Effect of instructions and nicotine on smoking cessation, withdrawal symptoms and self-administration of nicotine gum.

Seventy-seven smokers quit smoking and were randomly assigned to a 3 x 2 design contrasting instructions (told received nicotine gum versus told received placebo gum versus not told which gum received) and receipt of nicotine (received nicotine gum versus received placebo gum). Both being told one received nicotine and actual receipt of nicotine increased the number of days abstinent and decreased the number of cigarettes smoked (P less than 0.05). Receipt of nicotine but not instructions appeared to influence withdrawal (P = 0.06). Instructions but not receipt of nicotine appeared to influence craving (P = 0.08), gum self-administration (P = 0.06) and reported helpfulness of the gum (P = 0.02). Neither nicotine nor instructions influenced side-effects. Instructions and nicotine interacted in several ways. For example, nicotine appeared to increase abstinence in the blind and told placebo conditions more than in the told nicotine condition (P less than 0.05). Our results suggest the effects of instructions and nicotine 1) are not mutually exclusive, 2) vary across dependent variables and 3) can interact such that instructions modify the therapeutic and subjective effects of nicotine.