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. Author manuscript; available in PMC: 2017 Feb 1.
Published in final edited form as: Drug Alcohol Depend. 2015 Dec 17;159:101–108. doi: 10.1016/j.drugalcdep.2015.11.039

Fig. 3. Number of days of nonmedical pain reliever misuse (nmpr) in past-year among levels (quartiles) of cannabis use: 2003 and 2013 NSDUH.

Fig. 3

To examine how the relative quartiles changed over time, cannabis use was standardized for 2003 and 2013 based on the observed cut-points in each year. For 2003, the marijuana use quartiles (based on number of days used per year), the quartiles for 2013 were Q1 (1–4 days), Q2 (5–43 days), Q3 (44–155 days) and Q4 (156–365 days). The quartiles for 2013 were Q1 (1–5 days), Q2 (6–51 days), Q3 (52–207 days), and Q4 (208–365 days). Two sets of statistical tests are presented, a test between 2003 and 2013 within each quartile that represents changes over time in the number of days of either NMPR or alcohol within each quartile. An overall chi-square test for 2003 and 2013 represents differences for NMPR and alcohol between the four quartiles within each separate year.

Source: 2003 and 2013 National Survey on Drug Use and Health (NSDUH, 2003 and 2013).