Maryland Alcohol Sales Tax and Sexually Transmitted Infections: A Natural Experiment.

Introduction: Sexually transmitted infections are common causes of morbidity and mortality, including infertility and certain types of cancer. Alcohol tax increases may decrease sexually transmitted infection rates overall and differentially across population subgroups by decreasing alcohol consumption in general and prior to sex, thus decreasing sexual risk taking and sexually transmitted infection acquisition. This study investigated the effects of a Maryland increase in alcohol beverage sales tax on statewide gonorrhea and chlamydia rates overall and within age, gender, and race/ethnicity subpopulations.

Methods: This study used an interrupted time series design, including multiple cross-state comparisons, to examine the effects of the 2011 alcohol tax increase in Maryland on chlamydia and gonorrhea cases reported to the U.S. National Notifiable Disease Surveillance System for January 2003 to December 2012 (N=120 repeated monthly observations, analyzed in 2015). Effects were assessed with Box-Jenkins autoregressive moving average models with structural parameters.

Results: After the alcohol-specific sales tax increase, gonorrhea rates decreased 24% (95% CI=11%, 37%), resulting in 1,600 fewer statewide gonorrhea cases annually. Cohen's d indicated a substantial effect of the tax increase on gonorrhea rates (range across control group models, -1.25 to -1.42). The study did not find evidence of an effect on chlamydia or differential effects across age, race/ethnicity, or gender subgroups.

Conclusions: Results strengthen the evidence from prior studies of alcohol taxes influencing gonorrhea rates and extend health prevention effects from alcohol excise to sales taxes. Alcohol tax increases may be an efficient strategy for reducing sexually transmitted infections.