Discounting of money, health, and freedom in substance abusers and controls.

Impulsivity is implicated in drug dependence, and discounting of delayed events may be an objective indicator of impulsiveness. This study evaluated the manner in which outcomes are devalued over time in drug abusers (n=101) and non-substance abusing controls (n=40). Four conditions were presented in which participants chose between hypothetical outcomes available after various delays or immediately. Two were monetary outcomes, and the other two were non-monetary-months of health or freedom. In all conditions, hyperbolic discounting functions provided a good fit of the data. One hundred dollars were discounted more rapidly than $1000, and freedom was discounted more rapidly than health. Drug abusers discounted all types of delayed outcomes at higher rates than controls, even though they placed equivalent subjective monetary values on freedom and health. Rates of discounting were not correlated across domains. These results replicate prior studies showing that drug abusers discount delayed monetary outcomes more rapidly than controls, and they extend these findings to new domains. The rapid discounting of freedom and health may provide a theoretical framework for understanding illegal and risky health behaviors in drug abusers.