Effects of Daily Caffeine Intake on Smoking Behavior in the Natural Environment

The effects of changes in daily caffeine intake on cigarette smoking were investigated. Forty cigarette smokers consumed caffeine ad lib on a baseline day then consumed controlled multiple doses of caffeine (100 mg and 500 mg per day) for two-day trials. Smokers recorded the number of cigarettes consumed, and measurements of expired-air carbon monoxide and salivary cotinine concentration were obtained to estimate smoke and nicotine intake. Baseline caffeine intake averaged 449 mg per day, with wide variations among participants. The 5-fold change in caffeine dose on treatment days did not affect any measure of smoking behavior in these participants. Results suggest that daily caffeine intake has little influence on cigarette smoking in the natural environment. Coffee drinking and cigarette smoking are commonly associated behaviors, although the links between them are not yet understood. Results raise doubts that the influence of coffee drinking on smoking, if any, can be attributed to the effects of caffeine.