Here is a short oversight over the brainchanges that come with pornaddiction (from yourbrainonporn.com)
In simple, and very broad, terms the major fundamental brain changes are: 1) Sensitization, 2) Desensitization, 3) Hypofrontality, 4) Dysfunctional stress circuits. All 4 of these brain changes have been identified among the 25 neuroscience-based studies on porn users (See this page for a continuously updated list of brain studies) :
1. Sensitization ("A super memory of pleasure"): Rewired nerve connections cause the reward circuitry to buzz in response to addiction-related cues or thoughts. This Pavlovian memory makes the addiction more compelling than other activities in the addict's life. Cues, such as turning on the computer, seeing a pop-up, or being alone, trigger intense cravings for porn. Some describe a sensitized porn response as ?entering a tunnel that has only one escape: porn?. Maybe you feel a rush, rapid heartbeat, even trembling, and all you can think about is logging onto your favorite tube site. These are examples of sensitized addiction pathways activating your reward circuit, screaming, ?Do it now!? (Studies reporting sensitization in porn users: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
2. Desensitization ("A numbed pleasure response"): Among other changes, dopamine and opioids decline, as do certain dopamine receptors and opioid receptors. This leaves the individual less sensitive to pleasure, and "hungry" for dopamine-raising activities/substances of all kinds. Desensitization often manifests as the need for greater and greater stimulation to achieve the same buzz (?tolerance?). (Studies reporting desensitization in porn users: 1, 2, 3, 4, 5)
3. Hypofrontality ("Willpower erodes"): Alterations in frontal-lobe gray matter and white matter correlate with reduced impulse control and the weakened ability to foresee consequences. Hypofrontality shows up as the feeling that two parts of your brain are engaged in a tug-of-war. The sensitized addiction pathways are screaming ?Yes!? while your ?higher brain? is saying, ?No, not again!? While the executive-control portions of your brain are in a weakened condition the addiction pathways usually win. (Studies reporting "hypofrontality" in porn users: 1, 2, 3, 4, 5, 6, 7)
4. Dysfunctional stress circuits - which can make even minor stress lead to cravings and relapse because they activate powerful sensitized pathways. (Studies reporting dysfunctional stress responses in porn users: 1)