The first Surgeon General’s report on the morbidity and mortality associated with cigarette smoking was released 45 years ago (US Public Health Service 1964
); however, 20.6% of adults (46 million) in the US are current smokers (Centers for Disease Control and Prevention [CDC] 2009
). In 2008, 45% of smokers (21 million) tried to quit smoking (CDC 2009
), but only 4–7% was likely successful (Fiore et al. 2008
). In most smokers trying to quit, withdrawal symptoms and various nonpharmacological factors (e.g., cigarette availability) typically lead to relapse within a few days or weeks. One component of the nicotine withdrawal syndrome is difficulty concentrating (American Psychiatric Association [APA] 2000
), which is generally regarded as a relapse factor and as a factor in the maintenance of smoking in tobacco-dependent individuals not attempting to quit smoking (Heishman et al. 1994
). Smokers report that one of the reasons they smoke is for the perceived cognitive benefits of nicotine (West 1993
). Experimental investigation for more than 40 years has attempted to validate self-reported claims of performance benefits and to delineate the conditions under which nicotine might enhance the various domains of human performance.
Research in the 1970s and 1980s suggested that tobacco smoking enhanced human performance; however, because of their design, the majority of these studies only demonstrated that smoking reversed withdrawal-induced performance deficits in tobacco-dependent smokers (Heishman et al. 1994
). Previous reviews of this literature (Heishman et al. 1994
; Heishman 1998
; Sherwood 1993
) concluded that smoking or nicotine produced small beneficial effects on a limited range of performance measures in nonsmokers and nondeprived or minimally deprived smokers. Behaviors most reliably enhanced were motor responding, focused and sustained attention, and recognition memory.
Nicotine’s ability to enhance cognitive processing has led to a greater understanding of the role of cholinergic mechanisms in cognitive functioning. Nicotine binds to presynaptic nicotinic acetylcholine receptors (nAChRs) in the brain and facilitates the release of acetylcholine, dopamine, serotonin, glutamate, and other neurotransmitters known to be involved in cognitive processes (Di Matteo et al. 2007
). Cholinergic projections to the prefrontal cortex are involved in attentional processing (Poorthuis et al. 2009
). Furthermore, α7 and α4β2 subunits of nAChRs in the hippocampus and basolateral amygdala mediate nicotine’s role in memory (Levin et al. 2006
; Mansvelder et al. 2006
). Nicotine and other nicotinic agents have been suggested as treatment medications for several neuropsychiatric disorders. For example, nicotine has been shown to attenuate certain attentional and cognitive deficits associated with schizophrenia, attention deficit/hyperactivity disorder, Alzheimer’s and Parkinson’s diseases, and age-related cognitive decline (Evans and Drobes 2008
; Levin et al. 2006
; Newhouse et al. 2004
). Such translational research can be guided by a knowledge of which aspects of cognition are reliably affected by nicotine.
Two extensive literature reviews on the effect of nicotine and tobacco smoking on human performance were published in the early 1990s (Heishman et al. 1994
; Sherwood 1993
). As noted in these reviews, the effect of nicotine and smoking on cognitive functioning was inconsistent, with nearly an equal number of studies reporting enhancement and no effect. Since then, numerous articles have been published investigating the effects of nicotine and smoking on attention and cognition. The purpose of this study was to conduct a meta-analysis of studies investigating the effects of nicotine on human performance published in the 15 years since our previous review (Heishman et al. 1994
). Because many studies have documented the ability of nicotine or tobacco smoking to reverse performance deficits observed following some period of tobacco deprivation (Heishman et al. 1994
), we sought to determine which aspects of human performance are enhanced by nicotine or tobacco smoking without the confound of withdrawal relief. We thus examined data from only those studies testing nonsmokers (never smokers and former smokers), nondeprived smokers, and smokers deprived for less than 2 h (minimally deprived).
The aims of this meta-analysis were (a) to synthesize the human literature on nicotine and performance published from 1994 to 2008, (b) to determine which aspects of performance were most sensitive to the enhancing effects of nicotine and tobacco smoking by calculating effect sizes on all reported outcome measures, and (c) to determine if methodological and design deficiencies noted in our previous review (Heishman et al. 1994
) were still evident.