To determine whether between-group differences in drug exposure may have contributed to the lack of association found with ATR controls, we compared ATR controls to neighborhood controls not dependent on illicit drugs. We found significantly greater lifetime use for all examined illicit drug categories in non-dependent neighborhood controls; differences were most pronounced for cocaine and stimulants (see Table 3). Extending the comparison of non-dependent neighborhood controls vs. ATR controls to use more than 11 times lifetime (not shown in Table 3), a similar pattern of between-group differences was observed: stimulants, 18.2% vs. 1.4%, respectively (OR=15.64; 95%CI, 9.38–26.08); any non-cannabis illicit drug, 19.7% vs. 3.0%, respectively (OR=7.90; 95%CI, 5.30–11.78); and any illicit drug, 45.3% vs. 15.7%, respectively (OR=4.46; 95%CI, 3.45–5.76). In an assessment not used for ATR controls, 35.5% of non-dependent neighborhood controls reported having seen someone use heroin and 28.4% reported have been offered heroin. These results provide strong evidence that the neighborhood controls not dependent on illicit drugs had substantially greater levels of lifetime drug use than the ATR controls. In addition, a surprisingly large proportion of these individuals had ready access to heroin.
