The dynamic effects of nicotine on the developing brain

Inhibitory control in siblings discordant for exposure to maternal smoking during pregnancy

Maternal smoking during pregnancy (SDP) has been linked to poorer offspring executive function across development, but SDP does not occur independent of other familial risk factors. As such, poor and inconsistent control for potential confounds, notably shared familial (i.e., genetic and environmental) confounds, preclude concluding causal effects of SDP on child outcomes. We examined the within-family association between SDP and one component of executive function, inhibitory control, in a sample of families (N = 173) specifically selected for sibling pairs discordant for exposure to SDP. Thus, the present study examines if the SDP-inhibitory control association withstands rigorous control for potential child and familial confounds. 79% of the variation in child inhibitory control was attributable to within-family differences and 21% was attributable to differences between families, indicating that the variability in inhibitory control was primarily a function of differences between siblings rather than differences across families. Further, the association between SDP and inhibitory control was fully attenuated when confounds were considered. These findings suggest that co-occurring vulnerabilities act as more salient risk factors for poorer child inhibitory control than SDP and may serve as effective targets of interventions seeking to improve children's inhibitory control in families with nicotine dependent mothers. (PsycINFO Database Record

E-Cigarettes and Smoking Cessation: A Primer for Oncology Clinicians

BACKGROUND

Electronic cigarettes 
(e-cigarettes) are a psychosocial phenomenon of the 21st century with serious implications to public and individual health. The significant increase of their popularity and use has raised concerns in the healthcare community regarding their potential benefits and harm, particularly their use as a smoking cessation methodology.

OBJECTIVES

Current knowledge is presented about e-cigarettes, including the clinical implications of their use, and associated controversies are analyzed. In addition, practice recommendations and communication guidance are provided.

METHODS

An integrative review was performed.

FINDINGS

The long-term effect of e-cigarettes on individual and public health is unknown. Evidence from short-term studies, although limited, shows that e-cigarette use is less harmful than smoking. However, the evidence does not support the use of e-cigarettes as a smoking cessation methodology. Such recommendation remains a judgment call for the clinician based on each individual case.

Impact of juvenile chronic stress on adult cortico-accumbal function: Implications for cognition and addiction

Repeated exposure to stress during childhood is associated with increased risk for neuropsychiatric illness, substance use disorders and other behavioral problems in adulthood. However, it is not clear how chronic childhood stress can lead to emergence of such a wide range of symptoms and disorders in later life. One possible explanation lies in stress-induced disruption to the development of specific brain regions associated with executive function and reward processing, deficits in which are common to the disorders promoted by childhood stress. Evidence of aberrations in prefrontal cortex and nucleus accumbens function following repeated exposure of juvenile (pre- and adolescent) organisms to a variety of different stressors would account not only for the similarity in symptoms across the wide range of childhood stress-associated mental illnesses, but also their persistence into adulthood in the absence of further stress. Therefore, the goal of this review is to evaluate the current knowledge regarding disruption to executive function and reward processing in adult animals or humans exposed to chronic stress over the juvenile period, and the underlying neurobiology, with particular emphasis on the prefrontal cortex and nucleus accumbens. First, the role of these brain regions in mediating executive function and reward processing is highlighted. Second, the neurobehavioral development of these systems is discussed to illustrate how juvenile stress may exert long-lasting effects on prefrontal cortex-accumbal activity and related behavioral functions. Finally, a critical review of current animal and human findings is presented, which strongly supports the supposition that exposure to chronic stress (particularly social aggression and isolation in animal studies) in the juvenile period produces impairments in executive function in adulthood, especially in working memory and inhibitory control. Chronic juvenile stress also results in aberrations to reward processing and seeking, with increased sensitivity to drugs of abuse particularly noted in animal models, which is in line with greater incidence of substance use disorders seen in clinical studies. These consequences are potentially mediated by monoamine and glutamatergic dysfunction in the prefrontal cortex and nucleus accumbens, providing translatable therapeutic targets. However, the predominant use of male subjects and social-based stressors in preclinical studies points to a clear need for determining how both sex differences and stressor heterogeneity may differentially contribute to stress-induced changes to substrates mediating executive function and reward processing, before the impact of chronic juvenile stress in promoting adult psychopathology can be fully understood.

Effect of tobacco smoking on frontal cortical thickness development: A longitudinal study in a mixed cohort of ADHD-affected and -unaffected youth

Smoking rates are particularly high during adolescence and young adulthood, when the brain is still undergoing significant developmental changes. Cross-sectional studies have revealed altered brain structure in smokers, such as thinner frontal cortical areas. Attention-deficit/hyperactivity disorder (ADHD) increases the risk of becoming nicotine-dependent, and has also been associated with abnormalities in frontal gray matter structure. The present study examines the relationships between smoking, cortical thickness and ADHD symptoms in a longitudinal design that compares adolescent and young adult smokers (n=44; 35 ADHD-affected) and non-smokers (n=45; 32 ADHD-affected) on frontal cortical thickness. Average frontal cortical thickness was estimated through structural magnetic resonance imaging (MRI) at two time points (mean ages 17.7 and 21.1 years), on average 3.4 years apart. Smokers had a 2.6% thinner frontal cortex than non-smokers and this difference was not explained by ADHD or other confounding factors. The rate of cortical thinning across the 3.4-year MRI measurement interval was similar in the total group of smokers compared to non-smokers. However, speeded thinning did occur in smokers who had started regular smoking more recently, in between the two measurements. These novel regular smokers did not differ significantly from the non-smokers at baseline. This suggests that the thinner frontal cortex was not a predisposing factor but rather a consequence of smoking. Although smokers had more ADHD symptoms overall, smoking did not influence the developmental course of ADHD symptoms.

Prenatal Exposure to Environmental Tobacco Smoke and Hyperactivity Behavior in Chinese Young Children

This study aimed to examine the association between prenatal environmental tobacco smoke (ETS) exposure and hyperactivity behaviors in young children. A cross-sectional study was undertaken among 21,243 participants from all of the kindergartens in Longhua District of Shenzhen, China. Multivariate logistic regression models and hierarchical linear models were employed to assess the associations. After adjusting for potential confounders of gender, preterm birth, birth asphyxiation, etc., prenatal ETS exposure was significantly associated with an increased risk of hyperactivity behaviors in young children (OR (95% CI) = 1.51 (1.28-1.77); β (95% CI) = 0.017 (0.013-0.020)). Along with increases in children's prenatal ETS exposure dose (measured by daily ETS exposure duration, daily cigarette consumption by household members, and overall score of prenatal ETS exposure), the children were also increasingly more likely to exhibit hyperactivity behaviors. Furthermore, children whose mothers had prenatal ETS exposure in any one or more of the pregnancy trimesters were more likely to exhibit hyperactivity behaviors as compared with those born to non-exposure mothers (all p < 0.05). Overall, prenatal ETS exposure could be associated with a detrimental impact on offspring's hyperactivity behaviors, and public health efforts are needed to reduce prenatal ETS exposure.

Alteration of adolescent aversive nicotine response and anxiety-like behavior in nicotine-exposed rats during late lactation period

Early nicotine exposure is an important cause of further habitual tobacco smoking. Although nicotine has not only rewarding but also aversive properties, the effects of early nicotine exposure on the distinct properties of nicotine are not well known. To reveal the effects of early adolescent nicotine exposure on further persistent tobacco smoking, we demonstrated developmental changes in nicotine-related appetitive and aversive behaviors of rats exposed to nicotine during the late lactation period. Sprague-Dawley rats were injected with saline or nicotine (2, 6 and 12mg/kg). We performed a two bottle free-choice test using escalating doses of nicotine (25, 50 and 100μg/ml), saccharin and quinine and the open field test in both adolescent and adult rats. The rats' aversive response to nicotine was increased according to the increase in nicotine concentration. Adolescent rats showed higher nicotine preference and consumption behaviors than did adult rats at an aversive dose of nicotine. Nicotine-exposed rats increased adolescent nicotine consumption when the nicotine concentration was 12mg/kg. We observed significant increases in anxious behaviors in adolescent nicotine-injected rats compared to saline-injected rats, but there were no alterations in adult rats. In both adolescent and adult rats, saccharin and quinine intake were not significantly different between groups. Taken together, it suggests that repeated nicotine exposure in late lactation period affect changes in aversive nicotine responses and anxious behaviors during adolescence but there is no difference in adults.

E-cigarette Use, Cigarette Smoking, Dual Use, and Problem Behaviors Among U.S. Adolescents: Results From a National Survey

PURPOSE

There is a need to obtain greater clarity regarding adolescents' e-cigarette use and the associations of use with a wider range of risk behaviors. This study examines the associations among past-month e-cigarette use only, traditional cigarette smoking only, dual use (i.e., concurrent e-cigarette use and cigarette smoking), school-related (i.e., truancy and poor academic performance) risk behaviors, and substance-related (i.e., alcohol use, binge drinking, marijuana use, illicit drug use, and nonmedical prescription drug use) risk behaviors.

METHODS

Data were collected via self-administered questionnaires from a nationally representative sample of 8,696 high school seniors.

RESULTS

An estimated 9.9% of U.S. high school seniors reported past-month e-cigarette use only, 6.0% reported past-month cigarette smoking only, and 7.3% reported past-month dual use. School- and substance-related risk behaviors had strong associations with past-month e-cigarette use. Adolescents who only used e-cigarettes had significantly greater odds of all school- and substance-related risk behaviors relative to nonusers. Dual users had significantly greater odds of frequent/daily e-cigarette use as well as all school- and substance-related risk behaviors relative to those who only used e-cigarettes. Finally, adolescents who engaged in frequent/daily e-cigarette use had significantly greater odds of binge drinking, marijuana use, other illicit drug use and nonmedical prescription drug use, relative to experimental e-cigarette users.

CONCLUSIONS

E-cigarette use is common among U.S. adolescents, and there are robust associations between e-cigarette use and school- and substance-related risk behaviors. There is evidence that e-cigarette use clusters with risk behaviors and appears to represent a problem behavior, especially dual use of e-cigarettes and traditional cigarettes.

Genotype-environment interaction on human cognitive function conditioned on the status of breastfeeding and maternal smoking around birth

We estimated genotype by environment interaction (G × E) on later cognitive performance and educational attainment across four unique environments, i.e. 1) breastfed without maternal smoking, 2) breastfed with maternal smoking, 3) non-breastfed without maternal smoking and 4) non-breastfed with maternal smoking, using a novel design and statistical approach that was facilitated by the availability of datasets with the genome-wide single nucleotide polymorphisms (SNPs). There was significant G × E for both fluid intelligence (p-value = 1.0E-03) and educational attainment (p-value = 8.3E-05) when comparing genetic effects in the group of individuals who were breastfed without maternal smoking with those not breastfed without maternal smoking. There was also significant G × E for fluid intelligence (p-value = 3.9E-05) when comparing the group of individuals who were breastfed with maternal smoking with those not breastfed without maternal smoking. Genome-wide significant SNPs were different between different environmental groups. Genomic prediction accuracies were significantly higher when using the target and discovery sample from the same environmental group than when using those from the different environmental groups. This finding demonstrates G × E has important implications for future studies on the genetic architecture, genome-wide association studies and genomic predictions.

Maternal Smoking During Pregnancy Is Associated With Offspring's Musculoskeletal Pain in Adolescence: Structural Equation Modeling

Introduction

Smoking and behavioral problems are related to musculoskeletal (MS) pain in adolescence. Maternal smoking during pregnancy (MSDP) is associated with offspring's behavioral problems but its relation to MS pain in adolescence is unknown. Our purpose was to investigate whether there is an association between MSDP, the number of pain sites in adolescence, and the factors that potentially mediate this relationship.

Methods

We evaluated the association of MSDP with offspring's MS pain at 16 years among participants of the Northern Finland Birth Cohort 1986 (n = 6436, 3360 girls, 68% of all births) using Chi-square test and independent samples t test. We used structural equation modeling to assess the mediating factors stratified by gender.

Results

MSDP was frequent (22%) associating with paternal smoking (p < .001), externalization problems at 8 years (p = .009 boys, p = .002 girls), offspring's smoking at 16 years (p < .001), externalizing problems at 16 years (p < .001), family's social class (p < .001) and intactness of the family status (p < .001). The mean number of offspring's MS pain sites was higher among adolescents whose mothers had smoked during pregnancy than among those whose mothers were nonsmokers (p = .002 boys, p = .012 girls). The association between MSDP and MS pain at 16 years was mediated by externalizing problems at 8 years (p < .001) and 16 years (p < 0.001).

Conclusions

MSDP increased the risk of offspring's MS pain in adolescence, and the association was mediated by offspring's externalizing problems during childhood and early adolescence.

Implications

This study indicates that MSDP increases the risk of MS pain in adolescence and the effect is mediated by externalizing problems. Our results add to the evidence on harmfulness of MSDP for offspring, and can be used as additional information in interventions aiming to influence MSDP.

Counterfeit Electronic Cigarette Products with Mislabeled Nicotine Concentrations

OBJECTIVES

We compared nicotine concentrations in one brand of refill fluids that were purchased in 4 countries and labeled 0 mg of nicotine/mL. We then identified counterfeit e-cigarette products from these countries.

METHODS

Overall, 125 e-cigarette refill fluids were purchased in Nigeria, the United States (US), England, and China. Nicotine concentrations were measured using high performance liquid chromatography and compared to labeled concentrations. Refill fluids were examined to identify physical differences and grouped into authentic and counterfeit products.

RESULTS

Whereas nicotine was in 51.7% (15/29) of the Nigerian, 3.7% (1/27) of the Chinese and 1.6% (1/61) of the American refill fluids (range = 0.4 - 20.4 mg/mL), 8 British products did not contain nicotine. Products from China, the US, and Nigeria with trace amounts of nicotine (0.4 to 0.6 mg/mL) were authentic; however, all products from Nigeria with more than 3.7 mg/mL were counterfeit.

CONCLUSIONS

We introduce 2 novel issues in the e-cigarette industry, the production of counterfeit refill fluids under a brandjacked label and inclusion of nicotine in 81.3% of the counterfeit products labeled 0 mg/mL. This study emphasizes the need for better control and monitoring of nicotine containing products and sales outlets.

Maternal smoking and autism spectrum disorder: meta-analysis with population smoking metrics as moderators

While exposure to nicotine during developmental periods can significantly affect brain development, studies examining the association between maternal smoking and autism spectrum disorder (ASD) in offspring have produced conflicting findings, and prior meta-analyses have found no significant association. Our meta-analysis used a novel approach of investigating population-level smoking metrics as moderators. The main meta-analysis, with 22 observational studies comprising 795,632 cases and 1,829,256 control participants, used a random-effects model to find no significant association between maternal smoking during pregnancy and ASD in offspring (pooled odds ratio (OR) = 1.16, 95% CI: 0.97–1.40). However, meta-regression analyses with moderators were significant when we matched pooled ORs with adult male smoking prevalence (z = 2.55, p = 0.01) in each country, using World Health Organization data. Our study shows that using population-level smoking metrics uncovers significant relationships between maternal smoking and ASD risk. Correlational analyses show that male smoking prevalence approximates secondhand smoke exposure. While we cannot exclude the possibility that our findings reflect the role of paternal or postnatal nicotine exposure, as opposed to maternal or in utero nicotine exposure, this study underlines the importance of investigating paternal and secondhand smoking in addition to maternal smoking in ASD.

Larval exposure to field-realistic concentrations of clothianidin has no effect on development rate, over-winter survival or adult metabolic rate in a solitary bee, Osmia bicornis

There is widespread concern regarding the effects of agro-chemical exposure on bee health, of which neonicotinoids, systemic insecticides detected in the pollen and nectar of both crops and wildflowers, have been the most strongly debated. The majority of studies examining the effect of neonicotinoids on bees have focussed on social species, namely honey bees and bumble bees. However, most bee species are solitary, their life histories differing considerably from these social species, and thus it is possible that their susceptibility to pesticides may be quite different. Studies that have included solitary bees have produced mixed results regarding the impact of neonicotinoid exposure on survival and reproductive success. While the majority of studies have focused on the effects of adult exposure, bees are also likely to be exposed as larvae via the consumption of contaminated pollen. Here we examined the effect of exposure of Osmia bicornis larvae to a range of field-realistic concentrations (0–10 ppb) of the neonicotinoid clothianidin, observing no effect on larval development time, overwintering survival or adult weight. Flow-through respirometry was used to test for latent effects of larval exposure on adult physiological function. We observed differences between male and female bees in the propensity to engage in discontinuous gas exchange; however, no effect of larval clothianidin exposure was observed. Our results suggest that previously reported adverse effects of neonicotinoids on O. bicornis are most likely mediated by impacts on adults.

Camellia sinensis Prevents Perinatal Nicotine-Induced Neurobehavioral Alterations, Tissue Injury, and Oxidative Stress in Male and Female Mice Newborns

Nicotine exposure during pregnancy induces oxidative stress and leads to behavioral alterations in early childhood and young adulthood. The current study aimed to investigate the possible protective effects of green tea (Camellia sinensis) against perinatal nicotine-induced behavioral alterations and oxidative stress in mice newborns. Pregnant mice received 50 mg/kg C. sinensis on gestational day 1 (PD1) to postnatal day 15 (D15) and were subcutaneously injected with 0.25 mg/kg nicotine from PD12 to D15. Nicotine-exposed newborns showed significant delay in eye opening and hair appearance and declined body weight at birth and at D21. Nicotine induced neuromotor alterations in both male and female newborns evidenced by the suppressed righting, rotating, and cliff avoidance reflexes. Nicotine-exposed newborns exhibited declined memory, learning, and equilibrium capabilities, as well as marked anxiety behavior. C. sinensis significantly improved the physical development, neuromotor maturation, and behavioral performance in nicotine-exposed male and female newborns. In addition, C. sinensis prevented nicotine-induced tissue injury and lipid peroxidation and enhanced antioxidant defenses in the cerebellum and medulla oblongata of male and female newborns. In conclusion, this study shows that C. sinensis confers protective effects against perinatal nicotine-induced neurobehavioral alterations, tissue injury, and oxidative stress in mice newborns.

Thiamethoxam Actara® induced alterations in kidney liver cerebellum and hippocampus of male rats

Thiamethoxam (TMX), a second-generation neonicotinoid insecticide, is one of the most widely used insecticides in Algeria. The present study assessed the effects of repeated subchronic exposure to the commercial formulation of thiamethoxam (Actara®, 25% WG) in albino male rats. The toxic effects of thiamethoxam (TMX) were studied biochemically and histopathologically. Twenty-eight male albino rats weighing between 226 and 243 g were randomly assigned to four groups. One group served as control, and the other three were served as experimental groups administered a neonicotinoid thiamethoxam (TMX; 26, 39 and 78 mg/kg/day) for 6 weeks. The effects of the insecticide on various biochemical parameters were evaluated at 2, 4 and 6 weeks. Histopathological studies were carried out in the liver, kidney, cerebellum and hippocampus at the end of the experiment. Changes in biochemical parameters glucose, ALT (alanine aminotransferase), AST (aspartate aminotransferase), γGT (gamma-glutamyltransferase) ALP (alkaline phosphatase) urea and creatinine were observed in treated-groups in a dose dependent manner when compared to the control. Histopathological alterations were more intense in male rats from the TMX high dose group than those from group 2 and 3. Based on these results, subchronic oral administration of thiamethoxam altered the biochemical parameters, which correlated with histopathological changes in the liver kidney and brain.

Maternal Folic Acid Supplementation During Pregnancy Improves Neurobehavioral Development in Rat Offspring

Maternal folate status during pregnancy may influence central nervous system (CNS) development in offspring. However, the recommended intakes of folic acid for women of childbearing age differ among countries and there is still no consensus about whether folic acid should be supplemented continuously throughout pregnancy. We hypothesized that folic acid supplementation may be more beneficial for offspring's neurobehavioral development if prolonged throughout pregnancy instead of being limited to the periconceptional period. In this study, three groups of the female rats were fed folate-normal, folate-deficient, or folate-supplemented diets throughout pregnancy. In another group, the female rats were fed folate-supplemented diet from mating for 10 consecutive days and then fed folate-normal diet for remainder days of pregnancy. The results showed that maternal folate deficiency increased plasma homocysteine (Hcy) concentration in dams, delayed early sensory-motor reflex development, impaired spatial learning and memory ability, and caused ultrastructural damages in the hippocampus of offspring. Maternal folic acid supplementation would be more effective on improving early sensory-motor reflex development and spatial learning and memory ability in offspring if prolonged throughout pregnancy instead of being limited to the periconceptional period. In conclusion, prolonged maternal folic acid supplementation throughout pregnancy would be more effective in neurobehavioral development of offspring in rats.

Perceptions and Experiences with Flavored Non-Menthol Tobacco Products: A Systematic Review of Qualitative Studies

Although a few countries have banned flavored cigarettes (except menthol), flavors in most tobacco products remain unregulated across the globe. We conducted a systematic review of qualitative studies examining perceptions of and experiences with flavored non-menthol tobacco products. Of 20 studies on flavored tobacco products included in our qualitative systematic review, 10 examined hookah, six examined e-cigarettes, two examined little cigars and cigarillos (LCCs), and three examined other tobacco products, including cigarettes. The majority of studies, regardless of product type, reported positive perceptions of flavored tobacco products, particularly among young adults and adolescents. In six studies that assessed perceptions of harm (including hookah, LCCs, and other flavored tobacco products), participants believed flavored tobacco products to be less harmful than cigarettes. In studies that examined the role of flavors in experimentation and/or initiation (including three studies on e-cigarettes, one hookah study and one LCC study), participants mentioned flavors as specifically leading to their experimentation and/or initiation of flavored tobacco products. Given that many countries have not yet banned flavors in tobacco products, these findings add to existing research on why individuals use flavored tobacco products and how they perceive harm in flavored tobacco products, providing further support for banning non-menthol flavors in most tobacco products.

Plausible Roles for RAGE in Conditions Exacerbated by Direct and Indirect (Secondhand) Smoke Exposure

Approximately 1 billion people smoke worldwide, and the burden placed on society by primary and secondhand smokers is expected to increase. Smoking is the leading risk factor for myriad health complications stemming from diverse pathogenic programs. First- and second-hand cigarette smoke contains thousands of constituents, including several carcinogens and cytotoxic chemicals that orchestrate chronic inflammatory responses and destructive remodeling events. In the current review, we outline details related to compromised pulmonary and systemic conditions related to smoke exposure. Specifically, data are discussed relative to impaired lung physiology, cancer mechanisms, maternal-fetal complications, cardiometabolic, and joint disorders in the context of smoke exposure exacerbations. As a general unifying mechanism, the receptor for advanced glycation end-products (RAGE) and its signaling axis is increasingly considered central to smoke-related pathogenesis. RAGE is a multi-ligand cell surface receptor whose expression increases following cigarette smoke exposure. RAGE signaling participates in the underpinning of inflammatory mechanisms mediated by requisite cytokines, chemokines, and remodeling enzymes. Understanding the biological contributions of RAGE during cigarette smoke-induced inflammation may provide critically important insight into the pathology of lung disease and systemic complications that combine during the demise of those exposed.

Cross-sectional study examining the prevalence, correlates and sequencing of electronic cigarette and tobacco use among 11-16-year olds in schools in Wales

OBJECTIVES

To examine the prevalence and frequency of electronic (e)-cigarette use among young people in Wales, associations with socio-demographic characteristics, smoking and other substances and the sequencing of e-cigarette and tobacco use.

DESIGN

A cross-sectional survey of school students in Wales undertaken in 2015.

SETTING

87 secondary schools in Wales.

PARTICIPANTS

Students aged 11-16 (n=32 479).

RESULTS

Overall, students were nearly twice as likely to report ever using e-cigarettes (18.5%) as smoking tobacco (10.5%). Use of e-cigarettes at least weekly was 2.7% in the whole sample, rising to 5.7% among those aged 15-16. Almost half (41.8%) of daily smokers reported being regular e-cigarette users. Regular e-cigarette use was more prevalent among current cannabis users (relative risk ratio (RRR)=41.82; 95% CI 33.48 to 52.25)), binge drinkers (RRR=47.88; 95% CI 35.77 to 64.11), users of mephedrone (RRR=32.38; 95% CI 23.05 to 45.52) and laughing gas users (RRR=3.71; 95% CI 3.04 to 4.51). Multivariate analysis combining demographics and smoking status showed that only gender (being male) and tobacco use independently predicted regular use of e-cigarettes (p<0.001). Among weekly smokers who had tried tobacco and e-cigarettes (n=877), the vast majority reported that they tried tobacco before using an e-cigarette (n=727; 82.9%).

CONCLUSIONS

Since 2013, youth experimentation with e-cigarettes has grown rapidly in Wales and is now almost twice as common as experimentation with tobacco. Regular use has almost doubled, and is increasing among never and non-smokers. These data suggest that e-cigarette use among youth is an emerging public health issue, even though there remains no evidence that it represents a new pathway into smoking. Mixed methods longitudinal research is needed to explore why young people use e-cigarettes, and to develop interventions to prevent further increases in use.

In utero exposure to maternal smoking is associated with DNA methylation alterations and reduced neuronal content in the developing fetal brain

Background

Intrauterine exposure to maternal smoking is linked to impaired executive function and behavioral problems in the offspring. Maternal smoking is associated with reduced fetal brain growth and smaller volume of cortical gray matter in childhood, indicating that prenatal exposure to tobacco may impact cortical development and manifest as behavioral problems. Cellular development is mediated by changes in epigenetic modifications such as DNA methylation, which can be affected by exposure to tobacco.

Results

In this study, we sought to ascertain how maternal smoking during pregnancy affects global DNA methylation profiles of the developing dorsolateral prefrontal cortex (DLPFC) during the second trimester of gestation. When DLPFC methylation profiles (assayed via Illumina, HM450) of smoking-exposed and unexposed fetuses were compared, no differentially methylated regions (DMRs) passed the false discovery correction (FDR ≤ 0.05). However, the most significant DMRs were hypomethylated CpG Islands within the promoter regions of GNA15 and SDHAP3 of smoking-exposed fetuses. Interestingly, the developmental up-regulation of SDHAP3 mRNA was delayed in smoking-exposed fetuses. Interaction analysis between gestational age and smoking exposure identified significant DMRs annotated to SYCE3, C21orf56/LSS, SPAG1 and RNU12/POLDIP3 that passed FDR. Furthermore, utilizing established methods to estimate cell proportions by DNA methylation, we found that exposed DLPFC samples contained a lower proportion of neurons in samples from fetuses exposed to maternal smoking. We also show through in vitro experiments that nicotine impedes the differentiation of neurons independent of cell death.

Conclusions

We found evidence that intrauterine smoking exposure alters the developmental patterning of DNA methylation and gene expression and is associated with reduced mature neuronal content, effects that are likely driven by nicotine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13072-017-0111-y) contains supplementary material, which is available to authorized users.

Adolescents' attitudes towards e-cigarette ingredients, safety, addictive properties, social norms, and regulation

E-cigarette use has dramatically increased. While studies have examined adolescents' attitudes towards smoking, few have extended this research to adolescents' attitudes towards e-cigarettes. The goal of this study was to examine adolescents' attitudes regarding e-cigarette ingredients, safety, addictive properties, social norms, accessibility, price, and regulation; and determine whether attitudes differ by past cigarette/e-cigarette use. Participants were 786 9th and 12th graders from California (63.21% females; mean age=16.10years [SD=1.6]; 26.61% White, 21.98% Asian/Pacific Islander, 29.82% Hispanic, and 21.59% other). Results indicated that 19.05% of participants believed smoke from e-cigarettes is water; 23.03% believed e-cigarettes aren't a tobacco product; 40.36% considered e-cigarettes to be for cessation, and 43.13% felt they were safer than cigarettes. Participants felt it was more acceptable to use e-cigarettes indoors and outdoors compared to cigarettes (p<0.0001), 23.13% felt raising e-cigarette taxes is a bad idea, 63.95% thought e-cigarettes were easier to get than cigarettes, 54.42% felt e-cigarettes cost too much, 64.33% felt the age for buying e-cigarettes should be raised, and 64.37% favored e-cigarette regulation. Adolescents who used e-cigarettes and/or cigarettes had significantly more favorable e-cigarette attitudes than non-users. This study indicates that adolescents are aware of some of the risks of e-cigarettes, although many harbor misperceptions and hold more favorable attitudes towards e-cigarettes than cigarettes. Of concern is the relationship between favorable e-cigarette attitudes and use. Findings suggest the need to provide adolescents with correct information about e-cigarette ingredients, risks, and the insufficient evidence of their role in cigarette cessation.

The effect of prenatal smoking exposure on daily smoking among teenage offspring

AIMS

To study the predictive associations between maternal smoking and the impact of quitting smoking during pregnancy and offspring daily smoking at age 15-16 years.

DESIGN

The Northern Finland Birth Cohort 1986 (NFBC86) includes 99% of all births in the region and has an ongoing follow-up. Data were collected using questionnaires at 24th gestational week during pregnancy and after delivery, and at follow-up in 2001-02, when the offspring were aged 15-16 years.

SETTING

Northern Finland.

PARTICIPANTS

NFBC86 included 9432 live born children. Data regarding maternal smoking during pregnancy and offspring smoking at age 15-16 years were available for 4462 subjects (47.3% of the original sample).

MEASUREMENTS

The outcome was offspring's self-reported daily smoking. Maternal smoking during pregnancy was considered using a four-class variable: (1) no smoking, (2) mother had smoked, but had quit smoking before becoming pregnant, (3) mother quit smoking during the 1st trimester and (4) mother quit smoking after the 1st trimester or continued smoking throughout the pregnancy. Information regarding paternal smoking during pregnancy, maternal and paternal smoking and education level, family structure and dwelling at offspring's age 15-16 years were considered potential confounding variables.

FINDINGS

Continuing smoking after the 1st trimester increased the odds of daily smoking among offspring, independently of confounding factors [odds ratio (OR) = 1.8, 95% confidence interval (CI) = 1.3-2.5]. Continuing to smoke after the 1st trimester was associated with higher odds compared with quitting smoking during the 1st trimester. Also, parental smoking at offspring age 15-16 years increased the odds of offspring daily smoking, independently of prenatal smoking exposure.

CONCLUSIONS

Prenatal smoking exposure increases the risk for offspring adolescent daily smoking. Quitting smoking during the early stages of pregnancy may decrease the odds for offspring smoking.

Elevated kynurenine pathway metabolism during neurodevelopment: Implications for brain and behavior

The kynurenine pathway (KP) of tryptophan degradation contains several neuroactive metabolites that may influence brain function in health and disease. Mounting focus has been dedicated to investigating the role of these metabolites during neurodevelopment and elucidating their involvement in the pathophysiology of psychiatric disorders with a developmental component, such as schizophrenia. In this review, we describe the changes in KP metabolism in the brain from gestation until adulthood and illustrate how environmental and genetic factors affect the KP during development. With a particular focus on kynurenic acid, the antagonist of α7 nicotinic acetylcholine (α7nACh) and N-methyl-d-aspartate (NMDA) receptors, both implicated in modulating brain development, we review animal models designed to ascertain the role of perinatal KP elevation on long-lasting biochemical, neuropathological, and behavioral deficits later in life. We present new data demonstrating that combining perinatal choline-supplementation, to potentially increase activation of α7nACh receptors during development, with embryonic kynurenine manipulation is effective in attenuating cognitive impairments in adult rat offspring. With these findings in mind, we conclude the review by discussing the advancement of therapeutic interventions that would target not only symptoms, but potentially the root cause of central nervous system diseases that manifest from a perinatal KP insult. This article is part of the Special Issue entitled 'The Kynurenine Pathway in Health and Disease'.

Impact of advertisements promoting candy-like flavoured e-cigarettes on appeal of tobacco smoking among children: an experimental study

BACKGROUND

There are concerns that the marketing of e-cigarettes may increase the appeal of tobacco smoking in children. We examined this concern by assessing the impact on appeal of tobacco smoking after exposure to advertisements for e-cigarettes with and without candy-like flavours, such as, bubble gum and milk chocolate.

METHODS

We assigned 598 English school children (aged 11-16 years) to 1 of 3 different conditions corresponding to the adverts to which they were exposed: adverts for flavoured e-cigarettes, adverts for non-flavoured e-cigarettes or a control condition in which no adverts were shown. The primary endpoint was appeal of tobacco smoking. Secondary endpoints were: appeal of using e-cigarettes, susceptibility to tobacco smoking, perceived harm of tobacco, appeal of e-cigarette adverts and interest in buying and trying e-cigarettes.

RESULTS

Tobacco smokers and e-cigarette users were excluded from analyses (final sample=471). Exposure to either set of adverts did not increase the appeal of tobacco smoking, the appeal of using e-cigarettes, or susceptibility to tobacco smoking. Also, it did not reduce the perceived harm of tobacco smoking, which was high. Flavoured e-cigarette adverts were, however, more appealing than adverts for non-flavoured e-cigarettes and elicited greater interest in buying and trying e-cigarettes.

CONCLUSIONS

Exposure to adverts for e-cigarettes does not seem to increase the appeal of tobacco smoking in children. Flavoured, compared with non-flavoured, e-cigarette adverts did, however, elicit greater appeal and interest in buying and trying e-cigarettes. Further studies extending the current research are needed to elucidate the impact of flavoured and non-flavoured e-cigarette adverts.

Adolescent Awareness and Use of Electronic Cigarettes: A Review of Emerging Trends and Findings

Adult electronic cigarette (e-cigarette) use is increasing globally, and early studies have suggested that similar trends may be observed among the adolescent population, albeit at lower levels. The current literature review presents data collected since 2014 from 21 cross-sectional studies and one cohort study that were all published in English. In particular, it focuses on awareness, ever use, past 30-day use, and regular use of e-cigarettes. The article suggests that adolescents are nearing complete awareness of e-cigarettes. Furthermore, in relation to ever use and past 30-day use, higher prevalence rates continue to be reported across time, especially in the United States. Nonetheless, reported regular use of e-cigarettes remains much lower than past 30-day use, although conclusions are limited due to inconsistencies with measurement and consequent lack of cross-cultural applicability. The majority of studies do not report whether adolescents use non-nicotine e-cigarettes. There is a current absence of longitudinal studies that explore any association between e-cigarettes and tobacco use and little qualitative data that may illuminate how and why adolescents use e-cigarettes. Through addressing these methodological limitations, future research will be able to inform health care and policy more effectively.

DNA methylation and substance-use risk: a prospective, genome-wide study spanning gestation to adolescence

Epigenetic processes have been implicated in addiction; yet, it remains unclear whether these represent a risk factor and/or a consequence of substance use. Here, we believe we conducted the first genome-wide, longitudinal study to investigate whether DNA methylation patterns in early life prospectively associate with substance use in adolescence. The sample comprised of 244 youth (51% female) from the Avon Longitudinal Study of Parents and Children (ALSPAC), with repeated assessments of DNA methylation (Illumina 450k array; cord blood at birth, whole blood at age 7) and substance use (tobacco, alcohol and cannabis use; age 14-18). We found that, at birth, epigenetic variation across a tightly interconnected genetic network (n=65 loci; q<0.05) associated with greater levels of substance use during adolescence, as well as an earlier age of onset amongst users. Associations were specific to the neonatal period and not observed at age 7. Key annotated genes included PACSIN1, NEUROD4 and NTRK2, implicated in neurodevelopmental processes. Several of the identified loci were associated with known methylation quantitative trait loci, and consequently likely to be under significant genetic control. Collectively, these 65 loci were also found to partially mediate the effect of prenatal maternal tobacco smoking on adolescent substance use. Together, findings lend novel insights into epigenetic correlates of substance use, highlight birth as a potentially sensitive window of biological vulnerability and provide preliminary evidence of an indirect epigenetic pathway linking prenatal tobacco exposure and adolescent substance use.

Impacts on prenatal development of the human cerebellum: a systematic review

PURPOSE

The cerebellum is essential for normal neurodevelopment and is particularly susceptible for intra-uterine disruptions. Although some causal prenatal exposures have been identified, the origin of neurodevelopmental disorders remains mostly unclear. Therefore, a systematic literature search was conducted to provide an overview of parental environmental exposures and intrinsic factors influencing prenatal cerebellar growth and development in humans.

MATERIALS AND METHODS

The literature search was limited to human studies in the English language and was conducted in Embase, Medline, Cochrane, Web of Science, Pubmed and GoogleScholar. Eligible studies were selected by three independent reviewers and study quality was scored by two independent reviewers.

RESULTS

The search yielded 3872 articles. We found 15 eligible studies reporting associations between cerebellar development and maternal smoking (4), use of alcohol (3), in vitro fertilization mediums (1), mercury (1), mifepristone (2), aminopropionitriles (1), ethnicity (2) and cortisol levels (1). No studies reported on paternal factors.

CONCLUSIONS

Current literature on associations between parental environmental exposures, intrinsic factors and human cerebellar development is scarce. Yet, this systematic review provided an essential overview of human studies demonstrating the vulnerability of the cerebellum to the intra-uterine environment.

Changes in Electronic Cigarette Use from 2013 to 2015 and Reasons for Use among Finnish Adolescents

Electronic cigarettes are quite a new potential source of nicotine addiction among youth. More research is needed, particularly on e-liquid use and socioeconomic factors as potential determinants. We studied changes from 2013 to 2015 in adolescent e-cigarette awareness and ever-use, types of e-liquids, and determinants in Finland. In 2015, we studied weekly use and reasons for ever-use. Data were from two national surveys of 12–18-year-old Finns (2013, n = 3535, response rate 38%; 2015, n = 6698, 41%). Descriptive statistics and logistic regression analysis were used. Awareness and ever-use of e-cigarettes increased significantly from 2013 to 2015 in all age and gender groups. Ever-use increased from 17.4% to 25%, with half having tried nicotine e-liquids. In 2015, weekly use was rare (1.5%). Daily cigarette smoking was the strongest determinant (OR 51.75; 95% CI 38.18–70.14) for e-cigarette ever-use, as for e-cigarette weekly use, but smoking experimentation and ever-use of snus (Swedish type moist snuff) and waterpipes alongside parental smoking and poor academic achievement also increased the odds for ever-use. The most common reason behind e-cigarette ever-use was the desire to try something new. To conclude, adolescent e-cigarette ever-use is increasing, and also among never-smokers. Tobacco-related factors are stronger determinants for e-cigarette use than socioeconomic factors.

Perinatal smoking exposure and behavioral problems in Japanese children aged 5 years: The Kyushu Okinawa Maternal and Child Health Study

BACKGROUND

Epidemiological evidence regarding the relationship between maternal secondhand smoke (SHS) exposure during pregnancy and postnatal SHS exposure and childhood behavioral problems is scarce.

OBJECTIVE

The present prebirth cohort study investigated the association between perinatal smoking exposure and behavioral problems in Japanese children aged 5 years.

METHODS

Subjects were 1200 mother-child pairs. Data on variables under study were obtained using parent questionnaires. Emotional problems, conduct problems, hyperactivity problems, and peer problems were assessed using the Strengths and Difficulties Questionnaire. Adjustment was made for maternal age, gestation at baseline, region of residence at baseline, number of children at baseline, maternal and paternal education, household income, maternal depressive symptoms during pregnancy, maternal alcohol intake during pregnancy, child's birth weight, child's sex, and breastfeeding duration.

RESULTS

Maternal smoking during pregnancy was independently associated with increased risk of conduct problems and hyperactivity problems (adjusted odds ratios: ORs [95% confidence intervals: CIs]=1.93 [1.15-3.17] and 1.89 [1.03-3.33], respectively). Maternal SHS exposure at work during pregnancy was independently positively related to conduct problems and hyperactivity problems (adjusted ORs [95% CI]=1.54 [1.01-2.31] and 1.69 [1.04-2.67], respectively). Smoking by any household member, and especially by the child's father, during the first year of life was independently associated with an increased risk of emotional problems (adjusted ORs [95% CI]=1.55 [1.06-2.26] and 1.63 [1.11-2.40], respectively).

CONCLUSIONS

Maternal smoking and maternal SHS exposure at work during pregnancy may increase the risk of conduct problems and hyperactivity problems. Smoking by any household member, and especially by the child's father, may increase the risk of emotional problems.

Preference for gain- or loss-framed electronic cigarette prevention messages

BACKGROUND

Effective electronic cigarette (e-cigarette) prevention messages are needed to combat the rising popularity/uptake of e-cigarettes among youth. We examined preferences for e-cigarette prevention messages that either emphasized gains (e.g., You save money by not using e-cigarettes) or losses (e.g., You spend money by using e-cigarettes) among adolescents and young adults.

METHODS

Using surveys in two middle schools, four high schools, and one college in CT (N=5405), we assessed students' preferences for gain- or loss-framed e-cigarette prevention messages related to four themes: financial cost, health risks, addiction potential, and social labeling as a smoker. We also assessed whether preferences for each message framing theme differed by sex, school level, cigarette-use status, and e-cigarette use-status. We also examined whether preference for message framing differed by cigarette and e-cigarette susceptibility status among never e-cigarette users.

RESULTS

Overall, loss-framing was preferred for message themes related to health risks, addiction potential, and social labeling as a smoker, whereas gain-framing was preferred for message themes related to financial cost. Logistic regression analyses showed that 1) females preferred loss-framed messages for all themes relative to males, 2) lifetime e-cigarette users preferred loss-framed health risks and social labeling messages relative to never users, and 3) high school students preferred gain-framed social labeling messages relative to college students. The preference for message framing did not differ by cigarette or e-cigarette susceptibility.

CONCLUSIONS

Preference for message framing differed by themes and individual characteristics. This formative research could inform the construction of persuasive e-cigarette prevention messages.

Adolescent Maturational Transitions in the Prefrontal Cortex and Dopamine Signaling as a Risk Factor for the Development of Obesity and High Fat/High Sugar Diet Induced Cognitive Deficits

Adolescence poses as both a transitional period in neurodevelopment and lifestyle practices. In particular, the developmental trajectory of the prefrontal cortex (PFC), a critical region for behavioral control and self-regulation, is enduring, not reaching functional maturity until the early 20 s in humans. Furthermore, the neurotransmitter dopamine is particularly abundant during adolescence, tuning the brain to rapidly learn about rewards and regulating aspects of neuroplasticity. Thus, adolescence is proposed to represent a period of vulnerability towards reward-driven behaviors such as the consumption of palatable high fat and high sugar diets. This is reflected in the increasing prevalence of obesity in children and adolescents as they are the greatest consumers of “junk foods”. Excessive consumption of diets laden in saturated fat and refined sugars not only leads to weight gain and the development of obesity, but experimental studies with rodents indicate they evoke cognitive deficits in learning and memory process by disrupting neuroplasticity and altering reward processing neurocircuitry. Consumption of these high fat and high sugar diets have been reported to have a particularly pronounced impact on cognition when consumed during adolescence, demonstrating a susceptibility of the adolescent brain to enduring cognitive deficits. The adolescent brain, with heightened reward sensitivity and diminished behavioral control compared to the mature adult brain, appears to be a risk for aberrant eating behaviors that may underpin the development of obesity. This review explores the neurodevelopmental changes in the PFC and mesocortical dopamine signaling that occur during adolescence, and how these potentially underpin the overconsumption of palatable food and development of obesogenic diet-induced cognitive deficits.

Functional Connectivity Abnormalities of Brain Regions with Structural Deficits in Young Adult Male Smokers

Smoking is one of the most prevalent dependence disorders. Previous studies have detected structural and functional deficits in smokers. However, few studies focused on the changes of resting state functional connectivity (RSFC) of the brain regions with structural deficits in young adult smokers. Twenty-six young adult smokers and 26 well-matched healthy non-smokers participated in our study. Voxel-based morphometry (VBM) and RSFC were employed to investigate the structural and functional changes in young adult smokers. Compared with healthy non-smokers, young smokers showed increased gray matter (GM) volume in the left putamen and decreased GM volume in the left anterior cingulate cortex (ACC). Moreover, GM volume in the left ACC has a negative correlation trend with pack-years and GM volume in the left putamen was positively correlated with pack-years. The left ACC and putamen with abnormal volumes were chosen as the regions of interest (ROIs) for the RSFC analysis. We found that smokers showed increased RSFC between the left ACC and right amygdala and between the left putamen and right anterior insula. We revealed structural and functional deficits within the frontostriatal circuits in young smokers, which may shed new insights into the neural mechanisms of smoking.

Smoking during pregnancy and ADHD risk: A genetically informed, multiple-rater approach

Maternal smoking during pregnancy (SDP) is a significant public health concern with adverse consequences to the health and well-being of the developing child, including behavioral outcomes such as Attention-Deficit Hyperactivity Disorder (ADHD). There is substantial interest in understanding the nature of this reported association, particularly in light of more recent genetically informed studies that suggest that the SDP-ADHD link is less clear than once thought. In a sample of families (N = 173) specifically selected for sibling pairs discordant for prenatal smoking exposure, we use a sibling-comparison approach that controls for shared genetic and familial influences to assess the effects of SDP on ADHD symptom dimensions. ADHD was measured by both parent and teacher report on the Conners report forms and the Child Behavior Checklist/Teacher Report Form (CBCL/TRF). Results for the CBCL/TRF Total ADHD score are consistent with prior genetically informed approaches and suggest that previously reported associations between SDP and ADHD are largely due to familial confounding rather than causal teratogenic effects. However, results from the Conners parent report suggest a potentially causal effect of SDP on hyperactive/impulsive and, to a lesser extent, total ADHD symptoms; SDP results in increased parent-reported hyperactive/impulsive and total ADHD symptoms even after accounting for genetic and familial confounding factors. This suggests that the Conners assessment (parent-report) may provide a sensitive measure for use in studies examining child specific SDP effects on continuous and dimensional aspects of ADHD. © 2016 Wiley Periodicals, Inc.

Ever-Use and Curiosity About Cigarettes, Cigars, Smokeless Tobacco, and Electronic Cigarettes Among US Middle and High School Students, 2012-2014

Introduction

Among young people, curiosity about tobacco products is a primary reason for tobacco experimentation and is a risk factor for future use. We examined whether curiosity about and ever-use of tobacco products among US middle and high school students changed from 2012 to 2014.

Methods

Data came from the 2012 and 2014 National Youth Tobacco Surveys, nationally representative surveys of US students in grades 6 through 12. For cigarettes, cigars, smokeless tobacco, and e-cigarettes (2014 only), students were classified as ever-users or never-users of each product. Among never-users, curiosity about using each product was assessed by asking participants if they had “definitely,” “probably,” “probably not,” or “definitely not” been curious about using the product.

Results

From 2012 to 2014, there were declines in ever-use of cigarettes (26% to 22%; P = .005) and cigars (21% to 18%; P = .003) overall and among students who were Hispanic (cigarettes, P = .001; cigars, P = .001) or black (cigarettes, P = .004; cigars, P = .01). The proportion of never-users reporting they were “definitely not” curious increased for cigarettes (51% to 54%; P = .01) and cigars (60% to 63%; P = .03). Ever-use and curiosity about smokeless tobacco did not change significantly from 2012 to 2014. In 2014, the proportion of young people who were “definitely” or “probably” curious never-users of each product was as follows: cigarettes, 11.4%; e-cigarettes, 10.8%; cigars, 10.3%; and smokeless tobacco, 4.4%.

Conclusion

The proportion of US students who are never users and are not curious about cigarettes and cigars increased. However, many young people remain curious about tobacco products, including e-cigarettes. Understanding factors driving curiosity can inform tobacco use prevention for youth.

Impaired function of α2-containing nicotinic acetylcholine receptors on oriens-lacunosum moleculare cells causes hippocampus-dependent memory impairments

Children of mothers who smoked during pregnancy are at significantly greater risk for cognitive impairments including memory deficits, but the mechanisms underlying this effect remain to be understood. In rodent models of smoking during pregnancy, early postnatal nicotine exposure results in impaired long-term hippocampus-dependent memory, functional loss of α2-containing nicotinic acetylcholine receptors (α2^∗ nAChRs) in oriens-lacunosum moleculare (OLM) cells, increased CA1 network excitation, and unexpected facilitation of long-term potentiation (LTP) at Schaffer collateral-CA1 synapses. Here we demonstrate that α2 knockout mice show the same pattern of memory impairment as previously observed in wild-type mice exposed to early postnatal nicotine. However, α2 knockout mice and α2 knockout mice exposed to early postnatal nicotine did not share all of the anomalies in hippocampal function observed in wild-type mice treated with nicotine during development. Unlike nicotine-treated wild-type mice, α2 knockout mice and nicotine-exposed α2 knockout mice did not demonstrate increased CA1 network excitation following Schaffer collateral stimulation and facilitated LTP, indicating that the effects are likely adaptive changes caused by activation of α2^∗ nAChRs during nicotine exposure and are unlikely related to the associated memory impairment. Thus, the functional loss of α2^∗ nAChRs in OLM cells likely plays a critical role in mediating this developmental-nicotine-induced hippocampal memory deficit.

Adolescents' interest in trying flavoured e-cigarettes

BACKGROUND

More US adolescents use e-cigarettes than smoke cigarettes. Research suggests flavoured e-cigarettes appeal to youth, but little is known about perceptions of and reasons for attraction to specific flavours.

METHODS

A national sample of adolescents (n=1125) ages 13-17 participated in a phone survey from November 2014 to June 2015. We randomly assigned adolescents to respond to survey items about 1 of 5 e-cigarette flavours (tobacco, alcohol, menthol, candy or fruit) and used regression analysis to examine the impact of flavour on interest in trying e-cigarettes and harm beliefs.

RESULTS

Adolescents were more likely to report interest in trying an e-cigarette offered by a friend if it were flavoured like menthol (OR=4.00, 95% CI 1.46 to 10.97), candy (OR=4.53, 95% CI 1.67 to 12.31) or fruit (OR=6.49, 95% CI 2.48 to 17.01) compared with tobacco. Adolescents believed that fruit-flavoured e-cigarettes were less harmful to health than tobacco-flavoured e-cigarettes (p<0.05). Perceived harm mediated the relationship between some flavours and interest in trying e-cigarettes. A minority of adolescents believed that e-cigarettes did not have nicotine (14.6%) or did not know whether they had nicotine (3.6%); these beliefs did not vary by flavour.

DISCUSSION

Candy-flavoured, fruit-flavoured and menthol-flavoured e-cigarettes appeal to adolescents more than tobacco-flavoured or alcohol-flavoured e-cigarettes. This appeal is only partially explained by beliefs about reduced harm. Given adolescents' interest in trying e-cigarettes with certain flavours, policymakers should consider restricting advertisements promoting flavoured products in media that reach large numbers of young people. Future research should examine other reasons for the appeal of individual flavours, such as novelty and perceived luxury.

What is the impact of e-cigarette adverts on children's perceptions of tobacco smoking? An experimental study

OBJECTIVE

Exposure to e-cigarette adverts increases children's positive attitudes towards using them. Given the similarity in appearance between e-cigarettes and tobacco cigarettes, we examined whether exposure to e-cigarette adverts has a cross-product impact on perceptions and attitudes towards smoking tobacco cigarettes.

METHODS

Children aged 11-16 (n=564) were interviewed in their homes and randomised to one of three groups: two groups saw different sets of 10 images of e-cigarette adverts and one group saw no adverts. Of the 20 e-cigarette adverts, 10 depicted the product as glamorous and 10 depicted it as healthy. The children then self-completed a questionnaire assessing perceived appeal, harms and benefits of smoking tobacco cigarettes.

RESULTS

The analyses were conducted on 411 children who reported never having smoked tobacco cigarettes or used e-cigarettes. Exposure to the adverts had no impact on the appeal or perceived benefits of smoking tobacco cigarettes. While the perceived harm of smoking more than 10 cigarettes per day was similar across groups, those exposed to either set of adverts perceived the harms of smoking one or two tobacco cigarettes occasionally to be lower than those in the control group.

CONCLUSIONS

This study provides the first evidence that exposure to e-cigarette adverts might influence children's perceptions of smoking tobacco cigarettes, reducing their perceived harm of occasional smoking. These results suggest the potential for e-cigarette adverts to undermine tobacco control efforts by reducing a potential barrier (ie, beliefs about harm) to occasional smoking.

Reasons for Trying E-cigarettes and Risk of Continued Use

BACKGROUND

Longitudinal research is needed to identify predictors of continued electronic cigarette (e-cigarette) use among youth. We expected that certain reasons for first trying e-cigarettes would predict continued use over time (eg, good flavors, friends use), whereas other reasons would not predict continued use (eg, curiosity).

METHODS

Longitudinal surveys from middle and high school students from fall 2013 (wave 1) and spring 2014 (wave 2) were used to examine reasons for trying e-cigarettes as predictors of continued e-cigarette use over time. Ever e-cigarette users (n = 340) at wave 1 were categorized into those using or not using e-cigarettes at wave 2. Among those who continued using e-cigarettes, reasons for trying e-cigarettes were examined as predictors of use frequency, measured as the number of days using e-cigarettes in the past 30 days at wave 2. Covariates included age, sex, race, and smoking of traditional cigarettes.

RESULTS

Several reasons for first trying e-cigarettes predicted continued use, including low cost, the ability to use e-cigarettes anywhere, and to quit smoking regular cigarettes. Trying e-cigarettes because of low cost also predicted more days of e-cigarette use at wave 2. Being younger or a current smoker of traditional cigarettes also predicted continued use and more frequent use over time.

CONCLUSIONS

Regulatory strategies such as increasing cost or prohibiting e-cigarette use in certain places may be important for preventing continued use in youth. In addition, interventions targeting current cigarette smokers and younger students may also be needed.

Prenatal smoking exposure and neuropsychiatric comorbidity of ADHD: a finnish nationwide population-based cohort study

BACKGROUND

Prenatal smoking exposure has been associated with attention-deficit/hyperactivity disorder (ADHD). ADHD is commonly associated with a wide spectrum of psychiatric comorbidity. The association between smoking and neuropsychiatric comorbidity of ADHD has remained understudied. The aim of this study is to examine the association between prenatal exposure to maternal smoking and offspring ADHD, and test whether the smoking-ADHD associations are stronger when ADHD is accompanied by other lifetime neuropsychiatric comorbidities.

METHODS

The study is based on a nested case-control design and includes all Finnish singletons born between 1991 and 2005 and diagnosed with ADHD by 2011 (n = 10,132), matched with four controls (n = 38,811) on date of birth, sex and residence in Finland.

RESULTS

The risk for ADHD with or without comorbidity was significantly increased among offspring exposed to maternal smoking on adjusting for potential confounders (OR = 1.75, CI 95 % = 1.65-1.86). Compared to the only ADHD cases, subjects with comorbid conduct disorder or oppositional defiant disorder had a significantly stronger association with smoking exposure (OR = 1.80, CI 95 % = 1.55-2.11).

CONCLUSIONS

Prenatal smoking represents an important risk factor for the ADHD comorbid with CD/ODD. Further research on the association between prenatal smoking exposure and neuropsychiatric comorbidity of ADHD is needed considering the increased risk among these subjects of an overall poor health outcome as compared to only ADHD. In particular, studies utilizing biomarkers or including subjects with neuropsychiatric conditions with and without comorbid ADHD are needed.

Mechanisms and genetic factors underlying co-use of nicotine and alcohol or other drugs of abuse

Concurrent use of tobacco and alcohol or psychostimulants represents a major public health concern, with use of one substance influencing consumption of the other. Co-abuse of these drugs leads to substantial negative health outcomes, reduced cessation, and high economic costs, but the underlying mechanisms are poorly understood. Epidemiological data suggest that tobacco use during adolescence plays a particularly significant role. Adolescence is a sensitive period of development marked by major neurobiological maturation of brain regions critical for reward processing, learning and memory, and executive function. Nicotine exposure during this time produces a unique and long-lasting vulnerability to subsequent substance use, likely via actions at cholinergic, dopaminergic, and serotonergic systems. In this review, we discuss recent clinical and preclinical data examining the genetic factors and mechanisms underlying co-use of nicotine and alcohol or cocaine and amphetamines. We evaluate the critical role of nicotinic acetylcholine receptors throughout, and emphasize the dearth of preclinical studies assessing concurrent drug exposure. We stress important age and sex differences in drug responses, and highlight a brief, low-dose nicotine exposure paradigm that may better model early use of tobacco products. The escalating use of e-cigarettes among youth necessitates a closer look at the consequences of early adolescent nicotine exposure on subsequent alcohol and drug abuse.

Postsynaptic nicotinic acetylcholine receptors facilitate excitation of developing CA1 pyramidal neurons

The hippocampus plays a key role in learning and memory. The normal development and mature function of hippocampal networks supporting these cognitive functions depends on afferent cholinergic neurotransmission mediated by nicotinic acetylcholine receptors. Whereas it is well-established that nicotinic receptors are present on GABAergic interneurons and on glutamatergic presynaptic terminals within the hippocampus, the ability of these receptors to mediate postsynaptic signaling in pyramidal neurons is not well understood. We use whole cell electrophysiology to show that heteromeric nicotinic receptors mediate direct inward currents, depolarization from rest and enhanced excitability in hippocampus CA1 pyramidal neurons of male mice. Measurements made throughout postnatal development provide a thorough developmental profile for these heteromeric nicotinic responses, which are greatest during the first 2 wk of postnatal life and decrease to low adult levels shortly thereafter. Pharmacological experiments show that responses are blocked by a competitive antagonist of α4β2* nicotinic receptors and augmented by a positive allosteric modulator of α5 subunit-containing receptors, which is consistent with expression studies suggesting the presence of α4β2 and α4β2α5 nicotinic receptors within the developing CA1 pyramidal cell layer. These findings demonstrate that functional heteromeric nicotinic receptors are present on CA1 pyramidal neurons during a period of major hippocampal development, placing these receptors in a prime position to play an important role in the establishment of hippocampal cognitive networks.

Comparing young adults to older adults in e-cigarette perceptions and motivations for use: implications for health communication

PURPOSE

Use of electronic cigarettes ('e-cigarettes' is rapidly rising, and is especially prevalent among young adults. A better understanding of e-cigarette perceptions and motivations for use is needed to inform health communication and educational efforts. This study aims to explore these aspects of use with a focus on comparing young adults to older adults.

METHODS

In this qualitative study, the investigator conducted semi-structured interviews among a purposive sample of e-cigarette users. Thematic content analysis was used to analyze qualitative data and document themes.

RESULTS

e-cigarettes were most commonly used for smoking cessation among both age groups. Young adults described other motivations for use including doing smoke tricks, being able to consume a wide variety of flavors, and helping them study. Some interviewees (11%) believed e-cigarettes were a healthy alternative to conventional cigarettes, while many other users (30%) expressed concerns about the unknown risks of e-cigarettes.

CONCLUSION

Findings were generally consistent across both age groups in their perceptions of harm from e-cigarettes and in subjective effects such as perceived addictiveness. However, individuals under 30 described unique motivations for e-cigarette use. Health messaging targeted to young adults should emphasize the potential health risks of e-cigarette use and recognize their distinct motivational aspects.

Consequences of adolescent use of alcohol and other drugs: Studies using rodent models

Studies using animal models of adolescent exposure to alcohol, nicotine, cannabinoids, and the stimulants cocaine, 3,4-methylenedioxymethampethamine and methamphetamine have revealed a variety of persisting neural and behavioral consequences. Affected brain regions often include mesolimbic and prefrontal regions undergoing notable ontogenetic change during adolescence, although it is unclear whether this represents areas of specific vulnerability or particular scrutiny to date. Persisting alterations in forebrain systems critical for modulating reward, socioemotional processing and cognition have emerged, including apparent induction of a hyper-dopaminergic state with some drugs and/or attenuations in neurons expressing cholinergic markers. Disruptions in cognitive functions such as working memory, alterations in affect including increases in social anxiety, and mixed evidence for increases in later drug self-administration has also been reported. When consequences of adolescent and adult exposure were compared, adolescents were generally found to be more vulnerable to alcohol, nicotine, and cannabinoids, but generally not to stimulants. More work is needed to determine how adolescent drug exposure influences sculpting of the adolescent brain, and provide approaches to prevent/reverse these effects.

Influence of developmental nicotine exposure on glutamatergic neurotransmission in rhythmically active hypoglossal motoneurons

Developmental nicotine exposure (DNE) is associated with increased risk of cardiorespiratory, intellectual, and behavioral abnormalities in neonates, and is a risk factor for apnea of prematurity, altered arousal responses and Sudden Infant Death Syndrome. Alterations in nicotinic acetylcholine receptor signaling (nAChRs) after DNE lead to changes in excitatory neurotransmission in neural networks that control breathing, including a heightened excitatory response to AMPA microinjection into the hypoglossal motor nucleus. Here, we report on experiments designed to probe possible postsynaptic and presynaptic mechanisms that may underlie this plasticity. Pregnant dams were exposed to nicotine or saline via an osmotic mini-pump implanted on the 5th day of gestation. We used whole-cell patch clamp electrophysiology to record from hypoglossal motoneurons (XIIMNs) in thick medullary slices from neonatal rat pups (N=26 control and 24 DNE cells). To enable the translation of our findings to breathing-related consequences of DNE, we only studied XIIMNs that were receiving rhythmic excitatory drive from the respiratory central pattern generator. Tetrodotoxin was used to isolate XIIMNs from presynaptic input, and their postsynaptic responses to bath application of l-glutamic acid (glutamate) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) were studied under voltage clamp. DNE had no influence on inward current magnitude evoked by either glutamate or AMPA. However, in cells from DNE animals, bath application of AMPA was associated with a right shift in the amplitude distribution (P=0.0004), but no change in the inter-event interval distribution of miniature excitatory postsynaptic currents (mEPSCs). DNE had no influence on mEPSC amplitude or frequency evoked by glutamate application, or under (unstimulated) baseline conditions. Thus, in the presence of AMPA, DNE is associated with a small but significant increase in quantal size, but no change in the probability of glutamate release.

Temporal Changes in the Correlates of U.S. Adolescent Electronic Cigarette Use and Utilization in Tobacco Cessation, 2011 to 2013

OBJECTIVE

To examine temporal changes in the correlates of experimental and current e-cigarette use and associations with tobacco quit attempts.

METHOD

Repeated cross-sectional analyses of data from the 2011 ( n = 17,741), 2012 ( n = 23,194), and 2013 ( n = 16,858) National Youth Tobacco Surveys-a nationally representative sample of U.S. middle and high school students. Respondents were asked about lifetime and past-month e-cigarette use, conventional cigarette use, and number of quit attempts made in the prior year among current smokers.

RESULTS

Multinomial logistic regression models indicate higher odds of experimental or current e-cigarette use versus abstinence in the 2012 and 2013 survey years (vs. 2011). Respondents in the 2013 survey were more likely to use e-cigarettes in 2012, and they were significantly more likely to be current versus experimental users. Temporal increases in past-month e-cigarette use were uneven across demographic subgroups. Among current smokers of conventional cigarettes, fully adjusted models show that across all survey years the probability of past-month e-cigarette use was not significantly different for those who attempted to quit using tobacco in the past year from those who did not.

CONCLUSIONS

Adolescent e-cigarette use has become more common between 2011 and 2013 and shows signs of becoming increasingly characterized by current rather than experimental use. Temporal patterns suggest that recent population increases were initially driven by select subgroups (e.g., Whites), with other subgroups contributing to the increase more recently (e.g., Black). Tobacco cessation has remained unrelated to current e-cigarette use over time, suggesting that e-cigarette use may be contributing to increased nicotine use.