International Journal of Drug Policy - 2014

Volume 25 Issue 3 May 2014

Issue link: http://digitalreprints.elsevier.com/i/364061

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C. Morrison et al. / International Journal of Drug Policy 25 (2014) 508–515 511 Table 1 Characteristics of telephone survey respondents (n = 5940). Variable n (%) Male 2626 (44.2) Ethnicity African American 268 (4.5) White 3507 (59.0) Hispanic 1836 (30.9) Asian/Pacific Islander 356 (6.0) Age 20–29 years 439 (7.4) 30–39 years 891 (15.0) 40–49 years 941 (15.8) ≥50 years 2352 (39.6) Highest educational achievement High school/GED 2392 (40.3) Undergraduate 1494 (25.2) Postgraduate/medical school 1235 (20.8) Employment status Full time employed 2175 (36.6) Unemployed 447 (7.5) Household income per year <$20,000 1361 (22.9) $20,000–60,000 2198 (37.0) $60,000–100,000 1241 (20.9) >$100,000 1140 (19.2) Any cannabis use in last 365 days 350 (5.9) Mean SD Days cannabis use 5.0 [37.0] The individual-level censored regression model was performed using STATA v10.1 (StataCorp, 2007). Geoprocessing was com- pleted with ArcGIS v 10 (ESRI, 2011), and the block-group multilevel Bayesian models were estimated using WinBUGS v.4.3.1 (Lunn, Thomas, Best, & Spiegelhalter, 2000). Uninformed priors were spec- ified for all random effects. Trace plots showed that all parameters in all four models had stabilized and converged after a 2000 itera- tion Markov Chain Monte Carlo (MCMC) burn-in. Two chains with different initial values were used in each model. Posterior estimates were sampled for 20,000 iterations to provide model results. Results Characteristics of the survey respondent group are shown in Table 1, and the results of the censored regression model are shown in Table 2. Very few people in the sample reported using cannabis in the last 365 days (5.9%). Whites (b = 73.6 [95%CI = 18.4, 128.8]), men (70.0 [42.8, 97.2]) and people aged 20–29 (82.1 [35.0, 129.2]) used cannabis on more days than the comparison group (i.e. women, aged 18 and 19, "other" ethnicity, household income <$20,000). Older adults (>50 years) were likely to report less cannabis use, as were Asian/Pacific Islander and Hispanic respon- dents. McFadden pseudo-R 2 was very low (0.039), indicating that the covariates in the model accounted for very little variance in reported cannabis use. Of the 7538 block groups in the sample, 371 (4.9%) contained at least one of the 505 cannabis dispensaries. Table 3 shows the descriptive statistics for the study block groups. Mean demand per block group was 5628 person-days (SD 5492), with mean per capita use of 3.2 days (SD = 1.3). Table 4 shows the four multilevel Bayesian conditional autore- gressive logit models, including the median estimated effect from the sampled posterior distribution for each variable and a 95% credible interval. The 95% credible interval is the 2.5th and 97.5th percentile of the estimated effect for each variable, and can be inter- preted in a similar manner to a 95% confidence interval from a regular logit model (Mair, Gruenewald, Ponicki, & Remer, 2013). Model 1 (the basic economic geographic model) shows that the positive association between cannabis demand and increased odds Table 2 Censored regression model for self-reported days of cannabis use in the last year (n = 5940). Variable B-Coefficient (95%CI) p-Value Male 69.99 42.77 97.21 <0.001 Ethnicity African American 10.18 −65.60 85.97 0.792 White 73.59 18.39 128.80 0.009 Hispanic −88.71 −146.65 −30.77 0.003 Asian/Pacific Islander −121.74 −208.55 −34.93 0.006 Age Age 20–29 years 82.10 34.96 129.23 0.001 Age 30–39 years −11.60 −55.63 32.43 0.606 Age 40–49 years 15.58 −22.69 53.85 0.425 Age ≥50 years −160.36 −199.86 −120.86 <0.001 Highest educational achievement High school/GED 83.55 26.53 140.57 0.004 Undergraduate 72.64 10.91 134.37 0.021 Postgraduate/medical school 42.53 −23.23 108.30 0.205 Employment status Full time employed −31.82 −63.63 0.00 0.050 Unemployed 36.10 −9.28 81.48 0.119 Household income per year $20,000–60,000 −18.14 −56.65 20.37 0.356 $60,000–100,000 −27.35 −72.00 17.30 0.230 >$100,000 −29.47 −77.10 18.16 0.225 Constant −435.95 −526.26 −345.65 <0.001 Sigma 242.67 of having a dispensary is well supported. Model 2 demonstrates that block groups with higher populations were at increased odds of having a dispensary, as were those with higher estimated per capita cannabis use. Table 3 Descriptive statistics for block groups in study region (n = 7538). Variable Mean (SD) Population (×10 3 ) 1.72 (1.26) Area (miles 2 ) 0.65 (2.50) Population density (×1000/mile 2 ) 9.53 (9.98) Cannabis demand a Block group (×10 3 person-days) 0.56 (0.55) Per capita (days) 3.20 (1.27) Lagged block group (×10 3 person-days) 0.58 (0.35) City level (×10 6 person-days) 1.53 (0.78) Alcohol outlet density (per mile 2 ) 13.62 (25.56) Portion of alcohol outlets that are bars/pubs (%) 6.42 (12.44) Portion of alcohol outlets that are off premise (%) 58.15 (26.80) Male (%) 49.32 (4.61) Ethnicity African American (%) 7.83 (13.11) White (%) 76.05 (19.31) Hispanic (%) 38.12 (28.08) Asian/Pacific Islander (%) 12.01 (14.34) Age Age 20–29 years (%) 14.20 (3.28) Age 30–39 years (%) 13.41 (3.45) Age 40–49 years (%) 14.29 (2.77) Age ≥50 years (%) 58.04 (22.61) Employment status Full time employed (%) 44.13 (12.91) Unemployed (%) 5.11 (5.12) Highest educational achievement High school/GED (%) 42.45 (13.42) Undergraduate (%) 21.63 (13.47) Postgraduate/medical school (%) 8.00 (8.93) Household income per year <$20,000 (%) 20.14 (15.29) $20,000–60,000 (%) 41.33 (13.86) $60,000–100,000 (%) 21.41 (11.45) >$100,000 (%) 14.69 (15.09) Living under 150% poverty line (×10%) 2.40 (1.89) Median household income (×$10,000/year) 5.09 (2.50) a Cannabis demand estimates are calculated using the B-coefficients from Table 2 and the demographic profile of Census block groups.

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