Prevalence of problematic and injecting drug use for Drug Action Team areas in England

National and local monitoring of policies on illicit drug use requires information on the number of problematic drug users in a country. This article reports the findings from a study that estimated the number of problematic and injecting drug users for all Drug Action Teams (DATs) in England for 2001.

The Multiple Indicator Method (MIM) is a statistical technique for using aggregated data to estimate numbers of drug users across a large number of areas. The MIM was used to combine eight indicators available for all DATs, with prevalence estimates available from a small number of DATs. The indicators were drug possession and supply offences, arrest referrals, people recorded in drug treatment databases, methadone prescriptions, drug-related hospital episodes, drug-related deaths and DATs' Townsend score. The latter is a measure of material deprivation. A three-stage process involved, (i) factor analysis of the drug indicators, (ii) regression linking factor scores to known prevalence estimates and (iii) imputation of estimates to all other DATs.

Factor analysis yielded two statistically significant factors underlying the drug indicators in 150 DATs in England. The estimated prevalence rate of problematic drug use in the DATs varied from 0.2 to 1.5 per cent of the population. The estimated average number of problematic drug users per DAT was 1943 (standard deviation = 1300). The estimated average number of injecting drug users per DAT was 627 (standard deviation = 572). The estimates for England in 2001 were 287,670 (population rate = 0.64 per cent) problem drug users, and 93,185 (population rate = 0.23 per cent) injecting drug users.

Although the model cannot take account of specific local factors, the results are likely to be accurate in areas that do not have these idiosyncrasies. The estimated prevalence figures provide a basis for all DATs to assess their contact rates with problematic and injecting drug users.