Can the use of psychoactive drugs in the general adult population be estimated based on data from a roadside survey of drugs and driving?

Abstract

A roadside survey of drugs and driving was performed in south-eastern Norway in 2005-6. Samples of saliva from a total of 10,503 drivers above 20 years of age were analysed, and the results were weighted for under- and over-sampling compared to the population distribution in the study area. Weighted results were compared with data on dispensed prescriptions of zopiclone, codeine and diazepam at Norwegian pharmacies in the same area and with self-reported use of cannabis. When using roadside data to estimate drug use, the use of medicinal drugs was under-estimated by 17-59% compared to amounts dispensed. One of the main reasons for the under-estimation may be that a large proportion of the users of psychoactive medicinal drugs are not frequent drivers. For cannabis, self-reported data corresponded approximately to the estimated prevalence range. The results indicate that roadside surveys cannot be used for accurate estimations of drug use in the population, but may provide minimum figures.