People who are addicted to pornography show similar brain activity to alcoholics or drug addicts, a study has revealed.

MRI scans of test subjects who admitted to compulsive pornography use showed that the reward centres of the brain reacted to seeing explicit material in the same way as an alcoholic’s might on seeing a drinks advert.

The research by Cambridge University assessed the brain activity of 19 addictive pornography users against a control group of people who said they were not compulsive users.

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Lead scientist Dr Valerie Voon, an honorary consultant neuropsychiatrist, told the Sunday Times: “We found greater activity in an area of the brain called the ventral striatum, which is a reward centre, involved in processing reward, motivation and pleasure.

“When an alcoholic sees an ad for a drink, their brain will light up in a certain way and they will be stimulated in a certain way. We are seeing this same kind of activity in users of pornography.”

The study is yet to be published, but will feature in a Channel 4 documentary called Porn on the Brain, which airs at 10pm on Monday 30 September.

The findings, which tally with recent but unconfirmed reports in the US that porn addiction is no different from chemical or substance addiction, will be seen as an argument in favour of David Cameron's proposals to limit access to some pornographic websites.

They come as a three-day conference for adult website operators began in London today, with talks including “State of the Industry: The War on Porn”.

Women’s rights activists plan to protest outside the meet at the Radisson Edwardian Bloomsbury Hotel today, wearing overalls and masks in defiance of an industry which they describe as “toxic”.

Dr Julia Long from the London Feminist Network said: “At the very moment we are having a national debate on the harms of pornography, and not least the enormous amount of porn in teenagers' and children's lives, XBIZ is holding sessions specifically aimed at combating any attempts to curb access to internet pornography.

“Pornographers don't care about the damage their industry does. Their only concern is profit.”

Conference organisers said the debate – featuring panellists from the adult industry – would look at the Government's plans.

Industry lawyer Myles Jackman told the conference website: “Successive governments have mounted a sustained campaign against the UK porn industry and now's the time to fight back.”