Sex addiction triggers activities similar to drug addiction in the brain, a new study finds.

Researchers from the University of Cambridge found that watching pornography triggers brain activities in sex addicts similar to drug addiction. For the study, researchers looked at the brain activity of 19 male sex addicts and compared the observations it with 19 healthy male volunteers without  the addiction.

"The patients in our trial were all people who had substantial difficulties controlling their sexual behavior and this was having significant consequences for them, affecting their lives and relationships," explained Dr Valerie Voon, a Wellcome Trust Intermediate Clinical Fellow at the University of Cambridge, in a press statement. "In many ways, they show similarities in their behavior to patients with drug addictions. We wanted to see if these similarities were reflected in brain activity, too."

The participants were made to watch a series of short videos containing either sexually explicit content or sports. While they watched the videos, researchers recorded brain activities using functional magnetic resonance imaging (fMRI), which uses a blood oxygen level dependent (BOLD) signal.

They found that three areas of the brain - the ventral striatum, dorsal anterior cingulate and amygdala - were more active in sex addicts than in the healthy participants. What's interesting is that these areas are also active in people with drug addictions .The ventral striatum is involved in processing reward and motivation, whilst the dorsal anterior cingulate is implicated in anticipating rewards and drug craving. The amygdala is involved in processing the significance of events and emotions.

There is a phenomenon known as incentive motivation in drug addicts. To see if this is also common in sex addicts, researchers asked the study participants to record the level of sexual desire they felt while watching the videos and how much they enjoyed watching them. Researchers found that the participants experienced high levels of sexual desire while watching the videos but did not necessarily like the videos.

The researchers said that further study is needed as their research cannot be used as diagnostic tool for porn addiction. Also any relationship between compulsive sexual behaviour and drug addiction needs to be investigated.

"Compulsive behaviors, including watching porn to excess, over-eating and gambling, are increasingly common. This study takes us a step further to finding out why we carry on repeating behaviors that we know are potentially damaging to us. Whether we are tackling sex addiction, substance abuse or eating disorders, knowing how best, and when, to intervene in order to break the cycle is an important goal of this research," Dr John Williams, Head of Neuroscience and Mental Health at the Wellcome Trust said.

According to statistics revealed by Myaddiction.com, more than 12 million people in the United States suffer from sexual addiction and about 40 million are involved in some kind of sexual activity over the Internet. In fact, 25 percent of search engine requests are pornography related with sex being the number one topic searched on the Internet.

.The current study was published online in the journal PLOS ONE. The project was funded by the Wellcome Trust.