Context: Several studies have found a relationship between abortion and prior substance use, suggesting that a reduction in substance use might help decrease abortion rates. However, such a conclusion requires a greater understanding of the processes linking abortion and prior substance use.
Method: Path analysis of longitudinal data from 1,224 women was used to simultaneously test two pathways from adolescent substance use to abortion by age 29, one mediated by higher rates of unplanned pregnancy and the other independent of unplanned pregnancy rates. The model was then expanded to examine how these pathways change when unconventional attitudes and behaviors (such as rebelliousness and low religiosity) are taken into consideration.
Results: In the analysis that did not control for unconventionality, women who reported smoking cigarettes or using marijuana or hard drugs at age 18 had an increased likelihood of subsequent unplanned pregnancy and, as a result, higher rates of abortion. In addition, women who had used marijuana had an increased likelihood of abortion independent of unplanned pregnancy rates. In the final model, unconventionality strongly predicted both abortion and unplanned pregnancy. Moreover, it explained the associations between the use of hard drugs or marijuana and abortion that were due to higher unplanned pregnancy rates.
Conclusions: Unconventionality mediates certain associations between substance use and abortion, perhaps because unconventional women are more likely both to use substances and to engage in behaviors that increase their risk of unplanned pregnancy. Hence, it seems unlikely that reducing substance use will result in substantially fewer abortions.