Background: Greater temporal discounting has been associated with a range of problematic impulsive behaviors including substance abuse, obesity, and pathological gambling. It is not known whether greater temporal discounting precedes or is an effect of these behaviors. Here we examine temporal discounting and cannabis use in a large longitudinal sample of adolescents collected by the IMAGEN consortium (http://www.imagen-europe.com).
Methods: Individual temporal discounting rates measured by Kirby's Monetary Choice Questionnaire and lifetime use of cannabis estimated by the European School Survey on Alcohol and Other Drugs (ESPAD) was assessed at three time points: 14, 16, and 18 years old. Complete data at each timepoint was available in 1120 adolescents. The bidirectional relationships between these two variables across time were examined using an autoregressive cross-lagged model in Mplus.
Results: The overall model fit was good (a;250.16, df52, p50.9; RMSEA 5 0.001; CFI 5 1.0). There were three main findings: i) stability paths for temporal discounting and cannabis use were significant across time, ii) temporal discounting and cannabis use were significantly correlated at each time point, and iii) temporal discounting significantly predicted future cannabis use but cannabis use did not predict future rates of temporal discounting.
Conclusions: The results are consistent with the notion that impulsivity is a cause rather than an effect of cannabis use. Early interventions which lower temporal discounting in impulsive adolescents may be an effective investment against future problematic drug use.