A double-blind placebo controlled experimental study of nicotine: I - effects on incentive motivation

Rationale Brain reward pathways implicated in addiction appear to be less reactive in regular drug users; behavioural manifestations may include decreased sensitivity to natural reinforcers. Objectives This study aimed to replicate earlier findings of abstinence-associated incentive motivation deficits in smokers and to determine whether these can be reversed with nicotine in the form of lozenge. Methods One hundred forty-five smokers were each tested twice, once after receiving nicotine, and once after receiving placebo lozenge in counterbalanced order. Participants completed various tests of incentive motivational functioning: a measure of subjective enjoyment, the Snaith-Hamilton pleasure scale (SHAPS); a simple card sorting task, the card arranging reward responsivity objective test (CARROT) with and without financial incentive; the modified emotional Stroop test; a cue-reactivity task; and a novel reaction time task to explore effects of signals of reward, the incentive motivational enhancement of response speed task. Results Compared with performance during abstinence (placebo condition), nicotine was associated with: higher self-reported pleasure expectations on the SHAPS; enhanced responsiveness to financial reward on the CARROT in smokers who smoked 15 or more cigarettes a day; and greater interference from appetitive words on the Stroop task. Conclusions These results are generally consistent with contemporary neurobiological theories of addiction and suggest that short-term smoking abstinence is associated with impaired reward motivation which can be reversed with nicotine.