There is no such thing as sex addiction, with people who suffer from 'hypersexuality' being no different from people who simply have a high libido.

Researchers from the UCLA (University of California, Los Angeles) looked at the brains of people who believe they are addicted to sex and found their response to sexual images was not related to an addiction, but to their level of sexual desire.

The term sex addiction was first coined in the 1970s by members of Alcoholics Anonymous who were looking to apply recovery principles to their compulsive sexual behaviours.

Since its conception, hypersexuality has been blamed for ruining relationships, careers and people's lives. Celebrities who profess to be sex addicts include Russell Brand, David Duchovny and Tiger Woods.

People with a sex addiction supposedly have sexual urges that feel out of control. They frequently engage in sexual behaviour and suffer consequences in their personal lives because of it.

The UCLA researchers say people with hypersexuality do not have a different brain response to sexual images to people with a high libido, and that symptoms are not representative of an addiction.

By looking at the brain scans, the team was able to monitor the brain response to sexual stimuli. If they had a real addiction, the response would expected to be higher - in previous studies, cocaine addicts have been found to react more to images of drugs than non-addicts.

Nichole Prause, one of the researchers, said this was the first time scientists have studied the brains of sex addicts.

The 52 study participants filled out questionnaires about sex and then viewed images while being monitored with electroencephalography (EEG) - which measures brainwaves.

"The volunteers were shown a set of photographs that were carefully chosen to evoke pleasant or unpleasant feelings," Prause said. "The pictures included images of dismembered bodies, people preparing food, people skiing - and, of course, sex.

"Some of the sexual images were romantic images, while others showed explicit intercourse between one man and one woman."

They looked specifically at the brain response 300 milliseconds after each picture - known as the P300 - which will spike if a picture is new or especially interesting.

The team was expecting P300 responses to correlate to levels of sexual desire found in the questionnaires, and that in people with an "addiction", there would be a spike in the P300 reaction to sexual images.

However they found there were no spikes or decreases related to the severity of the participant's sex addiction.

Prause said: "The brain's response to sexual pictures was not predicted by any of the three questionnaire measures of hypersexuality.

"Brain response was only related to the measure of sexual desire. In other words, hypersexuality does not appear to explain brain responses to sexual images any more than just having a high libido.

"If our study can be replicated, these findings would represent a major challenge to existing theories of a sex 'addiction.' "