title: Heroin and cocaine abusers have higher discount rates for delayed rewards than alcoholics or non-drug-using controls.
abstract: OBJECTIVE
  To test a prediction of the discounting model of impulsiveness that discount rates would be positively associated with addiction. The delay-discount rate refers to the rate of reduction in the present value of a future reward as the delay to that reward increases.
  
  
  METHODS
  We estimated participants' discount rates on the basis of their pattern of choices between smaller immediate rewards ($11-80) and larger, delayed rewards ($25-85; at delays from 1 week to 6 months) in a questionnaire format. Participants had a one-in-six chance of winning a reward that they chose on one randomly selected trial.
  
  
  METHODS
  Heroin (n = 27), cocaine (n = 41) and alcohol (n = 33) abusers and non-drug-using controls (n = 44) were recruited from advertisements. They were tested in a drug abuse research clinic at a medical school.
  
  
  RESULTS
  On average, the cocaine and heroin groups had higher rates than controls (both P < 0.001), but alcoholics did not (P = 0.44). Abstinence was associated with lower rates for heroin abusers (P = 0.03), but not for cocaine or alcohol abusers (both P > 0.50).
  
  
  CONCLUSIONS
  These data suggest that discount rates vary with the preferred drug of abuse, and that high discount rates should be considered in the development of substance abuse prevention and treatment efforts.
authors.affiliation: Department of Psychology, Williams College, Williamstown, MA, USA. kkirby@williams.edu
authors.forename: Kris N
authors.initials: KN
authors.lastname: Kirby
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Petry
mesh_terms: D000328:Adult; D000437:Alcoholism / Q000523:psychology*; D002755:Choice Behavior; D019970:Cocaine-Related Disorders / Q000523:psychology*; D005260:Female; D006556:Heroin Dependence / Q000523:psychology*; D006801:Humans; D007175:Impulsive Behavior / Q000523:psychology; D008297:Male; D008875:Middle Aged; D009042:Motivation; D012201:Reward; D011795:Surveys and Questionnaires; D013997:Time Factors