Empirically, teenagers who use soft drugs are more likely to use hard drugs in the future. This pattern can be explained by a causal effect (i.e., state dependence between drugs or stepping-stone effects) or by unobserved characteristics that make people more likely to use both soft and hard...

This paper estimates the effect of alcohol use on consumption of hard drugs using the exogenous decrease in the cost of accessing alcohol that occurs when individuals reach the minimum legal drinking age. By using a regression discontinuity design and the National Longitudinal Study of Youth...