He has reported from war zones in Iraq and Afghanistan and witnessed the horrors of the Sri Lankan civil war.

But broadcaster Jon Snow has said yesterday that smoking strong cannabis for a scientific experiment terrified him more than any battlefield.

The news host has taken part in a programme to demonstrate the effects on the brain of potent ‘skunk’ cannabis.

Channel 4 News host Jon Snow, pictured, who has smoked strong cannabis for a scientific experiment says it terrified him more than any war zone he has visited

The Channel 4 programme, called Drugs Live: Cannabis on Trial, will be broadcast on March 3 and sees Mr Snow, former MP Matthew Parris and former BBC royal correspondent Jennie Bond smoke the drug in a six-month trial approved by the Home Office.

Writing on his Channel 4 blog, Mr Snow said: ‘By the time I was completely stoned I felt utterly bereft. I felt as if my soul had been wrenched from my body. There was no one in my world.

‘I was frightened, paranoid, and felt physically and mentally wrapped in a dense blanket of fog.

‘I’ve worked in war zones, but I’ve never been as overwhelmingly frightened as I was when I was in the MRI scanner after taking skunk. I would never do it again.’

His comments come as a study published by the Lancet medical journal this week found that the risk of psychosis is three times higher for users of skunk cannabis than for non-users.

The drug has also been linked to paranoid episodes, memory loss and lack of educational attainment.

Writing on his Channel 4 blog, Mr Snow said: ‘By the time I was completely stoned I felt utterly bereft. I felt as if my soul had been wrenched from my body'

Mr Snow, who admitted to having been passed the ‘odd spliff of cannabis’ a dozen times in the past, said last night that smoking the much stronger skunk ‘outstripped anything’ he had previously experienced.

Skunk is thought to account for around for 80 per cent of the UK drug market and is believed to be more addictive than normal herbal cannabis or its solid form, hash.

A study published by the Lancet medical journal this week found that the risk of psychosis is three times higher for users of skunk cannabis than for non-users.

Professor Val Curran, a University College London neurologist who organised the trial, said: ‘This is a hugely exciting and important research project which will show how skunk and hash can produce different effects on the human brain, mind and behaviour.

‘My research group were concerned that cannabis addiction in the UK has increased over recent years alongside the increased market dominance of skunk.

‘I hope this new programme will scientifically inform those who use, have used or are thinking of using this drug about the diverse effects of different types of cannabis.’

Skunk has also been linked to paranoid episodes, memory loss and lack of educational attainment

Mr Parris added: ‘Smoking skunk wasn’t cool. It was just horrible, I felt stoned and stupid. The very smell now repels me.’

He said that after inhaling the drug during the experiment he would sometimes find it hard to stand up, according to the Times.

'Losing control is my worst nightmare,' Mr Parris reportedly told the newspaper.

'Yet I have to report that the two weirdest things these sessions did to me — memory blanks even while I was talking and distortions in the perception of time — were only extreme cases of things I’ve often noticed in myself in normal circumstances and drug-free.

'The cannabis heightened and intensified; it did not create.'

During the six-month trial, on three separate occasions the volunteers took controlled doses of different forms of medicinal cannabis as well as a placebo under laboratory conditions at UCL.

Unlike most other studies, which simply ask people what type of cannabis they use, this trial administered carefully measured amounts of cannabis each with a specified chemical profile.

The previous programme, which was broadcast in September 2012, was fiercely criticised as little more than an advert for ecstasy.