Initial tobacco use episodes in children and adolescents: current knowledge, future directions

Impact of acute nicotine exposure on monoaminergic systems in adolescent and adult male and female rats

Adolescence is a period of risk for beginning tobacco addiction. Differential neural response to nicotine in adolescents vs. adults may help explain the increased vulnerability to nicotine self-administration seen with adolescent onset. We indexed the effects of acute nicotine ditartrate (0.4 mg/kg, salt weight) administration on dopamine (DA) and serotonin (5HT) as well as the DA metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in several brain regions (nucleus accumbens, striatum and frontal cortex) of 6-week old (adolescent) and 10-week old (young adult) Sprague-Dawley rats. When nicotine was administered DA concentrations in the accumbens were significantly higher in adults than in adolescents, whereas there was no age-related difference without nicotine. However neither age group showed a significant effect of nicotine vs. age-matched controls. DA turnover in the accumbens was significantly greater in adolescent females in response to nicotine, but adult females did not show this effect and neither did males of either age group. DA turnover in the striatum was significantly higher in adolescents than adults regardless of nicotine administration. In the frontal cortex, there was a more complex effect. Without nicotine, adult male rats had higher DA concentrations than adolescent males, whereas female rats did not differ from adolescent to adult ages. When given nicotine, the age effect was no longer seen in males. However, there was not a significant effect of nicotine vs. age-matched controls in either age group. No age or nicotine effects were seen in females. 5HT in the accumbens was significantly increased by nicotine administration in adults but not in adolescents. Altered neural responsivity of adolescents to nicotine-induced neural effects particularly in accumbens DA and 5HT may be related to the increased nicotine dose concentrations they self-administer.

Multifactorial Etiology of Adolescent Nicotine Addiction: A Review of the Neurobiology of Nicotine Addiction and Its Implications for Smoking Cessation Pharmacotherapy

Nicotine is the primary pharmacologic component of tobacco, and its highly addictive nature is responsible for its widespread use and significant withdrawal effects that result in challenges to smoking cessation therapeutics. Nicotine addiction often begins in adolescence and this is at least partially attributed to the fact that adolescent brain is most susceptible to the neuro-inflammatory effects of nicotine. There is increasing evidence for the involvement of microglial cells, which are the brain's primary homeostatic sensor, in drug dependence and its associated behavioral manifestations particularly in the adolescent brain. A hallmark of neuro-inflammation is microglial activation and activation of microglia by nicotine during adolescent development, which may result in long-term addiction to nicotine. This non-systematic review examines multifactorial etiology of adolescent nicotine addiction, neurobiology of nicotine addiction and the potential mechanisms that underlie the effects of nicotine on inflammatory signaling in the microglia, understanding how nicotine affects the adolescent brain. We speculate, that modulating homeostatic balance in microglia, could have promising therapeutic potential in withdrawal, tolerance, and abstinence-related neural adaptations in nicotine addiction, in the adolescent brain. Further, we discuss nicotine addiction in the context of the sensitization-homeostasis model which provides a theoretical framework for addressing the potential role of microglial homeostasis in neural adaptations underlying nicotine abuse.

Adolescent Use and Perceptions of JUUL and Other Pod-Style e-Cigarettes: A Qualitative Study to Inform Prevention

JUUL, a discrete pod-style e-cigarette, popular among adolescents, delivers high levels of nicotine. Limited research has assessed social and environmental influences that contribute to use of JUUL and other pod-style devices. We examined how these factors, as well as individual characteristics, shape adolescent use. Twenty-nine middle and high school students participated in six focus groups in June 2019 (58.6% female, 65.5% White, 27.6% Hispanic). Groups were stratified by e-cigarette use status and grade to understand perceptions and experiences among groups. Transcripts were coded using thematic analysis for individual, social, and environmental factors contributing to use. Users (n = 13) described their first experience with JUUL as mostly negative, mentioning reactions such as burning in the throat, coughing, wheezing, and headaches. Despite a negative first experience, stress relief and addiction were mentioned as reasons for continued use. Users and non-users identified vaping as a source of disruption to their daily life. Social factors included peer and parental influences, lack of support for quitting, and accessibility. Environmental factors included contrasting messages about long- and short-term health effects of e-cigarettes, as well as a lack of school vaping policy enforcement, health education, medical screenings, and cessation resources. Findings highlight the complex social system that influences adolescent e-cigarette use and have important implications for school and community responses. Strategies to prevent or reduce use may include reviewing existing school tobacco policies, providing counseling and cessation resources, training staff, and increasing knowledge through public education campaigns.

Subjective responses predict d-amphetamine choice in healthy volunteers

BACKGROUND

It is commonly believed that drugs, including stimulants, are used recreationally because of their ability to induce pleasurable subjective effects. However, recreational drug use sometimes occurs in the absence of positive subjective effects, suggesting that other factors contribute. Here, we examine the extent to which the direct subjective effects of amphetamine, a commonly misused stimulant, predict subsequent choice of the drug vs placebo.

METHODS

Healthy adults (N = 112) participated in a five-session amphetamine choice study. On the first four sessions, participants sampled either 20 mg d-amphetamine or placebo in color-coded capsules two times each. On the fifth session, they chose which color (d-amphetamine or placebo) they preferred. We examined the choice of drug vs placebo in relation to demographic characteristics, baseline mood states, personality and subjective and cardiovascular responses to acute administration of the drug.

RESULTS

Eighty-one participants chose amphetamine (Choosers) while 31 chose placebo (Non-choosers). Overall, amphetamine produced typical stimulant-like effects on subjective questionnaires, and it elevated heart rate and blood pressure vs placebo. Choosers reported greater positive mood, elation and stimulant-like effects following amphetamine compared to Non-choosers. The Choosers also exhibited a greater increase in systolic blood pressure, but not heart rate. The groups did not differ on demographic characteristics, mood states before drug administration or personality.

CONCLUSIONS

These findings support the idea that pleasurable subjective responses to amphetamine, including positive mood, elation, and stimulant-like effects influence behavioral choice of the drug.

Web-Based Contingency Management for Adolescent Tobacco Smokers: A Clinical Trial

INTRODUCTION

Adolescence is a critical time when the majority of tobacco users initiate smoking. Contingency management for adolescent smoking cessation has shown promise in previous studies, but efficacy following removal of contingencies is not well understood. This study examined a remote form of contingency management among non-treatment-seeking adolescent smokers.

METHODS

Participants (N = 127) submitted breath carbon monoxide (CO) three times daily throughout a 42-day program. For this randomized trial, participants in the active condition (n = 63) were reinforced for providing CO measurements on schedule and below a set criterion, whereas those in the control condition (n = 64) were reinforced for providing CO measurements on schedule. Self-reported smoking and urinary cotinine levels were collected at several timepoints.

RESULTS

Active condition showed greater within-group reductions in CO levels relative to control condition, but not at 3- or 6-month follow-up. Active condition reported significantly less smoking during treatment compared to control condition, but not at follow-up. There were no significant differences for urinary cotinine. Overall treatment adherence was low, with only 37% and 51% of possible CO samples being submitted among active and control, respectively. Poor treatment adherence may explain the disparity between CO and cotinine results, and poor follow-up treatment efficacy.

CONCLUSIONS

This study replicates feasibility of a remote form of contingency management for adolescent smoking. CO results suggest active condition reduced smoking within group, but treatment adherence and posttreatment efficacy was poor. Future research should focus on increasing adherence for this type of program among adolescent smokers.

IMPLICATIONS

This study demonstrates feasibility of a remote form of contingency management therapy for smoking cessation among adolescents, while providing posttreatment efficacy data. Within-group efficacy of this form of treatment is suggested, but treatment adherence and follow-up efficacy were poor. This study underscores the need for further development of contingency management therapy for adolescent smoking cessation, which emphasizes better treatment adherence and posttreatment efficacy.

Drug instrumentalization

Psychoactive drugs with addiction potential are widely used by people of virtually all cultures in a non-addictive way. In order to understand this behaviour, its population penetrance, and its persistence, drug instrumentalization was suggested as a driving force for this consumption. Drug instrumentalization theory holds that psychoactive drugs are consumed in a very systematic way in order to make other, non-drug-related behaviours more efficient. Here, we review the evolutionary origin of this behaviour and its psychological mechanisms and explore the neurobiological and neuropharmacological mechanisms underlying them. Instrumentalization goals are discussed, for which an environmentally selective and mental state-dependent consumption of psychoactive drugs can be learned and maintained in a non-addictive way. A small percentage of people who regularly instrumentalize psychoactive drugs make a transition to addiction, which often starts with qualitative and quantitative changes in the instrumentalization goals. As such, addiction is proposed to develop from previously established long-term drug instrumentalization. Thus, preventing and treating drug addiction in an individualized medicine approach may essentially require understanding and supporting personal instrumentalization goals.

Non-pharmacological factors that determine drug use and addiction

Based on their pharmacological properties, psychoactive drugs are supposed to take control of the natural reward system to finally drive compulsory drug seeking and consumption. However, psychoactive drugs are not used in an arbitrary way as pure pharmacological reinforcement would suggest, but rather in a highly specific manner depending on non-pharmacological factors. While pharmacological effects of psychoactive drugs are well studied, neurobiological mechanisms of non-pharmacological factors are less well understood. Here we review the emerging neurobiological mechanisms beyond pharmacological reinforcement which determine drug effects and use frequency. Important progress was made on the understanding of how the character of an environment and social stress determine drug self-administration. This is expanded by new evidence on how behavioral alternatives and opportunities for drug instrumentalization generate different patterns of drug choice. Emerging evidence suggests that the neurobiology of non-pharmacological factors strongly determines pharmacological and behavioral drug action and may, thus, give rise for an expanded system's approach of psychoactive drug use and addiction.

Factors Associated with the Initial Sensations of Smoking among Smokers with Mental Illness

People with mental illnesses (MI) have a disproportionate smoking prevalence and associated disease burden. Smoking initiation among people with MI is poorly understood. However, the sensations experienced during smoking initiation predict continued smoking and nicotine dependence. Yet, few studies have examined the initial experiences of smoking among people with MI. Thus, the aim of this study was to explore factors associated with the initial sensations of smoking in people with MI. Smokers in an inpatient psychiatric facility (n = 123) were surveyed. Data obtained included information on demographics, smoking and secondhand smoke (SHS) exposure, psychiatric diagnoses, and sensations of initial smoking. Spearman correlations explored associations among initial smoking sensation variables; and binary logistic regression analyses examined the associations between study variables and groupings derived from initial sensations (i.e., "pleasant + buzz," "unpleasant + buzz," and "all" sensations). The most frequently reported initial smoking sensation was feeling dizzy (87%) and there were low to moderate correlations between unpleasant (e.g., cough, sick, nervous) and pleasant (e.g., good, relaxed) sensations. In logistic regression analyses, having higher perceived SHS exposure was significantly associated with the "pleasant + buzz" sensation grouping; and lower past week SHS exposure was associated with the "unpleasant + buzz" sensation grouping; but, no variables were associated with "all" sensation group. Initial smoking sensations are an uncharted avenue of exploration in understanding smoking initiation among people with MI. SHS exposure may be an important factor associated with the report of both unpleasant and pleasant initial sensations. Future studies are needed to further explore initial sensations in relation to the context of smoking initiation among people with MI.

Sexual and Gender Minority College Students and Tobacco Use in Texas

Introduction

Most research regarding sexual and gender minority (SGM) populations is limited to examination of cigarette or general tobacco use or does not examine heterogeneity across SGM groups other than lesbian or gay and bisexual individuals. This study examined differences in the odds of current use and age of initiation of five tobacco/nicotine products among three groups of SGM young adults who self-identified as (1) gay or lesbian, (2) bisexual, and (3) queer, transgender, or "other," compared to their heterosexual peers.

Methods

Participants were 4252 college students aged 18-29 years from 24 colleges in Texas who completed an online tobacco use survey. Multilevel logistic regression models were used to examine the odds of SGM participants currently using each tobacco product. Multilevel linear regression models were used to examine the association of current product users' SGM status with self-reported age of each product's initiation. All models were adjusted for sociodemographic factors and accounted for students clustered within each college.

Results

At least one SGM group had significantly greater odds of currently using every tobacco product type compared to heterosexual participants, except hookah. There were few differences across groups in age of initiation. However, queer, transgender, and "other-" identified participants initiated e-cigarettes 1.34 years younger than heterosexual participants, and bisexual participants initiated smokeless tobacco 3.66 years younger than heterosexual participants.

Conclusions

Findings highlight some significant tobacco use disparities among SGM young adults compared to their heterosexual peers. Longitudinal studies with larger group sizes will identify prospective predictors of sustained SGM-related tobacco use disparities.

Implications

This study extends the current literature by including the sexual and gender minority identity options of queer, transgender, and "other," highlighting disparities in tobacco use between young adults in these subgroups compared to their heterosexual peers, particularly in noncigarette tobacco product use. Findings underscore the need for the Food and Drug Association and other health agencies to tailor health communication efforts specific to sexual and gender minority populations pertaining to the risks and harms surrounding tobacco product use.

Social and anxiety-like behaviors contribute to nicotine self-administration in adolescent outbred rats

Both emotional and social traits interact with genetic factors to influence smoking behavior. We previously established a socially acquired nicotine intravenous self-administration model where social learning of a nicotine-associated odor cue reversed conditioned flavor aversion and promoted nicotine intake. In this study, we first phenotyped ~800 adolescent heterogeneous stock rats in open field, novel object interaction, social interaction, elevated plus maze, and marble burying behaviors. These rats were then phenotyped on socially acquired nicotine self-administration. We found 243 significant correlations between different behavioral tests. Principal component regression analysis found that ~10-20% of the variance in nicotine-related measures, such as intake during the first or the last three fixed-ratio sessions, the progressive ratio session, and reinstatement behavior, can be explained by variations in behavioral traits. Factors corresponding to social behavior and anxiety were among the strongest predictors of nicotine intake and reinstatement of nicotine-seeking behavior. We also found many sex differences in behavioral measures. These data indicated that the genetic diversity of this population, in combination with social behaviour and anxiety, are significant contributors to the divergent nicotine self-administration behavior and indicated a high probability of discovering sex-specific genetic mechanisms for nicotine intake in future genome-wide association studies.

Associations Between Initial Subjective Experiences with Tobacco and Self-Reported Recent Use in Young Adulthood

BACKGROUND

Youth tobacco use behaviors are predictive of patterns in adulthood and effect long-term health outcomes. Yet, few studies have examined the effect of initial subjective experiences (ISEs) during first tobacco use, which has been found to be an indicator of individuals. sensitivity to nicotine and vulnerability to dependence.

OBJECTIVE

The present study aimed to determine the prevalence of ISEs across a variety of tobacco products, evaluate the factor structure of ISEs by first tobacco product used, and examine the relationship between ISEs and recent (30-day) use of tobacco products across time, using a university sample.

METHODS

Exploratory factor analyses were conducted to identify latent factors present with respect to items measuring ISEs with tobacco, separately by tobacco product (e.g. cigarettes, cigars, hookah, e-cigarettes). Factor scores for positive and negative ISEs were calculated. Multiple logistic regression analyses were conducted to examine associations between ISEs and recent use of each tobacco product, adjusted for age at first use, sex, race/ethnicity, and cohort.

RESULTS

ISEs differ by the first tobacco product used. Associations between factor scores for positive and negative ISEs and recent use were found across a variety of tobacco products. Overall, positive ISEs were more strongly associated with recent use, relative to negative ISEs.

CONCLUSIONS

Further research is needed to identify genetic and biological pathways and social contexts influencing initial subjective experiences with tobacco use, in efforts to delay the initiation for tobacco use and reduce risk for continued use among young adults.

A Study on Tobacco Use Among School Children

Tobacco use among school children is becoming a serious problem. The early age of initiation underscores the urgent need to intervene and protect this vulnerable group from falling prey to this addiction. The present study was undertaken to assess (i) the prevalence and pattern of tobacco use among school children in India (ii) relation of tobacco use prevalence and pattern with socio-economic status (SES) of student's family. This is a cross sectional 16 months study done in school going Indian students aged ≥ 6 years with sample size of 1460. The prevalence of tobacco use in children from lower SES families was 9.4% compared to 5.7% in children from middle SES families (p = 0.017). Among children who used tobacco, mean age of onset was younger among children from lower SES (9.97 year vs 11.85 year, p = < 0.01) and they were more likely to use smokeless tobacco only (79.1% vs 61.3%, p = .0.006). However there was no significant difference between two groups in factors which motivated them towards first experience of tobacco. Also there was no significant difference between family histories of two groups in terms of tobacco use. The high prevalence of tobacco consumption, especially smokeless tobacco among children highlights the need for early intervention like regular screening at school level. Also tobacco use cases need to be followed up with intensive treatment.

Risky decision-making is associated with impulsive action and sensitivity to first-time nicotine exposure

Excessive risk-taking is common in multiple psychiatric conditions, including substance use disorders. The risky decision-making task (RDT) models addiction-relevant risk-taking in rats by measuring preference for a small food reward vs. a large food reward associated with systematically increasing risk of shock. Here, we examined the relationship between risk-taking in the RDT and multiple addiction-relevant phenotypes. Risk-taking was associated with elevated impulsive action, but not impulsive choice or habit formation. Furthermore, risk-taking predicted locomotor sensitivity to first-time nicotine exposure and resilience to nicotine-evoked anxiety. These data demonstrate that risk preference in the RDT predicts other traits associated with substance use disorder, and may have utility for identification of neurobiological and genetic biomarkers that engender addiction vulnerability.

The impact of flavour, device type and warning messages on youth preferences for electronic nicotine delivery systems: evidence from an online discrete choice experiment

OBJECTIVE

To examine the impact of flavour, device type and health warning messages on youth preference for electronic nicotine delivery systems (ENDS), and to provide evidence and data to inform the Food and Drug Administration's potential regulatory actions on ENDS.

DESIGN

An online discrete choice experiment was conducted in September 2015. Each participant was given nine choice sets and asked to choose one out of two alternative ENDS products, with varying characteristics in three attributes (flavour, device type and warning message). The impact of the attributes on the probability of choosing ENDS was analysed using conditional and nested logit regressions, controlling for individual sociodemographic characteristics and current smoking status.

SETTING AND PARTICIPANTS

A general population sample of 515 participants (50 ever-users and 465 never-users of ENDS) aged 14-17 years were recruited to complete the experiment using an online panel.

RESULTS

Fruit/sweets/beverage flavours significantly increase the probability of choosing ENDS among youth (p<0.01 for never-users and <0.1 for ever-users) and flavour has the most pronounced impact among three attributes. Among never-users, menthol flavour also increases (p<0.05) the probability of choosing ENDS compared with tobacco flavour. Vaping devices that are modifiable, compared with cigarette-like e-cigarettes, increase (p<0.05) the probability of choosing ENDS among adolescent never-users. Warning messages reduce (p<0.01) the probability of choosing ENDS among never-users.

CONCLUSIONS AND RELEVANCE

Restricting fruit/sweets/beverage flavours in ENDS, regulating modifiable vaping devices and adopting strong health warning messages may reduce the uptake of ENDS among youth.

Conditioned taste aversions: From poisons to pain to drugs of abuse

Learning what to eat and what not to eat is fundamental to our well-being, quality of life, and survival. In particular, the acquisition of conditioned taste aversions (CTAs) protects all animals (including humans) against ingesting foods that contain poisons or toxins. Counterintuitively, CTAs can also develop in situations in which we know with absolute certainty that the food did not cause the subsequent aversive systemic effect. Recent nonhuman animal research, analyzing palatability shifts, has indicated that a wider range of stimuli than has been traditionally acknowledged can induce CTAs. This article integrates these new findings with a reappraisal of some known characteristics of CTA and presents a novel conceptual analysis that is broader and more comprehensive than previous accounts of CTA learning.

Flavour preferences in youth versus adults: a review

OBJECTIVE

To understand the available evidence of how children and adults differ in their preferences for flavours that may be used in tobacco products.

DATA SOURCES

A total of 474 articles published between 1931 and August 2015 were retrieved through searches conducted in PubMed, EMBASE, Web of Science and PsycINFO.

STUDY SELECTION AND EXTRACTION

A 2-phase relevancy review process resulted in the identification of 59 articles and information was extracted by 2 independent reviewers.

DATA SYNTHESIS

Findings were grouped by taste and smell preferences, which are important components of overall flavour. For taste, evidence is summarised in the following categories: sweet, salty, sour, bitter, umami and fat; within each of them, findings are organised by age categories. For smell, evidence is summarised as follows: fruit/herbal/spices, tobacco and coffee and other odours. Major findings from this search indicated that sweet preference in children and adolescents was higher than in adults. Examples of preferred food-related tastes and odours for young people included cherry, candy, strawberry, orange, apple and cinnamon. Currently, all these are used to flavour cigars, cartridges for electronic cigarettes, hookah (waterpipe) and smokeless tobacco products.

CONCLUSIONS

Infants and children exhibited elevated sweet and salty preference relative to adults. Age-related changes in bitter, sour, umami and fat taste were not clear and more research would be useful. 'Sweet' food odours were highly preferred by children. Tobacco products in flavours preferred by young people may impact tobacco use and initiation, while flavours preferred by adults may impact product switching or dual use.

Abuse liability assessment of an e-cigarette refill liquid using intracranial self-stimulation and self-administration models in rats

BACKGROUND

The popularity of electronic cigarettes (ECs) has increased dramatically despite their unknown health consequences. Because the abuse liability of ECs is one of the leading concerns of the Food and Drug Administration (FDA), models to assess it are urgently needed to inform FDA regulatory decisions regarding these products. The purpose of this study was to assess the relative abuse liability of an EC liquid compared to nicotine alone in rats. Because this EC liquid contains non-nicotine constituents that may enhance its abuse liability, we hypothesized that it would have greater abuse liability than nicotine alone.

METHODS

Nicotine alone and nicotine dose-equivalent concentrations of EC liquid were compared in terms of their acute effects on intracranial self-stimulation (ICSS) thresholds, acquisition of self-administration, reinforcing efficacy (i.e., elasticity of demand), blockade of these behavioral effects by mecamylamine, nicotine pharmacokinetics and nicotinic acetylcholine receptor binding and activation.

RESULTS

There were no significant differences between formulations on any measure, except that EC liquid produced less of an elevation in ICSS thresholds at high nicotine doses.

CONCLUSIONS

Collectively, these findings suggest that the relative abuse liability of this EC liquid is similar to that of nicotine alone in terms of its reinforcing and reinforcement-enhancing effects, but that it may have less aversive/anhedonic effects at high doses. The present methods may be useful for assessing the abuse liability of other ECs to inform potential FDA regulation of those products.

How Intravenous Nicotine Administration in Smokers Can Inform Tobacco Regulatory Science

Reducing the negative health effects caused by tobacco products continues to be a public health priority. The Family Smoking Prevention and Tobacco Control Act of 2009 gives the Food Drug Administration authority to pursue several new strategies, including regulating levels of nicotine and other ingredients in tobacco products. A nicotine reduction strategy proposed by Benowitz and Henningfield aims to reduce the nicotine content of tobacco products to an amount below a threshold that supports neither the development nor maintenance of addiction. Many factors must be considered to determine the viability and efficacy of this approach. For example, the policy should be based on precise information on the dose-dependent effects of nicotine on reinforcement and factors that contribute to individual differences in these effects. However, there have been few studies on these topics in humans. Here, we briefly review nicotine pharmacology and reinforcement then present several studies illustrating the application of intravenous (IV) nicotine delivery to study nicotine reinforcement in humans. We discuss how nicotine delivery by IV infusion may be uniquely suited for studying nicotine's dose-dependent effects, and how this can inform tobacco regulatory science to facilitate the development of effective tobacco control policies.

Role of Central Amygdala Neuronal Ensembles in Incubation of Nicotine Craving

The craving response to smoking-associated cues in humans or to intravenous nicotine-associated cues in adult rats progressively increases or incubates after withdrawal. Here, we further characterized incubation of nicotine craving in the rat model by determining whether this incubation is observed after adolescent-onset nicotine self-administration. We also used the neuronal activity marker Fos and the Daun02 chemogenetic inactivation procedure to identify cue-activated neuronal ensembles that mediate incubation of nicotine craving. We trained adolescent and adult male rats to self-administer nicotine (2 h/d for 12 d) and assessed cue-induced nicotine seeking in extinction tests (1 h) after 1, 7, 14, or 28 withdrawal days. In both adult and adolescent rats, nicotine seeking in the relapse tests followed an inverted U-shaped curve, with maximal responding on withdrawal day 14. Independent of the withdrawal day, nicotine seeking in the relapse tests was higher in adult than in adolescent rats. Analysis of Fos expression in different brain areas of adolescent and adult rats on withdrawal days 1 and 14 showed time-dependent increases in the number of Fos-positive neurons in central and basolateral amygdala, orbitofrontal cortex, ventral and dorsal medial prefrontal cortex, and nucleus accumbens core and shell. In adult Fos-lacZ transgenic rats, selective inactivation of nicotine-cue-activated Fos neurons in central amygdala, but not orbitofrontal cortex, decreased "incubated" nicotine seeking on withdrawal day 14. Our results demonstrate that incubation of nicotine craving occurs after adolescent-onset nicotine self-administration and that neuronal ensembles in central amygdala play a critical role in this incubation.

SIGNIFICANCE STATEMENT

The craving response to smoking-associated cues in humans or to intravenous nicotine-associated cues in adult rats progressively increases or incubates after withdrawal. It is currently unknown whether incubation of craving also occurs after adolescent-onset nicotine self-administration. The brain areas that mediate such incubation are also unknown. Here, we used a rat model of incubation of drug craving, the neuronal activity marker Fos, and the Daun02 chemogenetic inactivation method to demonstrate that incubation of nicotine craving is also observed after adolescent-onset nicotine self-administration and that neuronal ensembles in the central nucleus of the amygdala play a critical role in this incubation in adult rats.

Drugs as instruments: a new framework for non-addictive psychoactive drug use

Most people who are regular consumers of psychoactive drugs are not drug addicts, nor will they ever become addicts. In neurobiological theories, non-addictive drug consumption is acknowledged only as a "necessary" prerequisite for addiction, but not as a stable and widespread behavior in its own right. This target article proposes a new neurobiological framework theory for non-addictive psychoactive drug consumption, introducing the concept of "drug instrumentalization." Psychoactive drugs are consumed for their effects on mental states. Humans are able to learn that mental states can be changed on purpose by drugs, in order to facilitate other, non-drug-related behaviors. We discuss specific "instrumentalization goals" and outline neurobiological mechanisms of how major classes of psychoactive drugs change mental states and serve non-drug-related behaviors. We argue that drug instrumentalization behavior may provide a functional adaptation to modern environments based on a historical selection for learning mechanisms that allow the dynamic modification of consummatory behavior. It is assumed that in order to effectively instrumentalize psychoactive drugs, the establishment of and retrieval from a drug memory is required. Here, we propose a new classification of different drug memory subtypes and discuss how they interact during drug instrumentalization learning and retrieval. Understanding the everyday utility and the learning mechanisms of non-addictive psychotropic drug use may help to prevent abuse and the transition to drug addiction in the future.

Socially acquired nicotine self-administration with an aversive flavor cue in adolescent female rats

RATIONALE

Establishing a behavioral model for the effect of social environment on nicotine intake in rodents facilitates the investigation of molecular mechanisms critical for the interaction between social environment and cigarette smoking.

OBJECTIVES

Our main objective was to test the hypothesis that nicotine is the primary reinforcer in the socially acquired nicotine intravenous self-administration (IVSA) model by using an aversive flavor cue.

METHODS

Adolescent female rats were placed in operant conditioning chambers equipped with two lickometers. Operant licking triggered concurrent deliveries of a flavor (i.e., taste and odor) cue containing either quinine or saccharin and an i.v. infusion (30 μg/kg nicotine or saline). An audiovisual cue was provided for some groups of rats. A second rat that did not receive nicotine was placed in the operant conditioning chambers to provide either a neutral or an inducing (i.e., by consuming the flavored solution) social environment. These two rats were separated by a divider that allowed orofacial interactions.

RESULTS

Rats acquired stable nicotine IVSA with either the aversive or the appetitive flavor cue in the inducing social environment, and obtained similar amounts of infusions. The neutral social environment did not support nicotine IVSA with either cue. The audiovisual cue per se did not support nicotine IVSA but enhanced nicotine intake. Nicotine increased the number of concurrent nose pokes by the two rats into the center divider, a measure of social interaction.

CONCLUSIONS

Despite its aversive effects, nicotine is the primary reinforcer for the operant responses in the socially acquired nicotine IVSA model.

Secondhand tobacco smoke exposure and susceptibility to smoking, perceived addiction, and psychobehavioral symptoms among college students

OBJECTIVE

To examine the association of secondhand smoke (SHS) exposure with susceptibility to smoking, perceived addiction, and psychobehavioral effects of exposure among never- and ever-smoking college students.

PARTICIPANTS

Participants were 665 college students at a large, southeastern university in the United States.

METHODS

This study is a secondary analysis of online cross-sectional survey data from randomly selected students in April 2013.

RESULTS

Thirty-eight percent of the sample had moderate to high SHS exposure. Among never-smokers, SHS exposure was associated with increased susceptibility to initiating smoking. Among ever-smokers, SHS exposure was not associated with their perceived addiction to tobacco. In the total sample, SHS exposure was associated with greater psychobehavioral symptoms of exposure.

CONCLUSIONS

SHS exposure may the increase risk of smoking, especially among never-smoking college students. This study strengthens the need for prevention strategies that limit SHS exposure in college environments.

Eyes on the price: Human culture and its teaching

Kline proposes an evolutionary framework for teaching as a major base of human culture, in which she outlines how different types of teaching may solve adaptive problems with a focus on human behavior. Here it is argued that the ability to teach and the different types of teaching behavior may not only solve adaptive problems, but also create them.

Carbon disulfide mediates socially-acquired nicotine self-administration

The social environment plays a critical role in smoking initiation as well as relapse. We previously reported that rats acquired nicotine self-administration with an olfactogustatory cue only when another rat consuming the same cue was present during self-administration. Because carbon disulfide (CS₂) mediates social learning of food preference in rodents, we hypothesized that socially acquired nicotine self-administration is also mediated by CS₂. We tested this hypothesis by placing female adolescent Sprague-Dawley rats in operant chambers equipped with two lickometers. Licking on the active spout meeting a fixed-ratio 10 schedule triggered the concurrent delivery of an i.v. infusion (saline, or 30 µg/kg nicotine, free base) and an appetitive olfactogustatory cue containing CS₂ (0–500 ppm). Rats that self-administered nicotine with the olfactogustatory cue alone licked less on the active spout than on the inactive spout. Adding CS₂ to the olfactogustatory cue reversed the preference for the spouts. The group that received 500 ppm CS₂ and the olfactogustatory cue obtained a significantly greater number of nicotine infusions than other groups. After extinction training, the original self-administration context reinstated nicotine-seeking behavior in all nicotine groups. In addition, in rats that received the olfactogustatory cue and 500 ppm CS₂ during SA, a social environment where the nicotine-associated olfactory cue is present, induced much stronger drug-seeking behavior compared to a social environment lacking the olfactogustatory cue. These data established that CS₂ is a critical signal that mediates social learning of nicotine self-administration with olfactogustatory cues in rodents. Additionally, these data showed that the social context can further enhance the drug-seeking behavior induced by the drug-taking environment.

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.

Initial reactions to tobacco and cannabis smoking: a twin study

BACKGROUND AND AIMS

Initial subjective reactions to cannabis and tobacco, broadly classified as positive or negative, have previously been explored for their associations with onset and maintenance of subsequent abuse/dependence. We examine (i) the factorial architecture of self-reported initial reactions to cannabis and tobacco; (ii) whether these factors associate with concurrently reported age at onset of DSM-IV diagnosis of nicotine dependence and cannabis abuse/dependence; and (iii) estimate heritable variation in and covariation between the factors.

DESIGN

Factorial and exploratory structural equation modeling was conducted to examine the factor structure of initial reactions. Cox proportional hazards modeling was employed to examine their association with time to onset of diagnosis of DSM-IV nicotine dependence and cannabis abuse/dependence. Classical twin modeling, using univariate and multivariate models, was used to parse variance in each factor (and the covariance between factors) to their additive genetic, shared environmental and non-shared environmental sources.

SETTING AND PARTICIPANTS

General population sample of Caucasian female twins aged 18-32 years, with a life-time history of tobacco [n = 2393] and cannabis [n = 1445] use.

MEASUREMENT

Self-report of initial subjective reactions to tobacco (cigarettes) and cannabis the first time they were used and time to onset of life-time history of DSM-IV diagnosis of abuse (cannabis) and dependence (cannabis or nicotine).

FINDINGS

Factors representing putatively positive and negative reactions to cannabis and tobacco emerged. Initial reactions to tobacco were associated with onset of DSM-IV diagnosis of nicotine dependence and cannabis abuse/dependence while initial reactions to cannabis were associated with onset of DSM-IV diagnosis of cannabis abuse/dependence alone. Genetic factors played a moderate role in each factor (heritability of 27-35%, P < 0.05), with the remaining variance attributed to individual-specific environment. Covariation across the factors indexing positive and negative initial reactions was attributable to genetic sources (0.18-0.58, P < 0.05) and to overlapping individual-specific environmental factors (-0.16 to 0.36, P < 0.05).

CONCLUSIONS

Initial subjective reactions to tobacco are associated with onset of DSM-IV diagnosis of nicotine dependence and cannabis abuse/dependence while initial subjective reactions to cannabis are only associated with onset of diagnosis of DSM-IV cannabis abuse/dependence. Genetic and environmental factors underpin the overlap across the factors representing initial reactions, both positive and negative.

Propensity for social interaction predicts nicotine-reinforced behaviors in outbred rats

Social and genetic factors can influence smoking behavior. Using olfactogustatory stimuli as the sensory cue for intravenous nicotine self-administration (SA), we previously showed that social learning of nicotine contingent odor cue prevented rats from developing conditioned taste aversion and allowed them to instead establish stable nicotine SA. We hypothesized that genetic factors influenced socially acquired nicotine SA. A heterogeneous stock (HS; N/NIH) of outbred rats was trained to self-administer nicotine using the social learning protocol. Both male and female HS rats acquired nicotine SA, but females self-administered more nicotine than males. After extinction, the context previously paired with nicotine SA, in conjunction with socially transmitted drug cues, was sufficient to cause reinstatement of drug-seeking behavior. Wide variation in both nicotine intake and reinstatement was observed. Using multiple regression analysis, we found that measures of social interaction were significant predictors of nicotine intake and reinstatement of drug seeking in both males and females. Furthermore, measures of depression were predictors of nicotine intake in both males and females, anxiety was a predictor only in males and response to novelty was a predictor only in females. In males, measures of both depression and anxiety predicted nicotine reinstatement. Together, these data supported the ideas that genetically determined propensities for emotional and social phenotypes are significant determinants for nicotine-reinforced behavior, and that the HS rat is a suitable tool for dissecting genetic mechanisms that may underlie the interaction between social behavior, anxiety, depression and smoking.

Factor structure of early smoking experiences and associations with smoking behavior: valence or sensitivity model?

The Early Smoking Experience (ESE) questionnaire is the most widely used questionnaire to assess initial subjective experiences of cigarette smoking. However, its factor structure is not clearly defined and can be perceived from two main standpoints: valence, or positive and negative experiences, and sensitivity to nicotine. This article explores the ESE's factor structure and determines which standpoint was more relevant. It compares two groups of young Swiss men (German- and French-speaking). We examined baseline data on 3,368 tobacco users from a representative sample in the ongoing Cohort Study on Substance Use Risk Factors (C-SURF). ESE, continued tobacco use, weekly smoking and nicotine dependence were assessed. Exploratory structural equation modeling (ESEM) and structural equation modeling (SEM) were performed. ESEM clearly distinguished positive experiences from negative experiences, but negative experiences were divided in experiences related to dizziness and experiences related to irritations. SEM underlined the reinforcing effects of positive experiences, but also of experiences related to dizziness on nicotine dependence and weekly smoking. The best ESE structure for predictive accuracy of experiences on smoking behavior was a compromise between the valence and sensitivity standpoints, which showed clinical relevance.

Hookah use among adolescents in the United States: results of a national survey

INTRODUCTION

U.S. adolescents increasingly use alternative tobacco products (ATPs), including hookah. No study has previously assessed correlates of adolescent hookah use in a nationally representative sample.

METHODS

Cross-sectional, nationally representative data of adolescents from the 2011 National Youth Tobacco Survey (NYTS) were used. Student demographics and their use of, exposure to, and beliefs about tobacco were examined as correlates of hookah use.

RESULTS

Of adolescents nationwide, 7.3% reported ever trying hookah and 2.6% reported using hookah within the past month. Increasing age was associated with trying hookah, but not current hookah use. Sex was unassociated with hookah use. Asians were most likely to have tried hookah; Hispanics and those of another race reported greater current hookah use. Hookah use increased with perceived ease of access to and willingness to try tobacco. Students with a hookah user at home were more likely to have tried hookah and to currently use hookah. Current cigarette use was not associated with current hookah use (odds ratio [OR] = 1.3, 95% CI = 0.8-2.1), but was associated with trying hookah (OR = 1.5, 95% CI = 1.1-2.2). Non-cigarette tobacco use was associated with trying hookah (OR = 2.7, 95% CI = 2.1-3.5) and current hookah use (OR = 4.8, 95% CI = 2.7-8.7).

CONCLUSIONS

A sizeable minority of U.S. adolescents use hookah, particularly those living with hookah users, those who use other ATPs, and those who perceive tobacco as easily accessible. Current cigarette use was not associated with current hookah use. Future studies assessing the dangers of hookah use and interventions to curb this emerging problem appear warranted.

Adolescence is a period of development characterized by short- and long-term vulnerability to the rewarding effects of nicotine and reduced sensitivity to the anorectic effects of this drug

This study compared nicotine intake and changes in food intake and weight gain in naïve adolescent, naïve adult, and adult rats that were exposed to nicotine during adolescence. An extended intravenous self-administration (IVSA) model was used whereby rats had 23-hour access to saline or increasing doses of nicotine (0.03, 0.06, and 0.09 mg/kg/0.1 mL infusion) for 4-day intervals separated by 3-day periods of abstinence. Rats began IVSA as adolescents (PND 32-34) or adults (PND 75). A separate group of rats was exposed to nicotine via osmotic pumps (4.7 mg/kg) for 14 days during adolescence and then began nicotine IVSA as adults (PND 75). The rats that completed the nicotine IVSA regimen were also tested for nicotine-seeking behavior during extinction. The results revealed that nicotine intake was highest in adolescents followed by adults that were pre-exposed to nicotine during adolescence as compared to naïve adults. A similar pattern of nicotine-seeking behavior was observed during extinction. In contrast to nicotine intake, naïve adults displayed robust appetite and weight suppressant effects of nicotine, an effect that was absent in adolescents and adults that were pre-exposed to nicotine during adolescence. Our findings suggest that adolescence is a unique period of enhanced vulnerability to the reinforcing effects of nicotine. Although adolescents gain weight faster than adults, the food intake and weight suppressant effects of nicotine are reduced during adolescence. Importantly, our findings suggest that adolescent nicotine exposure produces long-lasting consequences that enhance nicotine reward and promote tolerance to the anorectic effects of this drug.

The relationship between subjective experiences during first use of tobacco and cannabis and the effect of the substance experienced first

INTRODUCTION

We examined the positive and negative subjective feelings associated with initial tobacco and cannabis use as well as the role of these experiences in regular use. Additionally, we investigated the effect of the first substance experienced on initial subjective experiences and later regular use.

METHODS

Baseline data from a representative sample of young Swiss men were obtained from an ongoing Cohort Study on Substance Use Risk Factors, which includes 2,321 lifetime tobacco and cannabis users. We assessed the age of first tobacco and cannabis use along with the subjective experiences associated with initial use. Additionally, subjective experiences related to regular use of both substances were analyzed.

RESULTS

The initial subjective experiences were divided into positive and negative for each substance, and we found that the feelings associated with first use of tobacco and cannabis were similar. Moreover, the participants who used cannabis before tobacco reported fewer negative experiences associated with first tobacco use, whereas the participants who initially used tobacco reported more negative experiences related to first cannabis use. Also, we identified that regular use was encouraged by positive experiences and that negative experiences were more adverse for regular use of cannabis compared with tobacco.

CONCLUSIONS

Taken together, these results indicate that similar subjective experiences were associated with the first use of tobacco and cannabis. Also, the use of cannabis before tobacco, which occurred in only a minority of users, had the potential to enhance the effects of initial tobacco use.

Episodic memories and their relevance for psychoactive drug use and addiction

The majority of adult people in western societies regularly consume psychoactive drugs. While this consumption is integrated in everyday life activities and controlled in most consumers, it may escalate and result in drug addiction. Non-addicted drug use requires the systematic establishment of highly organized behaviors, such as drug-seeking and -taking. While a significant role for classical and instrumental learning processes is well established in drug use and abuse, declarative drug memories have largely been neglected in research. Episodic memories are an important part of the declarative memories. Here a role of episodic drug memories in the establishment of non-addicted drug use and its transition to addiction is suggested. In relation to psychoactive drug consumption, episodic drug memories are formed when a person prepares for consumption, when the drug is consumed and, most important, when acute effects, withdrawal, craving, and relapse are experienced. Episodic drug memories are one-trial memories with emotional components that can be much stronger than "normal" episodic memories. Their establishment coincides with drug-induced neuronal activation and plasticity. These memories may be highly extinction resistant and influence psychoactive drug consumption, in particular during initial establishment and at the transition to "drug instrumentalization." In that, understanding how addictive drugs interact with episodic memory circuits in the brain may provide crucial information for how drug use and addiction are established.

Genetic factors control nicotine self-administration in isogenic adolescent rat strains

Adult cigarette smokers usually become dependent on cigarettes during adolescence. Despite recent advances in addiction genetics, little data delineates the genetic factors that account for the vulnerability of humans to smoke tobacco. We studied the operant nicotine self-administration (SA) behavior of six inbred strains of adolescent male rats (Fisher 344, Brown Norway, Dark Agouti, Spontaneous Hypertensive Rat, Wistar Kyoto and Lewis) and six selected F1 hybrids. All rats were trained to press a lever to obtain food starting on postnatal day (PN) 32, and then nicotine (0.03 mg/kg/infusion, i.v.) reinforcement was made available on PN41-42 (10 consecutive daily 2 h sessions). Of the 12 isogenic strains, Fisher rats self-administered the fewest nicotine infusions (1.45 ± 0.36/d) during the last 3 d, while Lewis rats took the most nicotine (13.0 ± 1.4/d). These strains sorted into high, intermediate and low self-administration groups in 2, 2, and 8 strains, respectively. The influence of heredity on nicotine SA (0.64) is similar to that reported for humans. Therefore, this panel of isogenic rat strains effectively models the overall impact of genetics on the vulnerability to acquire nicotine-reinforced behavior during adolescence. Separate groups of rats responded for food starting on PN41. The correlation between nicotine and food reward was not significant. Hence, the genetic control of the motivation to obtain nicotine is distinctly different from food reward, indicating the specificity of the underlying genetic mechanisms. Lastly, the behavior of F1 hybrids was not predicted from the additive behavior of the parental strains, indicating the impact of significant gene-gene interactions on the susceptibility to nicotine reward. Taken together, the behavioral characteristics of this model indicate its strong potential to identify specific genes mediating the human vulnerability to smoke cigarettes.

Do initial responses to drugs predict future use or abuse?

Individuals vary in their initial reactions to drugs of abuse in ways that may contribute to the likelihood of subsequent drug use. In humans, most drugs of abuse produce positive subjective states such as euphoria and feelings of well-being, which may facilitate repeated use. In nonhumans, many drugs initially increase locomotor activity and produce discriminative stimulus effects, both of which have been considered to be models of human stimulant and subjective states. Both humans and nonhumans vary in their sensitivity to early acute drug effects in ways that may predict future use or self-administration, and some of these variations appear to be genetic in origin. However, it is not known exactly how the initial responses to drugs in either humans or nonhumans relate to subsequent use or abuse. In humans, positive effects of drugs facilitate continued use of a drug while negative effects discourage use, and in nonhumans, greater genetic risk for drug intake is predicted by reduced sensitivity to drug aversive effects; but whether these initial responses affect escalation of drug use, and the development of dependence is currently unknown. Although early use of a drug is a necessary step in the progression to abuse and dependence, other variables may be of greater importance in the transition from use to abuse. Alternatively, the same variables that predict initial acute drug effects and early use may significantly contribute to continued use, escalation and dependence. Here we review the existing evidence for relations between initial direct drug effects, early use, and continued use. Ultimately, these relations can only be determined from systematic longitudinal studies with comprehensive assessments from early drug responses to progression of problem drug use. In parallel, additional investigation of initial responses in animal models as predictors of drug use will shed light on the underlying mechanisms.

The relationship between the genetic and environmental influences on common externalizing psychopathology and mental wellbeing

To determine the relationship between the genetic and environmental risk factors for externalizing psychopathology and mental wellbeing, we examined detailed measures of emotional, social and psychological wellbeing, and a history of alcohol-related problems and smoking behavior in the last year in 1,386 individual twins from same-sex pairs from the MIDUS national US sample assessed in 1995. Cholesky decomposition analyses were performed withthe Mx program. The best fit model contained one highly heritable common externalizing psychopathology factor for both substance use/abuse measures, and one strongly heritable common factor for the three wellbeing measures. Genetic and environmental risk factors for externalizing psychopathology were both negatively associated with levels of mental wellbeing and accounted for, respectively, 7% and 21% of its genetic and environmental influences. Adding internalizing psychopathology assessed in the last year to the model, genetic risk factors unique for externalizing psychopathology were now positively related to levels of mental wellbeing, although accounting for only 5% of the genetic variance. Environmental risk factors unique to externalizing psychopathology continued to be negatively associated with mental wellbeing, accounting for 26% of the environmental variance. When both internalizing psychopathology and externalizing psychopathology are associated with mental wellbeing, the strongest risk factors for low mental wellbeing are genetic factors that impact on both internalizing psychopathology and externalizing psychopathology, and environmental factors unique to externalizing psychopathology. In this model, genetic risk factors for externalizing psychopathology predict, albeit weakly, higher levels of mental wellbeing.

Risk and protective factors for nicotine dependence in adolescence

BACKGROUND

We investigated the role of psychosocial and proximal contextual factors on nicotine dependence in adolescence.

METHODS

Data on a multiethnic cohort of 6th to 10th graders from the Chicago public schools were obtained from four household interviews conducted with adolescents over two years and one interview with mothers. Structural equation models were estimated on 660 youths who had smoked cigarettes by the first interview.

RESULTS

Pleasant initial sensitivity to tobacco use, parental nicotine dependence (ND), adolescent ND and extensiveness of smoking at the initial interview had the strongest total effects on adolescent ND two years later. Perceived peer smoking and adolescent conduct problems were of lesser importance. Parental ND directly impacted adolescent ND two years later and had indirect effects through pleasant initial sensitivity and initial extensiveness of smoking. Parental depression affected initial adolescent dependence and depression but adolescent depression had no effect on ND. The model had greater explanatory power for males than females due partly to the stronger effect of conduct problems on dependence for males than females.

CONCLUSIONS

The findings underscore the importance of the initial drug experience and familial factors on adolescent nicotine dependence and highlight the factors to be the focus of efforts targeted toward preventing ND among adolescents.

Effects of nicotine on electroencephalography and affect in adolescent females with major depressive disorder: a pilot study

BACKGROUND

Given that smoking is typically initiated during adolescence, and that this period in brain development seems to be uniquely sensitive to nicotine, depressed youth may be most susceptible to the neuromodulatory and mood-altering effects of nicotine. Electroencephalographic (EEG) studies suggest that individuals with major depressive disorder (MDD) exhibit left frontal lobe hypoactivation (indexed by increased EEG alpha), a region implicated in positive affect regulation, as well as right parietal hypoactivation. Smoking/nicotine abstinence has been associated with increased left frontal and right parietal alpha activity (reduced activation), which has been correlated with increased depression ratings; nicotine administration seems to normalize this depression-associated asymmetry.

OBJECTIVES

This pilot study investigated whether acute nicotine administration in adolescent female smokers with MDD would alter resting EEG activity and affect.

METHODS

Subjective mood ratings and EEG recordings were acquired before and 2 hours after administering a transdermal placebo or nicotine (21 mg) patch to 8 adolescent female smokers with MDD.

RESULTS

Nicotine induced a modest increase in alpha1 amplitude in the right hemisphere and simultaneously decreased left-favoring alpha1 amplitude asymmetry. It also attenuated left alpha1 and alpha2 amplitude in the central region. Consistent with nicotine's stimulatory action, nicotine decreased theta amplitude in the right parietal region. No accompanying mood alterations were found, although smoking withdrawal and craving as well as physical symptom scores were reduced with nicotine.

CONCLUSIONS

The results of this pilot study, the first to examine the electrocortical effects of nicotine in depressed adolescents, indicate that nicotine modulates EEG asymmetry measures, laying the stage for further research regarding the role of nicotine on affective neurocircuitry in this population.

Threshold of adulthood for the onset of nicotine self-administration in male and female rats

The great majority of tobacco addiction begins during adolescence. More heavily addicted smokers begin smoking earlier, but differentiating the neurobehavioral impact of nicotine self-administration during adolescence from self-selection bias (whereby people more prone to heavy addiction also begin earlier) cannot be ethically unconfounded in humans. The goals of this research were to determine the age threshold for the adult-like nicotine self-administration and determine sex differences. Male and female Sprague-Dawley rats were tested for nicotine self-administration starting at 4, 5, 6, 7, and 8 weeks of age in an operant FR1 schedule for IV nicotine (0.03 mg/kg/infusion) in 45-min sessions for 2 weeks, with 1 week of enforced abstinence and 1 week of resumed access. This study replicated our earlier work that nicotine self-administration was increased in adolescent vs. adult rats and that the effect was more pronounced in adolescent males, but the increased nicotine self-administration was more persistent in adolescent-onset females. The age threshold for adult-like behavior was 6-7 weeks of age. Adolescent-onset nicotine self-administration had persisting effects of eggaurated increases of nicotine self-administration when fixed-ratio requirements for self-administration were lowered. Female rats that had begun nicotine self-administration during adolescence showed exaggerated increases in nicotine self-administration after a switch back to FR1 from FR8, indicating a lessened control over their self-administration. Adolescent-onset nicotine self-administration was not found to potentiate cocaine self-administration. Adolescent-onset nicotine self-administration causes persistent increases in nicotine self-administration in female rats even after they reach adulthood and disrupts control over self-administration behavior.

Determinants of smoking experimentation and initiation among adolescent students in the city of Salvador, Brazil

OBJECTIVE

To identify the factors associated with smoking experimentation and initiation among adolescent students (11-14 years of age).

METHODS

A cross-sectional, population-based study involving adolescent (middle and high school) students at public and private schools in the city of Salvador, Brazil. A multiple-stage sampling protocol was used. The participants completed an anonymous, voluntary, self-report questionnaire. The dependent variables were age at smoking experimentation and smoking initiation. Sociodemographic and educational variables, as well as those related to media influence and alcohol consumption, were considered independent variables. Multivariate logistic regression analysis was performed, followed by analysis of the fit of the final logistic regression model.

RESULTS

The prevalence of smoking experimentation was 16.1% (95% CI: 15.1-17.2). Of the 5,347 students evaluated, 757 had experimented with cigarettes, and 462 (61.2%) of those 757 had done so before the age of 15 (mean age at smoking experimentation, 13.9 ± 1.8 years). Smoking initiation was associated with paternal smoking (OR = 1.53; 83% CI = 1.07-2.19) and with media influence (OR = 2.43; 83% CI: 1.46-4.04). Smoking experimentation was associated with alcohol consumption (OR = 6.04; 83% CI: 4.62-7.88), having friends who smoke (OR = 3.18; 83% CI: 2.54-3.99), having a boyfriend/girlfriend who smokes (OR = 3.42; 83% CI: 1.78-6.56), and coercive/aggressive educational interventions by the parents (OR = 1.60; 83% CI: 1.26-2.04).

CONCLUSIONS

Alcohol consumption and the influence of peers and relatives who smoke showed a strong association with smoking experimentation. Paternal smoking and media influence were found to increase the chances of adolescent smoking.

Dizziness and the genetic influences on subjective experiences to initial cigarette use

AIM

To examine individual differences in positive and negative subjective experiences to initial cigarette use.

DESIGN

Retrospective self-reports of initial subjective experiences were examined to estimate the genetic and environmental influences and the extent of their covariation across different effects.

PARTICIPANTS

Data was drawn from 2482 young adult same-and opposite sex twins- and siblings participating in the National Longitudinal Study of Adolescent Health.

MEASUREMENT

Subjective experiences were retrospectively collected using the Early Smoking Experience (ESE) questionnaire.

FINDINGS

Positive experiences evidenced moderate heritable contributions (40%, 95% CI: 0.22 to 0.56), as did an overall hedonic measure (34%, 95% CI: 0.22 to 0.46) and dizziness (34%, 95% CI: 0.15 to 0.52). Negative experiences evidenced small heritable contributions (13%, 95% CI: 0.00 to 0.36). Individual specific environmental influences were strong and accounted for the remaining proportion of observed variation in these experiences. Multivariate genetic modeling identified a moderately heritable underlying factor (37%, 95% CI: 0.22 to 0.52) that influenced the covariation of diverse subjective experiences and loaded most heavily on dizziness. Positive experiences also evidence residual genetic influences that were uncorrelated with other subjective experiences.

CONCLUSIONS

How a person experiences their initial few cigarettes is due to both heritable contributions and environmental experiences unique to the person. The covariation of diverse subjective experiences appears to be due to a heritable latent sensitivity to the chemicals contained in an average cigarette and is best indexed by dizziness.

Changes in genetic and environmental influences on the development of nicotine dependence and major depressive disorder from middle adolescence to early adulthood

This longitudinal study used a representative community sample of same-sex twins (485 monozygotic pairs, 271 dizygotic pairs) to study longitudinal changes in genetic and environmental influences on nicotine dependence (NicD) symptoms and major depressive disorder (MDD) symptoms and the longitudinal relationships between NicD and MDD symptoms at three relatively discrete ages spanning middle adolescence to early adulthood (ages 15, 18, and 21). Clinical interviews were used to assess NicD and MDD symptoms lifetime at age 15 and during the previous 3 years at the two subsequent assessments. Biometric models revealed similar patterns of findings for NicD and MDD. Heritability increased with age, particularly between ages 15 and 18. Shared environmental influences were small, and the proportion of variance attributed to shared environmental influences decreased with age. Nonshared environmental influences were moderate to large in magnitude and were entirely age specific. Both NicD and MDD symptoms showed considerable stability from age 15 to 21, and at each age those with one disorder showed elevated rates of the other. However, a cross-lagged model revealed no longitudinal predictive relationships between MDD symptoms and NicD symptoms after accounting for stability of symptoms within disorders. In summary, the transition between middle and late adolescence is a critical period for developmental shifts in the magnitudes of genetic and environmental influences on both MDD and NicD symptoms. Despite similarities in the development of genetic and environmental influences for the two phenotypes, the association between NicD and MDD reflects concurrent covariation rather than one phenotype being an antecedent influence on the subsequent development of the other.

Is tobacco use associated with academic failure among government school students in urban India?

BACKGROUND

Not much is known about the academic correlates of tobacco use among students in developing countries. This study investigated associations between multiple forms of tobacco use, psychosocial risk factors, and academic failure among 10- to 16-year-old government school students in Delhi and Chennai, India.

METHODS

This study was a secondary analysis of data gathered from students in 7 government schools during a larger tobacco intervention trial in India. Mixed-effects regression analyses were carried out on a cross-sectional sample of 3799 students and a retrospective cohort of 2586 students. Data on tobacco use and risk factors were collected from self-reported student surveys in 2006 and 2004. Using school records, academic failure was defined as repeating the same grade level once or twice between 2004 and 2006.

RESULTS

In 2006, academic failure was significantly more prevalent among students who reported use of chewing tobacco, bidis, or cigarettes, as compared with nonusers. Students with academic failure had greater social susceptibility and intentions for future tobacco use, and poor knowledge and self-efficacy for avoiding tobacco. Cohort analyses showed that students who had reported tobacco use in 2004 were more likely to have academic failure by 2006, as compared with nonusers.

CONCLUSIONS

School health programs that incorporate tobacco control measures should be offered to government school students with poor academic outcomes in India, along with remedial education efforts. School-based longitudinal research is needed to assess effects of tobacco use in early adolescence on academic, social, and behavioral outcomes in later adolescence and young adulthood.

Secondhand smoke avoidance by preteens living with smokers: to leave or stay?

INTRODUCTION

Secondhand smoke (SHS) is hazardous to children's health. Designing interventions to reduce exposure requires understanding children's behavior in the presence of smokers, yet little is known about this behavior.

PURPOSE

To determine whether children's avoidance of SHS is associated with lower exposure and to explore predictors of avoidance based on a behavioral ecological model.

METHOD

Preteens aged 8-13 (N=358) living with a smoker identified their primary source of SHS exposure, and reported whether they left (avoided exposure) or stayed the last time they were exposed to that person's smoke. The SHS avoidance measure was validated by examining associations with SHS exposure. Multiple Logistic Regression was used to determine predictors of SHS avoidance.

RESULTS

Based on urine cotinine and reported exposure, preteens who left the presence of SHS had lower exposure than those who stayed. Preteens were more likely to leave SHS if they were less physically mature, had not tried smoking, had a firm commitment not to smoke, did not assist family smoking, had family/friends who discouraged breathing SHS, or had friends who disliked smoking.

DISCUSSION

Most SHS exposure reduction interventions have targeted changes in smokers' behavior. Reductions can also be achieved by changing exposed nonsmokers' behavior, such as avoiding the exposure. Future studies should measure young people's SHS avoidance and test interventions to increase their avoidance practices.

Do early smoking experiences count in development of smoking?: temporal stability and predictive validity of an early smoking experience questionnaire in adolescents

AIMS

The experience during initial experimentation with smoking might influence later development of smoking behavior; however, measuring early smoking experience (ESE) usually requires self-reports for which stability and predictive validity are relatively understudied. The aims of the study are (a) to examine temporal stability of the ESE questionnaire and (b) to test the hypothesis that early pleasant and unpleasant experience scales predict changes in smoking status among adolescents.

METHODS

In two waves of the Budapest Adolescent Smoking study, a school-based longitudinal study, 1,286 ninth-grade students reported their ESE on both occasions (45.9% girls; mean age = 15.3, SD = 0.54). Questions related to smoking behavior and ESEs were administered in both waves (average 5 month apart). To examine temporal stability, test-retest correlations and a multiindicator autoregressive model were estimated. To test the predictive validity, 2 structural equation models with binary outcome variables (change in smoking status) were estimated in experimenters (N = 798) and nondaily smokers (N = 506) separately.

RESULTS

Test-retest correlations of pleasant and unpleasant experiences were .63 and .66, respectively. Pleasant and unpleasant experiences predict the change of smoking status in the group of experimenters (odds ratio [OR] = 1.57 [1.00-2.48] and 0.58 [0.42-0.80], respectively), but these coefficients (OR = 1.53 [0.79-1.74] and 1.17 [0.82-2.83], respectively) did not reach the level of significance in nondaily smokers.

CONCLUSIONS

Self-reports of ESE demonstrate good short-term temporal stability. The early unpleasant smoking experience might have a different role in different stages of smoking acquisition.