12 months; I smoke cigarettes once or a couple of times each month; I smoke cigarettes once or a couple of times each week; I smoke cigarettes everyday”, and 2. A recall of cigarette use in each of the 3 months preceding completion of the survey. Here, the number of days smoked was multiplied by the average number of cigarettes smoked per day on smoking days. Smokers were defined as participants who had ever puffed on a cigarette, and quitting smoking (abstinence for ≥12 months) was defined as subsequently having ≥4 consecutive surveys with a value of 0 for the total number of cigarettes smoked. Among those who quit smoking, measures of nicotine dependence were computed in the survey immediately preceding the onset of quitting smoking, including craving scores, derived from 14 items assessing craving frequency, physical and mental addiction, and ability to refrain from smoking; nicotine withdrawal scores, assessing irritability, restlessness, anxiety, urge to smoke, and difficulty sleeping and concentrating while abstinent; and self-medication scores, where subjects either endorsed or refuted statements that smoking improves their functioning, concentration, affect, energy, and stress.
