Validity of a demand curve measure of nicotine reinforcement with adolescent smokers

Abstract

High or inelastic demand for drugs is central to many laboratory and theoretical models of drug abuse, but it has not been widely measured with human substance abusers. The authors used a simulated cigarette purchase task to generate a demand curve measure of nicotine reinforcement in a sample of 138 adolescent smokers. Participants reported the number of cigarettes they would purchase and smoke in a hypothetical day across a range of prices, and their responses were well-described by a regression equation that has been used to construct demand curves in drug self-administration studies. Several demand curve measures were generated, including breakpoint, intensity, elasticity, P(max), and O(max). Although simulated cigarette smoking was price sensitive, smoking levels were high (8+ cigarettes/day) at prices up to 50¢ per cigarette, and the majority of the sample reported that they would purchase at least 1 cigarette at prices as high as $2.50 per cigarette. Higher scores on the demand indices O(max) (maximum cigarette purchase expenditure), intensity (reported smoking level when cigarettes were free), and breakpoint (the first price to completely suppress consumption), and lower elasticity (sensitivity of cigarette consumption to increases in cost), were associated with greater levels of naturalistic smoking and nicotine dependence. Greater demand intensity was associated with lower motivation to change smoking. These results provide initial support for the validity of a self-report cigarette purchase task as a measure of economic demand for nicotine with adolescent smokers.

Figure 1

Panel A depicts the mean number of cigarettes that participants reported that they would smoke at 26 different prices (left axis), as well as the percentage of the sample that reported they would abstain at each price (right axis). Error bars represent +/− 1 Standard Error of the Mean (SEM). As expected, cigarette smoking exhibited a decelerating trend in response to price increases. Abstinence rates were extremely low at prices up to $1 per cigarette. The sample abstinence rate first exceeded 50% at a price of $3 per cigarette (55% abstinent) and increased rapidly thereafter. Panel B depicts response output (mean cigarette expenditures, computed as reported cigarette consumption x cigarette price). Error bars represent +/− 1 SEM. Response output conformed to an inverted U-shaped function up to the point where the extremely large prices resulted in high mean expenditure values despite the fact that most participants had reached breakpoint. Panels C and D also depict demand and expenditure curves plotted in conventional double logarithmic coordinates for proportionality.