"In talking to the subjects, researchers discovered that high exposure to pornography videos apparently resulted in lower responsivity and an increased need for more extreme, specialized or “k+++y” material to become aroused."[1]
This effect can be clearly seen in that pornography websites promote this extreme, vile and obscure content, such as incest, exhibitionism, and even depictions of non-consensual interaction and physical abuse.[2] Obviously, these matters have no place in a healthy relationship, and it's pretty basic psychology that regular consumption of this content causes the normalization of such practices, especially in impressionable teenagers whom do not yet have legitimate experience in healthy, normal relationships.
A majority of adults watches pornography.[3] And we're dealing with a massive loneliness epidemic under younger generations, together with a significant rise in "hook-up culture" over forming serious relationships. Coincidence?
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC5039517/
[2] Just go to one of those websites. I'm not going to do that, neither am I going to link to that here.
[3] https://www.statista.com/statistics/1402222/us-adults-pornog...