3.1 UK data

3.1.1 Our research into cannabis consumption , was originally based on two surveys (1982 and 1984) of self-selected regular cannabis users, finding that the "average" (mean) cannabis usage was just over one ounce per month (29.3-29.9g). Both surveys showed very similar patterns, with a large number of relatively moderate users (median usage was 14g/month), but a smaller number of heavy and very heavy users (mean use for "more than daily" users was 65.8g), with the maximum usage of 150g, or just over 6 ounces, per month. Users of imported herbal cannabis had a higher mean consumption (57.1g/month) than users of resin.

3.1.2 Results from "Regular Users", our 1994 survey of cannabis consumption, using data collected from 1333 drug users, from a UK pop festival in June 1994, and further samples distributed by direct mail and by snowballing, suggested very little difference from the 1984 figures. The overall mean monthly cannabis consumption of the respondents was 24.8g per month.

 3.1.3 Consumption of cannabis by daily users averaged 34.8g per month, with mean purchase of 60.1g per month. These daily users averaged 7.7 "spliffs" per day, as against the overall average of 5.98 per day. The maximum accepted personal consumption (10 respondents) was 200-250g, or 7-9oz per month.

 3.1.4 The 1994 and 1997 survey samples both showed similar mean cannabis usage (overall 24.8g, 23.92g respectively) and distributions, and were combined to form a total sample of 2469 users. The distribution of monthly consumption (fig 1) is shown below.

Fig 1 - Distribution of monthly cannabis use

 

3.1.5 As with our previous studies, the majority of cannabis users consume relatively modest amounts, although there are a minority of heavy users who consume substantially more than "average". The top credible consumption was 400g or approximately 1/2oz per day, by a grower who had produced 208 plants in his most recent crop. At 3%-15% THC, this could represent between 400mg and 2000mg THC per day. He reported "memory loss" as a health problem and did not report any health benefits! There was a small cluster of 19 respondents in the range 200-250g (approx. 2oz per week), representing THC intakes of between 200mg and 1250mg per day. This contrasts with the maximum reported cannabis use in the literature of 10g/day (McBride) in the UK, and 50g per day (Schaeffer et al) in the Caribbean (estimated at 4000mg THC/day based on determined 8% THC content).

3.1.6 Fairbairn"s 1973 study of reefer content quoted regular use by three groups of experimental subjects of (a) 2g to 6g of cannabis per day (mean 3.8g) (b) 0.1g to 1g per day (mean 0.3g), (c) 0.3g to 8.3g per day (mean 2.8g), some users smoking 10-20 reefers per day. The heaviest user in this study would have consumed 252g per month, consistent with the heaviest reported use from our surveys.

3.1.7 Caplin & Woodward, for the BBC"s Drugwatch TV special, conducted a survey of drug users in 1984. The "cannabis only" users spent an average £12 per week, representing 3.8g to 5.9g per week at 1984 prices. The heaviest 8%, spending up to £30 per week, would have used 9.6g to 15.8g per week at 1984 prices. However, these did not include the "cannabis plus" (other drugs) users, who spent up to £200 per week in total. The Drugwatch study can be criticised on a number of grounds, as it asked viewers to write in for a detailed questionnaire following graphic portrayals of the problems associated with hard drug use. The overall response rate is not stated, (3000 questionnaires were distributed) although the "cannabis only" group constituted only 3% of the total sample.

3.1.9 McBride"s recent study of cannabis use in 100 attendees at a drug and alcohol clinic in South Wales, found average cannabis use of 10.5g per week (approx. 45g per month) with the heaviest user reporting 70g per week at a cost of £250. McBride calculated, on the basis of responses to questions about the number of joints per "eighth" or "sixteenth", that users would consume 350mg of cannabis resin, or 620mg herbal cannabis, in a joint. Those who did not use tobacco consumed about 27% more cannabis or resin per cigarette or pipe than those who used a mix, although there was no difference in the overall cannabis usage between these two groups.

3.1.10 Approximately 2-5% of regular cannabis users purchase the drug on a "less than monthly" basis, buying several ounces at a time to take account of bulk prices. The average quantity purchased per transaction increases sharply with the duration of use (particularly among users of over 20 years standing), and the proportion reported to be used personally is also highest amongst this age group.

 

3.2 World data

3.2.1 In countries where use of cannabis is traditional, and where plentiful supplies are cultivated locally, the amount consumed can exceed 2oz (56g) per day, e.g. Schaeffer, Carter. Looking at the dosage of THC to which smokers were exposed, Rubin, Bowman & Pihl, and Beaubrun found THC dosages of 60 to 420 mg/day, equivalent to smoking 4 to 28 grams (1/8oz to 1oz) of cannabis per day with 3% THC (allowing for wastage during smoking). Stephanis et alia found that hashish users in Greece used an average of 7.48g (approx. 1/4 oz) per day.

3.2.2 To put these figures into perspective, a person who smokes 30 cigarettes per day will consume roughly 1 ounce (28g) of tobacco per day, as each filter cigarette contains approximately 800mg-1.0g of tobacco.

 

3.3 Composition of "Joints"

3.3.1 Published and unpublished Home Office data suggests that the average (mean) amount of cannabis (normally mixed with tobacco) in what they call a "reefer" cigarette is approximately 200mg. However, a crude average can represent either a broad or a narrow distribution of results. These, and other reports have shown a very wide range of amounts of cannabis in a "joint", from a few milligrams to over one gram, with virtually all reports showing a significant minority of cigarettes containing over 300mg of cannabis. The main criticism of these reports is that they have only analysed cannabis reefers rolled with tobacco. Very few complete unsmoked reefers rolled with "home grown" appear in the samples.

3.3.2 Results from our 1994 survey give similar distributions. By dividing the reported monthly cannabis use by the total number of pipes and reefers smoked, it was possible to arrive at a crude estimate of the amounts of cannabis in reefers. The mean amount was 155mg, with 10.6% of the estimates being over 300mg, 3.3% over 500mg, and 1.7% over 750mg.

3.3.3 From the combined 1994-97 surveys, the distributions of number of "spliffs" (reefers) smoked per day are shown in fig 1 below.

 

Fig 2 - Distribution of number of "spliffs" smoked per day

 

3.4 Eating and Drinking cannabis

3.4.1 Around 1 to 2% of users consume 50% or more of their cannabis in food or drink, and around 25% eat or drink their cannabis on occasions. Consumption of cannabis in a tea is increasingly common, particularly among non-smokers seeking a medicinal benefit, and in West Indian (Ganja tea) and Asian communities (bhang).

3.4.2 Recipes for cannabis typically call for up to half an ounce or more of cannabis leaves, which can also be used as a salad vegetable. Cannabis tea is likely to require 2-3 grams of leaves per cup - a Brooke Bond tea bag contains just over 3 grams of tea.

 

3.5 Summary of consumption statistics

3.5.1 The equivalent consumption levels and "reefers per day" of users at different percentiles of the above range is as shown in table 1 below. The top 4% would use 1oz per week or more (one user in 25), 1% would smoke 200-250g per month. The most commonly reported use was 28g, or one ounce per month, although median usage was equivalent to one eighth ounce per week.

Table 1

Cannabis Use Percentiles (1994-97 - n = 2469 )

Percentile

Monthly use

Weekly use

Daily use

THC @ 3%

THC @ 15%

Joints per day

50% (median)

14g

3.5g

0.5g

15mg

75mg

5

Top 25% (mode)

28g

7g

1g

30mg

150mg

10

Top 10%

56g

14g

2g

60mg

300mg

15

Top 5%

76g

19g

2.7g

81mg

405mg

17

Top 1%

200g

50g

7.1g

213mg

1065mg

23

Maximum

400g

100g

13.3g

400mg

2000mg

47