Does nicotine do what we think it does? A meta-analytic review of the subjective effects of nicotine in nasal spray and intravenous studies with smokers and nonsmokers

Hormone-based models for comparing menstrual cycle and hormonal contraceptive effects on human resting-state functional connectivity

Oral contraceptives (OCs) are widely used yet understudied given their potential for public health consequences. Emerging investigations scaling from single-subject, dense-sampling neuroimaging studies to population-level metrics have linked OCs to altered brain structure and function. Modeling the hypogonadal, hypergonadal, or mixed state effects of OCs in terms of their impact on hormone action in the brain is a valuable approach to synthesizing results across neuroimaging studies and comparing OC effects to companion findings from research on menstrual cycle phase effects on brain anatomy and function. Resting-state functional connectivity studies provide a powerful tool to evaluate the role of OCs on the intrinsic network connectivity that underlies multiple behavioral domains. The preponderance (but not consensus) of the current literature indicates that (1) as the menstrual cycle proceeds from a low to high progesterone state, prefrontal connectivity increases and parietal connectivity decreases; (2) OCs tend to mimic this connectivity pattern; therefore (3) OCs may produce a hyperprogestogenic state in the brain, in spite of overall reductions in endogenous steroid hormone levels. Alternative models are also considered.

The role of the SLC6A3 3' UTR VNTR in nicotine effects on cognitive, affective, and motor function

RATIONALE

Nicotine has been widely studied for its pro-dopaminergic effects. However, at the behavioural level, past investigations have yielded heterogeneous results concerning effects on cognitive, affective, and motor outcomes, possibly linked to individual differences at the level of genetics. A candidate polymorphism is the 40-base-pair variable number of tandem repeats polymorphism (rs28363170) in the SLC6A3 gene coding for the dopamine transporter (DAT). The polymorphism has been associated with striatal DAT availability (9R-carriers > 10R-homozygotes), and 9R-carriers have been shown to react more strongly to dopamine agonistic pharmacological challenges than 10R-homozygotes.

OBJECTIVES

In this preregistered study, we hypothesized that 9R-carriers would be more responsive to nicotine due to genotype-related differences in DAT availability and resulting dopamine activity.

METHODS

N=194 non-smokers were grouped according to their genotype (9R-carriers, 10R-homozygotes) and received either 2-mg nicotine or placebo gum in a between-subject design. Spontaneous blink rate (SBR) was obtained as an indirect measure of striatal dopamine activity and smooth pursuit, stop signal, simple choice and affective processing tasks were carried out in randomized order.

RESULTS

Reaction times were decreased under nicotine compared to placebo in the simple choice and stop signal tasks, but nicotine and genotype had no effects on any of the other task outcomes. Conditional process analyses testing the mediating effect of SBR on performance and how this is affected by genotype yielded no significant results.

CONCLUSIONS

Overall, we could not confirm our main hypothesis. Individual differences in nicotine response could not be explained by rs28363170 genotype.

Pharmacokinetic and subjective assessment of prototype JUUL2 electronic nicotine delivery system in two nicotine concentrations, JUUL system, IQOS, and combustible cigarette

RATIONALE

Electronic nicotine delivery systems and heated tobacco products are noncombustible alternatives for adult smokers. Evidence suggests sufficient nicotine delivery and satisfying effects are necessary to facilitate switching away from smoking; nicotine delivery varies across electronic nicotine delivery systems within limited nicotine concentrations.

OBJECTIVES

To assess the nicotine delivery and subjective effects of prototype JUUL2 System in two nicotine concentrations, currently-marketed US JUUL System ("JUUL"), IQOS-brand heated tobacco product, and combustible cigarettes.

METHODS

Adult smokers (N = 40) completed a 5-arm cross-over product-use laboratory confinement study. Nicotine pharmacokinetics and subjective effects were assessed following use of: (1) JUUL2 prototype 18 mg/mL nicotine; (2) JUUL2 prototype 40 mg/mL; (3) JUUL 59 mg/mL; (4) IQOS 18 mg/g; and (5) usual brand combustible cigarette, each evaluated during ad libitum (10 min) and controlled (5 min, 10 standardized puffs) use.

RESULTS

Nicotine delivery was greatest for combustible cigarettes, followed by JUUL2 prototype 40 mg/mL, IQOS, JUUL2 prototype 18 mg/mL, and JUUL 59 mg/mL. Nicotine delivery from JUUL2 prototype 18 mg/mL was significantly greater than JUUL 59 mg/mL after ad libitum use. JUUL products were significantly more satisfying and effective at reducing craving than IQOS. JUUL2 prototype 40 mg/mL was significantly more aversive than other JUUL products.

CONCLUSIONS

Prototype JUUL2 and JUUL 59 mg/mL products were rated higher than IQOS on subjective measures associated with switching away from smoking. The JUUL2 prototype 40 mg/mL produced aversive responses and would require modifications to be a viable product for adult smokers. Nicotine delivery and subjective responses to JUUL2 prototype 18 mg/mL suggest a product based on this prototype may facilitate increased switching among adult smokers.

Withdrawal Symptoms From E-Cigarette Abstinence Among Adult Never-Smokers: A Pilot Experimental Study

INTRODUCTION

Use of e-cigarettes among never-smokers has substantially increased; yet there are few descriptions of the consequences of such use. We assessed whether adult never-smokers can have withdrawal from cessation of e-cigarettes.

METHODS

In an un-blinded pre-post clinical trial, 30 never-smoker daily e-cigarette users used their own nicotine-containing e-cigarette for 7 days followed by 6 days of biologically confirmed abstinence. Participants monitored symptoms of nicotine withdrawal nightly via an Interactive Voice Response system. They attended three lab visits/week to provide expired carbon monoxide and urine samples to determine compliance.

FINDINGS

Abstinence increased all the DSM5 symptoms of tobacco withdrawal and this occurred in the majority of participants. The increase in severity of withdrawal was small and rarely impaired functioning.

CONCLUSIONS

Our finding suggests that withdrawal symptoms can occur in never-smokers who stop e-cigarettes abruptly. However, the severity of withdrawal appears to be small and may not be of clinical or regulatory significance. Although our sample size was small and thus replication tests of our results are indicated, it may be prudent to warn never-smokers that withdrawal symptoms may occur.

IMPLICATIONS

This study indicates that withdrawal symptoms can occur in never-smokers who are daily e-cigarette users. However, the severity of withdrawal from e-cigarette abstinence in never-smokers appears to be small and may not be of clinical or regulatory significance. Given our small sample size, replication of our results is warranted. Nevertheless, it might be prudent to warn never-smokers of addiction to e-cigarettes.Clinical Trial Registration = NCT02825459.

Effects of nicotine on smooth pursuit eye movements in healthy non-smokers

RATIONALE

The non-selective nicotinic acetylcholine receptor (nAChR) agonist nicotine has been argued to improve attention via enhanced filtering of irrelevant stimuli. Here, we tested this hypothesis in the context of smooth pursuit eye movements (SPEMs), an oculomotor function previously shown to improve with nicotine in some but not all studies.

OBJECTIVES

In order to test whether nicotine improves performance particularly when the inhibition of distracting stimuli is required, SPEM was elicited in conditions with or without peripheral distractors. Additionally, different target frequencies were employed in order to parametrically vary general processing demands on the SPEM system.

METHODS

Healthy adult non-smokers (N = 18 females, N = 13 males) completed a horizontal sinusoidal SPEM task at different target frequencies (0.2 Hz, 0.4 Hz, 0.6 Hz) in the presence or absence of peripheral distractors in a double-blind, placebo-controlled, cross-over design using a 2 mg nicotine gum.

RESULTS

Nicotine increased peak pursuit gain relative to placebo (p < .001), but an interaction with distractor condition (p = .001) indicated that this effect was most pronounced in the presence of distractors. Catch-up saccade frequency was reduced by nicotine (p = .01), particularly at higher target frequencies (two-way interaction, p = .04). However, a three-way interaction (p = .006) indicated that the reduction with nicotine was strongest at the highest target frequency (0.6 Hz) only without distractors, whereas in the presence of distractors, it was strongest at 0.4-Hz target frequency. There were no effects of nicotine on subjective state measures.

CONCLUSIONS

Together, these findings support a role of both distractor inhibition and general processing load in the effects of nicotine on smooth pursuit.

Genetics of addictive behavior: the example of nicotine dependence

The majority of addictive disorders have a significant heritability—roughly around 50%. Surprisingly, the most convincing association (a nicotinic acetylcholine receptor CHRNA5-A3-B4 gene cluster in nicotine dependence), with a unique attributable risk of 14%, was detected through a genome-wide association study (GWAS) on lung cancer, although lung cancer has a low heritability. We propose some explanations of this finding, potentially helping to understand how a GWAS strategy can be successful. Many endophenotypes were also assessed as potentially modulating the effect of nicotine, indirectly facilitating the development of nicotine dependence. Challenging the involved phenotype led to the demonstration that other potentially overlapping disorders, such as schizophrenia and Parkinson disease, could also be involved, and further modulated by parent monitoring or the existence of a smoking partner. Such a complex mechanism of action is compatible with a gene-environment interaction, most clearly explained by epigenetic factors, especially as such factors were shown to be, at least partly, genetically driven.

Sex Differences in Subjective Responses To Moderate Versus Very Low Nicotine Content Cigarettes

Introduction

Men and women may be differentially sensitive to the acute perceptual responses to smoking cigarettes that vary in nicotine content ("dose") but are matched on non-nicotine constituents.

Methods

Dependent adult smokers (43 M, 31 F) took four controlled puffs from Spectrum research cigarettes that were moderate (16-17 mg/g) or very low (0.4 mg/g) in nicotine content, and matched on "tar." To ensure reliable responses, each cigarette was administered singly five times in random order under blind conditions, with one or the other provided every 15 minutes over a 2.5-hour session following overnight abstinence. Subjective perceptions (eg, "satisfying", "how much nicotine") were rated after each cigarette.

Results

Subjective ratings differed due to cigarette nicotine content, as expected, and did so differentially between men and women. The interaction of nicotine content by sex was significant for most rated subjective perceptions of the cigarette, as multivariate analyses showed that differences due to nicotine content were highly significant for men (p < .001) but only marginal for women (p = .08).

Conclusions

Relative to men, women's subjective responses to acute smoking are less sensitive to differences in cigarette nicotine content. To our knowledge, this is the first comparison of sex differences in response to very carefully controlled doses of smoked nicotine per se. Further research should examine possible sex differences in nicotine dosing administered by other smoked and nonsmoked methods, as well as the developmental pattern of these differences during onset and during cessation of dependent smoking.

Implications

Subjective perceptions of smoking cigarettes varying in nicotine contents differ between men and women. These results with research cigarettes are similar to other studies with carefully dosed nicotine administration by other means, supporting the notion that women, relative to men, are less sensitive to pharmacological factors and more sensitive to nonpharmacological factors in acute cigarette smoking. Future studies are warranted to examine sex differences in other responses to controlled nicotine intake via smoking, and via other smoked and nonsmoked methods of administering nicotine doses.

Sex differences in nicotine intravenous self-administration: A meta-analytic review

OBJECTIVE

This report reflects a meta-analysis that systematically reviewed the literature on intravenous self-administration (IVSA) of nicotine in female and male rats. The goal was to determine if sex differences in nicotine IVSA exist, estimate the magnitude of the effect, and identify potential moderators of the relationship between sex differences and nicotine consumption.

METHODS

Extensive search procedures identified 20 studies that met the inclusion criteria of employing both female and male rats in nicotine IVSA procedures. The meta-analysis was conducted on effect size values that were calculated from mean total intake or nicotine deliveries using the Hedges' unbiased g^u statistic.

RESULTS

A random effects analysis revealed that overall females self-administered more nicotine than males (weighted g^u=0.18, 95% CI [0.003, 0.34]). Subsequent moderator variable analyses revealed that certain procedural conditions influenced the magnitude of sex differences in nicotine IVSA. Specifically, higher reinforcement requirements (>FR1) and extended-access sessions (23h) were associated with greater nicotine IVSA in females versus males. Females also displayed higher nicotine intake than males when the experiment included a light cue that signaled nicotine delivery. Sex differences were not influenced by the diurnal phase of testing, dose of nicotine, or prior operant training.

CONCLUSION

Overall, the results revealed that female rats display higher levels of nicotine IVSA than males, suggesting that the strong reinforcing effects of nicotine promote tobacco use in women.

The effects of arousal on apical amplification and conscious state

Neocortical pyramidal cells can integrate two classes of input separately and use one to modulate response to the other. Their tuft dendrites are electrotonically separated from basal dendrites and soma by the apical dendrite, and apical hyperpolarization-activated currents (Ih) further isolate subthreshold integration of tuft inputs. When apical depolarization exceeds a threshold, however, it can enhance response to the basal inputs that specify the cell's selective sensitivity. This process is referred to as apical amplification (AA). We review evidence suggesting that, by regulating Ih in the apical compartments, adrenergic arousal controls the coupling between apical and somatic integration zones thus modifying cognitive capabilities closely associated with consciousness. Evidence relating AA to schizophrenia, sleep, and anesthesia is reviewed, and we assess theories that emphasize the relevance of AA to consciousness. Implications for theories of neocortical computation that emphasize context-sensitive modulation are summarized. We conclude that the findings concerning AA and its regulation by arousal offer a new perspective on states of consciousness, the function and evolution of neocortex, and psychopathology. Many issues worthy of closer examination arise.

Breakdowns of eye movement control toward smoking cues in young adult light smokers

BACKGROUND

Many studies suggest that dependent smokers have a preference or attentional bias toward smoking cues. The purpose of this study was to test the ability of infrequent non-dependent light smokers to control their eye movements by look away from smoking cues. Poor control in the lightest of smokers would suggest nicotine cue-elicited behavior occurring even prior to nicotine dependency as measured by daily smoking.

METHODS

17 infrequent non-dependent light smokers and 17 lifetime non-smokers performed an antisaccade task (look away from suddenly appearing cue) on smoking, alcohol, neutral, and dot cues.

RESULTS

The light smokers, who were confirmed light smokers and non-dependent (MFaegerström Dependency Score=0.35), were significantly worse at controlling their eye movements to smoking cues relative to both neutral cues (p<.04) and alcohol cues (p<.02). Light smokers made significantly more errors to smoking cues than non-smokers (p<.004).

CONCLUSIONS

These data suggest that prior to developing clinical symptoms of severe dependence or progressing to heavier smoking (e.g., daily smoking), the lightest of smokers are showing a specific deficit in control of nicotine cue-elicited behavior.

Nicotine reinforcement in never-smokers

RATIONALE

Global tobacco-related mortality dwarfs that of all other drugs. Nicotine is believed to be the primary agent responsible for tobacco use and addiction. However, nicotine is a relatively weak and inconsistent reinforcer in nonhumans and nicotine reinforcement has not been demonstrated in never-smokers.

OBJECTIVES

This study investigated the discriminative, subjective, and reinforcing effects of nicotine in never-smokers.

METHODS

Eighteen never-smokers (< 50 lifetime nicotine exposures) participated in a double-blind study. During a drug discrimination phase, volunteers ingested oral nicotine and placebo capsules (quasi-random order) at least 2 h apart and rated subjective effects repeatedly for 2 h after ingestion in daily sessions. Blocks of 10 sessions were continued until significant discrimination was achieved (p ≤ 0.05, binomial test; ≥ 8 of 10). Following discrimination, nicotine choice was tested by having volunteers choose which capsule set to ingest on each daily session. Successive blocks of 10 sessions were conducted until choice for nicotine or placebo met significance within each volunteer (≥ 8 of 10 sessions).

RESULTS

All 18 volunteers significantly discriminated nicotine from placebo; the lowest dose discriminated ranged from 1.0 to 4.0 mg/70 kg. Nine volunteers significantly chose nicotine (choosers) and nine significantly chose placebo (nicotine avoiders). The choosers reported predominately positive nicotine subjective effects (e.g., alert/attentive, good effects, liking), while avoiders tended to report negative effects (e.g., dizzy, upset stomach, disliking). Both choosers and avoiders attributed their choice to the qualitative nature of drug effects.

CONCLUSIONS

These results provide the first evidence that nicotine can function as a reinforcer in some never-smokers.

Genetic risks to nicotine dependence predict negative mood and affect in current non-smokers

Nicotine is the psychoactive agent involved in nicotine dependence. However, nicotine as a drug, and its effects on human psychology are largely under-investigated in genetic studies. In this study, we recruited 208 current non-smokers to evaluate the effect of nicotine and its relationship to genetic risks to nicotine dependence. Exploratory and confirmatory factor analyses, as well as measurement invariance testing, were conducted to evaluate the latent factor structures of the POMS, PANAS and DEN questionnaires across 3 nicotine doses. Structural models were used to examine the effects of nicotine and their relationship to genetic risks of nicotine dependence. We found that nicotine administration led to the change of both measurement construct and factor means, indicating the causal effect of nicotine on the psychological responses. The genotypes of rs588765 predicted the scores of the DEN Confused and Dizzy factors (p = 0.0003 and 0.001 respectively), and rs16969968 and rs588765 were associated with the PANAS Nervous factor (p = 0.006 and 0.007 respectively). Our study suggested that genetic risk of nicotine dependence is associated with acute psychological responses. The integration of psychometric analyses and dose effects could be a powerful approach for genetic study of nicotine dependence.

Young adult waterpipe smokers: Smoking behaviors and associated subjective and physiological effects

INTRODUCTION

The purpose of this pilot study was to investigate smoking behaviors and subjective and physiological effects of nicotine on young adult occasional waterpipe smokers.

METHODS

This study utilized a repeated-measures design that included one repeated factor for condition (nicotine and non-nicotine). For each participant, the sequencing of the repeated factor was assigned using random allocation. The two nicotine conditions were nicotine (0.75 g) and non-nicotine (0 g placebo) tobacco. Over the course of two weeks, twenty-two participants completed subjective (Acute Subjective Effects of Nicotine) and physiological (blood pressure, heart rate, and CO level) measures. Additional measures (QSU and MNWS-R) were used to assess for withdrawal symptoms.

SAMPLE

The participants (n=22) were young adults (23 ± 3.1years); 71% smoked waterpipe once a month in the past year and 29% smoked waterpipe 1-2 times per week. In addition, 60% reported sharing their waterpipe with friends while smoking. None of the participants reported using any other forms of tobacco products.

RESULTS

Under the nicotine condition, participants tended to smoke longer (i.e. smoking duration, p=0.004), take more puffs (p=0.03), take shorter puffs (p=0.03), and inhale less volume with each puff (p=0.02). The repeated measures analysis of the factor headrush revealed an effect of the nicotine condition (F=9.69, p<0.001, partial η(2)=0.31) and time (F=8.17, p=0.02, partial η(2)=0.30). Heart rate increased significantly across the nicotine condition (F=7.92, p=0.01, partial η(2)=0.31) and over time (F=12.64, p=0.01, partial η(2)=0.41).

CONCLUSIONS

This study demonstrates how differences between nicotine and non-nicotine waterpipe smoking are associated with changes in smoking behaviors, experiencing a headrush and an increase in heart rate.

Effects of nicotine on social cognition, social competence and self-reported stress in schizophrenia patients and healthy controls

More than 80 % of patients diagnosed with schizophrenia are nicotine-dependent. Self-medication of cognitive deficits and an increased vulnerability to stress are discussed as promoting factors for the development of nicotine dependence. However, the effects of nicotine on social cognition and subjective stress responses in schizophrenia are largely unexplored. A 2 × 2-factorial design (drug × group) was used to investigate the effects of nicotine versus placebo in smoking schizophrenia patients and healthy controls after 24 h of abstinence from smoking. Participants performed a facial affect recognition task and a semi-standardized role-play task, after which social competence and self-reported stress during social interaction were assessed. Data analysis revealed no significant group differences in the facial affect recognition task. During social interaction, healthy controls showed more non-verbal expressions and a lower subjective stress level than schizophrenia patients. There were no significant effects of nicotine in terms of an enhanced recognition of facial affect, more expressive behaviour or reduced subjective stress during social interaction. While schizophrenia patients unexpectedly recognized facial affect not significantly worse than healthy controls, the observed group differences in subjective stress and non-verbal expression during social interaction in the role-play situation are in line with previous findings. Contrary to expectations derived from the self-medication hypothesis, nicotine showed no significant effects on the dependent variables, perhaps because of the dosage used and the delay between the administration of nicotine and the performance of the role-play.

Acute mood effect of donepezil in young, healthy volunteers

OBJECTIVE

Chronic use of the acetylcholinesterase inhibitor donepezil has been found to improve mood or to induce mania/hypomania in many neuropsychiatric patients with altered cholinergic and dopaminergic tone. Our aim was to determine whether acutely administered donepezil would alter mood in volunteers with no such alterations.

METHODS

This investigation was a double-blind, crossover design study of 15 young, healthy male participants who were allocated in random order to three oral treatments: placebo and 5-mg and 7.5-mg donepezil (doses which exert clinical and acute cognitive effects without considerable peripheral side effects). At the theoretical peak-plasma concentrations of donepezil, volunteers rated how they felt on validated questionnaires, which included various dimensions of subjective feelings. We also assessed changes in brain-derived neurotrophic factor (BDNF), which is increased by donepezil after chronic regimes and is related to modulation of mood.

RESULTS

Donepezil significantly increased ratings of vigour and anxiety symptoms (medium effect sizes). No changes in bodily symptoms or BDNF were observed.

CONCLUSIONS

Acute donepezil administration in participants with unaltered cholinergic and dopaminergic tone led to positive and negative changes in affect. These results call for further research on the direct mood effects of donepezil.

Pain, nicotine, and smoking: research findings and mechanistic considerations

Tobacco addiction and chronic pain represent 2 highly prevalent and comorbid conditions that engender substantial burdens upon individuals and systems. Interrelations between pain and smoking have been of clinical and empirical interest for decades, and research in this area has increased dramatically over the past 5 years. We conceptualize the interaction of pain and smoking as a prototypical example of the biopsychosocial model. Accordingly, we extrapolated from behavioral, cognitive, affective, biomedical, and social perspectives to propose causal mechanisms that may contribute to the observed comorbidity between these 2 conditions. The extant literature was 1st dichotomized into investigations of either effects of smoking on pain or effects of pain on smoking. We then integrated these findings to present a reciprocal model of pain and smoking that is hypothesized to interact in the manner of a positive feedback loop, resulting in greater pain and increased smoking. Finally, we proposed directions for future research and discussed clinical implications for smokers with comorbid pain disorders. We observed modest evidence that smoking may be a risk factor in the multifactorial etiology of some chronically painful conditions and that pain may come to serve as a potent motivator of smoking. We also found that whereas animal studies yielded consistent support for direct pain-inhibitory effects of nicotine and tobacco, results from human studies were much less consistent. Future research in the emerging area of pain and smoking has the potential to inform theoretical and clinical applications with respect to tobacco smoking, chronic pain, and their comorbid presentation. (PsycINFO Database Record (c) 2011 APA, all rights reserved).

Review of pharmacological treatment in mood disorders and future directions for drug development

After a series of serendipitous discoveries of pharmacological treatments for mania and depression several decades ago, relatively little progress has been made for novel hypothesis-driven drug development in mood disorders. Multifactorial etiologies of, and lack of a full understanding of, the core neurobiology of these conditions clearly have contributed to these development challenges. There are, however, relatively novel targets that have raised opportunities for progress in the field, such as glutamate and cholinergic receptor modulators, circadian regulators, and enzyme inhibitors, for alternative treatment. This review will discuss these promising new treatments in mood disorders, the underlying mechanisms of action, and critical issues of their clinical application. For these new treatments to be successful in clinical practice, it is also important to design innovative clinical trials that identify the specific actions of new drugs, and, ideally, to develop biomarkers for monitoring individualized treatment response. It is predicted that future drug development will identify new agents targeting the molecular mechanisms involved in the pathophysiology of mood disorders.

[Pharmacotherapeutic treatment strategies for smoking cessation]

Regular tobacco smoking occurs in about 35% of the male and 25% of the female German population. Individual attempts to independently quit smoking and to remain abstinent for 1 year have been shown to be successful in less than 5% of cases. This rate can be doubled by means of individual consulting and cognitive-behavioral interventions and additional pharmacological treatment might increase abstinence rates up to 25%. Apart from nicotine substitution (e.g. transdermal, oral and inhalative applications) and bupropion, recent studies have shown beneficial effects of varenicline for smoking cessation and abstinence. Varenicline, a selective partial nicotinergic agonist, has been specifically developed for the purpose of smoking cessation. Currently available data suggest that varenicline is more effective compared to nicotine substitution therapy and bupropion, increasing the abstinence likelihood by a factor of 2.3 compared to a placebo. Recent data regarding anti-nicotine vaccines suggest that this approach might yield a comparable treatment outcome and probably even better relapse-preventing effects than conventional psychopharmacological strategies. The first anti-nicotine vaccines are expected to be approved by national authorities within the forthcoming 1-2 years.

Effects of 24 hours of tobacco withdrawal and subsequent tobacco smoking among low and high sensation seekers

INTRODUCTION

Previous studies have indicated that high sensation seekers are more sensitive to the reinforcing effects of nicotine, initiate smoking at an earlier age, and smoke greater amounts of cigarettes. This study examined the influence of sensation-seeking status on tobacco smoking following deprivation in regular tobacco users.

METHODS

Twenty healthy tobacco-smoking volunteers with low or high impulsive sensation-seeking subscale scores completed 2 consecutive test days per week for 3 consecutive weeks. Each week, a range of self-report, performance, and cardiovascular assessments were completed during ad libitum smoking on Day 1 and before and after the paced smoking of a tobacco cigarette containing 0.05, 0.6, or 0.9 mg of nicotine following 24 hr of tobacco deprivation on Day 2. In addition, self-administration behavior was analyzed during a 2-hr free access period after the initial tobacco administration.

RESULTS

In high sensation seekers, tobacco smoking independent of nicotine yield ameliorated deprivation effects, whereas amelioration of deprivation effects was dependent on nicotine yield among low sensation seekers. However, this effect was limited to a small subset of measures. Subsequent cigarette self-administration increased in a nicotine-dependent manner for high sensation seekers only.

CONCLUSIONS

Compared with low sensation seekers, high sensation seekers were more sensitive to the withdrawal relieving effects of nonnicotine components of smoking following 24 hr of deprivation on selective measures and more sensitive to nicotine yield during subsequent tobacco self-administration. These results are consistent with studies suggesting that factors driving tobacco dependence may vary as a function of sensation-seeking status.

If the data contradict the theory, throw out the data: Nicotine addiction in the 2010 report of the Surgeon General

The reports of US Surgeon General on smoking are considered the authoritative statement on the scientific state of the art in this field. The previous report on nicotine addiction published in 1988 is one of the most cited references in scientific articles on smoking and often the only citation provided for specific statements of facts regarding nicotine addiction. In this commentary we review the chapter on nicotine addiction presented in the recent report of the Surgeon General. We show that the nicotine addiction model presented in this chapter, which closely resembles its 22 years old predecessor, could only be sustained by systematically ignoring all contradictory evidence. As a result, the present SG's chapter on nicotine addiction, which purportedly "documents how nicotine compares with heroin and cocaine in its hold on users and its effects on the brain," is remarkably biased and misleading.

Subjective effects of transdermal nicotine among nonsmokers

The subjective experience of nicotine, which may be influenced by personality traits as well as environmental factors, may be important for understanding the factors associated with the initiation and maintenance of nicotine dependence. The present study examined the effects of 7 mg transdermal nicotine among a relatively large sample (n = 91; 44 women) of college-aged nonsmokers. Using a placebo controlled, double-blind, within-subjects design, nicotine's effects were examined at rest and again after participants completed a sustained attention task. Sex and personality factors (Behavioral Inhibition and Behavioral Approach; BIS/BAS Scales; Carver & White, 1994) were examined as potential moderators. Overall, the effects of nicotine were generally modest and unpleasant. In the context of the cognitive task, nicotine increased nausea and negative affect but reduced fatigue, relative to placebo. In contrast, effects of nicotine during the initial 4 hr of patch administration, in which participants were in their natural environments, were moderated by individual differences in behavioral approach. Neither behavioral inhibition nor gender reliably moderated any subjective effects of nicotine. The present work suggests transdermal nicotine exerts only modest, mostly negative effects among nonsmokers. Future work should examine both contextual and personality moderators in large samples of participants who are exposed to nicotine through multiple routes of administration.

Cigarette smoking as a coping strategy: negative implications for subsequent psychological distress among lesbian, gay, and bisexual youths

OBJECTIVE

The heightened risk of cigarette smoking found among lesbian, gay, and bisexual (LGB) youths may be because smoking serves as a coping strategy used to adapt to the greater stress experienced by LGB youths. The current report examines whether smoking moderates the relation between stress and subsequent psychological distress, and whether alternative coping resources (i.e., social support) moderate the relation between smoking and subsequent distress.

METHOD

An ethnically diverse sample of 156 LGB youths was followed longitudinally for 1 year.

RESULTS

Significant interactions demonstrated that smoking amplified the association between stress and subsequent anxious distress, depressive distress, and conduct problems. Both friend and family support buffered the association between smoking and subsequent distress.

CONCLUSIONS

Smoking has negative implications for the distress of LGB youths, especially those reporting high levels of stress or few supports. Interventions and supportive services for LGB youths should incorporate smoking cessation to maximally alleviate distress.

Subjective effects to cannabis are associated with use, abuse and dependence after adjusting for genetic and environmental influences

BACKGROUND

Previous reports in adults have suggested that the effects experienced after cannabis use can be described in terms of positive and negative subtypes that are heritable and are associated with abuse and dependence. This study extends existing research by inclusion of adolescents and young adults in an offspring of twins design which makes it possible to take into account genetic and environmental risks for substance use disorder.

METHODS

Data were collected from 725 twin members of the Vietnam Era Twin Registry, 839 of their 12-32 year old biological offspring and 427 mothers. Offspring who had ever used cannabis (n=464) were asked the degree to which they typically experienced 13 subjective effects shortly after using cannabis. Latent class analysis (LCA) was used to derive subjective effect classes and logistic regression models were computed to test associations between subjective effect class and heavy cannabis use, abuse and dependence after adjusting for familial risk and psychopathology and sociodemographics.

RESULTS

The best fitting LCA model included 4 classes of responders which were characterized as 'high responders' (39%), 'positive responders' (28%), 'mixed/relaxed' (22%), and 'low responders' (11%). Compared to low responders, members of other classes were heavier users (OR range 3.0-11.8). Compared to mixed/relaxed responders and positive responders, high responders were more likely to have cannabis abuse and dependence.

CONCLUSIONS

Subjective reactions to cannabis use are associated with use to heavy use, abuse and dependence in adolescents and young adults. This association exists above and beyond the genetic vulnerability for problem cannabis use.

Discriminative stimulus effects of nicotine in humans

Behavioral discrimination procedures clearly demonstrate that nicotine elicits interoceptive stimulus effects in humans that are malleable by various pharmacological manipulations as well as by some behavioral manipulations. The parameters of nicotine discrimination and both chronic and acute factors that may alter discrimination behavior are addressed in this chapter, which emphasizes research by the author involving nicotine delivered by nasal spray. Human discrimination of nicotine is centrally mediated, as the central and peripheral nicotine antagonist mecamylamine blocks discrimination but the peripheral antagonist trimethaphan does not. The threshold dose for discrimination of nicotine via spray appears to be very low in smokers as well as nonsmokers. Because smoked tobacco delivers nicotine more rapidly than spray, the threshold dose of nicotine via smoking is probably even lower. In terms of individual differences, smokers may become tolerant to the discriminative stimulus effects of higher nicotine doses but not of low doses. Men may be more sensitive than women to nicotine's discriminative stimulus effects, consistent with other research suggesting that nicotine is more reinforcing in men than in women. Other potential individual differences in nicotine discrimination have not been clearly tested, but may include genetics, obesity, and dependence on other drugs. Acute environmental factors that alter nicotine discrimination include the specific training and testing conditions, pointing to the need for careful control over such conditions during research. Other factors, such as concurrent acute use of alcohol or caffeine, do not appear to alter nicotine discrimination, suggesting that changes in nicotine discrimination are not likely explanations for the association of smoking behavior with use of those drugs. Concurrent physical activity also does not appear to alter nicotine discrimination, indicating that results from studies of discrimination in subjects at quiet rest, the standard approach in this research, generalize well to discrimination in subjects engaged in various activities, as often occurs in the natural environment. Future research should more clearly examine the potential role of nicotine's discriminative stimulus effects in nicotine reinforcement and determine the generalizability of these findings to nicotine delivered by other means, particularly tobacco smoking.

Variability in initial nicotine sensitivity due to sex, history of other drug use, and parental smoking

Initial sensitivity to nicotine's effects during early exposure to tobacco may relate to dependence vulnerability. We examined the association of initial nicotine sensitivity with individual difference factors of sex, other drug use history (i.e. cross-tolerance or cross-sensitization), and parental smoking status in young adult nonsmokers (N=131). Participants engaged in 4 sessions, the first 3 to assess the dose-response effects of nasal spray nicotine (0, 5, 10 microg/kg) on rewarding, mood, physiological, sensory processing, and performance effects, and the fourth to assess nicotine reinforcement using a choice procedure. Men had greater initial sensitivity than women to some self-reported effects of nicotine related to reward and incentive salience and to impairment in sensory processing, but men and women did not differ on most other effects. Prior marijuana use was associated with greater nicotine reward, nicotine reinforcement was greater in men versus women among those with prior marijuana use, and having parents who smoked was related to increased incentive salience. However, history of other drug use and parental smoking were not otherwise associated with initial nicotine sensitivity. These findings warrant replication with other methods of nicotine administration, especially cigarette smoking, and in more diverse samples of subjects naïve to nicotine. Yet, they suggest that sex differences in initial sensitivity to nicotine reward occur before the onset of dependence. They also suggest that parental smoking may not increase risk of nicotine dependence in offspring by altering initial nicotine sensitivity, and that cross-tolerance between other drugs and nicotine may not be robust in humans.

Gene and gene by sex associations with initial sensitivity to nicotine in nonsmokers

Genetic variation may influence initial sensitivity to nicotine (i.e. during early tobacco exposure), perhaps helping to explain differential vulnerability to nicotine dependence. This study explored associations of functional candidate gene polymorphisms with initial sensitivity to nicotine in 101 young adult nonsmokers of European ancestry. Nicotine (0, 5, 10 microg/kg) was administered through nasal spray followed by mood, nicotine reward (e.g. 'liking') and perception (e.g. 'feel effects') measures, physiological responses, sensory processing (prepulse inhibition of startle), and performance tasks. Nicotine reinforcement was assessed in a separate session using a nicotine versus placebo spray choice procedure. For the dopamine D4 receptor [DRD4 variable number of tandem repeats (VNTR)], presence of the 7-repeat allele was associated with greater aversive responses to nicotine (decreases in 'vigor', positive affect, and rapid information processing; increased cortisol) and reduced nicotine choice. Individuals with at least one DRD4 7-repeat allele also reported increased 'feel effects' and greater startle response, but in men only. Other genetic associations were also observed in men but not women, such as greater 'feel effects' and anger, and reduced fatigue, in the dopamine D2 receptor (DRD2 C957T single nucleotide polymorphism) TT versus CT or CC genotypes. Very few or no significant associations were seen for the DRD2/ANKK1 TaqIA polymorphism, the serotonin transporter promoter VNTR or 5HTTLPR (SLC6A4), the dopamine transporter 3' VNTR (SLC6A3), and the mu opioid receptor A118G single nucleotide polymorphism (mu opioid receptor polymorphism 1). Although these results are preliminary, this study is the first to suggest that genetic polymorphisms related to function in the dopamine D4, and perhaps D2, receptor may modulate initial sensitivity to nicotine before the onset of dependence and may do so differentially between men and women.

Initial nicotine sensitivity in humans as a function of impulsivity

RATIONALE

Impulsivity is related to greater risk of nicotine dependence, perhaps by enhancing sensitivity to nicotine's reinforcing and rewarding effects during initial smoking experiences.

OBJECTIVE

We examined the influence of impulsivity characteristics on acute sensitivity to nicotine reward, reinforcement, and other effects in 131 young adult nonsmokers.

MATERIALS AND METHODS

Participants engaged in four sessions: the first three to assess dose-response effects of nasal spray nicotine (0, 5, 10 microg/kg) on reward, as well as mood, physiological, and performance effects, and the fourth to assess nicotine reinforcement using a choice procedure. Five impulsivity factors, derived from factor analysis of self-report (e.g., Barratt Impulsivity Scale, Sensation-Seeking Scale, Novelty seeking) and computer (stop-go, delay discounting, probability discounting) measures of impulsivity, were labeled "novelty seeking", "response disinhibition", "extraversion", "inhibition", and "probability/delay discounting".

RESULTS

The associations of novelty seeking with nicotine reinforcement and reward tended to move in opposite directions by sex, generally being directly related in men but inversely or unrelated in women. Similarly, response disinhibition was associated with reward and some mood responses to nicotine that differed by sex. Extraversion was inversely associated with nicotine reinforcement. Characteristics loading on to the other impulsivity factors had little association with nicotine sensitivity.

CONCLUSIONS

These results are preliminary, but they suggest that characteristics broadly related to impulsivity, especially novelty seeking and response disinhibition, are associated with initial sensitivity to some effects of acute nicotine, including reinforcement and reward, and may do so differentially between men and women.

Addiction to the nicotine gum in never smokers

Background

Addiction to nicotine gum has never been described in never smokers or in never users of tobacco.

Methods

Internet questionnaire in 2004–2006 in a self-selected sample of 434 daily users of nicotine gum. To assess dependence on nicotine gum, we used modified versions of the Nicotine Dependence Syndrome Scale (NDSS), the Fagerström Test for Nicotine Dependence and the Cigarette Dependence Scale.

Results

Five never smokers used the nicotine gum daily. They had been using the nicotine gum for longer than the 429 ever smokers (median = 6 years vs 0.8 years, p = 0.004), and they had higher NDSS-gum Tolerance scores (median = 0.73 vs = -1.0, p = 0.03), a difference of 1.5 standard deviation units. Two never smokers had never used smokeless tobacco, both answered "extremely true" to: "I use nicotine gums because I am addicted to them", both "fully agreed" with: "after a few hours without chewing a nicotine gum, I feel an irresistible urge to chew one" and: "I am a prisoner of nicotine gum".

Conclusion

This is to our knowledge the first report of addiction to nicotine gum in never users of tobacco. However, this phenomenon is rare, and although the long-term effect of nicotine gum is unknown, this product is significantly less harmful than tobacco.

Reevaluating the nicotine delivery kinetics hypothesis

RATIONALE

The view of smoking as an addiction to nicotine implies that nicotine is an addictive drug and a primary reinforcer. However, nicotine other than in tobacco does not appear to be very rewarding for smokers. This potential anomaly to the nicotine addiction thesis is resolved by the proposition that the reward associated with smoking depends on "high-nicotine boli." According to the nicotine delivery kinetics hypothesis, smoked nicotine reaches the brain in 5-10 s in high concentrations, which provide reinforcing "hits" of nicotine to the brain.

OBJECTIVES

Because of its essential role in the nicotine addiction thesis, this review set out to examine the current empirical basis of the nicotine delivery kinetics hypothesis.

MATERIALS AND METHODS

We reviewed studies that bear on two questions: First, does nicotine from cigarettes reach the brain significantly faster than from other nicotine delivery devices? Second, is there a relationship between delivery kinetics and any rewarding effects of nicotine?

RESULTS

There is little empirical support for the nicotine delivery kinetics hypothesis. Several studies found that arterial nicotine levels associated with smoking are much lower than predicted by the nicotine delivery kinetics thesis and not higher than with other nicotine delivery devices. More importantly, comparisons of nicotine delivery devices with varying speeds of delivery do not suggest any correlation between nicotine delivery profile and subjective reward.

CONCLUSIONS

This review indicates that the wide endorsement of the nicotine delivery kinetics hypothesis is unjustified. Critical research is required to resolve the anomalies within the nicotine addiction theory of smoking.

Euphoriant effects of nicotine in smokers: fact or artifact?

RATIONALE

The claim that nicotine in cigarettes is euphoriant to smokers is largely based on two studies (Pomerleau and Pomerleau, Psychopharmacology, 108:460-465, 1992; Tobacco Control, 3:374, 1994) in which smokers were instructed to respond to sensations of rush, buzz, or high while smoking low-nicotine or regular cigarettes. However, the assumption that these sensations are pleasurable was not tested and may have biased the results.

OBJECTIVES

The aim of this study was to re-examine the claim that smoked nicotine is euphoriant to smokers.

METHODS

Study 1 surveyed the frequency and pleasantness of the smoking-related sensations of rush, buzz, and high in a sample of smokers. Study 2 replicated Pomerleau and Pomerleau (Psychopharmacology, 108:460-465, 1992) with two sets of instruction. One set, as in the original study, defined these sensations as pleasurable, whereas the other defined them as unpleasant.

RESULTS

Study 1 found that whereas rush and high were perceived as pleasant, buzz was unpleasant to most smokers. Study 2 found that under both sets of instructions, smokers reported more sensations when smoking the regular, as compared to the low-nicotine cigarette. Additionally, the sensations of rush, buzz, and high were rated as more pleasant under the pleasant instructions as compared to the unpleasant instructions. Finally, in the pleasant instructions condition, many participants reported having pressed the button to indicate a pleasurable sensation despite having actually experienced that sensation as unpleasant.

CONCLUSIONS

Our results suggest that the findings of Pomerleau and Pomerleau (Psychopharmacology, 108:460-465, 1992; Tobacco Control, 3:374, 1994) may have been biased by the experimental instructions and cannot be taken as evidence that smoked nicotine is euphoriant to smokers.

Subjective effects and the main reason for smoking in outpatients with schizophrenia: a case-control study

This study examines in daily smokers (1) subjective effects and main reason for smoking after controlling for nicotine dependence level in 100 controls and 173 patients with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, schizophrenia and (2) the association of specific subjective effects and schizophrenia symptoms. The subjective effects and the main reason for smoking were studied using a questionnaire and the schizophrenia symptoms with the Positive and Negative Syndrome Scale. Proportions were compared by odds ratios controlling for the effects of sex, age, education, and level of nicotine dependence by logistic regression. Schizophrenia was strongly associated with subjective effects of cheerfulness, agility, alertness, concentration, and calmness. In patients with schizophrenia, a cheerfulness effect was associated with higher depressive symptoms; a calming effect, with higher anxiety symptoms; and a sociability effect, with lower negative symptoms. Compared with controls, desire for calmness as the main reason for smoking was more frequent in patients with schizophrenia. These survey data call for confirmation through experimental studies and may help in the design of more focused smoking cessation programs for these patients.