Select Committee on Science and Technology Ninth Report



  6.1     Cannabis is by far the most widely used illicit drug in the United Kingdom, as in most other Western countries; and almost all of this use is for recreational rather than medical purposes. According to the Department of Health, "Cannabis is now the third most commonly consumed drug after alcohol and tobacco" (p 47).

  6.2     Cannabis dominates the drug crime statistics, and the figures are rising. Figures for the whole United Kingdom for 1996 (Home Office Statistical Bulletin 10/98) show that 72,745 drug offenders (77 per cent of the total) committed offences involving cannabis (alone or with other drugs). There were 91,432 seizures of cannabis in 1996 (75 per cent of the total for all drugs) and this involved record quantities of cannabis resin (66,921 kg), herbal cannabis (34,373.6 kg) and cannabis plants (116,119 plants). These figures, which are the most recent available, represent more than a three­fold increase over 1990, with a particularly sharp increase in the number of offences related to the cultivation of cannabis plants and the numbers of plants seized.

  6.3     It is difficult to put a figure on the prevalence of cannabis use in the United Kingdom. The Parliamentary Office of Science and Technology, in their Cannabis Update of March 1998, gave figures from the British Crime Survey 1994 which indicate that in the adult population (16-59) 1 in 5 had "ever tried" cannabis (1 in 20 within the previous month) and in the 16­29 age group just over 1 in 3 had "ever tried" cannabis (1 in 20 within the previous month). These figures are not dissimilar to those in the WHO report for other countries in Europe[23], with somewhat higher figures for the USA, Canada and Australia. They suggest that as many as 7.5m people aged 16-59 in the United Kingdom have used cannabis at least once, and that between 1.5m and 2m take the drug at least once a month (cp Montgomery Q 559). The Royal College of Physicians have established a Joint Working Party with the Royal College of Psychiatrists which among other matters will review the epidemiology of illicit drug use in the United Kingdom.

Pattern of use

  6.4     The pattern of cannabis consumption in the United Kingdom varies according to geography, socio­economic conditions and the age of the user. Professor Edwards observed that cannabis is and has been used in very different ways in different times and places; for instance, there are people in south London who smoke 20 joints a day (Q 26). Dr Robson cautions that much of the use of cannabis in the community does not come to the attention of the health services or the police, and therefore little is known about it (Q 456).

  6.5     The Independent Drug Monitoring Unit conducted a survey of 1,333 regular cannabis users who attended a major pop festival in Britain in the summer of 1994 (p 231). The majority were daily cannabis users with an average consumption of about 24.8g of cannabis resin per month. Respondents gave highly positive subjective ratings to cannabis (as opposed to negative subjective ratings to solvents, cocaine and heroin). More than 60 per cent believed that cannabis had been of benefit to their physical or mental health. They would prefer that the law was more liberal, but a majority (70 per cent) did not think that they would use more if it was.

  6.6     Dr James Robertson, a GP working in Edinburgh, has reported the results of a survey (funded by the Royal College of General Practitioners) of 328 consecutive patients attending his surgery (average age 33.7 years)[24]. 200 patients (61 per cent) said that they had used cannabis at least once, and more detailed interviews of 101 of these revealed that 90 were regular users, with 67 using cannabis on a daily basis. Most spent £25 or less per week on cannabis, but a small number of individuals spent £100 or more per week.

  6.7     Neil Montgomery described for us various ways to take cannabis recreationally (QQ 544-554). He divides recreational users into three groups:

      ·   Casual    Irregular use, in amounts up to 1g of resin at a time, to an annual total of no more than 28g (Q 545);

      ·   Regular  Regular use, typically of 0.5g of resin a day (equivalent to 3 or 4 smokes of a joint or pipe), adding up to about 3.5g per week (Q 548);

      ·   Heavy    More or less permanently stoned, using more than 3.5g of resin per day and 28g or more per week (Q 554). The smallest group, around 5 per cent. "The extent to which a heavy user can consume cannabis is largely unappreciated."

Herbal cannabis appears to be consumed at twice the rate of cannabis resin, presumably because of its lower content of THC. Comparable data are provided by IDMU (pp 231—3).

  6.8     According to POST's Cannabis Update, 9 per cent of ever-users use cannabis daily, and 14 per cent several times a week, making it of all illegal drugs the one most likely to be used regularly. According to Professor John Strang, Director of the National Addiction Centre, few users end up in hospital with acute psychiatric problems, and most regular users are not nowadays advised by their doctor to change their habits (Q 244). For the risk of dependence, see Chapter 4.

  6.9     Many cannabis users also consume a variety of other psychoactive agents. As the commonest method of using cannabis in the United Kingdom is to smoke cannabis resin mixed with tobacco, nicotine use is very high among cannabis users. Among other things, this makes it difficult to assess the respiratory risks of smoked cannabis as they are confused with the well-established risks of smoked tobacco. Alcohol use is also common, but regular cannabis users may consume less than non-cannabis users. Drug treatment clinics often see poly-drug users, who are consuming a variety of illicit substances, of which cannabis is commonly one (QQ 42, 216, 487, 515, 562; DH p 47).

  6.10     According to the Department of Health, most cannabis users have discontinued by their mid to late 20s (p 46); and of those who have ever been daily users, only 15 per cent persist with daily use in their late 20s (p 45). Neil Montgomery has identified a group of regular users who stop in their 30s and start again in their 50s (Q 575).

Content of cannabis consumed in the United Kingdom

  6.11     Some of our witnesses expressed concern that the preparations of illicit cannabis used in the United Kingdom today are more potent than previously, exposing users to a greater risk of acute intoxication and long-term adverse effects. Professor Ashton (p 12) suggested that "a typical 1970s `reefer' contained about 10mg of THC..., while a typical `joint' today may contain 60-150mg or more of THC. This increase in potency results from sophisticated plant breeding and cultivation methods leading to highly potent varieties of cannabis, such as Skunkweed". Other witnesses made similar assertions (e.g. Q 33).

  6.12     However, the Home Office Forensic Science Service, who have data on the THC content of seized cannabis samples, do not support the view that most users in the United Kingdom are exposed to material containing ten times as much THC as in the 1960s and 1970s. They say, "Cannabis resin...has a mean THC content of 4-5 per cent, although the range is from less than 1 per cent to around 10 per cent. This pattern has remained unchanged for many years" (p 218). Cannabis resin, imported most commonly from Morocco, Afghanistan or Pakistan (IDMU p 230), is the form of cannabis most widely used in the United Kingdom, and accounted for two thirds by weight of all seized material in 1996 (Home Office Statistical Bulletin 10/98). One of our witnesses, a user and convicted dealer, claimed that most modern cannabis is in fact weaker than material from the 1960s.

  6.13     On the other hand, there appears to have been an increase in the THC content of herbal cannabis—probably because of the use of new strains of cannabis plant and improved growing conditions. In the United States, the University of Mississippi have analysed the THC content of seized cannabis on behalf of the US government since 1980 (see Appendix 4, paragraph 13). They report an increase in the THC content of herbal cannabis from around 2 per cent in 1980-81 to more than 4 per cent in 1997. The Forensic Science Service report that herbal cannabis in the United Kingdom currently also contains an average of 4-5 per cent THC. They also report that cannabis grown in the home, using improved growing techniques and improved plant varieties, now produces herbal cannabis with a considerably higher THC content, with an average close to 10 per cent THC and a range extending to over 20 per cent (p 218). Use of "hydroponic" cannabis (grown in a nutrient solution rather than in soil) appears to be increasing rapidly, with plant seizures in the United Kingdom up from 11,839 plants in 1992 to 116,119 in 1996.

  6.14     Professor Hall suggested, "More potent forms of cannabis need not inevitably have more adverse effects on users' health than less potent forms. Indeed, it is conceivable that increased potency may have little or no adverse effect if users are able to titrate their dose to achieve the desired state of intoxication. If users do titrate their dose, the use of more potent cannabis products would reduce the amounts of cannabis material that was smoked, thereby marginally reducing the respiratory risks of cannabis smoking" (p 221; cp IDMU p 235).

  6.15     The overall quality of imported cannabis resin appears to have fallen in recent years; many users perceive cannabis resin as adulterated and forensic analysis frequently confirms that this is the case, with the addition of caryophyllene, a constituent of cloves, being particularly common (IDMU p 230; Montgomery p 132 and QQ 577, 589). Yet Professor Hall considers that concern about herbicide contamination is unfounded, and that case history evidence of health problems from microbial contamination is limited. Neil Montgomery calls for research in this area.

The state of the law

  6.16     This Government show no sign of taking a softer line against recreational use of cannabis than their predecessors. According to the White Paper Tackling Drugs (Cm 3945) of April 1998, "The more evidence that becomes available about the risks of, for example, cannabis...the more discredited the notion that any of the substances currently controlled under the 1971 Act are harmless". This echoes the view of Professor Edwards of the ACMD: "We are in a rapidly changing field of knowledge"; and new knowledge is making cannabis look more dangerous, not less (QQ 21, 27).

  6.17     Most of our professional witnesses agree that the adverse effects of cannabis fully justify prohibition (e.g. Henry/RCPath p 224). The only argument on the other side is that cannabis is arguably less dangerous than alcohol or tobacco (e.g. RCGP p 281, Kendall p 268). Professor Hall acknowledged this, but noted "the difficulty in predicting the effect that relaxation of cannabis prohibition would have on current patterns of cannabis use and the harms caused by that use" (p 222).

  6.18     The Under-Secretary of State at the Home Office, George Howarth MP, told us confidently that legalising recreational use would cause such use to increase (Q 674). Professor Edwards, writing for the Royal Society, is less sure: "We would expect weakening of controls over cannabis to result in increased use levels, but this is an empirical question on which research at present is not conclusive...Removal of prohibition on cannabis would have to be described as a voyage into the unknown. Some added harm and some added costs would undoubtedly result" (p 303). There is international experience which might throw light on this question, but we have not explored it in detail.

  6.19     We have not considered the wider range of social and criminological issues which would be raised by any proposal to change the law on recreational cannabis use. These include enforcement, the impact on use of other illegal drugs, and the international context and the danger of "drug tourism"; as well as ethical, philosophical and religious questions about the freedom of the individual, the nature of society and the morality of mind-altering drugs. As we said when we began this enquiry, these matters fall outside our remit as a Science and Technology Committee. An Independent Inquiry into the Misuse of Drugs Act, chaired by Lady Runciman of Doxford and supported by the Police Foundation, is currently considering the matter in its wider context; they expect to report next year.

23   See also the Annual Report on the State of the Drugs Problem in the EU 1997, by the European Monitoring Centre for Drugs and Drug Addiction. Back
24   Br. J. Gen. Pract. 1996, 46, 671. Back

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