Cue-reactivity in experienced electronic cigarette users: Novel stimulus videos and a pilot fMRI study

A database of videos of physical exercise and sedentary behaviours to investigate automatic processes and perceptions related to physical exercise

OBJECTIVE

The Videos of Physical Exercise and Sedentary Behaviours (VPESB) database is a novel database designed to experimentally investigate neural reactivity to physical exercise. The aim of this database is to provide a variety of dynamic images with a minimum of confounding factors.

METHODS

A total of 196 healthy participants were recruited to evaluate 10 clips of sedentary activities and 10 clips of physical exercise. Each activity was performed by a male and female performer, resulting in a total of 40 video clips of 10 s each.

RESULTS

The validation procedure confirmed the ability of these videoclips to accurately represent both sedentary and physical activity. In addition, video clips of physical activity were associated with higher effort ratings than sedentary activities (p < 0.01).

CONCLUSIONS

The VPESB is a versatile, rapid and easy-to-use tool that can be used to understand emotional and behavioural approaches to physical activity and to better disentangle some clinical conditions in which physical activity plays a central role.

Parameter Space and Potential for Biomarker Development in 25 Years of fMRI Drug Cue Reactivity: A Systematic Review

Importance

In the last 25 years, functional magnetic resonance imaging drug cue reactivity (FDCR) studies have characterized some core aspects in the neurobiology of drug addiction. However, no FDCR-derived biomarkers have been approved for treatment development or clinical adoption. Traversing this translational gap requires a systematic assessment of the FDCR literature evidence, its heterogeneity, and an evaluation of possible clinical uses of FDCR-derived biomarkers.

Objective

To summarize the state of the field of FDCR, assess their potential for biomarker development, and outline a clear process for biomarker qualification to guide future research and validation efforts.

Evidence Review

The PubMed and Medline databases were searched for every original FDCR investigation published from database inception until December 2022. Collected data covered study design, participant characteristics, FDCR task design, and whether each study provided evidence that might potentially help develop susceptibility, diagnostic, response, prognostic, predictive, or severity biomarkers for 1 or more addictive disorders.

Findings

There were 415 FDCR studies published between 1998 and 2022. Most focused on nicotine (122 [29.6%]), alcohol (120 [29.2%]), or cocaine (46 [11.1%]), and most used visual cues (354 [85.3%]). Together, these studies recruited 19 311 participants, including 13 812 individuals with past or current substance use disorders. Most studies could potentially support biomarker development, including diagnostic (143 [32.7%]), treatment response (141 [32.3%]), severity (84 [19.2%]), prognostic (30 [6.9%]), predictive (25 [5.7%]), monitoring (12 [2.7%]), and susceptibility (2 [0.5%]) biomarkers. A total of 155 interventional studies used FDCR, mostly to investigate pharmacological (67 [43.2%]) or cognitive/behavioral (51 [32.9%]) interventions; 141 studies used FDCR as a response measure, of which 125 (88.7%) reported significant interventional FDCR alterations; and 25 studies used FDCR as an intervention outcome predictor, with 24 (96%) finding significant associations between FDCR markers and treatment outcomes.

Conclusions and Relevance

Based on this systematic review and the proposed biomarker development framework, there is a pathway for the development and regulatory qualification of FDCR-based biomarkers of addiction and recovery. Further validation could support the use of FDCR-derived measures, potentially accelerating treatment development and improving diagnostic, prognostic, and predictive clinical judgments.

Vaping and smoking cue reactivity in young adult electronic cigarette users who have never smoked combustible cigarettes: A functional neuroimaging study

Introduction

The rapid growth in the use of electronic cigarettes (e-cigarettes) among young adults who have never smoked combustible cigarettes is concerning, as it raises the potential for chronic vaping and nicotine addiction. A key characteristic of drug addiction is the elevated neural response to conditioned drug-related cues (i.e., cue reactivity). Generalized reactivity to both vaping and smoking cues may signify an increased risk for smoking initiation in non- smoking vapers. In this study, we used functional magnetic resonance imaging (fMRI) to evaluate brain responses to vaping and smoking cues in young adult never-smoking vapers.

Methods

Sixty-six young adult never-smoking vapers underwent functional MRI while viewing visual cues pertaining to vaping, smoking, and nicotine-unrelated unconditioned reward (i.e., food). A priori region-of-interest analysis combined with exploratory whole-brain analysis was performed to characterize neural reactivity to vaping and smoking cues in comparison to food cues.

Results

The medial prefrontal cortex and the posterior cingulate cortex, regions that play a key role in drug cue reactivity, showed significantly increased neural response to vaping cues compared to food cues. The posterior cingulate cortex additionally showed increased neural responses to smoking cues compared to food cues.

Conclusions

Despite never having smoked combustible cigarettes, young adult vapers exhibited heightened neural susceptibility to both vaping and smoking cues within brain systems associated with cue reactivity. The findings shed light on the mechanisms underlying nicotine addiction and smoking initiation risk in this critical population and may contribute to the development of science-based interventions and regulatory measures in the future.

IMPLICATIONS

The escalating vaping prevalence among US never-smoking young adults is alarming, due to its potential ramifications for nicotine addiction development. Nicotine addiction is characterized by elevated neural response to conditioned nicotine-related cues. Using functional neuroimaging, we showed that young adult non-smoking vapers exhibited heightened neural susceptibility to both vaping and smoking cues within brain systems previously associated with cue reactivity. Such cross-reactivity to both types of nicotine cues may serve as the mechanism underlying nicotine addiction and smoking initiation risk in this population. Our findings may contribute to the development of science-based interventions and regulatory measures addressing the vaping epidemic.

The development and validation of an electronic nicotine delivery system (ENDS) image cue stimulus set

RATIONALE

Responsiveness to drug-related cues assesses drug reward in research studies. There are currently no validated visual image cues related to electronic nicotine delivery systems (ENDS), thus, this study aimed to develop and validate affective ENDS image cues.

METHODS

ENDS users and non-vaping individuals in the United States and Canada were recruited via Amazon MTurk. A total of 120 ENDS-related images and 56 neutral images, matched for visual similarity, were assessed. These images were either selected from public databases or were photographed by study staff. Closely adhering to the International Affective Picture System procedure, each participant rated 66 images one-by-one on dimensions of valence, arousal, dominance, and desire-to-vape where higher scores indicated greater feelings of happiness, excitement, loss of control, and desire to vape.

RESULTS

After excluding patterned responses, the data from 926 participants (610 ENDS users, and 316 non-vaping controls) were analyzed. When viewing ENDS-related images, desire-to-vape scores were correlated with valence (r = 0.55, p < 0.0005), arousal (r = 0.72, p < 0.0005), and dominance (r = 0.58, p < 0.0005) scores. Images that elicited greater desires to vape also elicited greater feelings of happiness and excitement, but less perceived control. Correlations between arousal and valence (r = 0.42, p < 0.0005) and dominance (r = 0.71, p < 0.0005) suggest that images that increased feelings of excitement also increased happiness and decreased perceived control.

CONCLUSIONS

Correlational findings of the affective ENDS-related images were similar to those of previous studies validating collections of tobacco and alcohol picture cues, supporting the future use of these stimuli in ENDS research.

Cue Reactivity to Electronic Cigarettes: A Systematic Review

Cue reactivity to Electronic Nicotine Delivery Systems (ENDS) has been studied by several researchers, yet the variability in user types (smokers, former smokers, dual users, exclusive ENDS users) and ENDS designs used between the studies may have undermined consistent results. This systematic review aims to give an overview of ENDS cue reactivity and how smoking status and device design may moderate this. A systematic search of Medline, Embase, Web of Science, PubMed and Cochrane was completed. All studies which reported findings on reactivity to ENDS cues in the form of craving or desire for ENDS or cigarettes, attention to cue, delay of gratification or economic decisions were included. Exclusion criteria were non-human subjects, non-adult participants or participants with comorbidities. Literature selection was carried out by 2 independent reviewers. The risk of bias and study quality were assessed using tools developed by Cochrane, BMJ and NHLBI. A total of 711 papers were screened and 22 studies were included in the current review. Study design, research question(s), population of interest, number of participants, dependent variable(s), ENDS generation and nicotine content used and study results were extracted. ENDS cues reliably induced ENDS craving, with no clear moderation by smoking status and no apparent moderation by device generation. In about half of the studies, ENDS cues induced craving for conventional cigarettes. Most studies used a smoker sample, thus limiting the conclusions that can be drawn on the moderation of cue reactivity by smoking status. The quality varied among studies but comparing the findings against the outcomes of only high-quality studies did not yield any different results. The results of this review support the notion of cue reactivity to ENDS, identifies gaps in current research on different user types and implies that ENDS design iterations have little impact on cue reactivity.

Study protocol: evaluation of the addictive potential of e-cigarettes (EVAPE): neurobiological, sociological, and epidemiological perspectives

BACKGROUND

Tobacco use is the largest preventable cause of diseases and deaths; reducing tobacco intake is, therefore, an urgent public health goal. In recent years, e-cigarettes have been marketed as a 'healthier' alternative to tobacco smoking, whilst product features have evolved tremendously in the meantime. A lively scientific debate has developed regarding the potential benefits and risks of e-cigarettes although, surprisingly, there are few studies investigating the addictive potential of nicotine-containing e-cigarettes. The present work comprises three work packages investigating the addictive potential of e-cigarettes from different perspectives: (1) the neurobiological addictive potential of e-cigarettes; (2) the experience and perception of dependence symptoms among users of e-cigarettes in a social context; and (3) the epidemiological perspective regarding factors influencing the potential for dependence.

METHODS

Work package I: the neurobiological study will investigate the key elements of addiction in e-cigarettes compared to tobacco cigarettes using neurobiological and neuropsychological correlates associated with craving, incentive motivation, cue reactivity and attentional bias. Work package II: the sociological study part examines self-reports on the experience and perception of dependence symptoms in a social context, using focus group interviews and the analysis of posts in online discussion forums on e-cigarettes. Work package III: the epidemiological study part focuses on tolerance development and the role of psychosocial and product factors by analyzing longitudinal data from the International Tobacco Control Policy Evaluation Project (ITC).

DISCUSSION

The present study offers a chosen mix of three methodological approaches, thereby comprehensively examining core symptoms of positive and negative reinforcement in addiction. Whether e-cigarettes are as reinforcing and addictive as combustible tobacco cigarettes is an important public health issue with implications for prevention and treatment programs.

TRIAL REGISTRATION

Work package I: Registered at clinicaltrials.gov/ct2/show/NCT04772014. Work package II: Registered at OSF Registries: https://osf.io/dxgya (2021, January 14).

Nicotine absorption during electronic cigarette use among regular users

BACKGROUND

The capability of electronic cigarette devices (e-cigs) to deliver nicotine is key to their potential to replace combustible cigarettes. We compared nicotine delivery and subjective effects associated with the use of two classes of e-cigarettes and cigarettes.

METHODS

14 e-cigarette users were instructed to vape their own e-cigarette device every 20 seconds for 10 minutes while blood was drawn at 1, 2, 4, 6, 8, 10,12, and 15 minutes after initiating vaping. Users rated withdrawal symptoms and side effects before and after vaping. E-cigarette devices were classified as first-generation (same size as cigarette, no activation button) or advanced (larger than cigarette with an activation button). Separately, 10 cigarette smokers completed a similar protocol. Fisher's Exact Test and two-sided t-tests were used as appropriate to determine differences in outcomes between first-generation e-cigarette users, advanced e-cigarette users, and smokers.

RESULTS

Compared to first-generation devices, advanced devices were associated with greater serum nicotine Cmax (ng/ml) (11.5 v. 2.8, p = 0.0231) and greater nicotine boost (ng/ml) (10.8 v. 1.8, p = 0.0177). Overall, e-cigarettes users experienced a significant reduction in withdrawal and craving, although there were no significant differences between users of first-generation and advanced devices. Comparing e-cigarettes overall to cigarettes, cigarettes were associated with greater Cmax (25.9 v. 9.0, p = 0.0043) and greater nicotine boost (21.0 v. 8.2, p = 0.0128).

CONCLUSIONS

Advanced e-cigarettes delivered significantly more nicotine than first-generation devices but less than combustible cigarettes. Overall, e-cigarette use was associated with a reduction in withdrawal and craving with no reported side effects. The wide variation in nicotine absorption from different e-cigarette devices should be considered in studies of e-cigarettes for smoking cessation.

Cigarette and e-cigarette use and social perceptions over the transition to college: The role of ADHD symptoms

Cigarette and electronic cigarette (e-cigarette) use prevalence increases during adolescence and peaks in young adulthood, with substantial increases during the transition from high school to college especially more recently for e-cigarette use. It is important to identify the underlying factors that serve as risk factors for tobacco use and social perceptions about cigarette and e-cigarette use. It is unknown whether attention-deficit/hyperactivity disorder (ADHD) symptoms are associated with social perceptions about tobacco or increased tobacco use during the high school to college transition. This three timepoint prospective longitudinal study evaluates the reciprocal relationship between ADHD symptoms and social perceptions about tobacco as well as the frequency of cigarette and e-cigarette use in a sample of 150 high school seniors (Mage = 18.25, 66.0% female, 65.3% White) across the transition to college. ADHD symptoms in high school predicted increases in e-cigarette use during the first semester of college, and this association maintained through the end of the first year. ADHD symptoms predicted changes in social perceptions about cigarette and e-cigarette use after the transition to college. ADHD symptoms were predicted by social perceptions about e-cigarettes at the beginning of college. Understanding the psychosocial mechanisms underlying the pathways from ADHD symptoms to e-cigarette use may advance tobacco use etiology and prevention efforts, which is important considering the rapid growth in e-cigarette use among emerging adults. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

A fMRI study on the impact of advertising for flavored e-cigarettes on susceptible young adults

BACKGROUND

E-cigarettes are sold in flavors such as "skittles," "strawberrylicious," and "juicy fruit," and no restrictions are in place on marketing e-cigarettes to youth. Sweets/fruits depicted in e-cigarette advertisements may increase their appeal to youth and interfere with health warnings. This study tested a brain biomarker of product preference for sweet/fruit versus tobacco flavor e-cigarettes, and whether advertising for flavors interfered with warning labels.

METHODS

Participants (N = 26) were college-age young adults who had tried an e-cigarette and were susceptible to future e-cigarette use. They viewed advertisements in fMRI for sweet/fruit and tobacco flavor e-cigarettes, menthol and regular cigarettes, and control images of sweets/fruits/mints with no tobacco product. Cue-reactivity was measured in the nucleus accumbens, a brain biomarker of product preference. Advertisements randomly contained warning labels, and recognition of health warnings was tested post-scan. Visual attention was measured using eye-tracking.

RESULTS

There was a significant effect of e-cigarette condition (sweet/tobacco/control) on nucleus accumbens activity, that was not found for cigarette condition (menthol/regular/control). Nucleus accumbens activity was greater for sweet/fruit versus tobacco flavor e-cigarette advertisements and did not differ compared with control images of sweets and fruits. Greater nucleus accumbens activity was correlated with poorer memory for health warnings.

CONCLUSIONS

These and exploratory eye-tracking findings suggest that advertising for sweet/fruit flavors may increase positive associations with e-cigarettes and/or override negative associations with tobacco, and interfere with health warnings, suggesting that one way to reduce the appeal of e-cigarettes to youth and educate youth about e-cigarette health risks is to regulate advertising for flavors.

Influence of Risk Perception on Attitudes and Norms Regarding Electronic Cigarettes

The use of electronic cigarettes has grown substantially over the last few years. Currently, about 4% of adults use electronic cigarettes, about 16% of high school students report use in the past 30 days, as do approximately 11-25% of college students. A hallmark of the reduction in tobacco use has been the shift in social norms concerning smoking in public. Such norms may also drive views on acceptability of public electronic cigarette use. While normative factors have been given attention, little substantive application of the literature on risk perception has been brought to bear. The overall aim of this study was to place a cognitive-affective measure of risk perception within a model that also includes social cues for e-cigarettes, addictiveness beliefs, and tobacco use to predict perceived social acceptability for public use of e-cigarettes. To do so, a cross-sectional study using an online survey was conducted among a sample of undergraduate students at a Western university (n = 395). A structural equation model showed that the acceptability of public e-cigarette use was influenced by social cues, beliefs about addiction, and cognitive risk perception, even after controlling for nicotine use. What is revealed is that cognitive assessment of e-cigarette risk and perception of addictiveness had a suppressing effect on perceived acceptability of public vaping, while greater exposure to social cues exerted a countervailing effect. This is evidence of the role that risk perception and social norms may play in the increases in electronic cigarette use that have been observed.

Changes in resting state functional brain connectivity and withdrawal symptoms are associated with acute electronic cigarette use

Resting state functional brain connectivity (rsFC) may be an important neuromarker of smoking behavior. Prior research has shown, among cigarette smokers, that nicotine administration alters rsFC within frontal and parietal cortices involved in executive control, as well as striatal regions that drive reward processing. These changes in rsFC have been associated with reductions in withdrawal symptom severity. We currently have a limited understanding of how rsFC is affected by the use of electronic cigarettes (ecigs), an increasingly popular class of products, the members of which deliver nicotine with varying effectiveness. The current study used fMRI to determine the effects of ecig use on rsFC and withdrawal symptoms. Independent component, dual regression, and permutation analyses were conducted on rsFC collected from ecig users before and after an ecig use episode (n=9) that occurred after 14h of nicotine abstinence. Similar to the known effects of nicotine administration, ecig use decreased rsFC of two clusters in the right frontal pole and frontal medial cortex with an attentional control salience network, and decreased rsFC of five clusters in the left thalamus, insula, and brain stem with a reward network encompassing the striatum. Ecig use increased inverse coupling between the prefrontal reward network and the right frontoparietal executive control network. Reductions in craving and difficulty with concentration were correlated with decreases in coupling strength between reward and executive control networks. These preliminary results suggest that the effects of ecig use on rsFC are similar to those seen with nicotine administration in other forms. In order to gain insight into the addictive potential of ecigs, further research is needed to understand the neural influence of ecigs across the range of nicotine delivery within this class of products.

Adolescents' behavioral and neural responses to e-cigarette advertising

Although adolescents are a group heavily targeted by the e-cigarette industry, research in cue-reactivity has not previously examined adolescents' behavioral and neural responses to e-cigarette advertising. This study addressed this gap through two experiments. In Experiment One, adult traditional cigarette smokers (n = 41) and non-smokers (n = 41) answered questions about e-cigarette and neutral advertising images. The 40 e-cigarette advertising images that most increased desire to use the product were matched to 40 neutral advertising images with similar content. In Experiment Two, the 80 advertising images selected in Experiment One were presented to adolescents (n = 30) during an functional magnetic resonance imaging brain scan. There was a range of traditional cigarette smoking across the sample with some adolescents engaging in daily smoking and others who had never smoked. Adolescents self-reported that viewing the e-cigarette advertising images increased their desire to smoke. Additionally, all participants regardless of smoking statuses showed significantly greater brain activation to e-cigarette advertisements in areas associated with cognitive control (left middle frontal gyrus), reward (right medial frontal gyrus), visual processing/attention (left lingual gyrus/fusiform gyrus, right inferior parietal lobule, left posterior cingulate, left angular gyrus) and memory (right parahippocampus, left insula). Further, an exploratory analysis showed that compared with age-matched non-smokers (n = 7), adolescent smokers (n = 7) displayed significantly greater neural activation to e-cigarette advertising images in the left inferior temporal gyrus/fusiform gyrus, compared with their responses to neutral advertising images. Overall, participants' brain responses to e-cigarette advertisements suggest a need to further investigate the long-run impact of e-cigarette advertising on adolescents.