The Cambridge University neuropsychiatrist Dr Valerie Voon has recently shown that men who describe themselves as addicted to porn (and who lost relationships because of it) develop changes in the same brain area – the reward centre – that changes in drug addicts. The study, not yet published, is featured next week in the Channel 4 TV show Porn on the Brain. Neurosceptics may argue that pictures of the brain lighting up in addicts tell us nothing new – we already know they are addicted. But they do help: knowing the reward centre is changed explains some porn paradoxes. http://www.theguardian.com/commentisfree/2013/sep/26/brain-scans-porn-addicts-sexual-tastes Joseph J. Plaud, a private, clinical forensic psychologist in Boston, Massachusetts, who has studied the effects of pornography.

When people look at sexual imagery, dopamine floods these brain regions, causing an intense feeling of pleasure. Over time, people come to associate those direct images (called reinforcers) with the pleasurable feelings. Anything associated with those images, including Playboy's trademark bunny image, could also prime people to seek out that positive rush. [6 (Other) Great Things Sex Can Do for You]

However, if that pleasure response gets triggered over and over — with frequent doses of Playboy or other sexually charged imagery — a person will need bigger hits to feel a response, Plaud said. "The more you do and the greater degree of access, the more explicit [it is], you seem to need more and more," Plaud told Live Science. http://livescience.com/52469-how-porn-affects-brains.html