The effects of nicotine content information on subjective and behavioural responses to nicotine-containing and denicotinized cigarettes

Effect of nicotine expectancy and nicotine dose reduction on cigarette demand, withdrawal alleviation, and puff topography

BACKGROUND

Current FDA plans include proposed nicotine reduction mandates by the end of 2023. Most research on reduced nicotine cigarettes has been dose-blinded, while a mandate would be known to the public. Few laboratory studies have examined specifically how low nicotine content labeling impacts behavioral response. The purpose of this within-subject, balanced-placebo, human laboratory study was to evaluate the main and interactive effects of nicotine dose expectancy and dose reduction on cigarette reinforcement, withdrawal alleviation, and puff topography.

METHODS

Participants who smoke daily (N=21; 9 female) completed one practice and four experimental sessions in which expectancy (labeled "average" versus "very low" nicotine) and nicotine dose (0.80mg versus 0.03mg yield) were manipulated. Participants in acute withdrawal sampled experimental cigarettes followed by withdrawal alleviation and puff topography measures. Cigarette demand was measured using an incentivized purchase task. Analyses evaluated main and interactive effects of expectancy and nicotine dose.

RESULTS

Nicotine dose manipulation produced expected physiological effects (e.g., heart rate increases) and both reduced nicotine dose and expectation manipulations reduced perceived nicotine content. Expectation of reduced nicotine alone or in combination with reduced nicotine dose did not alter demand, withdrawal alleviation, or topography. Effective withdrawal alleviation was observed in all conditions.

CONCLUSIONS

These data inform nicotine regulation policy by suggesting limited compensatory harms caused by reduced nicotine expectations. The minimal acute effects of reduced nicotine expectancy or exposure on demand suggests that reduced nicotine standards are likely to generate their greatest public health benefit through the slowing of newly initiating cigarette smoking.

Non-pharmacological Considerations in Human Research of Nicotine and Tobacco Effects: A Review

Human research of nicotine and tobacco effects demonstrates that non-pharmacological factors may systematically affect responses to administered substances and inert placebos. Failure to measure or manipulate these factors may compromise study reliability and validity. This is especially relevant for double-blind placebo-controlled research of nicotine, tobacco, and related substances. In this article, we review laboratory-based human research of the impact of non-pharmacological factors on responses to tobacco and nicotine administration. Results suggest that varying beliefs about drug content and effects, perceptions about drug use opportunities, and intentions to cease drug use systematically alter subjective, behavioral, and physiological responses to nicotine, tobacco, and placebo administration. These non-pharmacological factors should be considered when designing and interpreting the findings of human research of nicotine and tobacco effects, particularly when a double-blind placebo-controlled design is used. The clinical implications of these findings are discussed, and we propose methodological strategies to enhance the reliability and validity of future research.

IMPLICATIONS

Growing research demonstrates that non-pharmacological factors systematically alter responses to acute nicotine, tobacco, and placebo administration. Indeed, varying beliefs about nicotine and/or tobacco administration and effects, differing perceptions about nicotine and/or tobacco use opportunities, and inconsistent motivation to quit smoking have been found to exert important influences on subjective, physiological, and behavioral responses. These variables are infrequently measured or manipulated in nicotine and tobacco research, which compromises the validity of study findings. Incorporating methodological strategies to better account for these non-pharmacological factors has the potential to improve the quality of addiction research and treatment.

Nicotine Effects, Body Weight Concerns and Smoking: A Literature Review

How people become addicted to cigarette smoking and remain addicted despite repeated attempts to quit requires piecing together a rather complex puzzle. The present review contextualizes the role of nicotine and smoking sensory stimulation on maintaining smoking, describes nicotine's effects on feeding behavior and body weight, and explores the impact of smoking outcome expectancies, including the belief that nicotine suppresses appetite and body weight, on the decision to smoke or vape (use of e-cigarettes). The analysis concludes with a review of rat models of human nicotine intake that attempt to isolate the effects of nicotine on appetite and weight gain. Animal research replicates with relative closeness phenomena observed in smokers, but the rat model falls short of replicating the long-term weight gain observed post-smoking cessation.

Verbal suggestions of nicotine content modulate ventral tegmental neural activity during the presentation of a nicotine-free odor in cigarette smokers

Expectancies of nicotine content have been shown to impact smokers' subjective responses and smoking behaviors. However, little is known about the neural substrates modulated by verbally induced expectancies in smokers. In this study we used functional magnetic resonance imaging (fMRI) to investigate how verbally induced expectations, regarding the presence or absence of nicotine, modulated smokers' neural response to a nicotine-free odor. While laying in the scanner, all participants (N = 24) were given a nicotine-free odor, but whereas one group was correctly informed about the absence of nicotine (control group n = 12), the other group was led to believe that the presented odor contained nicotine (expectancy group n = 12). Smokers in the expectancy group had significantly increased blood-oxygen-level-dependent (BOLD) responses during the presentation of the nicotine-free odor in the left ventral tegmental area (VTA), and in the right insula, as compared to smokers in the control group (Regions of interest analysis with pFWE-corrected p ≤ 0.05). At a more liberal uncorrected statistical level (p-unc ≤ 0.001), increased bilateral reactivity in the dorsolateral prefrontal cortex (dlPFC) was also observed in the expectancy group as compared with the control group. Our findings suggest that nicotine-expectancies induced through verbal instructions can modulate nicotine relevant brain regions, without nicotine administration, and provide further neural support for the key role that cognitive expectancies play in the cause and treatment of nicotine dependence.

The Influence of Placebo Effect on Craving and Cognitive Performance in Alcohol, Caffeine, or Nicotine Consumers: A Systematic Review

OBJECTIVE

The present systematic review aims to analyze the evidence about the influence of placebo effect on craving and cognitive performance in alcohol, caffeine, and nicotine consumers.

METHODS

Relevant studies were identified via Pubmed, Web of Science, and Scopus databases (up to March 2020). Only those papers published between 2009 and 2019 were searched.

RESULTS

Of the 115 preliminary papers, 8 studies of database search and 9 of the manual search were finally included in this review. Findings showed that while alcohol expectancies increased craving, caffeine and nicotine expectancies tend to decrease it. Alcohol expectancies caused similar or slower reaction time when alcohol was not consumed, impairments on inhibitory control (especially after alcohol consumption) and similar post-error slowing. The effect of caffeine and nicotine on reaction time has not been elucidated yet, however, caffeine expectancies have been shown to improve accuracy and the attentional filtering of distracting stimuli.

CONCLUSIONS

Alcohol, caffeine, and nicotine expectancies play an important role on craving. Although expectancies produce an effect on cognitive performance, caffeine and nicotine beliefs show an ambiguous impact on reaction time. Only the influence of alcohol expectancies on reaction time has been clarified. Furthermore, caffeine beliefs enhance accuracy.

The impacts of actual and perceived nicotine administration on insula functional connectivity with the anterior cingulate cortex and nucleus accumbens

BACKGROUND

Changes in resting state functional connectivity between the insula and dorsal anterior cingulate cortex as well as between the insula and nucleus accumbens have been linked to nicotine withdrawal and/or administration. However, because many of nicotine's effects in humans appear to depend, at least in part, on the belief that nicotine has been administered, the relative contribution of nicotine's pharmacological actions to such effects requires clarification.

AIMS

The purpose of this study was to examine the impacts of perceived and actual nicotine administration on neural responses.

METHODS

Twenty-six smokers were randomly assigned to receive either a nicotine inhaler (4 mg deliverable) or a nicotine-free inhaler across two sessions. Inhaler content instructions (told nicotine vs told nicotine-free) differed across sessions. Resting state functional connectivity between sub-regions of the insula and the dorsal anterior cingulate cortex and nucleus accumbens was measured using magnetic resonance imaging before and after inhaler administration.

RESULTS

Both actual and perceived nicotine administration independently altered resting state functional connectivity between the anterior insula and the dorsal anterior cingulate cortex, with actual administration being associated with decreased resting state functional connectivity, and perceived administration with increased resting state functional connectivity. Actual nicotine administration also contralaterally reduced resting state functional connectivity between the anterior insula and nucleus accumbens, while reductions in resting state functional connectivity between the mid-insula and right nucleus accumbens were observed when nicotine was administered unexpectedly. Changes in resting state functional connectivity associated with actual or perceived nicotine administration were unrelated to changes in subjective withdrawal and craving. Changes in withdrawal and craving were however independently associated with resting state functional connectivity between the nucleus accumbens and insula.

CONCLUSIONS

Our findings highlight the importance of considering non-pharmacological factors when examining drug mechanisms of action.

Nicotine-induced behavioral sensitization in an adult rat model of attention deficit/hyperactivity disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) is associated with increased risk of tobacco dependence. Nicotine, the main psychoactive component of tobacco, appears to be implicated in ADHD-related tobacco dependence. However, the behavioral responsiveness to nicotine of the prevalent animal model of ADHD, the spontaneously hypertensive rat (SHR), is currently underinvestigated. The present study examined the activational effects of acute and chronic nicotine on the behavior of adult male SHRs, relative to Wistar Kyoto (WKY) controls. Experiment 1 verified baseline strain differences in open-field locomotor activity. Experiment 2 tested for baseline strain differences in rotational behavior using a Rotorat apparatus. Adult SHR and WKY rats were then exposed to a 7-day regimen of 0.6mg/kg/d s.c. nicotine, or saline, prior to each assessment. A separate group of SHRs underwent similar training, but was pre-treated with mecamylamine, a cholinergic antagonist. Nicotine sensitization, context conditioning, and mecamylamine effects were then tested. Baseline strain differences were observed in open-field performance and in the number of full rotations in the Rotorat apparatus, but not in the number of 90° rotations or direction changes. In these latter measures, SHRs displayed weaker nicotine-induced rotational suppression than WKYs. Both strains expressed nicotine-induced sensitization of rotational activity, but evidence for strain differences in sensitization was ambiguous; context conditioning was not observed. Mecamylamine reversed the effects of nicotine on SHR performance. These findings are consistent with the hypothesis that a reduced aversion to nicotine (expressed in rats as robust locomotion) may facilitate smoking among adults with ADHD.

Reduced Nicotine Content Expectancies Affect Initial Responses to Smoking

OBJECTIVES

We sought to determine if negative responses to reduced nicotine content (RNC) cigarettes during open-label trials result from smokers' (negative) expectancies. We examined the effects of nicotine content description - independent of actual nicotine content - on subjective responses (craving reduction, withdrawal suppression, mood changes, and sensory ratings) and smoking behaviors (topography measures and carbon monoxide [CO] boost).

METHODS

Thirty-six 12-hour-abstinent daily smokers completed a 3-session crossover trial. During each session, participants smoked their preferred brand cigarette - blinded and described as containing "usual," "low," and "very low" nicotine content - through a topography device and completed CO and subjective response assessments.

RESULTS

Although nicotine content was identical, compared to the "usual" content cigarette, participants experienced less craving reduction after smoking the "very low" nicotine cigarette, and rated its smoke as weaker (p < .05). Participants took shallower puffs of the "low" nicotine cigarette (p < .05), and rated the "low" and "very low" nicotine cigarettes as weaker and too mild (p < .01).

CONCLUSIONS

Negative responses to RNC cigarettes may be due, in part, to negative expectancies about using cigarettes containing less nicotine. In this context, RNC cigarette marketing and labeling are likely important considerations if a federal nicotine reduction policy is initiated.

Attentional bias to smoking and other motivationally relevant cues is affected by nicotine exposure and dose expectancy

We investigated the effects of acute nicotine dose and expected dose on attentional bias (AB) to smoking and affective cues in overnight nicotine-deprived smokers (n=51; 24 women) using a balanced placebo design, which counterbalanced given nicotine dose (Given-NIC vs. Given-DENIC) with instructed nicotine dose expectancy (Told-NIC vs. Told-DENIC). Before and after smoking a study cigarette, smokers completed a vigilance task where they pressed buttons to every third consecutive even or odd digit, while ignoring intermittent smoking, pleasant, unpleasant, and neutral picture distracters. We examined the early posterior negativity (EPN) and late positive potential (LPP) components of the event-related potentials (ERPs) to the distracters, reaction time (RT) to the target digits, and ratings of the study cigarettes. The EPN was sensitive to both given and instructed nicotine dose, while the instructed dose moderated the impact of given dose for the LPP. The RT metrics were sensitive to given but not to instructed dose. The effects of given dose on ratings following cigarette smoking (e.g. enjoyment) were moderated by the instructed dose. The ERP findings suggest that the anticipated effects of nicotine improve attention much like receiving actual nicotine.

The impact of social context on cigarette self-administration in nondependent smokers

Tobacco use in nondependent smokers (i.e. chippers) is believed to be largely determined by situational factors including social context. However, little empirical research has examined how different social contexts impact chippers' smoking behaviour. Twenty-eight (16 men) chippers completed two laboratory sessions where they were offered an opportunity to self-administer puffs of their preferred tobacco brand using a progressive ratio task. During an individual session, participants self-administered cigarettes alone and during a paired session, they self-administered cigarettes with a coparticipant who was also smoking. The strongest predictors for number of self-administered puffs and breakpoint during the paired session were coparticipants' number of puffs and breakpoint, respectively (P<0.001), followed by puffs taken and breakpoint during the individual session (P<0.01). Current smoking frequency (cigarettes/week) did not significantly predict puffs taken or breakpoint during the paired session. Latency to cigarette self-administration during the paired session was correlated positively with coparticipants' latency (P<0.05), but not with latency during the individual session or cigarettes per week. The findings suggest that the presence of another smoker exerts an important influence on the quantity of chippers' smoking behaviour, such that chippers match their smoking behaviour to that of other smokers in their proximate environment.

Does acute tobacco smoking prevent cue-induced craving?

BACKGROUND

Smoking cessation aids appear to be limited in their ability to prevent craving triggered by exposure to smoking-associated stimuli; however, the extent to which cue-induced cravings persist following denicotinized or nicotine-containing tobacco smoking is not known.

METHODS

Thirty (17 male) ⩾12-hour abstinent dependent smokers completed two sessions during which they smoked a nicotine-containing or denicotinized cigarette. Instructions regarding the nicotine content of the cigarette varied across sessions, and all participants were exposed to a neutral cue followed by a smoking cue after cigarette consumption. Craving was assessed before and after cigarette consumption and cue exposure.

RESULTS

Reduced intentions to smoke were associated with both nicotine expectancy (p<0.05) and nicotine administration (p<0.01), while reduced withdrawal-related craving was uniquely associated with nicotine administration (p<0.05). Smoking-associated stimuli increased craving regardless of nicotine expectancy or administration (p-values<0.001).

CONCLUSIONS

While both nicotine pharmacology and expectancy appear to contribute to craving reduction associated with acute tobacco smoking, neither smoking-related nicotine administration nor expectation prevents increases in craving following exposure to smoking-associated stimuli. These findings suggest that cue-induced craving may be resistant to various pharmacological and psychological interventions.

Belief about nicotine selectively modulates value and reward prediction error signals in smokers

Little is known about how prior beliefs impact biophysically described processes in the presence of neuroactive drugs, which presents a profound challenge to the understanding of the mechanisms and treatments of addiction. We engineered smokers' prior beliefs about the presence of nicotine in a cigarette smoked before a functional magnetic resonance imaging session where subjects carried out a sequential choice task. Using a model-based approach, we show that smokers' beliefs about nicotine specifically modulated learning signals (value and reward prediction error) defined by a computational model of mesolimbic dopamine systems. Belief of "no nicotine in cigarette" (compared with "nicotine in cigarette") strongly diminished neural responses in the striatum to value and reward prediction errors and reduced the impact of both on smokers' choices. These effects of belief could not be explained by global changes in visual attention and were specific to value and reward prediction errors. Thus, by modulating the expression of computationally explicit signals important for valuation and choice, beliefs can override the physical presence of a potent neuroactive compound like nicotine. These selective effects of belief demonstrate that belief can modulate model-based parameters important for learning. The implications of these findings may be far ranging because belief-dependent effects on learning signals could impact a host of other behaviors in addiction as well as in other mental health problems.

The effects of nicotine stimulus and response expectancies on male and female smokers' responses to nicotine-free electronic cigarettes

BACKGROUND

Electronic cigarettes (e-cigarettes) have been reported to reduce tobacco craving and withdrawal; however, the mechanisms underlying these effects have not been elucidated.

METHODS

This study examined the contributions of nicotine stimulus and response expectancies to responses to nicotine-free e-cigarettes in 21 e-cigarette naïve smokers (12 male). Participants completed two randomized experimental sessions in which they administered a nicotine-free e-cigarette. During one session they were informed that the e-cigarette contained nicotine and during the other session they were informed that the e-cigarette was nicotine-free. Participants completed subjective assessments before and immediately after sampling ten puffs from the e-cigarette and were then invited to earn additional puffs using a computerized progressive ratio task. Prior to their enrolment in the study, participants provided an estimate of the relative importance of the nicotine content of e-cigarettes for craving relief.

RESULTS

Instructions that the e-cigarette contained nicotine were found to reduce both intention to smoke (p=0.017) and withdrawal-related (p=0.018) craving, regardless of a-priori reported beliefs regarding the relative importance of nicotine. Nicotine content instructions were also found to be associated with a shorter latency to self-administration (p=0.005); however, a Sex×Instructions×Response Expectancy interaction (p=0.008) revealed that this effect was specific to women who had strong a-priori nicotine content craving relief expectations. Neither nicotine content instructions nor response expectancies impacted the number of puffs self-administered.

CONCLUSIONS

Findings suggest that nicotine content expectations contribute to smokers' responses to e-cigarettes, and that a-priori beliefs about nicotine effects may be especially important in women.

The effects of beliefs regarding drug assignment in experimental and field studies of nicotine delivery devices: a review

The placebo effect of a psychoactive drug can be defined as the effect of expecting the drug in the absence of its pharmacological actions. As nicotine is widely believed to be the primary factor driving cigarette smoking, smokers are likely to expect nicotine to alleviate craving and withdrawal. The present review examines the extent to which any observed effects of nicotine, and especially its craving- and withdrawal-reducing effects, can be attributed to placebo. We begin by reviewing studies that examined the placebo effects of nicotine in the laboratory and follow with a review of potential placebo effects that are typically not controlled in placebo-controlled studies of nicotine replacement therapy (NRT). In laboratory studies, nicotine instructions decrease tobacco smoking, craving and/or withdrawal, while nicotine-specific effects have not been consistently reported. In field trials of NRT, there is a general failure to assess smokers' beliefs regarding their drug assignment. This omission makes it difficult to unequivocally attribute findings of placebo-controlled NRT studies to the physiological effects of nicotine. In sum, our review indicates that the placebo effects of nicotine, and specifically nicotine content expectations, may account for many of the benefits associated with nicotine delivery devices in both laboratory and field studies.