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

All variables are statistically significant (p<0.05 or less) from one another, based on Pearson χ² tests of categorical variables (df = 3, χ² values larger than critical value 7.81) and ANOVA (F(3, 26,311) =  3,057, (p<0.001)) with Tukey-Kramer post-hoc tests for multiple pairwise comparisons for the age variable.

SD = 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.