did not converge, a repeated measures analysis of covariance was conducted that treated cohorts themselves as individual subjects, using cohort means as scores (termed an aggregate analysis; Hedeker, Gibbons, & Flay, 1994, p. 758). Effects found using an aggregate analysis were dismantled using contrasts based on two-level MMRM analyses. A different analytic approach was used for substance use, as described later.
