Effects of increasing income on polydrug use: a comparison of heroin, cocaine and alcohol abusers

Aims. To assess how income affects hypothetical drug and nan-drug purchasing decisions. Participants and setting. Ninety-four subjects (26 heroin abusers, 28 cocaine abusers, 15 alcohol abusers and 25 non-drug using controls) were recruited from advertisements. Intervention. Subjects were exposed to six conditions in which they "purchased" drugs as well as food, housing, and entertainment as income rose from $30 to $560 per day. Findings. Heroin abusers selected significantly more hypothetical heroin and cocaine as income rose and demand for these two drugs was income elastic, with purchases rising in greater proportion than income. Cocaine abusers significantly increased purchases of, and showed income elastic demand for, cocaine and alcohol. Among alcohol abusers, significant increases in purchases and income elastic demand mere found for alcohol and cigarettes, but not for other drugs. Across all four groups, demand for rent and food were income inelastic, such that purchases did nor rise in proportion to the changes in income, while demand for entertainment was income elastic. Hypothetical choices were reliable between and within subjects, and drug choices were correlated with urinalysis results and life-time years of drug use. Conclusions. Income is an important variable in understanding choices for drug and non-drug commodities across a variety of substance-abusing populations.