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Mazur, J.E. (1987) An adjusting procedure for studying delayed reinforcement. In: Commons, M. L., Mazur, J. E., Nevin, J. A. and Rachlin, H., Eds., The Effect of Delay and of Intervening Events on Reinforcement Value, Quantitative Analyses of Behavior, Erlbaum, Hillsdale, New Jersey, 55-73.

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• TITLE: Variation in the DRD2 gene affects impulsivity in intertemporal choice

  AUTHORS: Yoshiya Kawamura, Taiki Takahashi, Xiaoxi Liu, Nao Nishida, Yoshihiro Noda, Akane Yoshikawa, Tadashi Umekage, Tsukasa Sasaki

  KEYWORDS: Dopamine receptor D2 (DRD2); Impulsivity; Neuroeconomics; Single Nucleotide Polymorphism (SNP); Time-Discount Rate

  JOURNAL NAME: Open Journal of Psychiatry, Vol.3 No.1, January 29, 2013

  ABSTRACT: Introduction: Impulsivity in intertemporal choice has been operationalized as “delay discounting,” referring to the preference for a sooner, smaller reward in neuroeconomics. It is reportedly associated with the dopaminergic systems. Dopamine receptor D2 (DRD2) is the D2 subtype of the dopamine receptor of the G-protein coupled receptor family. The aim of this study was to explore the effect of single nucleotide polymorphisms (SNPs) in DRD2 gene on delay discounting. Methods: The participants consisted of 91 healthy Japanese people (66 males and 25 females with a mean age of 40.9 ± 6.9 years). Each participant completed the Kirby’s monetary choice questionnaire (MCQ) for delayed gain and donated a whole blood sample. Two SNPs (C957T (rs6277) and TaqI A (rs1800497)) in DRD2 were genotyped by using the DigiTag2 assay. SNP linear regression analyses with 100,000 permutations were conducted for the hyperbolic time-discount rate (k). Results: The SNP C957T showed a significant association; participants with more minor alleles (T) were more impulsive in intertemporal choice for delayed gain (multiplicity-corrected P = 0.041 with a small effect size). Conclusion: The variation in the DRD2 gene is associated with impulsive decision-making. This is the first study to demonstrate an association between DRD2 and impulsivity in intertemporal choice with a multiplicity-corrected significance.