Although the meta-analysis yields an overall estimate of relative change, the random intercepts result in separate prevalence estimates for each survey (which are expected to differ as evident from Figure 1). To visually compare magnitudes of absolute change and rank-order prevalence over time, we used the meta-analysis trend estimates in conjunction with prevalence for each outcome and each demographic group from the 2002 NSDUH to calculate overall and demographic-specific trend lines. The NSDUH prevalence estimates and the survey year (2002) are simply reference points to establish the intercepts in the modeled trend lines and are somewhat arbitrary, though the choice to use NSDUH is partially justified by the results showing that NSDUH trends were closest to those from the meta-analysis. Simulated prevalence for each outcome was calculated as Piy=exp(ln(Pi,NSDUH02)+(Y-2002)*βi)), where Piy is the simulated prevalence for that group as a function of year, Pi,NSDUH02 is the NSDUH prevalence estimate for 2002 for group i, Y is year, and βi is the meta-analytic trend estimate for that group.
