Cannabis strength more than doubles in 20 years, says report

THE strength of cannabis has more than doubled in Ireland in the last 20 years, according to a new report.

The study says the potency of cannabis resin the most common form of the drug in Ireland has almost doubled, while the strength of herbal cannabis, an increasingly available form of the drug, has jumped more than fourfold.

Statistics provided by Irish authorities to the European Centre for Drugs and Drug Addiction (EMCDDA) shows the concentration of THC, the primary active constituent in cannabis, jumped from:

2.3% in cannabis resin in 1981 to 4.2% in 2000.

1.4% in herbal cannabis in 1981 to 6.2% in 2000.

The EMCDDA report expressed concern at the health implications of the trend and called for European research into the matter.

Dr Des Corrigan of the School of Pharmacy in Trinity College Dublin, who contributed data to the report, said little was known for certain about the impact of the increase in potency.

"Their guess and mine would be the same, in terms of short-term panic attacks. If someone moved from relatively weaker resin to smoking home-grown sinsemilla type, known as skunk, there would be the risk of acute anxiety triggered off by increased levels of THC."

Dr Corrigan, who is the head of the National Advisory Committee on Drugs (NACD), said there was also the link between increased strength and mental illness.

"There is an increasing body of evidence from psychiatric studies of a link. But you can argue either way. You could argue quite validly that in relation to schizophrenia there's no overall increase, levels have stayed the same. Maybe the age it is occurring is lower."

The EMCDDA report said the rise in THC strength was largely due to an increase in home-grown cannabis plants, particularly in the Netherlands, which was subsequently trafficked to other EU countries.

Dr Corrigan supported the report's call for more research in the EU into the strength of cannabis and its effects. He said an NACD study into this area was due later this year.

He said the vast majority of psychiatric studies on cannabis come from the US or Australia where herbal cannabis is the main type consumed. Apart from the Netherlands, the vast majority of cannabis used in the EU is in resin form.

However, garda figures show a dramatic rise in seizures of herbal cannabis, from 207kg in 2000 to 5,600kg in 2002.

The number of home-grown cannabis plants seized jumped from 98 in 2000 to 770 in 2002.

Dr Corrigan said the potency of herbal cannabis here has probably dropped since the 2000 statistics, given the seizures then were of cannabis grown in the Netherlands, which had a high potency.

He said most herbal cannabis in Ireland now comes from Africa, and is less potent.