Temporal trends in marijuana attitudes, availability and use in Colorado compared to non-medical marijuana states: 2003-11

Abstract

Background: In 2009, policy changes were accompanied by a rapid increase in the number of medical marijuana cardholders in Colorado. Little published epidemiological work has tracked changes in the state around this time.

Methods: Using the National Survey on Drug Use and Health, we tested for temporal changes in marijuana attitudes and marijuana-use-related outcomes in Colorado (2003-11) and differences within-year between Colorado and thirty-four non-medical-marijuana states (NMMS). Using regression analyses, we further tested whether patterns seen in Colorado prior to (2006-8) and during (2009-11) marijuana commercialization differed from patterns in NMMS while controlling for demographics.

Results: Within Colorado those reporting "great-risk" to using marijuana 1-2 times/week dropped significantly in all age groups studied between 2007-8 and 2010-11 (e.g. from 45% to 31% among those 26 years and older; p=0.0006). By 2010-11 past-year marijuana abuse/dependence had become more prevalent in Colorado for 12-17 year olds (5% in Colorado, 3% in NMMS; p=0.03) and 18-25 year olds (9% vs. 5%; p=0.02). Regressions demonstrated significantly greater reductions in perceived risk (12-17 year olds, p=0.005; those 26 years and older, p=0.01), and trend for difference in changes in availability among those 26 years and older and marijuana abuse/dependence among 12-17 year olds in Colorado compared to NMMS in more recent years (2009-11 vs. 2006-8).

Conclusions: Our results show that commercialization of marijuana in Colorado has been associated with lower risk perception. Evidence is suggestive for marijuana abuse/dependence. Analyses including subsequent years 2012+ once available, will help determine whether such changes represent momentary vs. sustained effects.

Keywords: Cannabis; Decriminalization; Legalized marijuana; Marijuana policy; Medical marijuana.

Fig. 1

Measures of marijuana-related attitudes, change across time (2003-4 to 2010-11) within Colorado (Blue) and within 34 states without medical marijuana laws (NMMS, Red). A. Great risk to smoking marijuana 1-2 times per week. B. Fairly/very easy to obtain marijuana. C. Somewhat or strongly disapprove of adults trying. Row 1 represents 12-17 year olds, Row 2 represents 18-25 year olds and Row 3 represents those 26+ years. X– axis indicates year, while y-axis indicates percent of respondents endorsing an item. Dashed line indicates that years 2009-10 and 2010-11 are not independent. Brackets and associated asterisk(s) indicate a significant change within-Colorado across years. Asterisk below lines, just above the years (x-axis) indicate that Colorado and 34 non-medical marijuana states significantly differed. * <0.05

Fig. 2

Measures of marijuana-use-related outcomes, change across time (2003-4 to 2010-11) within Colorado (Blue) and within 34 states without medical marijuana laws (NMMS, Red). A. Past-year marijuana use. B. 20+ days used in the past month among users. C. Marijuana abuse/dependence in the past year. Row 1 represents 12-17 year olds, Row 2 represents 18-25 year olds and Row 3 represents those 26+ years. X– axis indicates year, while y-axis indicates percent of respondents for marijuana use, near daily use and abuse/dependence. Dashed line indicates that years 2009-10 and 2010-11 are not independent. Brackets and associated asterisk(s) indicate a significant change within-Colorado across years. Asterisk below lines, just above the years (x-axis) indicate that Colorado and 34 non-medical marijuana states significantly differed. * <0.05

Fig. 3

Significant and trend state-by-year interactions from regression analyses (Tables 1-3) presented as odds ratios within state (NMMS and Colorado) and time (2006-8 and 2009-11). Row 1 represents 12-17 year olds, Row 2 represents those 26+ years. X-axis indicates years (2006-8 and 2009-11), while y-axis indicates odds ratios.