Lot of interesting points here. Question: how do sexual sins effect brain chemistry?
Sex affects brain chemistry.
Lets loose all sorts of chemicals that can amount to a sort of high.
The associations we make with those experiences apparently help to determine when they occur again.
If someone has a fetish without which they may not experience this then their own brain is working against them.
God created our brains to work this way just as He gave us a context within which it might both serve His purposes and benefit us and our marriage relationship.
But when someone supplants His order for another this self same irrational system of brain chemistry is hijacked.
So sexuality, which can be holy in the right context, when coupled with sexual sin creates a sort of conditioning that reinforces itself.
I’m hoping I expressed the thought with adequate clarity.
Any sexual stimulus causes the release of brain chemicals which can affect not only brain physiology (function) but under some circumstances, even brain anatomy (the physical structure of the brain)--- if the sexual influence starts early in life.
Some of that info is here (LINK)
Bottom line: sexual stimulation is like an addictive drug (I'm not speaking metaphorically here, I'm speaking physiologically). It causes measurable chemical changes in the pleasure centers of the brain and results in a rewiring or "patterning" which can be penetrating, persistent, and difficult to eradicate even if you want to
That's why sexual stimulation should be reserved for husband and wife only: it becomes a valuable part of the marriage bond that brings them together and keeps them together..