex, oral sex, and facials have gone up between partners as prevalence in porn has gone up. That suggests but does not prove a direct statistical harm caused by even "ethically produced CSAM
Can we look at trends between consenting adults (who are likely watching porn of real people by the way) as an indicator of what pedophiles will do? I’m not so sure. It’s not like step sibling sex is suddenly through the roof now with it being the “trend” in porn.
Looking specifically at fake rape porn maybe and seeing if it increases rates of rape in the real world might be a better indicator.