Effects of nicotine on brain responses to emotional pictures.

Given that nicotine reduces negative affect, one would expect nicotine to have different effects on brain responses to emotionally negative stimuli than it does on responses to emotionally neutral or positive stimuli. However, no studies have assessed this possibility. The present study assessed the effects of nicotine patch versus placebo patch on brain event-related potential (ERP) responses to emotion-inducing negative, positive, and neutral color pictures in 16 smokers in a double-blind, counterbalanced, within-subjects design. The study included four experimental sessions. After overnight smoking deprivation (12 hr or more), active nicotine patches were applied to participants during one of the first two sessions and during one of the last two sessions. Placebo patches were applied during the other two sessions. Nicotine reduced frontal ERP processing voltage negativity (from 144-488 ms poststimulus onset) evoked by viewing emotionally negative pictures to a greater extent than it did when emotionally neutral pictures were viewed, whereas it had no effect on processing negativity evoked by positive pictures. Nicotine also enhanced P390 amplitudes evoked by emotionally negative pictures more than it did when emotionally neutral and positive pictures were viewed. Across picture types, nicotine (relative to placebo) reduced N300 amplitude (more at anterior and dorsal sites) and increased P390 amplitude. Overall, nicotine influenced ERPs to emotionally neutral and positive pictures less than it did to negative pictures.     

Brain indices of nicotine's effects on attentional bias to smoking and emotional pictures and to task-relevant targets.

Aversive and smoking-related stimuli are related to smoking urges and relapse and can be potent distractors of selective attention. It has been suggested that the beneficial effect of nicotine replacement therapy may be mediated partly by the ability of nicotine to reduce distraction by such stimuli and thereby to facilitate attention to task-relevant stimuli. The present study tested the hypothesis that nicotine reduces distraction by aversive and smoking-related stimuli as indexed by the parietal P3b brain response to a task-relevant target digit. We assessed the effect of nicotine on distraction by emotionally negative, positive, neutral, and smoking-related pictures immediately preceding target digits during a rapid visual information processing task in 16 smokers in a double-blind, counterbalanced, within-subjects design. The study included two experimental sessions. After overnight smoking deprivation (12+ hr), active nicotine patches were applied to participants during one of the sessions and placebo patches were applied during the other session. Nicotine enhanced P3b responses associated with target digits immediately subsequent to negative emotional pictures bilaterally and subsequent to smoking-related pictures only in the right hemisphere. No effects of nicotine were observed for P3bs subsequent to positive and neutral distractor pictures. Another measure of attention, contingent negative variation amplitude in anticipation of the target digits also was increased by nicotine, especially in the left hemisphere and at posterior sites. Together, these findings suggest that nicotine reduces the distraction by emotionally negative and smoking-related stimuli and promotes attention to task-related stimuli by modulating somewhat lateralized and task-specific neural networks.     

The effects of smoking deprivation and nicotine administration on emotional reactivity.

Although converging lines of evidence suggest that nicotine and mood are related at a fundamental biological level, this link has not been reliably demonstrated in laboratory studies. In this study, startle probe methodology was used to examine the effects of nicotine administration and deprivation on emotional processes associated with motivation. Smokers (N = 115) completed four laboratory sessions crossing deprivation (12-hr deprived vs. nondeprived) with nicotine spray (active vs. placebo). Participants viewed affective pictures (positive, negative, neutral) and pictures involving cigarette cues, while startle probes were administered. Deprivation decreased startle responding to cigarette cues, suggesting an activation of appetitive processes. Nicotine administration suppressed overall startle responding during deprivation. In addition, during deprivation, random exposure to negative stimuli over two blocks of trials resulted in decreased adaptation of the startle response, suggesting that some sensitization to negative emotional cues may take place during nicotine withdrawal. These effects are consistent with formulations of addiction, stressing that withdrawal may both increase the reinforcement salience of smoking stimuli and decrease habituation to negative emotional stimuli.     

The reinforcing effects of nicotine and stimulant medication in the everyday lives of adult smokers with ADHD: A preliminary examination.

Whereas the smoking prevalence rates in the general population are declining, rates among people diagnosed with attention-deficit/hyperactivity disorder (ADHD) continue to be elevated. Previous research has shown that nicotine may improve attention and mood, suggesting that nicotine may help ameliorate the attentional and emotional problems associated with ADHD. The present study examined the effects of nicotine with and without stimulant medication on ADHD symptoms, moods, and arousal in the everyday lives of smokers with ADHD. A total of 10 smokers with ADHD who were being treated with stimulant medication were asked to abstain from smoking while participating in the study. Participants underwent four conditions in randomized order: (a) Nicotine patch+stimulant medication, (b) nicotine patch only, (c) placebo patch+stimulant medication, and (d) placebo patch only. Each condition continued for 2 days, during which self-reports of ADHD symptoms and moods were obtained using electronic diaries. Lightweight ambulatory monitors recorded cardiovascular activity at each diary entry. Smoking abstinence was verified by expired carbon monoxide and salivary cotinine analysis. Results showed that nicotine patches and stimulant medication alone and in combination reduced difficulty concentrating and core ADHD symptoms compared with placebo patch only. Borderline improvement in impatience and self-control was seen with nicotine patch administration primarily on day 1. Nicotine patches also tended to elevate systolic and diastolic blood pressure compared with placebo patch during day 2. The findings suggest that smokers with ADHD experience nicotine-related reductions in ADHD symptoms during their everyday lives.     

Dopamine receptor (DRD2) genotype-dependent effects of nicotine on attention and distraction during rapid visual information processing.

The effects of nicotine, distractor type, and dopamine type-2 receptor (DRD2) genotype on rapid visual information processing (RVIP) task performance were assessed in habitual smokers. Four RVIP tasks differed in terms of distractor location (central vs. peripheral) and distractor type (numeric vs. emotional). Each participant performed each of the tasks on two different days, once while wearing an active nicotine patch and once while wearing a placebo patch. Overall, the nicotine patch produced more accurate detection of and faster reaction times to target sequences; however, these effects varied with distractor type and genotype. Nicotine speeded reaction time more with left-visual-field (LVF) than right-visual-field (RVF) emotional distractors but speeded reaction time more with RVF than LVF numeric distractors, especially when the distractor digit matched the target sequence in terms of numeric oddness or evenness. Nicotine tended to facilitate performance more in individuals with at least one A1 allele than in homozygous A2A2 individuals, especially with numeric distractors presented to the left hemisphere. Nicotine tended to reduce distraction by negative stimuli more than other types of stimuli. Few gender differences were observed. The overall pattern of results was consistent with the view that nicotine modulates selective attention or subsequent information processing in a manner that depends partly on the emotional versus numeric nature of task distractors, DRD2 genotype, and the brain hemisphere that initially processes the distractors (visual field of distractor).     

Rate of nicotine onset from nicotine replacement therapy and acute responses in smokers.

The subjective and reinforcing effects of drugs of abuse may depend partly on their rate of onset, with faster acting formulations typically producing stronger effects than slower ones. In this within-subjects study, we examined the acute effects of nicotine replacement therapy via nicotine nasal spray (fast delivery) vs. transdermal nicotine patch (slow delivery) on craving, withdrawal, cardiovascular responses, subjective ratings, and reinforcing effects of smoking. Smokers (N=30) not seeking treatment participated in three sessions, each after overnight smoking abstinence, involving 14-mg nicotine (Nicoderm) or placebo patch, followed 4 hr later by intermittent administration of nicotine (Nicotrol) or placebo nasal spray. Specifically, the three group comparisons were nicotine patch condition (with placebo spray), nicotine spray condition (with placebo patch), and placebo condition (placebo spray and patch). Nicotine patch and nicotine spray were never administered in the same session. Blood nicotine levels were similar between nicotine patch and nicotine spray conditions, by design. Heart rate and systolic blood pressure were higher following nicotine spray vs. the other conditions, as hypothesized. However, other than reductions in craving related to nicotine spray and patch at some points, no differences between conditions were observed in withdrawal, subjective effects of sprays and smoking, or smoking reinforcement assessed by a computer task. Thus, under these acute conditions, the speed of nicotine delivery from nasal spray vs. patch differentially affected cardiovascular responses and perhaps craving but did not influence withdrawal, subjective ratings, and smoking reinforcement.     

Nicotine decreases attentional bias to negative-affect-related Stroop words among smokers

The present study examined the hypothesis that nicotine is associated with reduced attentional bias to affective and smoking-related stimuli in a modified Stroop task. A total of 56 habitual smokers were each tested on 4 days with 14 mg nicotine patches and placebo patches, counterbalanced, as a within-subjects factor in a double-blind design. A modified Stroop using negative-affect words, smoking words, color words, and neutral words was presented via computer in blocked format. As predicted, nicotine, relative to placebo, was associated with decreased attentional bias to negative words. Nicotine speeded performance during smoking-word and color-word blocks to the same degree as during neutral words and thus appeared to also have a nonspecific performance-enhancing effect. In an exploratory analysis, nicotine-attention effects occurred only in the initial presentation of pairs of blocked word pages. Nicotine also was associated with improved mood. The results are discussed in terms of affect-attention and smoking literatures.     

Smokers' expectancies for nicotine replacement therapy vs. cigarettes.

Smokers (N=188) recruited from the local community completed a questionnaire that measured expected outcomes of using cigarettes, nicotine gum, nicotine patch, and nicotine nasal spray. Expectancy questions relating to negative affect, craving, weight, and health risks were derived from the Smoking Consequences Questionnaire-Adult. As predicted, smokers held much greater expectancies that cigarettes help control negative affect, craving, and weight relative to nicotine replacement therapy (NRT). All NRT products were expected to cause fewer health risks than cigarette smoking. As predicted, smokers held strong negative affect reduction expectancies for cigarette smoking. For NRT, although still relatively low, craving reduction was the strongest expectancy. Individuals who had experience using the nicotine patch had greater positive expectancies for NRT. Greater positive expectancies for NRT were correlated with more immediate plans to quit smoking. In summary, cigarette smokers' positive expectancies about cigarettes do not appear to generalize to NRT products, which may limit their use and effectiveness.     

A psychometric evaluation of cigarette stimuli used in a cue reactivity study.

Laboratory studies have demonstrated that cigarette smokers react with significant subjective and autonomic responses (e.g., increased craving and increased heart rate) in the presence of stimuli associated with smoking. Although cue reactivity effects are typically robust, a number of methodological considerations make interpretation and design of cue reactivity studies problematic. Previous research has paid scant attention to the psychometric properties of the cigarette cues presented, and standard cues would enhance comparison and synthesis of studies. In the present study, we evaluated 12 cigarette photos (compared with positive, negative, and neutral photos), used in a separate study, for their ability to evoke self-report of craving in both nicotine-deprived and nondeprived smokers. These photos performed as expected, with cigarette pictures evoking significantly higher craving than neutral pictures and deprived smokers showing a trend toward higher craving than nondeprived smokers. The cigarette picture set was evaluated for internal consistency (Cronbach's alpha = .97) as a 12-item scale and further reduced to multiple 2-item scales with reliability estimates ranging from .70 to .93. A cluster analysis of all pictures showed that, when rated for craving, cigarette pictures clustered together, indicating they had distinct properties compared with positive, negative, and neutral pictures. Effect sizes were calculated for each cigarette picture in both deprived and nondeprived smokers. The craving effect sizes ranged from .57 to .98 for nondeprived smokers, and from .61 to .99 for deprived smokers. The analyses suggest these cigarette pictures have excellent psychometric properties for use in future cue reactivity studies.     

Sex differences in long-term smoking cessation rates due to nicotine patch

Compared to men, women may be at greater risk for smoking-related diseases and have greater difficulty quitting smoking. Sex differences in medication response could guide treatment for smoking cessation to improve women's quit rates. We conducted a meta-analysis of the 14 placebo-controlled nicotine patch trials (N = 6,250) for which long-term (6 months) clinical outcome results could be determined separately by sex. This analysis updated a meta-analysis of 11 of these trials that found no significant sex differences due to nicotine patch. The increase in quitting due to the nicotine vs. placebo patch was only about half as large in women as in men. Pooled absolute quit rates at 6 months for nicotine and placebo patch, respectively, were 20.1% and 10.8% in men, and 14.7% and 10.1% in women. The odds ratio for quitting due to nicotine vs. placebo patch was lower in women (OR = 1.61) than in men (OR = 2.20), with an interaction odds ratio of 1.40 (95% CI = 1.02-1.93, p = .04). This sex difference did not vary significantly by whether or not formal counseling was provided. Poorer outcomes in women vs. men treated with nicotine patch suggests that increasing the quit rates of women smokers may require supplementing patch treatment or use of other medications.     

Seeing a meal is not eating it: Hedonic context effects differ for visually presented and actually eaten foods

A meal usually consists of several different foods presented together. This study investigates how side dishes (vegetables/starches) affect the hedonic ratings of the main food item (meat/meat substitute) when a plate of these foods is viewed and also after the meal is eaten. The main question is whether the hedonic rating of the main food item assimilates toward the hedonic rating of the side dishes or shows contrast, moving away from the hedonic rating of the side dishes. In Experiment 1, when subjects only viewed a picture of a meal consisting of an imitation chicken tender (main food item) with either hedonically positive or hedonically negative side dishes, no effect of the side dishes was seen on the hedonic rating of the main food item. In Experiment 2, when subjects ate the meal shown in the picture in Experiment 1, hedonic contrast was found. That is, the main food item was rated as less good when simultaneously presented with more hedonically positive side dishes than when presented with hedonically negative side dishes. Thus, when a meal is eaten, foods influence the evaluation of other foods on the same plate. The same is not true when foods are presented in a picture.     

Efficacy of naltrexone in smoking cessation: a preliminary study and an examination of sex differences.

This double-blinded, placebo-controlled trial evaluated the efficacy of naltrexone as an adjunct to standard smoking cessation treatment. Participants (N = 110) were adult male and female nicotine-dependent smokers who expressed interest in quitting smoking. All subjects received six sessions of behavioral counseling (1 hr/session for 6 weeks), and 1 month of the nicotine patch (21 mg for the first 2 weeks, 14 mg the third week, 7 mg the fourth week). Subjects were randomly assigned to the naltrexone or placebo group. The naltrexone group started at 25 mg daily for 3 days prior to the quit date, and increased to 50 mg/day on the quit date and following 8 weeks. At the end of medication treatment, the naltrexone group had better quit rates versus the placebo group (48% quit on naltrexone vs. 41% on placebo), but this difference was not statistically significant. However, men and women differed on several measures: in the placebo group, women had significantly lower quit rates than men (39% vs. 67%, p<.05), but in the naltrexone group, women had quit rates comparable with those of men (58% vs. 62%, p = ns). Further examination revealed that naltrexone significantly reduced men's and women's cessation-related weight gain and selectively reduced women's urge to smoke to relieve negative affect and withdrawal. The results suggest continued examination of naltrexone as an adjunct in smoking cessation, particularly in female smokers, who have historically shown worse outcomes with traditional treatment methods.     

Comparison of the effects of a 24-hour nicotine patch and a 16-hour nicotine patch on smoking urges and sleep.

This randomized, open-label, crossover study was conducted to compare the effects of a 24-hr nicotine patch and a 16-hr nicotine patch on morning smoking urges and sleep quality of dependent smokers during a short period of cigarette abstinence. A total of 20 smokers (9 women and 11 men) smoking at least 20 cigarettes/day completed the two smoke-free study periods. For each period, cigarette abstinence started on the first evening and a nicotine patch was applied the next morning (for 16 or 24 hr), after baseline measures; a second patch was applied the next morning, 1 hr before the end of the experimental period. Smoking urges, mood and behavior self-reports, psychomotor performance, and polysomnographic recordings were compared between the two types of nicotine patch according to changes from baseline. Both patches decreased morning smoking urges, although results were significantly superior for the 24-hr patch. Furthermore, the 24-hr patch was more effective than the 16-hr patch in reducing the positive reinforcing dimension of smoking urges. Regarding polysomnographic recordings, the proportion of slow wave sleep was significantly increased from baseline with the 24-hr patch compared with the 16-hr patch. As for psychomotor performance measured through the critical flicker fusion test, significant improvement in morning alertness was observed in the 24-hr patch group. In conclusion, the 24-hr nicotine patch formulation is more effective than the 16-hr formulation in alleviating morning smoking urges and more specifically the positive reinforcing factor. The present findings do not support the idea that nicotine delivery during bedtime might disturb sleep, but rather it improves restorative sleep and postwaking arousal.     

Instructions about nicotine dose influence acute responses to nasal spray.

Effects of substance use are typically assumed to be related to pharmacological actions. However, beliefs about the drug content of a substance may strongly influence subjective and reinforcing responses to that substance (i.e., "placebo" effects). We examined the subjective and reinforcing effects of a nasal spray containing no nicotine as a function of instructions about the nicotine content of the spray (Told Nicotine vs. Told No Nicotine). Smokers (n=49) not interested in quitting smoking abstained overnight prior to a single session in which they were randomly assigned to one of three groups, involving one of the two instructional sets or a group that got no spray. Following dose instructions, subjects in the two spray groups were administered one set of four sprays from the spray bottle and then rated them intermittently on items related to "reward" (e.g., "liking", amount they would pay for more) and other effects. At the same time points, they also rated mood, craving, and withdrawal, and had heart rate and blood pressure measured. Reinforcement was then determined by the number of ad libitum sprays they self-administered during a 20-min period. The no-spray group simply rested quietly during the session, while measures were assessed at the same time points as subjects in the other two groups. Those in the Told Nicotine group reported greater spray ratings of "how much nicotine," "liking," "satisfying," "buzz/head rush," and "similar to smoking" compared with the Told No Nicotine group. Craving decreased more for those Told Nicotine versus those Told No Nicotine, but also decreased more for those Told No Nicotine compared with the no spray group. There were no significant differences in amount they would pay for more sprays, withdrawal, mood, cardiovascular responses, or in spray self-administration. These results show that instructions about the nicotine content of a novel delivery device (nasal spray) can influence self-reported spray ratings and reduce craving but are limited with respect to effects on other measures of drug response.     

Smoking cessation patterns in methadone-maintained smokers.

To determine predictors of smoking cessation duration in a randomized clinical trial, we assigned participants to nicotine patch (8-12 weeks) plus either (a) a baseline tailored brief motivational intervention, a quit date behavioral skills counseling session, and a relapse prevention follow-up session, or (b) brief advice using the National Cancer Institute's 4A's model. A total of 383 smokers from five methadone maintenance treatment centers in Rhode Island were enrolled, of whom 312 (82%) completed 6-month follow-up assessments. The primary outcome was longest period of self-reported abstinence during follow-up. Participants were on average 40.5 years of age; 51.9% were male, and 77.6% were White. In multivariate analysis controlling for demographics, nicotine dependence, depressive symptoms, and smoking-related symptoms, we found longer periods of abstinence in persons reporting at least one 24-hr quit attempt in the year prior to baseline (OR = 1.97, p = .003), in those anticipating success in cessation (OR = 1.33, p = .024), and in those with a greater percentage of nicotine patch use days (OR = 2.78, p<.001). Past quit attempts, self-efficacy, and constant nicotine replacement were associated with duration of abstinence among methadone-maintained smokers. Attention to these domains in future intervention studies may improve treatment success.     

Effect of high-dose nicotine patch therapy on tobacco withdrawal symptoms among smokeless tobacco users.

No pharmacotherapies have been shown to increase long-term (> or = 6-month) abstinence rates among smokeless tobacco (ST) users. Available evidence suggests that underdosing may occur with standard-dose nicotine replacement therapy (NRT) in ST users. We investigated the effect of high-dose nicotine therapy on tobacco withdrawal symptoms among ST users in a randomized, controlled clinical pilot study. A total of 42 ST users using at least 3 cans or pouches per week were randomized to nicotine patch doses of 63, 42, or 21 mg/day or placebo for 8 weeks. Multiple daily assessments of tobacco withdrawal and nicotine toxicity were obtained with an electronic diary. During the first week of nicotine patch therapy, we observed a dose-response relationship such that higher nicotine patch doses were associated with less decreased arousal (chi2 = 6.87, p = .009), less negative affect (chi2 = 3.85, p = .05), and less restlessness (chi2 = 3.90, p = .048). During the second week, higher nicotine patch doses were associated with less decreased arousal (chi2 = 6.77, p = .009). Overall, the frequency of nicotine toxicity symptoms did not differ by dose group. Of specific symptoms, nausea was observed to be more frequent in the 63 mg/day dose group compared with placebo (p = .035). In conclusion, high-dose nicotine patch therapy resulted in a greater reduction of tobacco withdrawal symptoms among ST users using at least 3 cans per week. High-dose nicotine patch therapy is safe and well tolerated in this population of tobacco users.     

Transdermal nicotine use in postmenopausal women: does the treatment efficacy differ in women using and not using hormone replacement therapy?

This study of postmenopausal female smokers (N = 94) asked: During short-term smoking abstinence, do the beneficial effects of transdermal nicotine replacement therapy (NRT) on acute symptomatology (i.e., withdrawal, cigarette craving, smoking urges, mood, depressive symptoms, motor speed, and reaction time) differ in women who use and do not use hormone replacement therapy (HRT)? Participants were recruited according to HRT and non-HRT use (self-selecting), then randomized within strata to active nicotine or placebo nicotine patch. After 1 baseline week of smoking, participants quit smoking for 2 weeks. Women received cessation counseling and were monitored for abstinence. Dependent measures were collected during five clinic visits. Two-way analysis of covariance (ANCOVA) were run on change scores for dependent variables, with nicotine patch group (active/placebo) and HRT group (HRT/non-HRT) as independent variables and age as a covariate. No interactions were found between HRT and patch condition, but both showed specific effects. During the first abstinent week, women on active nicotine patch (compared with placebo) experienced less severe withdrawal, greater reductions in cigarette cravings, and lower (more favorable) Factor 1 scores on the Questionnaire of Smoking Urges. During the second abstinent week, women using HRT (compared with the non-HRT group) exhibited better mood (Profile of Mood States scores) and less depression (Beck Depression Inventory scores). These results suggest the following: First, the efficacy of transdermal nicotine replacement is not adversely modified by women's HRT use; second, ovarian hormones might influence women's responses to smoking cessation, and thus should be considered in developing effective strategies for women to quit smoking.     

Adolescent smoking trajectories and nicotine dependence.

The present study correlates empirically constructed prospective adolescent smoking trajectories with indicators of nicotine dependence assessed in adolescence and in adulthood. Excluding individuals who reported no smoking during repeat assessment (nonadopters), we identified five smoking trajectory groups: experimenters (n=116, 48.5%), late increasers (n=39, 16.3%), early increasers (n=37, 15.5%), quitters (n=22, 9.2%), and persistent smokers (n=25, 10.5%). Higher frequency of nicotine dependence symptoms in adolescence occurred in the quitters and persistent smokers groups, who smoked at higher levels relative to the experimenters, late increasers, and early increasers groups, who reported a similar frequency of nicotine dependence symptoms and smoked at low levels. Lifetime nicotine dependence was assessed in adulthood in lifetime daily smokers using the Fagerstr?m Test for Nicotine Dependence (FTND) and the Nicotine Dependence Scale (NDS). Lifetime FTND levels were similar across trajectory groups. Relative to experimenters, all remaining smoking trajectory groups had higher NDS levels that were similar to one another. These results suggest that higher levels of adolescent nicotine dependence were associated with heavier smoking trajectory groups, and that regardless of trajectory group membership, smoking more than a few cigarettes per week throughout adolescence resulted in similar levels of lifetime nicotine dependence as measured by the FTND and NDS.     

The relationship between cigarette use, nicotine dependence, and craving in laboratory volunteers.

Data from epidemiological studies suggest that individual differences in cigarettes per day (CPD) and duration of smoking account for only a small portion of the variance in Diagnostic and Statistical Manual of Mental Disorders (4th ed.) (DSM-IV) nicotine dependence. However, DSM-IV may be an insensitive measure of nicotine dependence; other measures might better reflect the true nature of the relationship between use and dependence. This paper describes the relationship between cigarettes per day (CPD) and years smoking and the severity of nicotine dependence as measured by the Nicotine Dependence Syndrome Scale (NDSS). Furthermore, we assessed the validity of individual differences in nicotine dependence by determining whether they related to cue-evoked craving during abstinence. Data were pooled from five laboratory studies of 489 regular (i.e., 15+ CPD) smokers. In contrast to previously reported data demonstrating a relatively strong relationship between CPD and dependence in chippers (Shiffman & Sayette, 2005), CPD and years smoking accounted for a statistically significant, but small (<6%), portion of the variance in nicotine dependence in daily smokers. Individual differences in both CPD and years smoking had little or no relationship with craving. However, the magnitude of craving was significantly related to the degree of nicotine dependence even after controlling for use variables and excluding craving-related items on the NDSS. These data suggest that among moderate to heavy daily smokers, meaningful individual differences in nicotine dependence are observed independent of differences in current daily cigarette consumption and duration of smoking. Further research into the sources of this variance is critical to understanding the process of and risk for nicotine dependence.     

Carry-over effects of smoking cue exposure on working memory performance.

The present study investigated the effects of drug cue exposure on working memory performance in cigarette smokers. Adult smokers (N = 23) deprived for 12 hr performed a working memory task during which they were exposed to three types of task-irrelevant stimuli: Pictures containing smoking related-content, pictures devoid of smoking content, and a fixation cross. Consistent with prior research, we found that drug cue exposure affected the processing of subsequent items (i.e., carry-over effects). Specifically, we found that working memory performance was worse on trials containing neutral pictures preceded by trials containing smoking cues compared with performance on trials containing neutral pictures preceded by trials not containing smoking-related stimuli. Previously observed effects of smoking cue exposure on cognitive processing were replicated but only after removing trials subject to carry-over effects. These results replicate and extend previous research demonstrating similar effects and highlight the significant methodological and conceptual implications of carry-over effects.