Cannabis is causing IQ loss in teenage boys, expert says

Cannabis cultivated in illegal "grow houses" is up to four times more potent than that previously on sale in Ireland and is causing IQ loss and retardation in the brains of teenage boys, according to a leading consultant.

Emergency medical consultant Dr Chris Luke said that while many of the substances found by Forensic Science Ireland in drugs like cocaine and heroin were harmful, he was most concerned about the increased tetrahydrocannabinol (THC) levels in cannabis.

“It is a massive concern,” he said. “That level of THC in homegrown cannabis is psychotoxic and it’s neurotoxic and it’s much more likely to drive admissions in terms of psychosis.”

He said that, of the hundreds of thousands of people in Ireland who smoke cannabis, it was teenagers, especially teenage boys, who were most at risk of lasting damage from the new form of the drug.

“The 15-year-old male brain becomes stuck,” he said.

“There’s a vulnerability for the 15-year-old male brain from smoking cannabis. It stops evolving in those who are smoking several joints per day.

“And that’s a very important concept in terms of IQ retardation and IQ loss - lost and not recovered - and in terms of psychiatric admissions.”

He said the drug also featured in cases of young people feeling very “demotivated and dropping out of school and feeling general psychiatric paranoia and agitation”.

Dr Luke said that while large numbers of people had “smoked dope” at some stage of their lives, the drug on sale today was not the same as that on sale decades ago.

“The drug was 5 to 7 per cent [THC content] in the 1970s in Dublin and now it’s gone up to 15-16 per cent. That’s much more psychiatric.

“In my youth, hardly anyone smoked dope. Now everyone smokes dope; it’s at the level of tobacco and alcohol.

“We’re at a mass population level now. So if you had even a one per cent complication rate, that’s massive numbers.”

He said that, in his experience, cannabis users would not limit the damage caused by smoking higher potency plants by reducing their smoking.

THC content

Director of chemical sciences at Forensic Science Ireland, Dr Tom Hannigan, said that while the THC content of cannabis seized in Ireland was previously between four and eight per cent, it was now between 11 and 16 per cent.

He told The Irish Times it was more potent now because Irish “grow houses” cultivated the crops using hydroponics and intensive lighting equipment, with the plants fed constantly on nutrients that increased THC content.

Forensic Science Ireland, which analyses drugs seized by the Garda, has released a report on the purity levels in a range of drugs analysed by it last year.

The average purity of street-level cocaine in Dublin is 28 per cent, falling to 19 per cent outside the capital.

The average purity of amphetamines seized by gardaí in 2015 was 9.2 per cent, while the average purity of street-level heroin was 33 per cent in Dublin and 35 per cent in the rest of the country.