THE GOVERNMENT’S leading adviser on illegal drugs has expressed concern about the high potency of cannabis being cultivated in cannabis grow-houses here, saying it is much more likely to cause psychosis than other forms of the drug.

The chairman of the National Advisory Committee on Drugs, Dr Des Corrigan, said the levels of tetrahydrocannabinol (THC), the substance that gives cannabis its potency, are much higher in the cannabis “skunk” now being grown here.

He was aware that those growing the crops were mixing THC chemicals into water being used to water the plants, and this was greatly increasing the potency. The same issue arose when cannabis grow-houses became popular in Britain midway through the last decade.

“We also know that a substance called CBD [cannabidiol] that is found in other cannabis, like cannabis resin, is in fact anti-psychotic, and this is absent from the skunk cannabis here, which contains pro-psychotic THC,” he told The Irish Times.

Dr Corrigan yesterday appeared before the Oireachtas Committee on Health and Children, where drug use, including alcohol, was being discussed.

As well as chairing the drugs advisory body, Dr Corrigan is also the director of the school of pharmacy at Trinity College Dublin.

He said an advisory subcommittee on emerging trends around drug use had also noticed an increase in the number of young people accruing financial debts relating to their use of cannabis skunk from grow-houses.

The potency and consumption of the drug had increased to such an extent since cannabis grow-houses were first discovered here three years ago that the drugs body is now researching cannabis potency and addiction levels.

The findings of the research would be published late this year, Dr Corrigan said.

Minister of State Róisín Shortall, who has responsibility for the National Drugs Strategy, has said she is concerned at the increasing grow-house phenomenon and the higher potency levels of the cannabis being produced in them.

She told the committee that gardaí had been successful in uncovering many of them and that the problem was not confined to the Republic, but was a feature in many European countries.

The Garda National Drugs Unit has set up a dedicated investigation, Operation Nitrogen, to combat the problem.

Officers working on the investigation have become the most prolific gardaí combating organised crime, finding scores of grow-houses to date.

The first grow-houses in the Republic appeared in Co Monaghan in 2008. Once dominated by Asian gangs, more and more Irish suspects are being arrested as grow-houses are being uncovered.