2005), so controlling for college attendance allowed us to examine whether our observed effects were driven by college attendance. Third, to address concerns that gene-by-environment effects may be confounded by the effects of gene-by-covariate and covariate-by-environment interactions (Keller, 2014), we fit a model including these interaction terms. Finally, to control for potential differences between the clinically ascertained and unascertained comparison families, we fit a variation of the original model including family ascertainment status as a time-invariant covariate.
