A well-characterized potential marker for addiction is impulsive choice, stably measured by delay discounting (DD) paradigms. While genetic influences partly account for inter-individual variance in impulsivity, environmental factors such as parenting practices may have an important role. The present study investigates how inconsistent fulfillment of delayed reward promises impacts on DD. A combined correlational and experimental functional magnetic resonance imaging (fMRI) design was performed in a sample of 48 healthy adolescents (13-15 years). More specifically, neural activation during a DD task was investigated at two assessment points (T0 and T1). Adolescents' self-reports of parenting and substance use were assessed at T0. Between assessment points, we experimentally varied the reliability of delayed reward promises, measuring the impact of this intervention on DD and neural value processing at T1. In the correlational part, same-sex parent reward inconsistency was associated with steeper DD and an attenuated subjective value (SV) representation in the nucleus accumbens (NAcc) and ventromedial prefrontal cortex (vmPFC). Steeper DD was in turn associated with alcohol use during the past year. In the experimental part, the reward inconsistency manipulation resulted in an attenuation of the NAcc SV representation, similar to the parental inconsistency effect. Together, our correlational and experimental findings raise new light on how parents may influence their children's degree of impulsivity, making parenting a potential target in addiction prevention.
