The discounting of delayed reinforcers among the drug dependent has been increasingly studied. The results of that research are consistent and reflect an important dimension of drug dependence. Specifically, these studies have shown that drug-dependent individuals discount money more than matched controls. Moreover, drug-dependent participants discount their drug of dependence more than they discount money. Ex-dependent or recently abstinent drug users discount money either at a rate intermediate between current drug-dependent individuals and matched controls, or at a rate that approximates discounting of the matched controls. Furthermore, reinforcing abstinence has been shown to decrease the discounting of money and cigarettes in the drug dependent. Overall, these studies suggest that drug-dependent individuals discount more than controls and the excessive discounting among the drug dependent may be a reversible effect of drug use. In this competing continuation, we propose to continue this productive research by addressing three specific aims. The first specific aim is to examine whether drug-dependent individuals with co-morbidity discount delayed reinforcers more than individuals without that co-morbidity. Exp. 1 will examine co-morbid substance dependence disorder by comparing the discounting of opioid-dependent cigarette smokers, opioid-dependent non-smokers, non-opioid-dependent smokers, and non-opioid- dependent, non-smoking matched controls. Exp.2 will examine a non-substance dependence co-morbid psychiatric disorder among cigarette smokers, namely, depression. Specifically, we will compare the discounting of depressed smokers, non-depressed smokers, depressed non-smokers, and non-depressed, non-smoking matched controls. The second specific aim is to extensively compare delay and probability discounting in smokers and non-smokers. A prior study reported that smokers did not differ from non-smokers on probability discounting. That prior report examined the discounting of money at only one magnitude. Exp.3 will systematically replicate and extend that prior study by examining and comparing delay and probability discounting. Specifically, we will compare those two types of discounting with several commodities, each at several magnitudes, in both smokers and matched controls. The third specific aim is to examine the relationship between discounting and abstinence. Previously we have shown that ex-smokers do not discount differently than non-smokers. Two hypotheses to explain that observation are (a) smokers who are successfully abstinent discounted less prior to the initiation of abstinence (less discounting leads to abstinence) and (b) abstinence leads to less discounting. These hypotheses may not be mutually exclusive. In Exp.4, we will examine whether individuals with proximate plans to quit cigarette smoking discount differently than both current smokers with no proximate plans to quit and ex-smokers. In Exp.5, we will follow up our initial observation regarding the effects of reinforced abstinence on discounting. Specifically, we propose to replicate and extend that observation with cigarette smokers by imposing and removing a contingency management procedure. If our prior work is replicated, then discounting should decrease when smoking abstinence is reinforced. We will extend that work by determining whether the decrease in discounting reverses when cigarette smokers relapse.
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