TABLE 4

Relative Risk Ratio for Misuse of Prescription Opioids in Follow-ups 1 to 3 for Respondents With Versus Without Legitimate Prescription Opioid Use by 12th Grade, by Risk Strata (95% Confidence Intervals in Parentheses)

Strata No.12345678
Predicted probability of opioid misuse after high school0%–<1.75%1.75%–<3%3%–<5%5%–<10%10%–<20%20%–<30%30%–<45%≥45%
Legitimate prescription opioid use by 12th grade0.97 (0.22–4.29)3.01** (1.79 –5.07)1.95* (1.15–3.34)1.24 (0.81–1.91)0.98 (0.66–1.44)1.06 (0.64–1.73)0.56 (0.31–1.01)0.86 (0.49–1.63)
  • The risk ratios in stratums 2 and 3 are significantly higher than those in the other stratums combined, as tested with multiplicative interaction terms. Test models included (a) all the predictors in model 2 of Table 2, (b) an indicator variable for risk stratum, and (c) a multiplicative interaction term of the risk stratum indicator and legitimate opioid prescription by 12th grade. In separate models, interactions were statistically significant (P < .05) when including an indicator for risk stratum 2, risk stratum 3, and an indicator for risk strata 2 and 3 combined. *P < .05; **P < .01.