Research on risk and protective factors often use an ecological model, which recognizes that each person functions within a complex network of individual, family, school, and community contexts that affect their capacity to avoid risk and maintain health [12]. In both reviews, more research focused on identi- fying individual factors (997 factors in the first review and 444 factors in the second one) than all other ecological levels combined. At the individual level, factors studies included: demographics; biological factors; substance use; schooling/ education; sexual and reproductive health knowledge, attitudes, and beliefs; previous sexual risk behaviors, and other risk behaviors. Other domains studied included: peer and partner level (135 factors in the first review and 73 in the second one); family level (306 factors in the first review and 138 in the second one); school level (22 factors in the first review and 21 in the second one), and community level (19 factors in the first review and 32 in the second one). In the second, more recent review, there was a slightly higher proportion of factors studied within the school and community levels compared with the first review (Figure 3).