Hypothesis 1: There is a relationship between cigarette smoking and depression among teens. Null hypothesis 0: There is no relationship between cigarette smoking and depression among teens.
Variables: The researchers used the following variables:
Tobacco Use—a category, one of: “never smoked,” “experimenters,” or “current smokers”; current smokers were further characterized by how much they smoked (i.e., <1 pack/week; 1 pack/week to 1 pack/day; at least 1 pack/day).
Depression—a measure of depression as determined by a specific measuring instrument, the CES-D (discussed below).
Demographics—including age, gender, self-identified racial/ethnic identities (one of: non-Hispanic white, non-Hispanic black, Hispanic, Asian/Pacific islander, other).
Socioeconomic Status—household income and highest parental education (as defined by interview with parents); income responses were categorized into 5 ordered levels based on tables from the U.S. Census Bureau, while education levels were categorizes as less than high school degree; high school degree-GED-vocational training other than high school; vocational training after high school or some college; college graduate; professional training beyond college.
Covariate data—these were data from the teens including self-reported health; GPA; self-esteem; trouble relaxing; delinquency; alcohol or other drug use; and peer smoking. Additional self-reported data from the parents included parental alcohol problems; understanding of the teen; assessment of how teen’s life was going; satisfaction in relationship with teen; assessment of teen’s bad temper.
Standardized Instrument: The key standard instrument used was the 20-item CES-D (Center for Epidemiologic Studies Depression), developed by the National Institute of Mental Health.
What the instrument measures The CES-D measures depression symptoms in the participants; it does not generate clinical diagnoses, but a high score indicates significant psychological distress (Prinstein, Boerger & Spirito, 2001)
How the instrument is administered The instrument is a self-administered questionnaire of 20 statements to which the patient replies with a numbered response of 1: rarely or none of the time; 2: some or a little of the time; 3: occasionally or a moderate amount of the time; or 4: most or all of the time.
Scoring the instrument The 20-item CES-D scores each item in the survey with a 0, 1, 2, or 3 points based on participant responses. For most items, the scores are: 0 for “rarely or never <1 day”; 1 for “some or a little 1-2 days”; 2 for “occasionally or moderate amount of time (3-4 days)”; and 3 for “more or all the time 5-7 days.” A few specific items are scored in reverse (i.e., 0 for “more or all the time” and so on.) The total points assigned are added up; all or all but one item must be completed for a valid score. Scores ≥16 suggest significant psychological distress, but is not indicative of a diagnosis of clinical depression (Huba et al., 1995).
Reliability of instrument for this hypothesis: The CES-D has been shown to have high internal consistency, test-stability and general validity (Radloff, 1977). Its usefulness with teens has also been demonstrated with a high internal consistency (>0.87) and good test-retest agreement after 30 days (Prinstein, Boerger & Spirito, 2001).