Medical marijuana laws, alcohol consumption, and cigarette use in the US adult population

Background:

Medical marijuana laws (MMLs) provide legal protection from state-level criminal penalties for patients qualified to use medical marijuana. Very few studies, however, have examined the potential impact of these laws on cigarette consumption, and evidence is mixed on how MMLs impact alcohol use.  This study identifies the effect of medical marijuana legalization on cigarette smoking, and also tests the mediating role of alcohol in this relationship.

Method:

Drawing upon individual-level data from the Behavioral Risk Factor Surveillance System surveys from 1994-2010 (N=1,655,578), this study employs a difference-in-difference estimation strategy to estimate the effect of implementing MMLs at the state level on the probability of individual cigarette smoking while controlling for alcohol use.  This approach exploits changes in smoking trends within states over time and controls for fixed unobserved state-level characteristics. Estimates are also generated for males and females, different age groups, and various race/ethnicity groups.

Results:

Approximately 24% of the sample reported being current smokers.  Preliminary estimates suggest that MMLs lead to a significant increase in the probability of cigarette smoking by 1.4 percentage points.  Similarly, individuals aged 30-39 experience a statistically significant increase in the probability of cigarette smoking by 1.7 percentage points.  The initial estimates also point to potential differences by race/ethnicity.

Conclusions:

Given that cigarette smoking accounts for nearly 1 in 5 deaths and is the leading cause of preventable disease in the U.S., this paper illustrates the importance of understanding the unintended consequences of medical marijuana laws on tobacco use.