Are We Losing the Most Relevant Cases First? Selective Dropout in Two Longitudinal Studies of Adolescent Pornography Use.

In longitudinal studies of pornography use, selective loss of participants who may be more vulnerable to the effects of pornography than their peers is a serious concern. To explore the potential for such selective dropout, we used data from two independent large-scale panel studies of adolescents' pornography use. Of the three types of attrition-early attrition, later attrition, and gaps in participation-only the first was substantially higher among more vulnerable adolescents, compared with other participants. Panel type (online vs. classroom-based) moderated only the association between vulnerability and participation gaps, which was significant in the classroom-based but not the online panel. Overall, this study's findings point to the importance of delaying selective dropout by developing a comprehensive plan of action, for which we offer some guidelines.