Table 4 Multivariate ORs jointly estimated for individual current smoking and excess concordance of smoking within twin pairs

From: Does smoking among friends explain apparent genetic effects on current smoking in adolescence and young adulthood?

 

Model 1

Model 2

Factor

OR

95% CI

P -value

OR

95% CI

P -value

Individual current smoking

 Monozygosity

0.77

0.63–0.94

0.01

0.77

0.62–0.94

0.01

 Parents smoke

1.86

1.63–2.11

<0.001

1.75

1.45–2.09

<0.001

 Wave 2

2.72

2.29–3.22

<0.001

1.20

0.99–1.46

0.06

 Wave 3

1.70

1.42–2.04

<0.001

1.61

1.29–2.02

<0.001

 Wave 4

1.93

1.64–2.27

<0.001

1.08

0.87–1.34

0.5

 Friends' smoking

NA

  

10.90

7.90–15.10

<0.001

Excess concordance of current smoking

 Monozygosity (wave 1)

1.99

1.26–3.15

0.003

2.60

1.47–4.60

0.001

 Monozygosity (wave 2)

1.83

1.22–2.76

0.004

1.12

0.78–1.60

0.5

 Monozygosity (wave 3)

1.68

1.07–2.66

0.03

1.13

0.79–1.62

0.5

 Monozygosity (wave 4)

1.30

0.86–1.98

0.2

1.18

0.66–1.68

0.5

Concordance of friends' smoking

NA

  

1.55

1.30–1.85

<0.001

  1. CI=confidence interval; OR=odds ratio; NA=not applicable.
  2. Excess concordance also adjusted for main effect of wave (no significant association).
  3. Estimates shown adjusted for all variables in model.
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