Table 3.
Within-pair associations (Odds Ratios [OR] with 95% confidence intervals [CI]) of standardized mean values of Smoking Dependence (FTCD) and dimensions from the Brief Wisconsin Inventory Dependence Motives (WISDM) with depression (CES-D ≥20) a among twin pairs discordant for depression, where both co-twins are current daily cigarette smokers with no missing values in any factors of interest or covariates in the Finnish Twin Cohort. Associations are presented by zygosity and for all pairs of known zygosity.
| Within pair analyses | np | FTCD OR (95% CI) b |
WISDM Dimensions | ||
|---|---|---|---|---|---|
| PDM OR (95% CI) b |
AE OR (95% CI) b |
Taste OR (95% CI) b |
|||
| BASIC MODEL c | |||||
| DZ and MZ pairs together | 38 | 1.77 (1.02, 3.08) | 2.30 (1.16, 4.50) | 1.77 (1.08, 2.89) | 1.35 (0.89, 2.06) |
| DZ pairs | 20 | 1.52 (0.82, 2.81) | 1.62 (0.83, 3.16) | 1.47 (0.85, 2.51) | 1.24 (0.75, 2.06) |
| MZ pairs | 18 | 2.55 (0.87, 7.49) | 30.3 (0.88, 1045) | 3.15 (0.96, 10.3) | 1.61 (0.75, 3.44) |
| LR test for MZ/DZ difference (p-value) | p=0.396 | p=0.023 | p=0.208 | p=0.573 | |
| MODEL 1 d | |||||
| DZ and MZ pairs together | 38 | 2.03 (0.91, 4.55) | 2.87 (1.13, 7.32) | 1.81 (0.99, 3.31) | 1.24 (0.78, 1.97) |
| DZ pairs | 20 | 1.45 (0.55, 3.85) | 1.54 (0.59, 3.98) | 1.35 (0.68, 2.69) | 1.09 (0.61, 1.95) |
| MZ pairs | 18 | 3.62 (0.86, 15.3) | 55.6 (1.21, 2552) | 3.55 (0.95, 13.2) | 1.54 (0.69, 3.46) |
| LR test for MZ/DZ difference (p-value) | p=0.448 | p=0.029 | p=0.207 | p=0.489 | |
| MODEL 2 e | |||||
| DZ and MZ pairs together | 38 | 1.14 (0.59, 2.23) | 1.51 (0.70, 3.24) | 1.35 (0.79, 2.31) | 1.16 (0.68, 2.00) |
| DZ pairs | 20 | 1.19 (0.56, 2.54) | 1.21 (0.56, 2.62) | 1.28 (0.70, 2.32) | 1.00 (0.49, 2.03) |
| MZ pairs | 18 | 0.99 (0.21, 4.57) | 23.2 (0.48, 1119) | 1.83 (0.46, 7.25) | 1.43 (0.62, 3.39) |
| LR test for MZ/DZ difference (p-value) | p=0.828 | p=0.094 | p=0.723 | p=0.526 | |
Fagerström Test for Cigarette Dependence (FTCD); Brief Wisconsin Inventory of Smoking Dependence Motives (WISDM); Primary Dependence Motives (PDM), Affective Enhancement (AE); Taste (T); OR=Odds Ratio; CI=Confidence Interval; DZ=Dizygotic; MZ=Monozygotic; np=Number of Twin Pairs Discordant for Depression; LR test=Likelihood-ratio test for difference between MZ and DZ pairs.
Depression defined by the Center for Epidemiologic Studies Depression (CES-D) scale with a cut-off value of 20 (Depression CES-D ≥20).
Conditional logistics regression odds ratios with 95% confidence intervals. Statistically significant associations (p<0.05) are in bold.
Basic model: Age and sex are automatically adjusted in the model (data includes only same-sexed twin pairs).
Model 1: Adjusted with age, sex and number of cigarettes smoked per day.
Model 2: Adjusted with age, sex and neuroticism.