Objectives: To examine the mechanisms of the association between age of sexual initiation and adult health.
Methods: Data from the Seattle Social Development Project (n = 808), in Seattle, Washington, included outcomes when participants were in their 30s (2005-2014): substance use disorders, depression, poor health, and obesity. Sexual consequence mediators included sexually transmitted infection, adolescent pregnancy, and a high number of sexual partners. We used linear logistic regression to model main effect and mediated associations.
Results: Age of sexual initiation was related to nicotine and marijuana disorders, physical health, and obesity, but not alcohol disorder or depression. Mediated association with nicotine disorder was not significant; association with marijuana disorder was reduced; significant relationships with poor health and obesity remained.
Conclusions: The relationship between age of sexual initiation and substance use was largely explained by consequences of sexual behavior. Earlier sexual initiation was linked to poorer physical health outcomes, though the nature of the association remains unclear. Public Health Implications. Prevention approaches need to address multiple risk factors and emphasize contraceptive methods to avoid sexual consequences. For physical health outcomes, broad prevention approaches, including addressing early sexual initiation, may be effective.