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Changes in Market Shares of Illegal Drugs since 1984

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Using data from our two similar studies in 1984 and 1994, some changes in the percentages of total drug spending spent on each drug can be seen. Cannabis declined as a proportion over the whole period, but rose in the last three years. Heroin and LSD use have declined consistently as proportions, amphetamines have risen. (Table 32).

Recent headlines suggesting an increase in heroin use are not confirmed by these results. It is likely that some proportion of the increase in registered addicts would be attributable to the wider availability of "user friendly" treatment options such as needle exchanges and maintenance prescribing, with reduced emphasis on abstinence-oriented treatment and advice. While the proportion of lifetime heroin use has fallen steadily in the surveys since 1994, the proportion of daily users has remained stable at around 0.5% to 1%. An increase in the prevalence of drug use in general would be expected to result in some increase in the numbers using heroin. However, the slight increase in average rating of heroin may suggest the drug to be losing some stigma among some individuals or groups within the drug using population.

Conclusions

Cannabis Prices

Prices of cannabis fell by 1.4% between 1994 and 1997. This represents a greater reduction in real economic terms. The modal retail price of cannabis resin remained steady at 15 per 1/8oz, but a higher proportion of users reported lower prices than in 1994.

There is evidence of increasing use and cultivation of "skunk" or other indoor cannabis varieties, and significantly reduced use of imported herbal cannabis. Consumption of "skunk" exceeded that of "homegrown (leaf)".

Home grown cannabis was most commonly given away free, however when it was sold prices could be as high as imported herbal varieties. As mature female cannabis plants produce broadly equivalent quantities of leaf and flowering tops when grown indoors, it would appear that roughly 75% of home-produced leaf material, even from good quality plants, may be discarded or otherwise not consumed.

Moroccan resin (also including the majority of "unknown" resin) appears to have consolidated its already dominant market share, largely at the expense of Asian resin. Lebanese resin, once the market leader, has virtually disappeared from the UK market. The "drought" of Moroccan resin widely reported during 1996 appears to have had no lasting effect on cannabis prices.

The mean price of cannabis (all varieties and weights consolidated) was lowest in the South West, most expensive in the Midlands. For small amounts these regional differences were negligible and did not reach statistical significance, with greater price differentials for imported herbal varieties. The mean price of 1/8oz cannabis was lowest in Wales, highest in Yorkshire-Humberside, although the mean price of 1oz was lowest in the North-West and highest in London.

The most commonly used varieties of cannabis are dark Moroccan (a.k.a "soapbar") and "skunk". Popularity ratings did not appear to have a direct effect on market share, as Moroccan had a low rating, and the most widespread use. Higher ratings of "Lebanese" and other rarer cannabis types would appear to represent novelty and/or nostalgia value.

Prices of other drugs

The price of most drugs fell in real terms between 1995 and 1997, with particularly noticeable falls in the prices of heroin, cocaine and ecstasy. Amphetamine prices had also fallen which, taken with the increased purity and indications of wider prevalence, suggests that greater quantities are available on the UK market. Both heroin prices and purities have fallen. For most drugs, bulk prices suggest roughly a 20-30% price reduction for every 10 fold increase in quantity, although the difference between "gram" and "ounce" prices for amphetamine is particularly substantial, suggesting that regular or heavy users would find it economically advantageous to buy in ounces.

For all illegal drugs (consolidated) the overall price is highest in Scotland, lowest in East Anglia. There are wide variations reported in the regional prices of powders (amphetamines, heroin, cocaine). In almost every case where comparisons could be made, average prices given by our respondents were lower than those given in official police statistics.

Purchasing Patterns

Users of most drugs buy these on a weekly, fortnightly or monthly basis. Daily purchase is rare, other than for heroin users. Those having most recently bought cannabis between 1 and 6 months previously had bought substantially more than other user groups, suggesting that a minority of users (approx. 2%) buy in bulk to sustain long-term consumption. Otherwise, purchase patterns may well reflect the availability of money, either though a weekly wage, fortnightly giro or monthly salary.

Although these data indicate that a substantial proportion of users purchase drugs for personal use on a monthly basis, those users who are arrested in possession of one months personal supply of cannabis or other drugs would normally expect to face "possession with intent" charges, with a real probability of conviction and imprisonment.

The purchase data suggests that the widespread police practice of quoting "gram deal" prices for cannabis is unjustified. Only 4% of purchases by regular users involved quantities of less than 1/8oz, a similar proportion to purchases exceeding one ounce. Experimental and casual users would appear to make up the bulk of those purchasing "sixteenths" or 5 deals.

Prevalence of other drug use

The lifetime prevalence of use of other illegal drugs was lower than in 1994, although ecstasy (up 7.2%), and amphetamine (up 1.2%) bucked the general trend, suggesting a real increase in the lifetime prevalence of these drugs since 1994. The ecstasy trend appears to reflect an increased saturation of the market, from 84.4% of potential users in 1994 to 92.9% in 1997 having tried the drug.

The overall pattern of use of other drugs was similar to previous years, with the majority of those having tried other drugs reporting experimental or occasional use. However around one in five respondents used amphetamine and/or ecstasy on a regular (monthly or weekly) basis, with around one in ten respondents considering themselves regular users of LSD or Mushrooms. The highest number of daily users for any illegal drug other than cannabis was for amphetamine (16 respondents, 1.4%), with only 8 reporting daily heroin use (0.7%), confirming the data from previous surveys showing that the vast majority of cannabis users do not become addicted to other drugs. The high incidence of frequent ecstasy use is a particular cause for concern, as dosage levels reported by some users would exceed those reported to cause serotonergic neurotoxicity in laboratory animals. Awareness of such risks appears not to have permeated the consciousness of ecstasy users by the summer of 1997, as subjective ecstasy ratings were higher than in 1994 (up from 6.36 to 6.86 out of 10).

The prevalence of other drugs not specifically mentioned in the questionnaire, requiring respondents to "write in" answers, will under-represent the wider incidence of use. Of these rarer drugs, Opium and Ketamine appear the most common and worthy of further investigation.

Estimating the Size of the UK Cannabis Market

Our estimates of the value of the cannabis market echo those published by the Office of National Statistics, who arrived at similar figures despite erroneous assumptions (underestimating annual personal consumption, and overestimating the risk of police arrest), the effect of which would largely be to cancel each other out. The main indicator used to derive our estimates are the incidence/probability of arrests among our users, and their reported levels of consumption, frequency of cannabis purchase, amounts purchased and prices paid.

The distribution of cannabis use is similar to previous years, with a slight reduction in overall mean monthly cannabis use from 24.8g to 23.9g per month.

The probability of arrest varies according to the size of deal currently purchased, those buying one ounce or more at a time were nearly twice as likely to have been arrested as buyers of 1/2oz or less. Based on the number of deals bought per year, and the number of busts per year per individual, the police seizure rate would vary between 1 bust every 750 to 2000 deals, or one bust every 25-30 years for the average user (3.5% chance of ever being busted per year of use).

Those users who had grown cannabis plants were three times as likely to have been arrested for cannabis offences compared to non growers (5.7% vs. 1.9% chance of bust per year of use). Given that most users will not have been growing throughout their use history, the chances of being "busted" during a growing season may be considerably higher than 5.7%. On the basis that three crops per year would be produced by indoor cultivation, with two being grown simultaneously (i.e.. in vegetative and flowering states), we estimate that police seize a minimum of 4% of the domestically produced crop.

Based on a range of alternative indicators, weighting and calculation methods, the value of the UK cannabis market can be estimated as between 1.71 billion and 9.03 billion per annum. Extrapolating prevalence from the police caution & conviction statistics and our estimated "bust rates", there would be approximately 2.3 million regular cannabis users in the UK. This does not assist with estimating lifetime prevalence, as there will be a larger but unknown number of occasional/experimental users and former users of the drug. This is slightly larger than the Home Office estimate from the British Crime Survey, but consistent with their figure in the light of under-reporting of cannabis use described by the Home Office study involving drug testing of arrestees.

The 1994 and 1997 samples both showed similar mean cannabis usage (24.8g, 23.92g per month respectively) and distributions, and were combined to form a sample of 2469 users. The distribution of monthly consumption, number of "spliffs" and the equivalent consumption levels of users at different percentiles of the range are shown below.

The top credible reported consumption was 400g or approximately 1/2 oz 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. 2 oz 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).

The top 4% of our respondents 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. One user in four would smoke 10 or more "spliffs" per day.

Younger users, including students (who have consistently shown lower average cannabis use than other occupation groups), tend to use less cannabis than those of 5-15 years standing.

There is no evidence of any significant increase in use with longer durations, as those users of 20 or more years standing used less cannabis than their less experienced counterparts. A typical pattern would be an experimental phase in mid teens, followed by heavier use of cannabis and experimental or occasional use of a range of other drugs (notably amphetamine, mushrooms, LSD) in early adulthood, and very few users of crack or heroin, mostly experimental users. In the late 20s and early 30s cannabis use appears to stabilise to between 1/8oz and 1/4oz per week with other drugs used rarely if ever. The cross-sectional evidence of use levels are consistent with the "up top down" pattern reported by Cohen & Sas among 49% of cannabis users in Amsterdam.

Further results from the consolidated data set, re consumption patterns and aspects of medicinal use are published in our House of Lords Submission.

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