The effects of price and perceived quality on the behavioural economics of alcohol, amphetamine, cannabis, cocaine, and ecstasy purchases.

Behavioural economic models of substance use describe the relationship between changes in unit price and consumption. However, these models rarely take account of the perceived quality (i.e. potency) of controlled drugs. Therefore we investigated the effects of both price and quality on the decision to purchase controlled drugs by polysubstance misusers. Forty current polysubstance misusers (29 males, 11 females; mean age 23.8) were recruited into the study. Participants were asked to hypothetically purchase drugs from a price list of alcohol, amphetamine, cannabis, cocaine and ecstasy at different levels of quality and price (i.e. better quality drugs cost more money). The disposable income available for those purchases was systematically varied in order to determine the impact of income on the decision to purchase drugs. Demand for both normal and strong alcohol was income inelastic. Demand for both poor and average quality cannabis and ecstasy was income inelastic, but demand for good quality cannabis and ecstasy was income elastic. The demand for poor quality cocaine was income inelastic, with the demand for both average and good quality cocaine being income elastic. Participants reported too few purchases of amphetamine, which precluded behavioural economic analysis. These results suggest that, like other goods, controlled drugs are purchased based upon the consumer's interpretations of their relative value. Therefore, it is probable that the purchase and subsequent use of controlled drugs by polysubstance misusers will be heavily influenced by the economic environment.