Specifically, the questions used were the lifetime frequency and quantity of tobacco use in childhood and early adolescence for T2 (1983, prior to T2), selleck chemical frequency and quantity of tobacco use during the past 2 years in adolescence for T3 (1985�C1986, T2�CT3), frequency and quantity of tobacco use during the past 5 years in the early 20s for T4 (1992, T3�CT4), frequency and quantity of tobacco use during the past 5 years in the late 20s for T5 (1997, T4�CT5), and frequency and quantity of tobacco use during the past 5 years in the late 20s and early 30s for T6 (2002, T5�CT6). The tobacco measure at each point in time had a scale coded as none (0), less than daily (1), 1�C5 cigarettes/day (2), about half a pack a day (3), about a pack a day (4), and about 1.5 packs a day or more (5).
The mean (SD) tobacco use scores at each point in time were 0.63 (1.12), 0.80 (1.29), 1.41 (1.63), 1.37 (1.61), and 1.25 (1.65), for T2�CT6, respectively. The tobacco measure has been found to predict young adult psychiatric disorders (D. W. Brook, Brook, Zhang, Cohen, & Whiteman, 2002) and health problems (J. S. Brook, Brook, Zhang, & Cohen, 2004). Obesity and overweight at T7 BMI is a measure of weight that also takes height into consideration. Height (in inches) and weight (in pounds) were assessed by self-report measures obtained at T7. BMI was calculated using weight in pounds and height in inches with the following equation (CDC, 2006): In the equation, 703 was a constant used to account for the conversion between metric and English measures.
For example, a person who weighs 220 pounds and is 6 feet 3 inches tall (75 inches) has a BMI of 27.5. The CDC classify adults more than 20 years of age into one of the following four categories: (a) underweight, BMI �� 18.5; (b) normal, 18.5 < BMI �� 24.9; (c) overweight, 24.9 < BMI �� 29.9; and (d) obese, BMI > 29.9. We calculated the participant��s BMI at T2. Due to the age span at T2 (9�C19 years) and weight and height differences between males and females, BMI was then adjusted by partialling out the effects of age and gender. That is, in regression analyses, T2 BMI was the dependent variable and age and gender were the independent variables. For each participant, the fitted T2 BMI score was subtracted from the observed T2 BMI score. This difference was labeled the age- and gender-adjusted BMI at T2, which was used as a covariate.
Other covariates At T6, the participant��s personality and behavioral attributes were assessed. The following were included as covariates: (a) healthy habits scale (six items; Cronbach��s �� = .72), which assessed habits such as eating (e.g., eating vegetables and fruits and avoiding fatty food), sleeping (e.g., getting at least Drug_discovery 7 hours of sleep per night), and physical exercise (e.g., jogging and swimming).