Socio-demographic and substance abuse covariates (%) of the four latent prescription opioid use classes (N = 26,314).

All variables are statistically significant (p2 tests of categorical variables (df = 3, χ2 values larger than critical value 7.81) and ANOVA (F(3, 26,311) = 3,057, (pSD = standard deviation.*For duration of use, illicit drugs include cocaine, amphetamines, hallucinogens, and inhalants; heroin is presented separately. Therapeutics include benzodiazepines, antidepressants, and methadone and exclude all other prescription opioids.