Degree of dependence influences the effects of smoking on psychomotor performance and working memory capacity.

OBJECTIVE Exploration of the variable effect of the degree of smoking dependence on psychomotor performance and working memory capacity. METHODS This is a randomized, controlled, prospective study conducted in the Department of Pharmacology, College of Medicine, Al-Mustansiriya University, Baghdad, Iraq from 15 January 2011 to 25 February 2011. After third stage male medical students completed the Fagerstrom Test for Nicotine Dependence questionnaire, we randomly selected a sample of 32 students and divided them into 3 groups: 10 participants with zero score (non-smokers), 11 participants with a score of 5 or less (light smokers), and 11 participants with a score of 6 or more (heavy smokers). Choice reaction time and flicker fusion were measured by the Leeds psychomotor performance test battery, and working memory capacity was measured by the N-back working memory test. RESULTS We found significant improvement in ascending flicker fusion test in heavy smokers in comparison with non-smokers (p=0.005, confidence interval [CI] 0.99-6), and light smokers (p=0.053, CI 0.39-4.5). Heavy smokers significantly deteriorated in the 3-back task in comparison with non-smokers (p=0.006, CI 4-25.8), and light smokers (p=0.009, CI 3-24.4). No significant changes were seen between groups in the descending critical flicker fusion, the components of choice reaction time, and in 1-, 2- back working memory tests. CONCLUSION Heavy smoking (high nicotine) enhances arousal, but impairs working memory capacity.