Here is a very interesting article on the scientific effects of pornography on the physical brain and brain chemistry: http://www.salvomag.com/new/articles/salvo13/13hilton.php.

It’s important to remember that, while Catholics are not materialists, neither are we Gnostics. We do not believe that man is merely matter, any more than we believe that man only exists as disembodied spirit. The article above shows the interaction between spirit and matter, and gives us a blueprint of the effects of sin. Sin indeed “re-wires” our brains, and addiction to pornography, overeating and gambling can be as physically devastating as addiction to drugs and alcohol. Thus the article is entitled “Slave Master”, for we have here the physical evidence of the means by which sin enslaves us spiritually. In fact, a better way of saying this is that sin enslaves us spiritually and physically at the same time, especially in the realm of pornography, where an addict’s entire life, his ability to love, understand, and relate to others, is, over the long haul, destroyed.