Table 5.
Parameter Estimates and Observed Correlations (95% Confidence Interval) from Full and Final Best-Fit Twin Models for Bulimic Symptoms and Alcohol Involvement in Girls and Boys
| Alcohol Involvement | Bulimic Symptoms | Correlations | |||||||
|---|---|---|---|---|---|---|---|---|---|
| a2 | c2 | e2 | a2 | c2 | e2 | ra | rc | re | |
| Girls | |||||||||
| Alcohol Use in Last Month | |||||||||
| ACE | 45 (12; 80) |
30 (0; 58) |
26 (18; 36) |
30 (0; 63) |
16 (0; 52) |
54 (36; 76) |
.27 (−1; 1) |
.70 (−1; 1) |
.12 (−.17; .40) |
| AE |
76 (70; 83) |
– |
24 (17; 33) |
47 (27; 65) |
– |
53 (35; 73) |
.42 (.20;.65) |
– |
.10 (−.17; .38) |
| Ever Intoxicated | |||||||||
| ACE | 50 (23; 83) |
46 (14; 71) |
4 (1; 11) |
37 (27; 65) |
11 (0; 50) |
52 (34; 72) |
.80 (−.06; 1) |
−.40 (−1; 1) |
.14 (−.54; .77) |
| ACE-no unique common environment on BU |
51 (23; 84) |
45 (13; 70) |
4 (1; 11) |
46 (20; 66) |
3 (0; 25) |
51 (34; 71) |
.76 (−.04; 1) |
−1.00a (−1; −1) |
.13 (−.54; .42) |
| Intoxication Frequency | |||||||||
| ACE | 47 (20; 80) |
35 (4; 61) |
18 (12; 27) |
32 (10; 63) |
14 (0; 46) |
54 (36; 70) |
.98 (.11; 1) |
−.53 (−1; 1) |
−.14 (−.42; .20) |
| AE |
84 (76; 90) |
– |
16 (11; 24) |
49 (29; 65) |
– |
51 (35; 71) |
.38 (.20;.60) |
– | −.10 (−.40; .23) |
| Boys | |||||||||
| Alcohol Use in Last Month | |||||||||
| ACE | 52 (21; 85) |
30 (0; 57) |
18 (12; 28) |
41 (0; 65) |
5 (0; 50) |
54 (35; 77) |
.58 (−1; 1) |
−.59 (−1; 1) |
−.01 (−.31; .30) |
| AE |
83 (75; 89) |
– |
17 (11; 26) |
47 (25; 65) |
– |
53 (35; 75) |
.31 (.10;.53) |
– |
.02 (−.28; .32) |
| Ever Intoxicated | |||||||||
| ACE |
37 (0; 38) |
50 (11; 80) |
13 (5; 29) |
42 (0; 64) |
3 (0; 50) |
55 (36; 80) |
.20 (−1; 1) |
.86 (−1; 1) |
.44 (−.10; 80) |
| CE | – |
76 (.63; .85) |
24 (15; 37) |
– |
36 (17; 52) |
64 (48; 83) |
– |
.28 (.01;.55) |
.37 (.07; .63) |
| Intoxication Frequency | |||||||||
| ACE | 30 (12; 61) |
57 (27; 80) |
13 (11; 18) |
40 (0; 63) |
5 (0; 50) |
56 (37; 80) |
−.15 (−1; 1) |
.82 (−1; 1) |
.42 (.04; .70) |
| ACE-no unique common environment on BU |
30 (5; 61) |
57 (30; 78) |
13 (8; 20) |
41 (10; 63) |
3 (0; 30) |
56 (37; 79) |
−.15 (−1; .85) |
1.00a (1; 1) |
.42 (.04; .61) |
Note. Final best-fitting model shown in bold. a2 = heritability. c2 = common environmental parameter estimate. e2 = individual-specific environment parameter estimate. ra = genetic correlation. rc = common environmental correlation. re = individual-specific environmental correlation. BU = bulimic symptoms.
a
= the confidence interval for the correlation in this bivariate association in the best-fit model is observed at +/−1.00; +/−1.00 because there are no environmental effects specific to bulimic symptoms that are not shared with alcohol involvement.