Abstract
RATIONALE: Despite consistent evidence of the familiality of substance misuse, the mechanisms by which family history (FH) increases the risk of addiction are not well understood. One behavioral trait that may mediate the risk for substance use and addiction is delay discounting (DD), which characterizes an individual's preferences for smaller immediate rewards compared to larger future rewards. OBJECTIVES: The aim of this study is to examine the interrelationships among FH, DD, and diverse aspects of personal substance use, and to test DD as a mediator of the relationship between FH and personal substance use. METHODS: The study used crowdsourcing to recruit a community sample of adults (N = 732). Family history was assessed using a brief assessment of perceived parental substance use problems, personal substance use was assessed using the Alcohol Use Disorders Identification Test and a measure of frequency of use, and delay discounting was assessed using a latent index of discounting preferences across six reward magnitudes. RESULTS: Steeper discounting was significantly associated with personal alcohol, tobacco, and marijuana use, and level of substance experimentation. Steeper DD was also associated with a denser parental FH of alcohol, tobacco, and overall substance misuse. Parental FH density was significantly associated with several aspects of personal substance use, and these relationships were partially mediated by DD. CONCLUSIONS: The current study suggests that impulsivity, as measured by DD, is one proximal mechanism by which parental FH increases substance use later in life. The causal role of DD in this relationship will need to be established in future longitudinal studies.