By: Andrey P. Anokhinemail, Julia D. Grant, Richard C. Mulligan, Andrew C. Heath
Biological Psychiatry
November 6, 2014
Abstract
Background
Delay discounting (DD), a decline in the subjective value of reward with increasing delay until its receipt, is an established behavioral model of impulsive choice, a key component of a broader impulsivity construct. Greater DD, i.e. a tendency to choose smaller-immediate over larger-delayed rewards, has been implicated as a potential intermediate phenotype (endophenotype) for addictive disorders and comorbid externalizing psychopathology, particularly in adolescence. However, genetic and environmental origins of DD remain unclear. Accordingly, the goal of the present study was to assess heritability of DD, an important aspect of its utility as an endophenotype.
Methods
A commonly used computerized procedure involving choice between varying amounts of money available immediately and a “standard” amount of $100 presented at variable delays was administered to a population-based sample of twins aged 16 and 18 (n=560, including 134 MZ and 142 DZ pairs). DD was quantified using area under the discounting curve (AUC) and the k coefficient estimated by fitting a hyperbolic model to individual data. Heritability was assessed using linear structural equation modeling of twin data.
Results
The genetic analysis revealed significant heritability of both DD measures (AUC: 46% and 62%; k: 35% and 55% at age 16 and 18, respectively).
