Table 1.
Standardized and unstandardized estimates of past-year drinking frequency as predicted by age at drinking onset and conduct disorder for the full sample and the monozygotic (MZ) twin samples
| Total sample |
MZ twins |
|||||
| Variable | Model 1 | Model 2 | Model 3 | Model 1 | Model 2 | Model 3 |
| Zygosity | 1.03 (0.04) | 0.67 (0.02) | 0.73 (0.02) | – | – | – |
| Gender | 17.94** (0.61) | 17.64** (0.60) | 18.56** (0.61) | 12.02** (0.55) | 11.85** (0.54) | 12.29** (0.56) |
| Age | 7.92** (0.05) | 8.09** (0.06) | 8.04** (0.06) | 5.49* (0.05) | 5.41** (0.05) | 5.33** (0.05) |
| Within-twin drinking onseta | -4.68** (-0.06) | -6.59** (-0.08) | -6.24** (-0.08) | -3.44** (-0.06) | -4.13** (-0.07) | -4.14** (-0.07) |
| Between-twin drinking onsetb | -14.89** (-0.12) | 18.30** (-0.15) | -18.56** (-0.15) | -11.66** (-0.12) | -14.21** (-0.15) | -.14.62** (-0.15) |
| Within Drinking Onset × Between Drinking Onset | -3.67* (-0.01) | -3.67* (-0.01) | -1.22 (-0.01) | -1.21 (-0.01) | ||
| Between Drinking Onset × Between Drinking Onset | -6.51** (-0.01) | -6.45** (-0.01) | -4.92* (-0.01) | -4.87* (-0.01) | ||
| Within-twin conduct disordera | 2.13 (0.12) | -0.06 (-0.005) | ||||
| Between-twin conduct disorderb | -1.19 (-0.04) | -1.53 (-0.08) | ||||
Notes: Unstandardized estimates in parentheses.
a
Level 1 (unique environment effect) variable;
b
Level 2 (familial context effect) variable.
*
p < .05;
**
p < .01.