The April 20 Cannabis Celebration and Fatal Traffic Crashes in the United States

Abstract

This data analysis examines the association between the April 20 cannabis celebrations in the United States and a population-level increase in the risk of fatal traffic crash involvement.

Figure 1.. Relative Risk of Traffic Crash on April 20

Forest plot showing relative increase in risk of a traffic crash on April 20 compared with control days exactly 1 week earlier and later. Solid squares indicate point estimate; relative dimensions, sample size; and horizontal lines, 95% CIs. Vertical columns show total counts between 4:20 PM and 11:59 PM on April 20 and control days. Main findings show an increase in relative risk on April 20, no significant contrary findings, and an accentuated effect for younger individuals. State-level estimates of the prevalence of marijuana use among adults from the 2002-2003 National Surveys on Drug Use and Health (near the midpoint of our study) were used to categorize states as "Higher use" (median and above) and "Less high use" (below the median).

Figure 2.. National Variation in Relative Risk of Traffic Crash On April 20

The map displays the United States for all contiguous states and offset images for noncontiguous states. Colors denote relative increase in traffic risks on April 20 compared with control days exactly 1 week earlier and later. Green corresponds to increased relative risk, yellow to neutral relative risk, and brown to decreased relative risk (spectrum scaled by logarithm transformation). Findings show that 30 states had a relative risk point estimate greater than unity (eg, Hawaii), while only 18 states had an estimate less than unity (eg, Minnesota), and 2 states had an estimate of exactly unity (eg, Montana).