Source: UK Parliament
Date Jul 18, 2006
Subj: Incorporation of advice into policy

2006年7月に発表されたイギリス下院科学技術委員会の 報告書 には、ドラッグ乱用問題諮問委員会(ACMD)の勧告に対して、政策に反映させたがらない政府の様子やマスコミからの影響について、過去の経緯なども含めて詳しく書かれている。


またこの報告書では、新しいドラッグ分類の提言 や、多岐にわたる分野の 専門家の証言 も充実しており、イギリスのカナビス問題を知る上では非常に有益な情報源にもなっている。



42. Cannabis comes from Cannabis sativa, a plant which is found growing wild in many parts of the world and readily cultivated in the UK. The three main forms of cannabis are: resin, which is scraped and compressed from dried plants; herbal cannabis, comprising chopped dried leaves; and cannabis oil, made by percolating solvent through the resin.[66] Cannabis is mainly used as resin or in herbal form in the UK, with cannabis oil accounting for less than 1% of usage.[67] Herbal cannabis is available in two forms. 'Traditional' herbal cannabis imported from overseas comprises a mixture of leaf, flowering tops and seeds. 'Sinsemilla' is a higher potency preparation, either imported or home-grown, made from the flowering tops of unfertilised female cannabis plants.[68] The primary psychoactive agent in cannabis is delta 9-tetrahydrocannabinol (THC). Preparations of cannabis vary considerably in their potency and there may be wide variation between different plant varieties in the amount of THC that can be derived from them.

43. There has been a long running debate over the appropriate classification for cannabis. The ACMD recommended that cannabis should be reclassified from Class B to Class C as early as 1979, on the grounds that cannabis was less harmful than other drugs in Class B and police resources could be deployed more effectively.[69] This view was endorsed by the Runciman report in 2000.[70] In October 2001, the then Home Secretary David Blunkett asked the ACMD to provide advice on the appropriate classification for cannabis. In March 2002, the ACMD presented its report to the Home Secretary, recommending that all cannabis products be reclassified as Class C. The report made reference to concerns about a possible link between chronic use of cannabis and mental illness, but concluded that "no clear causal link has been demonstrated". It also acknowledged that "cannabis use can unquestionably worsen schizophrenia (and other mental illnesses) and lead to relapse in some patients". The report did not address possible increases in cannabis potency.[71] The Government indicated that the recommendations of both the ACMD and the Home Affairs Committee had influenced its decision to support the reclassification of cannabis.[72]

44. Although the Home Office announced the decision to reclassify cannabis as Class C in July 2002, the change did not come into effect until January 2004. In the meantime, three new studies were published which examined the link between cannabis use and mental illness. The charity Rethink expressed concern about the time lag between the start of the ACMD review in 2001 and the implementation of reclassification in 2004: "In this period, a significant amount of new evidence emerged about cannabis and mental illness, but the cannabis decision was not revisited in the light of this".[73]

45. The weeks leading up to and following the implementation of reclassification saw a media maelstrom of reporting about cannabis. Many argued that the changes had caused widespread confusion about the legal status of cannabis and there were reports that this was being exacerbated by the fact that different approaches were being adopted by police in different areas.[74] Sir John Stevens, the then Metropolitan Police Commissioner, was quoted as saying: "We do need to clarify where we are in terms of drugs law", adding that junior officers in his force had told him they were "muddled" about the drug's status.[75] The Government defended its actions, saying that it had initiated a £1 million advertising campaign targeted at teenagers and later arguing that survey results indicated that the message had been widely understood by young people.[76] [77] However, the mental health charity Rethink criticised the fact that "the public health campaign that accompanied reclassification did not mention the possible mental health effects of cannabis, but instead concentrated solely on the physical health effects of use and its continued illegality".[78]

46. Moreover, Charles Clarke, who succeeded David Blunkett as Home Secretary in December 2004, deviated from the Government line and, in an implicit criticism of his predecessor's actions, said: "The thing that worries me most [about the decision to move cannabis to Class C] is confusion among the punters about what the legal status of cannabis is".[79] He also said he was "very worried" about emerging evidence suggesting a possible link between cannabis use and mental illness.[80] Changes in drug policy, especially classification decisions, must be accompanied by a comprehensive information campaign. We recognise that the Government did undertake a campaign when the reclassification of cannabis came into effect but in view of the subsequent confusion, which was publicly acknowledged by the Home Secretary, we can only conclude that these efforts were insufficient.

47. In March 2005, Charles Clarke asked the ACMD to revisit the classification of cannabis, also asking for advice on the extent to which the potency of cannabis products had increased窶蚤 response to anecdotal evidence that higher potency cannabis was being used more frequently. The ACMD reported its findings to the Home Secretary in December 2005, making a number of recommendations but not advocating any change in the classification of cannabis. The Council found that although cannabis had "real and significant" effects on mental health, "the consumption of cannabis is neither a necessary, nor a sufficient, cause for the development of schizophrenia".[81] The Council was not able to reach a definitive conclusion on the extent to which the potency of cannabis products had increased in recent years but noted that material seized by law enforcement officers suggested that while the potency of 'traditional' herbal cannabis and cannabis resin had stayed the same, the average potency of the less widely used sinsemilla had more than doubled.[82] The Home Secretary accepted the ACMD's recommendations in full in January 2006, simultaneously launching a fundamental review of the classification system itself. We recognise that the Home Secretary followed due process in asking the ACMD to review the classification of cannabis in response to concerns about the link between cannabis use and mental illness and perceptions that cannabis was becoming more potent. However, the timing of the second review against a backdrop of intense media hype and so soon after the change in cannabis classification had come into effect gave the impression that a media outcry was sufficient to trigger a review.

48. The Government has argued that the reclassification of cannabis has had the desired effect, with arrests for cannabis possession falling by one third in the first year since re-classification, saving an estimated 199,000 police hours.[83] Furthermore, British Crime Survey data suggest that reclassification has not led to an increase in the use of cannabis: the use of cannabis in the general population (16-59 year olds) has remained stable since 1998 while cannabis use among young people (16-24 year olds) has gradually declined since 1998.[84]

49. Nonetheless, the decision remains controversial. The 2006 World Drug Report published by the UN Office on Drugs and Crime (UNODC) devoted particular attention to cannabis. The report stated that it was used by an estimated 162 million people at least once in 2004, equivalent to 4% of the global population aged 15-64, making it the world's most abused illicit drug. UNODC Director, Antonio Maria Costa, speaking at the launch of the report, made a number of comments, including the assertion that "Many countries have the drug problem they deserve", which were widely interpreted as criticism of the UK stance on cannabis. He also argued that "the harmful characteristics of cannabis are no longer that different from those of other plant-based drugs such as cocaine and heroin" and that "Policy reversals leave young people confused as to just how dangerous cannabis is".[85]

50. Recent media reports have suggested that the Home Office is to drastically reduce the quantities of drugs that people can carry before the charge of possession is upgraded to the charge of possession with intent to supply. In evidence to this inquiry, Home Office Minister Vernon Coaker confirmed that the Government was reviewing this but said that no decisions had yet been taken regarding the limits to be set. According to The Guardian, the draft regulations would put the threshold for cannabis at 5g: "a sharp reversal from David Blunkett's decision 18 months ago to ensure that cannabis possession was normally to be dealt with by confiscation and an informal warning".[86] Jan Berry, Chair of the Police Federation, said in response: "The constant changes only add to public confusion".[87] Having already caused confusion by failing to adequately communicate the implications of the reclassification of cannabis to the public, the Government must be careful that any additional changes to policy relating to cannabis do not further cloud the picture.

Gateway theory

51. The 'gateway theory' refers to the concept that cannabis use in some way predisposes individuals窶蚤nd is therefore a gateway窶杯o subsequent use of 'harder' drugs. The theory is predicated on the observation that many users of Class A drugs have used cannabis before moving onto these drugs. Professor John Strang, Director of the National Addiction Centre, emphasised the importance of establishing whether the relationship between cannabis use and Class A drug use was causal. He told us: "It is a correct observation that people who are using heroin went through gates on the way to where they are now. The crucial question is: if you had had the power to stop them going through that gate would it have altered their subsequent journey?". He pointed out that "going to primary school is a gateway to being a heroin addict but you are not implying there is a causal relationship between the one and the other".

52. Professor Blakemore, MRC Chief Executive and Professor of Physiology at the University of Oxford, said he could not "think of a chemical or physiological basis" for a causal relationship. He also dismissed the idea that "If you are buying your first drug from a person who then tries to persuade you to use a 'better' one and a stronger one then there is a causal relationship which is determined by the supplier" on the grounds that "cannabis supply is, to a large extent, rather different from the supply of harder drugs". In addition, Professor Blakemore noted that in the Netherlands, while "the attitude to cannabis use is even more relaxed than it is in this country and […] cannabis use amongst the population is a little less than it is in this country", "hard drug use is about one third of the rate in this country".[88]

53. The ACMD considered the gateway theory in its 2002 report on cannabis. The report concluded that proving any causal relationship between cannabis use and later use of Class A drugs was "very difficult due to the many confounding factors that might also act as gateways", including the individual's personality and their environment and peer group.[89] The report also stated that "Even if the gateway theory is correct, it cannot be a very wide gate as the majority of cannabis users never move on to Class A drugs".[90] In addition, Sir Michael Rawlins, Chairman of the ACMD, commented in evidence to us that "the early use […] of nicotine and alcohol is a much wider gateway to subsequent misuse of drugs than cannabis or anything like that".[91] The RAND report also concluded that "the gateway theory has little evidence to support it despite copious research".[92] We note that recent results from animal models have suggested a possible biological mechanism for a gateway effect, at least in rats,[93] but in the course of this inquiry we have found no conclusive evidence to support the gateway theory.


[66]  66 Ruth Levitt, Edward Nason, Michael Hallsworth, The evidence base for the classification of drugs, Technical Report, RAND Europe, March 2006, http://www .rand.org/pubs/technical_reports/TR362/, para 31, combined figures, , para 90

[67]   67 As above, para 2.1

[68]  68 ACMD, Further consideration of the classification of cannabis under the Misuse of Drugs Act 1971, December 2005, para 2.2

[69]   69 RAND Report, para 98

[70]  70 Runciman Report

[71]  71 ACMD, The Classification of Cannabis under the Misuse of Drugs Act 1971, 2002

[72]  72 Home Office, The Government Reply to the Third Report from the Home Affairs Committee, The Government's Drug Policy: Is it working?, Cm 5573, July 2002, p 12

[73]  73 Ev 74

[74]  74 e.g. Law: Keep off the grass?, The Independent, 16 August 2004

[75]  75 Cloud of confusion over cannabis law, The Daily Telegraph, 23 January 2004

[76]  76 Home Office press notice 020/2004, 17 January 2004

[77]  77 Home Office press notice 183/2004, 17 May 2004

[78]  78 Ev 72

[79]  79 We misled public over downgrading cannabis, The Times, 5 January 2006

[80]  80 As above

[81]  81 ACMD, Further consideration of the classification of cannabis under the Misuse of Drugs Act 1971, December 2005, para 6.2-6.4

[82]  82 As above, letter from Sir Michael Rawlins to the Home Secretary

[83]  83 Cannabis Reclassification, Home Office press release, 28 January 2005

[84]  84 As above

[85]  85 UN drugs chief sounds warning about Afghan opium production, cocaine consumption in Europe, UNODC press release, 29 July 2006

[86]  Revealed: how 10 joints could lead to 14 years for dealing, The Guardian, 7 June 2006

[87]  87 Plans to toughen drugs law 'only sow confusion', The Times, 8 June 2006

[88]  88 Q 435

[89]  89 ACMD, The classification of cannabis under the Misuse of Drugs Act 1971, 2002, para 4.6.1-4.6.3

[90]  90 As above, para 4.6.2

[91]  91 Q 128

[92]  92 RAND Report, Executive Summary

[93]  93 Ellgren M., Spano S.M. and Hurd Y.L., Adolescent cannabis exposure alters opiate intake and opioid limbic neuronal populations in adult rats, Journal of Neuropsychopharmacology, doi:10.1038/sj.npp.1301127,July 2006