Causal Effect of Adolescent Depression On Later Sexual Risk Behaviors and Sexually Transmitted Infections

Introduction: The association between depression and sexual risk behaviors and sexually transmitted infections (STIs) has been well-established in the literature.  While the temporal sequencing of the events provides evidence of which comes first, inferring causation remains difficult as other variables might explain the association.  Causal inference techniques such as inverse propensity score weighting provide researchers with an opportunity to take into consideration these other variables to provide a stronger causal inference of the effect.  We apply a modern causal inference approach to estimate the long-term causal effect of adolescent depression on young adult sexual risk behavior and STIs.

Methods: The causal effect was estimated using data from 9,981 adolescents (aged 11-18 at Wave II) from the National Longitudinal Survey of Adolescent Health.  Separately, lifetime number of sexual partners (0, 1-2, 3 or more) and ever having an STI (measured at Wave IV) was regressed on a dichotomous measure of depression (measured at Wave II); propensity scores were derived using generalized boosted regression with numerous potential confounders (measured at Wave I) and sexual behavior (measured at Wave II).  Inverse propensity score weights were then used in the final analysis to estimate the causal effect of depression on each outcome.

Results: Preliminary results indicate that depression during adolescence does not have a causal effect on lifetime number of sexual partners for either gender.  However, results do suggest that adolescent depression does have a causal effect on having an STI by adulthood (OR = 1.29; 95% CI = 1.00, 1.66, p =.05); this effect did not differ by gender.   

Conclusions: Based on the results from these analyses, there appears to be a modest causal effect of depression in adolescence on risk of STIs by adulthood; however, there is no causal effect on number of sexual partners.  These data suggest that there are long-lasting consequences of depression during adolescence.  Although the exact mechanism of the causal effect cannot be determined from the current analyses, the robustness of this association warrants continued programmatic efforts to prevent and or treat depression during adolescence which can have an impact on sexual health later in life.