such that SELF1 has a causal effect on PEER1 (via B15), and vice versa (via B51). Model 2, a correlated factors model, postulates that the within- and cross-time correlations between SELF and PEER result from two correlated latent factors, the first of which loads directly onto SELF1-SELF4 and the second of which loads onto PEER1-PEER4. Time-specific factors also load onto each phenotype, but no forward transmission pathways are included in this model. Model 3 is a hybrid between Models 1 and 2, and has three key components: i) two uncorrelated latent factors, with the first loading on SELF1-SELF4 and the second loading onto PEER1-PEER4; ii) forward transmission within phenotype; and iii) bidirectional causal paths within time across phenotypes. Time-specific factors also load onto each phenotype. More detailed information is provided in the Supplementary Material.
