1) Difficulty Quitting smoking: more than one unsuccessful attempt to stop or cut down on smoking; 2) Smoking Persistence: any smoking within the last month; 3) Smoking Cessation Treatment: sought treatment in the form of nicotine replacement therapy, individual or group smoking cessation counseling, or some other form of treatment to quit smoking (not measured in the girls); 4) Nicotine withdrawal-related Impairment: one or more of the DSM-IV nicotine withdrawal symptoms caused difficulty at work, at home, with friends or family or interfered with life in some way; 5) Heavy Smoking: smoking 20 or more cigarettes per day at peak lifetime use; 6) Heaviness of Smoking Index (HSI; Heatherton et al., 1989; Heatherton et al., 1991): scores ranging from 0–6 on, which includes average number of cigarettes smoked per day and time to first cigarette at peak lifetime use.
