Excessive discounting of delayed rewards in substance abusers with gambling problems

This study evaluated delay discounting functions of substance abusing probl em gamblers, substance abusing non-problem gamblers, and non-problem gambli ng/non-substance abusing controls. Subjects chose between hypothetical mone tary amounts available after various delays or immediately. In one conditio n, a USUS$1000 reward was delayed at intervals ranging from 6 h to 25 years . At each delay interval, the immediately available rewards varied from USU S$1 to USUS$999 until choices reflected indifference between the smaller im mediate and larger delayed rewards. In a second condition, the delayed rewa rd was USUSS100, and immediate rewards varied from USUS$0.10 to USUS$99.90. In all three groups, hyperbolic discounting functions provided a good fit of the data, and the smaller reward was discounted at a higher rate than th e larger reward. Substance abusers discounted delayed rewards at significan tly higher rates than non-substance abusing controls, and problem gambling substance abusers discounted delayed rewards at higher rates than their non -problem gambling substance abusing counterparts. Discounting rates were no t associated with types or recency of drug use. These results provide furth er evidence of more rapid discounting of delayed rewards in substance abuse rs, and especially among substance abusers with a comorbid gambling problem . Rapid discounting of delayed rewards may be a feature central to impulse control and addictive disorders. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.