https://verilymag.com/2017/07/causes-of-divorce-effects-of-w...
https://www.science.org/content/article/divorce-rates-double...
You can find plenty of pro porn propaganda out there too. They want to fill the channels with, at least, uncertainty.
But use your own brain and human experience. Do many women you know celebrate porn use by their husbands/boyfriends? That it doesn't bother them at all?
I don't need a study to tell me a hot stove burns.
It effects your relationship even if you successfully keep it hidden. You can't hide the effects, particularly how you objectify the women about you. It's so common lots of people think this is normal. It's not normal, it's not good, and it causes unhappiness in a woman that wants to be really loved. Her. Not her body. Not that image you saw or that video you watched in your mind while you are with her so you can sustain an erection. Just, her.
But you won't be able to give that to her. We men often natter on about the emotional sensitivities or frailties of women when they complain about things we think we are doing right. But there is something missing and she feels it. This is squelching the voice that is trying to lead you to do better, be better. To be a source of warmth, love and happiness instead of a cold stone that gets off to equally cold sex objects.