Official Data Seen by guardian.co.uk Shows Potency of Marijuana Gathered in Police Seizures Has Fallen
The potency of cannabis gathered in police seizures has dropped, new official data reveals, casting doubt on one of the government's key arguments for reclassifying the drug from class C to class B.
Figures collected by the Forensic Science Service and seen by guardian.co.uk show that the potency of herbal cannabis, which includes the strong "skunk" strain, has dropped from 12.7% to 9.5% since 2004, when it was first moved from class B to the less serious class C.
This means that samples collected by the police are now weaker than when David Blunkett, the then-home secretary, downgraded the drug in 2004.
According to the figures the level of THC - the main psychoactive ingredient - in herbal cannabis was 12.7% in 2004, 13.5% in 2005 and 11.3% in 2006, before dropping to 9.5% in 2007, the year covered by the latest figures. Cannabis resin, a milder form, has decreased in strength from 3.4% to 2.6% between 2004 and 2007.
The FSS said the figures were not representative and were from too small a sample.
But David Porteous, a criminology lecturer from Middlesex University, said: "This information suggests that, in the time that it has been a class C drug, usage levels of cannabis have fallen and so has its strength. These findings make a mockery of the decision to re-reclassify cannabis and of the government's wider claim to base policy-making decisions on scientific research.
"Furthermore they call into question the validity of other controversial and publicly criticised government claims regarding drug policy, for example the link between cannabis and mental illness or the legitimacy of our current classification system."
Announcing the regrading of the drug in May, home secretary Jacqui Smith told the Commons that the potency of marijuana had "increased nearly threefold since 1995".
A spokesman for the Home Office said that the home secretary's assertion was based on a report from May this year entitled Home Office Cannabis Potency Study 2008. This report gave the median potency of sinsemilla ( stronger strains such as skunk ) as 15%, that of other herbal cannabis as 9%, and that of resin as 5%. No statistics for 1995 were given.
Another Home Office report, from April this year, also using FSS figures, casts further doubt on Smith's assertion. It says the strength of sinsemilla, intensively grown cannabis, rose from 5.8% in 1995 to 10.4% in 2007, less than a twofold increase. The strength of other forms of herbal cannabis was 3.9% in 1995 and 2.6% in 2007, a drop.
The FSS is a government organisation that supplies forensic science services to ministerial departments, government agencies and police forces. It released the new figures seen by guardian.co.uk earlier this month.
A spokeswoman for the FSS said that the figures seen by guardian.co.uk were "unlikely to be an accurate representation of THC in cannabis across the board as not all samples submitted to the FSS are routinely analysed for THC content. The FSS database also does not distinguish between sinsemilla cannabis and imported herbal cannabis."
She said the FSS had been involved in the May 2008 report used by Smith to make her decision. "The FSS participated in an in-depth study of THC content for the Home Office in partnership with other forensic agencies, and this is likely to be more representative of actual cannabis strength."
The Home Office spokesman said that skunk now made up "a staggering 81% of seized cannabis". This was up from 15% in 2002 and just over 50% in 2004-05.
In May, Smith told parliament the strength of cannabis had increased threefold and there was a "causal link, albeit a weak one, between cannabis use and psychotic illness".
Explaining why she was going to reclassify the drug as class B from next year, she said: "My decision takes into account issues such as public perception and the needs and consequences for policing priorities. There is a compelling case for us to act now rather than risk the future health of young people."
Smith's ruling went against the recommendations of the government's scientific experts, the Advisory Council on the Misuse of Drugs, which was asked by Smith to take its third look at cannabis classification in recent years. The council's advice was that cannabis should remain class C.
When cannabis was downgraded, the proportion of young people using it fell from 25.3% in 2003-04 to 20.9% now. Among those aged 16 to 59, the proportion over the same period fell from 10.8% to 8.2%, according to the British Crime Survey.
CANNABIS: POLICE SEIZURES SHOW DROP IN DRUG'S STRENGTH