People who are addicted to sex and those dealing with substance abuse apparently have something in common. Their brains work in similar ways, researchers of a study funded by the charitable foundation Wellcome Trust said.

For the new study published in the journal PLOS ONE on July 11, Valerie Voon, from the Behavioral and Clinical Neurosciences Institute at the University of Cambridge in the UK, and colleagues examined the brain activity of 19 healthy volunteers and 19 patients with compulsive sexual behavior (CSB), while they watched a series of videos that either have pornographic or sports content using functional magnetic resonance imaging (fMRI).

The participants in the study were all male and heterosexual but the CSB patients were noted to have started to watch pornography at an earlier age and in higher proportion compared with the healthy participants. They also experience difficulties in managing their sexual behavior, which affects their lives and their relationships. Two of the CSB patients involved in the study have in fact lost their jobs for watching sexually explicit videos at work.

The researchers observed that three particular regions in the brain namely the ventral striatum, which plays a role in the processing of rewards and motivation,  dorsal anterior cingulate, which is involved in impulse control and reward anticipation, and amygdala, which is involved in the processing of emotional reactions, were more active in the participants with CSB compared with the healthy participants. These regions also happen to be activated when drug addicts are exposed to drug stimuli.

"The observation of stronger activations of these regions in CSB versus healthy volunteer participants is similar to findings observed for substance cues in substance addictions, suggesting neurobiological similarities across the disorders," the researchers wrote.

The participants were also asked to rate how much they liked the videos and the researchers found that the participants with CSB had higher levels of desire towards videos with sexually explicit content albeit they did not necessarily give them higher ratings in liking scores. In comparison, drug addicts are believed to seek drugs not because they enjoy them but because they want them, a process known as incentive motivation.

"There are clear differences in brain activity between patients who have compulsive sexual behavior and healthy volunteers. These differences mirror those of drug addicts," Voon said.

The researchers however said that their study does not provide evidence that CSB patients are addicted to pornography. They also said that more research is still needed to better understand the link between drug addiction and compulsive sexual behavior.