Table 1.

Descriptive Statistics for Lifetime Smoking Involvement and DSM-IV Nicotine Dependence Symptoms by Age 17 in Three Combined Cohorts by Gender

	Combined Cohorts (N=345–647)^a		All Males (N=166–747)		All Females (N=181–900)		Male Versus Female Comparison		Gender Effect Size^c

Measure of Nicotine Involvement (% and N)	%	N	%	N	%	N	χ²	p	OR	95% CI

Ever used tobacco	59.9	2185	67.4	1178	53.0	1007	78.91	<0.001	1.83	1.60, 2.10
Ever smoked daily^b	25.4	883	28.6	475	22.5	408	17.29	<0.001	1.38	1.18, 1.61
Ever used ≥10 cigarettes/chews per day	14.4	498	17.5	289	11.6	209	24.85	<0.001	1.62	1.34,1.97

	Combined Cohorts (N=345–647)^a		AH Males (N=166–747)		AH Females (N=181–900)		Male Versus Female Comparison		Gender Effect Size^c

Measure of Nicotine Involvement (M and SD)	Mean	SD	Mean	SD	Mean	SD	t	p	d	95% CI

Age of smoking initiation	13.5	2.5	13.2	2.7	13.9	2.3	6.16	<0.001	0.27	018,035
DSM-IV Nicotine Dependence symptom count^d	.64	1.4	.73	1.4	.56	1.3	3.79	<0.001	0.13	006,020

N – 3457 (cigarettes per day), 3478 (daily smoking; dependence), 3629 (initiation age), and 3647 (ever used), or 92 – 97% of baseline sample.

Higher levels of smoking were combined into clinically meaningful categories above, though continuous or ordinal measures were used in regression analyses.

Effect sizes are expressed as odds ratios (OR) for categorical outcomes or Cohen’s d for quantitative outcomes. ORs significantly greater than 1 indicate a higher level of involvement for males than females (e.g., 1.38 = a 38% increase in the likelihood for males). For Cohen’s d, .2 corresponds to a small effect, with male gender associated with earlier initiation; males and females were reverse-coded for this comparison.

This raw nicotine dependence symptom count was log-transformed in regression analyses to mitigate positive skew.