Table 2.
Standardized and unstandardized estimates of past-year drinking quantity 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 | 0.01 (0.0003) | -0.09 (-0.003) | -0.22 (-0.007) | – | – | – |
| Gender | 9.76** (0.33) | 9.67** (0.33) | 8.68** (0.30) | 6.79** (0.31) | 6.77** (0.31) | 6.04** (0.28) |
| Age | -3.28** (-0.02) | -3.23** (-0.02) | -3.20** (-0.02) | -2.49** (-0.02) | -2.50** (-0.02) | -2.37** (-0.02) |
| Within-twin drinking onseta | -1.11* (-0.01) | -1.53* (-0.02) | -0.06 (-0.001) | -0.23 (-0.004) | -0.41 (-0.01) | -0.16 (-0.003) |
| Between-twin drinking onsetb | -3.00** (-0.02) | -4.02** (-0.03) | -3.25** (-0.03) | -2.20** (-0.02) | -2.64** (-0.03) | -1.95* (-0.02) |
| Within Drinking Onset × Between Drinking Onset | -0.77 (-0.002) | -0.89 (-0.002) | -0.41 (-0.002) | -0.54 (-0.003) | ||
| Between Drinking Onset × Between Drinking Onset | -1.98* (-0.003) | -2.06* (-0.003) | -0.84 (-0.002) | -0.91 (-0.002) | ||
| Within-twin drinking onset × Gender | -1.80** (-0.03) | -0.93 (-0.02) | ||||
| Within-twin conduct disordera | 1.48** (0.09) | 0.37 (0.03) | ||||
| Between-twin conduct disorderb | 3.03** (0.11) | 2.53** (0.12) | ||||
Notes: Unstandardized estimates are in parentheses.
a
Level 1 (unique environment effect) variable;
b
Level 2 (familial context effect) variable.
*
p < .05;
**
p < .01.