Table 1.
Model Fitting Procedure.
| Shared Liability Model | ||||||
| # | Model Description | Comparison | Δdf | Δχ2 | p-value | ΔAIC |
| 1 | Full model | n/a | (6109) | (−2LL=9012.77) | n/a | (−3205.23) |
| 2 | Set shared environmental influences to 0 | 2 vs. 1 | 5 | 0.12 | 1.00 | −9.88 |
| 3 | Drop genetic correlation between MD and INIT (a21) | 3 vs. 2 | 1 | 5.00 | 0.03 | 3.00 |
| 4 | Drop environmental correlation between MD and INIT (e21) | 4 vs. 2 | 1 | 0.17 | 0.68 | −1.83 |
| 5 | Drop direct genetic correlation between MD and FTND (a31) | 5 vs. 4 | 1 | 8.29 | <.01 | 6.29 |
| 61 | Drop direct environmental correlation between MD and FTND (e31) | 6 vs. 4 | 1 | 1.48 | 0.23 | −0.53 |
| Reciprocal Causation Model | ||||||
| # | Model Description | Comparison | Δdf | Δχ2 | p-value | ΔAIC |
| 1 | Full model | n/a | (6110) | (−2LL=9010.91) | n/a | (−3209.09) |
| 2 | Set shared environmental influences to 0 | 2 vs. 1 | 4 | 2.08 | 0.72 | −5.92 |
| 3 | Drop genetic correlation between MD and INIT (a21) | 3 vs. 2 | 1 | 0.48 | 0.49 | −1.52 |
| 4 | Drop environmental correlation between MD and INIT (e21) | 4 vs. 3 | 1 | 0.60 | 0.44 | −1.40 |
| 52 | Test causal path from MD to FTND (b31) | 5 vs. 4 | 1 | 1.10 | 0.29 | −0.90 |
| 6 | Test causal path from FTND to MD (b13) | 6 vs. 5 | 1 | 34.92 | <0.01 | 32.92 |
| 7 | Test causal path from FTND to MD (b13) with b31 intact | 7 vs. 4 | 1 | 10.80 | <0.01 | 8.80 |
Final models are in italicized text.
1
Fit statistics for final shared liability model: −2LL=9014.54; degrees of freedom=6116; AIC=−3217.46.
2
Fit statistics for final causal model: −2LL=9015.17; degrees of freedom=6117; AIC=−3218.83.