Abstract
Background: National studies often examine associations between sexual identity and substance use at a single point in time and neglect to examine whether these associations change over time. The present study examines U.S. trends in the past-year prevalence of binge drinking, marijuana use, illicit drug use, and polysubstance use across sexual identity subgroups (gay, lesbian, bisexual and heterosexual). Methods: The data come from four independent, cross-sectional samples measured by the National Survey of Family Growth (2006-2010, 2011-2013, 2013-2015, and 2015-2017). Based on the consistency in the sampling procedures used over time, merging the four data sets was possible. The target population is men and women 15-44 years of age. Results: Lesbian women had the sharpest decline in past-year binge drinking over time, followed by heterosexual women. The prevalence of binge drinking for bisexual women did not change significantly over time and was higher in 2015-2017 than for any sexual identity subgroup. In contrast, there were no significant differences in the prevalence of binge drinking among men by sexual identity subgroup. Past-year abstinence from substance use was consistently lower among lesbian women, gay men, and bisexual women relative to other sexual identity subgroups. Polysubstance use was consistently more prevalent among bisexual women (e.g., 32.3% in 2015-2017) as compared to other sexual identity subgroups. Conclusion: This is the first study to examine U.S. national trends in alcohol, marijuana, illicit drug, and polysubstance use across sexual identity subgroups, and demonstrates that sexual identity subgroup differences were robust with relatively few changes in trends over time. The consistently high rates of binge drinking and polysubstance use among bisexual women deserve much closer attention based on the related health consequences.