Table 2.

Dichotomous Nicotine Dependence Phenotypes Based on FTND: Association With SNP rs16969968 on Chromosome 15 (CHRNA5), SNP rs6474412 on Chromosome 8 (CHRNB3), and SNP rs3733829 on Chromosome 19 (EGLN2, near CYP2A6)

	Chromosome 15			Chromosome 8			Chromosome 19
	rs16969968			rs6474412			rs3733829
FTND dichotomous phenotypes	OR	95% CI	p value	OR	95% CI	p value	OR	95% CI	p value
FTND4	1.39	(1.22–1.58)	9.9 × 10−7	0.78	(0.67–0.91)	1.4 × 10−3	1.13	(0.99–1.28)	6.8 × 10−2
FTND items
Time to first cigarette of the day (TTF)a	1.37	(1.20–1.56)	3.2 × 10−6	0.78	(0.67–0.92)	2.1 × 10−3	1.12	(0.98–1.27)	9.0 × 10−2
Can’t refrain from smoking	1.23	(1.06–1.42)	6.3 × 10−3	0.73b	(0.61–0.88)	1.1 × 10−3	1.23c	(1.06–1.43)	5.3 × 10−3
Can’t give up first cigarette	1.27	(1.11–1.46)	5.6 × 10−4	0.89	(0.76–1.05)	1.8 × 10−1	1.05	(0.92–1.21)	4.5 × 10−1
Cigarettes per day (CPD)a	1.41b	(1.23–1.60)	4.6 × 10−7	0.78	(0.67–0.91)	1.5 × 10−3	1.11	(0.97–1.26)	1.3 × 10−1
Smoking more in first hours after waking than rest of the day	1.28	(1.10–1.49)	1.1 × 10−3	0.91	(0.76–1.10)	3.3 × 10−1	0.98	(0.84–1.14)	7.5 × 10−1
Smoking when ill	1.15	(1.00–1.33)	4.6 × 10−2	0.90	(0.76–1.06)	2.0 × 10−1	1.14	(0.99–1.31)	6.3 × 10−2

Note. All models were adjusted for age and gender. All dimensional phenotypes were Z-scored. FTND: Fagerström Test for Nicotine Dependence score. FTND4 is a dichotomous phenotype defined by FTND score of 4 or higher. TTF: time to the first cigarette of the day (0: >60 min, 1: 31—60 min, 2: 6–30 min, and 3: ≤5 min). CPD: Number of cigarette smoked per day (0: ≤10, 1: 11–20, 2: 21–30, and 3: >30). OR = odds ratio.

^aTTF and CPD as dichotomous phenotype with median split.

^bItem significant with p < .001 in stepwise regression models that remains significant after correction for multiple testing.

^cItem significant with p < .05 in stepwise regression models.