S. Bureau of Labor Statistics (2010; Children and Youth of the National Longitudinal Survey of Youth 1979 Cohort, http://www.bls.gov/nls/nlsy79ch.htm). The NLSY79-CYA employs a biennial, cohort-sequential design in which all children born to NLSY79 women by 1986 have been followed, as well as all subsequent children born after 1986. The NLSY79-CYA thus includes multiple selleck compound birth cohorts and multiple children-per-mother��children represent the unit of analysis, and one mother may appear in the dataset more than one time. We select respondents aged 14�C25 years observed at any of the biennial surveys between 1994 and 2006 (i.e., birth cohorts 1970�C1992). The NLSY79-CYA yearly completion rates range from 83.0% to 88.4% (Center for Human Resource Research, 2009).

By 2006, 6,643 youth aged 14 years and older were eligible for the NLSY79-CYA and had been located for at least one interview between 1994 and 2006. From this sample, 6,349 youth responded to questions about cigarette smoking at least once. The youth smoking trajectory was assessed by asking respondents if they had smoked cigarettes in the past 30 days (SPTD) at each biennial survey wave. A latent class analysis approach (described fully in Weden & Miles, 2011) was then employed to categorize each individual into one of four trajectory classes: early start, early experiment, late start, and nonsmokers. Early start (12.6% of the sample) begins to smoke at a relatively young age and continues into young adulthood. Their rates of SPTD increase rapidly from 30% to 90% between age 14 and 16 and remain high at each subsequent age through young adulthood (87% at age 25).

Early experiment smokers (2.6% of the sample) are likely to have smoked in the past 30 days at younger ages, but then the rates of SPTD drop back to 30% by age 21 and remain at an average of 35% through age 25, suggesting early initiation but then quitting during early adulthood. Late start smokers (19.1% of the sample) report almost no SPTD prior to age 16, but then have dramatically increasing rates (climbing from essentially zero to 69% over age 16�C19), with continued increases to age 25, when 90% report SPTD. Nonsmokers (67% of the sample) report no, or very low, SPTD at every age. The mean rate of SPTD over age 14�C25 was 2% across all years. To describe maternal smoking patterns before, during, and after the pregnancy and birth of the respondent, we used several measures from the NLSY. Mother ever smoked daily is a dichotomous indicator for any maternal report of ��daily�� smoking in the NLSY79 substance use history Drug_discovery supplements taken in 1992, 1994, and 1998.