RESUMEN
This randomized experiment tested whether the inclusion of a "something else" response option for a question about sexual identity in a national health survey would significantly moderate estimated differences between sexual identity subgroups in terms of various health outcomes, including substance use and reproductive health. We conducted secondary analyses of data from five consecutive years of the National Survey of Family Growth (NSFG; 2015-2019), where two large national half-samples were randomly assigned to receive one of two different versions of a question about sexual identity (a four-category version that included a "something else" response option or a three-category version omitting this option). We focused on national estimates of differences between subgroups defined by sexual identity. Multivariable models indicated that the estimated subgroup differences changed in a statistically significant fashion when using the four-category version of the sexual identity question for several measures, including 16% of male measures (household size, past-year cigarette use, and past-year illicit drug use) and 15% of female measures (wanting a/another child, ever had a sexually transmitted disease, and past-year marijuana use). The absence of a "something else" response option for questions about sexual identity in national health surveys may cause respondents to select options that do not accurately describe their identities, and this can have a significant effect on national estimates of differences between sexual identity subgroups in terms of selected health outcomes.