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| Science Board Translational Series: Delay Discounting and Drug Abuse |
| Saturday, May 23, 2009 |
| 3:30 PM–4:50 PM |
| North 226 C |
| Area: BPH/EAB; Domain: Experimental Analysis |
| Chair: Amy Odum (Utah State University) |
| Discussant: Amy Odum (Utah State University) |
| CE Instructor: Florence DiGennaro Reed, Ph.D. |
| Abstract: Delay discounting refers to the decrease in the value of an outcome by delay to its receipt. Choosing a smaller more immediate outcome over a larger but delayed outcome is one form of impulsivity. Delay discounting has been found to be related to drug abuse in several ways. This symposium focuses on delay discounting across a spectrum from basic research with non-humans to prediction of relapse following abstinence in cigarette smokers. Mitchell and Wilhelm will discuss basic laboratory research with rats and mice. They find that alcohol consumption and delay discounting are related, and that both are heritable. Carroll and colleagues have examined the role of delay discounting and other forms of impulsivity in basic laboratory models with rats and monkeys. They report that heightened impulsivity is linked to all phases of drug abuse in these models (e.g., acquisition of drug taking, relapse after abstinence, etc.). Finally, Bickel and colleagues will discuss their attempts to predict a number of treatment outcomes (e.g., initiation of abstinence, duration of abstinence) using measures of delay discounting in cigarette smokers. |
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| Shared heritability of delay discounting and alcohol abuse |
| SUZANNE H. MITCHELL (Oregon Health & Science Univ), Clare J. Wilhelm (Oregon Health & Science University) |
| Abstract: Alcoholics and heavy drinkers discount delayed rewards more than social or light drinkers, but the role of genetics in this relationship is unknown. Genetics is known to contribute to the development of alcoholism, and various experimental techniques have been developed to examine the role of genotype in heightened consumption of alcohol. Delay discounting was assessed in several studies using an adjusting amount procedure in which rats (N = 80) or mice (N= 240) chose between small immediate sucrose solution and larger delayed sucrose reinforcers. Hyperbolic equations were fit to quantify the gradient of the function (k value) relating the immediate amount of sucrose that was equivalent to the larger amount at a series of delays (up to 16 s). Studies using inbred strains demonstrated that k values have a heritable component and that there was a inter-strain correlation with alcohol consumption, i.e., high k value strains are documented as having higher levels of alcohol consumption. Studies using mice and rats selectively bred for different levels of alcohol consumption indicated that high consumption lines showed steeper discounting that low consumption lines. These studies indicate that delay discounting has a heritable component and includes genes associated with heightened alcohol consumption. |
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| Impulsivity, a Predictor and Outcome of
of Drug Abuse: Animal Models |
| MARILYN E. CARROLL (University of Minnesota), Justin J. Anker (University of Minnesota), Jennifer L. Newman (McLean Hospital, Harvard Medical School), Jami L. Mach (University of Minnesota), Jennifer L. Perry (Minneapolis Medical Research Foundation) |
| Abstract: There is a strong relationship between impulsive behavior, determined by choice of a small-immediate reward over a large-delayed reward (delay discounting task) and impaired inhibition of responding for a reward (Go/No-go task), and drug abuse. Several aspects of drug abuse have been modeled in rats and monkeys; such as, acquisition, maintenance, escalation, extinction, withdrawal, and reinstatement, and the influence of impulsivity on each of these phases has been determined in a series of experiments. Results indicate that impulsive behavior is a major risk factor for each stage of drug abuse, and some phases of drug abuse (e.g., withdrawal) elevate the animals’ impulsivity for nondrug substances, indicating that impulsive behavior mediates substitution of drug and nondrug reinforcers. Other risk factors for drug abuse that add to the vulnerability produced by impulsivity are also discussed, such as age, sex, and innate sweet preference. The role of impulsivity in drug abuse is discussed in terms of its ability to predict pathological behavior and as a potential target for prevention and treatment attempts. Supported by NIDA grants R01 DA002486, R01 DA003240, R01 DA019942, P20 DA024196, K05 DA015267 (MEC), F31 DA020237 (JLP), F31 DA023301 and T32 DA007097 (JLN). |
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| Delay Discounting: Comparison with Other Measures in the Prediction of Smoking Treatment Outcomes |
| WARREN K. BICKEL (University of Arkansas for Medical Sciences), Darren R. Christensen (University of Arkansas for Medical Sciences), Richard Yi (University of Arkansas for Medical Sciences), Christine E. Sheffer (University of Arkansas for Medical Sciences), Lisa Jackson (University of Arkansas for Medical Sciences), Reid D. Landes (University of Arkansas for Medical Sciences), John E. McGeary (Brown University), James MacKillop (University of Georgia) |
| Abstract: Relapse poses significant challenges to the treatment of a broad array of behavioral disorders such as cigarette smoking. One neurobehavioral process that may be related to relapse and other treatment outcomes is delay discounting, which refers to the reduced value or worth of a delayed reinforcer compared to the value of an immediate reinforcer. We are conducting a large study (N= 250) to examine whether delay discounting predicts treatment outcome measures. To accomplish this, cigarette smokers complete a battery of measures at intake prior to treatment and then receive a cognitive behavior therapy delivered for 6 weeks. Outcome measures include the initiation of abstinence, duration of abstinence, and time to relapse. To date, we have completed over a 100 participants and we will conduct an interim analysis of those data and present them as part of this symposium. Initial analyses indicate that those who fail to initiate a quit attempt, discount substantially more than those who do. We will also compare the predictive ability of discounting to other theoretically important factors including, trait impulsivity, negative affect, neuro-cognitive functioning, and dopamine alleles. These results should identify which of the several factors best predict relapse and other treatment outcomes. |
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