Nicotine dependence, depression, and gender: characterizing phenotypes based on withdrawal discomfort, response to smoking, and ability to abstain.

Smoking is often viewed as a comprehensive phenotype rather than a complex set of traits involving intermediate phenotypes. To explore this issue in a laboratory setting, we tested 69 smokers stratified on depression, nicotine dependence, and gender. On the third day of an initial withdrawal period, we tested for differences among participants in uncued and cued craving and withdrawal; on the fourth day, we exposed them to a controlled dose of smoke and assessed them for physiological and hedonic effects and reduction of craving and withdrawal. Following resumption of smoking for at least a week, we then tested participants on their ability to abstain for an 11-day interval. During the withdrawal test, high-depressed smokers and men exhibited elevated craving and withdrawal scores overall, whereas no differences emerged for dependence. Cue exposure produced significant increases in craving but not withdrawal. During the smoke-exposure test, men were significantly more likely than women, and high-depressed smokers more likely than low-depressed smokers, to show evidence of experiencing pleasurable "buzzes." High-dependent smokers showed significant increases in diastolic blood pressure, possibly suggestive of greater sensitivity to nicotine. During the quit test, high-dependent smokers had more difficulty abstaining than low-dependent smokers, and women more than men; no differences emerged based on depression. Independently of group membership, inability to abstain was predicted by increased anxiety, depression, and difficulty concentrating in response to cue exposure. These findings provide support for the existence of phenotypes that can be distinguished by withdrawal symptomatology (primarily driven by depression) and ability to remain abstinent (primarily driven by dependence).