Gritz 2003.

Methods	Cohort study Baseline Survey: Date unknown (prior to 1998) Follow‐up: 12 months Site: Houston‐Galveston, Texax, USA Research Question: Relationships of baseline predictor variables with two outcome variables, measured 1 year later: a) susceptibility to smoking, and b) onset of smoking. Focus was on ethnic specific predictors (White, African American, and Hispanic) Analysis: Logistic Regression. Stepwise regression was used to identify variables that predicted the outcome due to the large number of predictor variables.
Participants	659 students from 6 school districts in grades 5, 8 and 12 who were identified as never smokers at baseline and either were susceptible to smoking or had ever smoked at follow up. Of baseline sample (n=1,441), 82.1% were retained at follow‐up (n=1,004). Survey method: self‐report questionnaire (and saliva collection tube) distributed at school in a group setting.
Interventions	Exposure to pro‐tobacco and anti‐tobacco messages measured using one item, "Please mark all the following types of messages about smoking that you have seen or heard in the last month". Response categories included 5 major media sources: (1) television ads/show, (2) radio ads/programs, (3) billboards (road signs), (4) posters, and (5) newspaper/magazine ads. Students asked if they saw or heard messages "for smoking" or "against smoking" for each type. For each students, pro‐tobacco and anti‐tobacco scores were created by summing the number of sources marked.
Outcomes	At baseline, students categorized as Never Smokers if they had never tried a puff of a cigarette. At follow‐up, students who smoked at least one or more puffs in their lifetime were categorized into: Experimenters (tried one or more puffs but not the whole cigarette, smoked 1‐10 cigarettes in their lifetime, or smoked fewer than 12 times in the past 12 months); Current Smokers (smoked at least once a month); and Former Smokers (used to smoke but quit in the past 12 months or used to smoke but quit more than 12 months ago).
Notes