Covariates included sex, age, and race/ethnicity. Age was treated as a categorical variable with the following four groups: 18–25, 26–34, 35–49, and 50 years or older. Categories for race/ethnicity were defined by NSDUH as follows: White; Black; Hispanic; Native American or Alaskan Native; Asian (combined categories of Asian and Native Hawaiian/Other Pacific Islander); and multiracial.
