Fourth, the observed cross-lagged associations were often modest and did not fully explain the corresponding cross-sectional correlations. This implies that in addition to earlier substance use and educational achievement, other, unobserved, factors contributed to their association. This is not an unexpected finding, especially because the study waves in FT12 were at least two years apart. However, the cross-lagged effects between smoking and educational achievement we report are of similar magnitude as those reported in an earlier Finnish study with biannual assessments in adolescence (Pennanen et al., 2011).
