Effects of nicotine dependence on diurnal variations of subjective activation and mood

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Abstract
To study the influence of nicotine dependence on diurnal variations of subjective activation and mood in smokers, without restrictions in their usual smoking habits, compared with non-smokers. We analysed independently the impact of the postlunch phenomenon, a semicircadian rhythm overlapped with diurnal variations. Every hour, from 0800 to 2100 hours, 60 students, 40 smokers and 20 non-smokers, responded to questions on eight unipolar visual analogue scales; four referred to subjective activation and four to mood. Based on Fagerström's Test for Nicotine Dependence and on carbon monoxide expired air pre- and postsmoking, 20 smokers were classified as high-dependent and 20 as low-dependent smokers. At 0800 hours, smokers were in a state of nicotine deprivation. Circadian typology, sleep habits and other psychoactive substances consumption were controlled. Subjective activation and mood of smokers improved after they smoked their first morning cigarette, and this effect was greater for high-dependent subjects. Mood scores were lower in high-dependent smokers throughout the day, intermediate in low-dependent smokers and greater in non-smokers. Smokers showed a delay in the diurnal maximum of subjective activation of 2 hours for low-dependent and 3 hours for high-dependent smokers. Moreover, high-dependent smokers showed a lower amplitude of diurnal function of subjective activation. We observed a greater postlunch interference in smokers, with a larger decrease of subjective feelings in low-dependent smokers. Our data confirm that differences exist in the circadian rhythmicity between non-smokers and smokers, and that the level of nicotine dependence in smokers is a relevant factor for the interpretation of the diurnal variations. The profiles obtained in smokers are consistent with models of nicotine deprivation-reversal and with the hedonic homeostatic dysregulation nicotine addiction hypothesis.