], 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.

]. 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).

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