Newly incident cannabis use in the United States, 2002-2011: a regional and state level benchmark

Abstract

Background: Cannabis use and cannabis regulatory policies recently re-surfaced as noteworthy global research and social media topics, including claims that Mexicans have been sending cannabis and other drug supplies through a porous border into the United States. These circumstances prompted us to conduct an epidemiological test of whether the states bordering Mexico had exceptionally large cannabis incidence rates for 2002-2011. The resulting range of cannabis incidence rates disclosed here can serve as 2002-2011 benchmark values against which estimates from later years can be compared.

Methods: The population under study is 12-to-24-year-old non-institutionalized civilian community residents of the US, sampled and assessed with confidential audio computer-assisted self-interviews (ACASI) during National Surveys on Drug Use and Health, 2002-2011 (aggregate n ∼ 420,000) for which public use datasets were available. We estimated state-specific cannabis incidence rates based on independent replication sample surveys across these years, and derived meta-analysis estimates for 10 pre-specified regions, including the Mexico border region.

Results: From meta-analysis, the estimated annual incidence rate for cannabis use in the Mexico Border Region is 5% (95% CI [4%-7%]), which is not an exceptional value relative to the overall US estimate of 6% (95% CI [5%-6%]). Geographically quite distant from Mexico and from states of the western US with liberalized cannabis policies, the North Atlantic Region population has the numerically largest incidence estimate at 7% (95% CI [6%-8%]), while the Gulf of Mexico Border Region population has the lowest incidence rate at 5% (95% CI [4%-6%]). Within the set of state-specific estimates, Vermont's and Utah's populations have the largest and smallest incidence rates, respectively (VT: 9%; 95% CI [8%-10%]; UT: 3%; 95% CI [3%-4%]).

Discussion: Based on this study's estimates, among 12-to-24-year-old US community residents, an estimated 6% start to use cannabis each year (roughly one in 16). Relatively minor variation in region-wise and state-level estimates is seen, although Vermont and Utah might be exceptional. As of 2011, proximity to Mexico, to Canada, and to the western states with liberalized policies apparently has induced little variation in cannabis incidence rates. Our primary intent was to create a set of benchmark estimates for state-specific and region-specific population incidence rates for cannabis use, using meta-analysis based on independent US survey replications. Public health officials and policy analysts now can use these benchmark estimates from 2002-2011 for planning, and in comparisons with newer estimates.

Keywords: Cannabis; Incidence; NSDUH; Region; State-specific.

Figure 1. Reproduction of Fig. 2 in the Library of Congress report on cannabis (marijuana) availability in the United States (United States Library of Congress, 2003).

Figure 2. Region-specific annual incidence rate of cannabis use.

Data from United States National Surveys on Drug Use and Health 10-Year Restricted Data Analysis System, 2002–2011 (Unweighted n ∼ 420, 000 12–24 year olds). Note: reported estimates and their 95% CIs (i.e., numbers in the ‘Estimated Risk’ column) are rounded to the hundreds decimal point due to relatively small sample sizes in small regions.

Figure 3. Heat map representation of state-specific incidence rates.

Gradient heat map representation of each state of the United States in terms of its incidence rate for newly incident cannabis use as estimated for 12-to-24-year-old non-institutionalized civilian community residents. Data from the United States National Survey on Drug Use and Health, 2002–2011. Note: this heat map helps to show that (1) neither the Mexico border states, nor the Gulf of Mexico states have exceptionally large cannabis incidence rates, (2) the northeastern region (including Vermont) has relatively large cannabis incidence rates, and (3) Utah has a relatively small cannabis incidence rate. Comparison of Fig. 3 with Fig. 4 may be useful.

Figure 4. Cartogram representation of state-specific incidence rates.

Cartogram (‘blob map’) representation of each state of the United States in terms of relative size of its population incidence rate for newly incident cannabis use as estimated for 12-to-24-year-old non-institutionalized civilian community residents. Data from the United States National Survey on Drug Use and Health, 2002–2011. Note: this cartogram is oriented top (North), bottom (South), left (West), and right (East). It also helps to show that (1) neither the Mexico border states, nor the Gulf of Mexico states have exceptionally large cannabis incidence rates, (2) the northeastern region (including Vermont) has relatively larger cannabis incidence rates, and (3) Utah has a relatively small cannabis incidence rate. (Utah can be located in relation to the Southwest corner of the map where California has a Pacific coastline and shares a southern border with Mexico. California’s southeast corner has a border with Arizona, above which is Nevada. Utah can be seen as an L-shaped state just above Arizona and to the East of Nevada.) Comparison of Fig. 4 with Fig. 1 and 3 may be useful.