On the development of nicotine dependence in adolescence

Comparison of Indicators of Dependence for Vaping and Smoking: Trends Between 2017 and 2022 Among Youth in Canada, England, and the United States

INTRODUCTION

The current study sought to examine trends in indicators of dependence for youth vaping and smoking during a period of rapid evolution in the e-cigarette market.

AIMS AND METHODS

Data are from repeat cross-sectional online surveys conducted between 2017 and 2022 among youth aged 16-19 in Canada, England, and the United States (US). Participants were 23 145 respondents who vaped and/or smoked in the past 30 days. Four dependence indicators were assessed for smoking and vaping (perceived addiction, frequent strong urges, time to first use after waking, days used in past month) and two for vaping only (use events per day, e-cigarette dependence scale). Regression models examined differences by survey wave and country, adjusting for sex, age, race, and exclusive/dual use.

RESULTS

All six indicators of dependence increased between 2017 and 2022 among youth who vaped in the past 30 days (p < .001 for all). For example, more youth reported strong urges to vape at least most days in 2022 than in 2017 (Canada: 26.5% to 53.4%; England: 25.5% to 45.4%; US: 31.6% to 50.3%). In 2017, indicators of vaping dependence were substantially lower than for smoking; however, by 2022, youth vaping was associated with a greater number of days used in the past month (Canada, US), shorter time to first use (all countries), and a higher likelihood of frequent strong urges (Canada, US) compared to youth smoking.

CONCLUSIONS

From 2017 to 2022, indicators of vaping dependence increased substantially. By 2022, vaping dependence indices were comparable to those of smoking.

IMPLICATIONS

Indicators of vaping dependence among youth have increased substantially since 2017 to levels that are comparable to cigarette dependence among youth who smoke. Future research should examine factors underlying the increase in dependence among youth who vape, including changes to the nicotine profile and design of e-cigarette products.

Examining Predictors of Nicotine Dependence in Korean Adolescents : Comparing Ever Quitters and Never Quitters

Despite growing research on adolescent smokers, evidence for the differences between the two smoker groups who are ever quitters and never quitters is limited. The study aimed to examine predictors of nicotine dependence (ND) in Korean adolescents by comparing ever quitters and never quitters. Data from 349 adolescents were collected through an online survey. Among respondents, most of them were male, living with families, and were enrolled at schools. Data were analyzed by dividing participants into two groups - ever quitters and never quitters. The study found that adolescents' ND was commonly predicted by smoking peers and anxiety. However, schooling status was significantly associated with ever quitters' ND only. In the total sample, never-quitters were associated with higher ND compared to ever-quitters. This study did not control for differences among ever quitters in terms of the number of attempts to quit smoking and did not significantly control age effects in the sample. Based on study results, we suggest various policy implications. Cessation intervention should be designed keeping in mind the smokers' previous quit attempts and their motivation. It is also recommended that individually tailored smoking cessation programs be used to address the heterogenous nature of the adolescents.

The HINT1 Gene rs2526303 Polymorphism and Its Association with Personality Traits in Cigarette Smokers

The development of a substance use disorder (SUD) is a multifaceted process influenced by both genetic and environmental factors. Recent research has suggested the potential involvement of the HINT1 gene in various aspects of plasticity, mood regulation, anxiety-like behaviour, and stress-coping mechanisms. Moreover, personality traits are also recognised to be instrumental in developing substance dependency. Given these considerations, our study investigated the associations among cigarette smoking, personality traits, and the rs2526303 polymorphism. Additionally, we investigated the interactions between personality traits and rs2526303 in the HINT1 gene. The study group comprised 531 volunteers: 375 cigarette users (mean age = 29.42 ± 10.72; F = 49%, M = 51%) and 156 never-smokers (mean age = 26.93 ± 10.09; F = 79%, M = 21%). Genotyping was conducted using the real-time PCR method, and the NEO Five-Factor Personality Inventory and State-Trait Anxiety Inventory were administered. There were no statistically significant differences in the frequency of rs2526303 genotypes and alleles in the cigarette user group compared to the control group. Compared to the control group, the cigarette users obtained higher scores in the assessment of the NEO-FFI Extraversion scale and lower results for the NEO-FFI Openness, Agreeableness, and Conscientiousness scales. Additionally, there was a statistically significant effect of rs2526303 genotype interaction and cigarette-using status on the conscientiousness scale. These outcomes collectively suggest a notable association between cigarette smoking and specific dimensions of personality, particularly highlighting differences in extraversion, openness, agreeableness, and conscientiousness. Furthermore, the detected interaction effect involving rs2526303 concerning conscientiousness signifies a complex interplay between genetic factors and smoking behaviour.

Dopamine D1-like receptor activation decreases nicotine intake in rats with short or long access to nicotine

The use of nicotine and tobacco products is highly addictive. The dopaminergic system plays a key role in the initiation and maintenance of nicotine intake. Dopamine D1-like receptor blockade diminishes nicotine intake in rats with daily short (1 h) access to nicotine, but little is known about the effects of dopamine receptor antagonists or agonists on nicotine intake in rats with intermittent long (23 h) access. Because of the extended access conditions and high nicotine intake, the intermittent long access procedure might model smoking and vaping better than short access models. We investigated the effects of the dopamine D1-like receptor antagonist SCH 23390 and the D1-like receptor agonist A77636 on nicotine intake in male rats with intermittent short or long access to nicotine. The rats self-administered nicotine for 5 days (1 h/day) and were then given 15 intermittent short (1 h/day) or long (23 h/day) access sessions (3 sessions/week, 0.06 mg/kg/inf). The D1-like receptor antagonist SCH 23390 decreased nicotine intake to a similar degree in rats with short or long access to nicotine. The D1-like receptor agonist A77636 induced a greater decrease in nicotine intake in the rats with long access to nicotine than in rats with short access. Treatment with A77636 induced a prolonged decrease in nicotine intake that lasted throughout the dark and light phase in the long access rats. These findings indicate that blockade and stimulation of D1-like receptors decrease nicotine intake in an intermittent long access animal model that closely models human smoking and vaping.

Subjective effects as predictors of substance use disorders in a clinical sample: A longitudinal study

BACKGROUND

The literature on the association between subjective effects (SEs; i.e., how an individual perceives their physiological and psychological reactions to a drug) and substance use disorders (SUDs) is largely limited to community samples. The present study addressed the following aims in a clinical sample: whether SEs predict general versus substance-specific SUD in adolescence and adulthood after controlling for conduct disorder symptoms (CDsymp); whether SEs predict SUDs across drug classes; whether SEs predict change in SUD from adolescence to adulthood; and whether there are racial/ethnic differences in associations.

METHODS

Longitudinal analyses were conducted using data from a sample of 744 clinical probands recruited from residential and outpatient SUD treatment facilities in CO during adolescence (Mage = 16.26) and re-assessed twice in adulthood (Mages = 22.56 and 28.96), approximately seven and twelve years after first assessment. SEs and CDsymp were assessed in adolescence. SUD severity was assessed at adolescence and twice during adulthood.

RESULTS

SEs assessed in adolescence robustly predicted general SUD for legal and illegal substances in adolescence and adulthood, whereas CDsymp predicted SUD primarily in adolescence. Higher positive and negative SEs in adolescence were associated with greater SUD severity after controlling for CDsymp, with similar magnitudes. Results indicated cross-substance effects of SEs on SUD. We found no evidence for racial/ethnic differences in associations.

CONCLUSIONS

We investigated the progression of SUD in a high-risk sample with greater odds of sustained SUD. In contrast to CDsymp, both positive and negative SEs consistently predicted general SUD across substances in adolescence and adulthood.

Prenatal and postnatal drug exposure: focus on persistent central effects

Clinical studies indicate significant use of prescription, nonprescription and social/recreational drugs by women during pregnancy; however, limited knowledge exists about the detrimental effects that this practice may have on the developing central nervous system of the fetus. Importantly, few experimental and clinical data are available on how gestational exposure could exacerbate the effects of the same or a different drug consumed by the offspring later in life. The present review summarizes recent findings on the central toxicity elicited by several classes of drugs, administered prenatally and postnatally in experimental animals and humans, focusing on prescription and nonprescription analgesics, anti-inflammatory agents, alcohol and nicotine.

Development of Dependence in Smokers and Rodents With Voluntary Nicotine Intake: Similarities and Differences

INTRODUCTION

Smoking and vaping throughout adolescence and early adulthood lead to nicotine dependence. Nicotine withdrawal is associated with somatic and affective withdrawal symptoms that contribute to smoking and relapse. Affective nicotine withdrawal symptoms in humans include craving for cigarettes, depression, anxiety, trouble sleeping, and cognitive deficits.

METHODS

Herein, we review clinical studies that investigated nicotine dependence in people who smoke or vape. We also discuss studies that investigated the development of dependence in animals with oral nicotine intake, nicotine aerosol self-administration, and intravenous nicotine self-administration.

RESULTS

Clinical studies report that adolescents who smoke daily develop nicotine dependence before those who smoke infrequently, but ultimately all smokers become dependent in adulthood. Preclinical studies indicate that rats that self-administer nicotine also become dependent. Rats that self-administer nicotine display somatic withdrawal signs and affective withdrawal signs, including increased anxiety and depressive-like behavior, cognitive deficits, and allodynia. Most nicotine withdrawal signs were observed in rodents with daily (7 days/week) or intermittent long access (23-hour) to nicotine. Clinical smoking studies report symptoms of nicotine dependence in adolescents of both sexes, but virtually all preclinical nicotine self-administration studies have been done with adult male rats.

CONCLUSIONS

The role of sex and age in the development of dependence in nicotine self-administration studies remains under-investigated. However, the role of sex and age in nicotine withdrawal has been thoroughly evaluated in studies in which nicotine was administered noncontingently. We discuss the need for volitional nicotine self-administration studies that explore the gradual development of dependence during adolescence and adulthood in rodents of both sexes.

IMPLICATIONS

The reviewed clinical studies investigated the development of nicotine dependence in male and female adolescent and young adult smokers and vapers. These studies indicate that most adolescent smokers and vapers gradually become nicotine dependent. Preclinical studies with rodents show that nicotine intake in widely used self-administration models also leads to dependence. However, almost all animal studies that investigated the development of nicotine dependence have been conducted with adult male rats. To better model smoking and vaping, it is important that nicotine intake in rats or mice starts during adolescence and that both sexes are included.

Interaction of Nicotine and Social reward in group-reared male adolescent rats

Adolescents exhibit great sensitivity to nicotine and social interaction; accordingly, when both stimuli are presented together, they interact to enhance the incentive value of the context in which they occur. Noteworthy, most studies assessing the interaction between nicotine and social reward have used isolated-reared rats. Adolescent isolation is an adverse condition that impacts brain development and behavior, so it is not known if the interaction also occurs in rats without social deprivation. The present study used a conditioned place preference model (CPP) to examine the interaction between nicotine and social reward in group-reared male adolescent rats. At weaning, Wistar rats were randomly assigned to four groups: vehicle, vehicle and a social partner, nicotine (0.1mg/Kg s.c.), and nicotine and a social partner. Conditioning trials occurred on eight consecutive days followed by a test session in which the preference change was assessed. Besides the establishment of CPP, we examined the effects of nicotine on (1) social behaviors during CPP trials and (2) tyrosine hydroxylase (TH) and oxytocin (OT) as markers of changes in the neuronal mechanisms for reward and social affiliation. Similar to previous results, the joint presentation of nicotine and social reward induced CPP, whereas either nicotine or social interaction presented alone did not. This finding coincided with an increase in TH levels observed after nicotine administration only in socially conditioned rats. The interaction between nicotine and social reward is not related to the effects of nicotine on social investigation or social play.

E-Cigarette Users' Profiles and Their Association with Identified Impacts of COVID-19 on Vaping among Young Adults in Malaysia

Electronic cigarettes (ECs) users' profiles and behaviors during the COVID-19 pandemic remain unclear. This cross-sectional study aimed to explore Malaysian EC users' profiles and their associations with related behaviors during the pandemic. The EC users (N = 351) were recruited from an official national vape entity. Respondents were predominantly of Malay ethnicity (90.6%), aged 31 to 35 years (27.6%), males (97.7%), married (68.7%), from Malaysia's west region states (63.5%) and tertiary educated (69.2%). The majority (80.3%) were non-dual users, and most purchased their vaping products online (77.2%), liked that they can vape while working at home (83.8%) and vaped more because of boredom (55.3%), had low and moderate nicotine addiction levels (94.9%), had low motivation level to quit EC use (92.6%) and were more likely to perceive that vaping did not increase the chances of complications from COVID-19. Respondents with moderate to high addiction levels had twice the odds of checking on their current EC supplies, whilst respondents with low motivation to quit had higher odds of using their tank/pod until the last drop and distancing from others when vaping. EC users should be encouraged to quit EC use, especially during the COVID-19 pandemic.

A network approach to substance use, internalizing, and externalizing comorbidity in U.S. adults

INTRODUCTION

Use of conventional cigarettes (CIG), alcohol, marijuana, and sedatives [i.e., benzodiazepines and barbiturates]) commonly co-occur with internalizing and externalizing disorders. It is unclear how these relationships extend to electronic cigarettes (ECIGs) and prescription drugs not prescribed (i.e., sedatives, tranquilizers, and painkillers [PDNP]), and whether they differ by gender.

METHODS

Adult data (N = 30,211) from Wave 1 (2013-2014) of the Population Assessment of Tobacco and Health Study were used to estimate a network of current or past-month use for six substances, experiencing four internalizing symptoms in the past month, and experiencing seven externalizing symptoms in the past month. Visual comparisons, global strength invariance, network structure invariance, and edge strength invariance were tested to detail substance use and internalizing/externalizing symptom networks.

RESULTS

Overall, networks were consistent between men and women. The strongest substance use/mental health symptom connections estimated as edge-weights (EW) were between marijuana with lying (EW = 0.60, 95% CI = 0.49; 0.70), marijuana with engaging in fights (EW = 0.54, 95% CI = 0.27; 0.81), PDNP with having trouble sleeping (EW = 0.53, 95% CI = 0.40; 0.66), and alcohol and impulsivity (EW = 0.48, 95% CI = 0.42; 0.53).

DISCUSSION

There were many weak connections throughout the substance use and internalizing/externalizing network. A few important connections were identified and encourage future study. In particular, PDNP was most strongly associated with internalizing symptoms. Marijuana, alcohol and PDNP use were most strongly associated with externalizing symptoms.

Where should I start? A scoping review about the publications on clove cigarettes

INTRODUCTION

The general lack of knowledge about the composition of clove cigarettes and the large number of terms that can be used to define different types of cigarettes that contain cloves makes it difficult to find scientific articles focused on the subject. We reviewed the publications that cited clove cigarettes to assess their relevance.

METHODS

We searched publications on Scopus, ScienceDirect, PubMed, and Portal CAPES during the first semester of 2021, without date restrictions. Through a quality assessment, the studies found were assorted in ten different categories.

RESULTS

Indonesian clove cigarettes-also known as kretek-are a mixture of tobacco and cloves rolled in a cigarette and sprayed with oils, plant extract, and food flavorings, in an unknown quantity and composition, different from each brand, which is usually kept in secret. Due to the relatively low prevalence of use in the general population, most publications on tobacco products tend to ignore clove cigarettes or place them in an existing category. Clove cigarettes can be hand-rolled, machine-made, filtered, unfiltered, and each form can be named differently. The interchangeable use of each term, sometimes grouping conventional cigarettes in the mix, can lead the researcher to consider a publication that should be excluded.

CONCLUSION

The existing regulations on flavored cigarettes, although well-intentioned, are still somewhat vague and broad, leaving possible loopholes that can be exploited by the tobacco industries. Fully understanding the precise effects caused by clove cigarettes can be an important tool in future discussions about tobacco control.

E-cigarette initiation predicts subsequent academic performance among youth: Results from the PATH Study

Research shows cigarette smoking is associated with lower academic performance among youth. This study examines how initiating e-cigarette use is associated with subsequent academic performance. Data from Waves 2-4 youth and parent surveys of the Population Assessment of Tobacco and Health (PATH) Study were analyzed. Youth (12-15 years old) who reported never using any tobacco products at Wave 2 were included in the analysis (n = 4960). Initiation of e-cigarettes and cigarettes was assessed at Wave 3. Weighted multivariable linear regression models were tested to assess the association between e-cigarette and cigarette initiation at Wave 3 and academic performance at Wave 4, controlling for covariates at Wave 2. At Wave 3, 4.3% and 1.9% of youth initiated e-cigarette and cigarette use, respectively. Youth who initiated e-cigarette use at Wave 3 had lower academic performance at Wave 4, compared to those who did not initiate e-cigarette use (adjusted regression coefficient [ARC] -0.22, 95% confidence interval [CI] -0.43, -0.02). Initiating cigarettes was also associated with lower academic performance (ARC -0.51, 95% CI -0.84, -0.18). Results indicate that e-cigarette use initiation is associated with lower subsequent academic performance, independent from the association between cigarette use initiation and lower academic performance among U.S. youth. Future research needs to examine whether preventing youth e-cigarette and cigarette use can lead to improvement in academic performance.

Rodent models for nicotine withdrawal

BACKGROUND

Animal models are critical to improve our understanding of the neuronal mechanisms underlying nicotine withdrawal. Nicotine dependence in rodents can be established by repeated nicotine injections, chronic nicotine infusion via osmotic minipumps, oral nicotine intake, tobacco smoke exposure, nicotine vapor exposure, and e-cigarette aerosol exposure. The time course of nicotine withdrawal symptoms associated with these methods has not been reviewed in the literature.

AIM

The goal of this review is to discuss nicotine withdrawal symptoms associated with the cessation of nicotine, tobacco smoke, nicotine vapor, and e-cigarette aerosol exposure in rats and mice. Furthermore, age and sex differences in nicotine withdrawal symptoms are reviewed.

RESULTS

Cessation of nicotine, tobacco smoke, nicotine vapor, and e-cigarette aerosol exposure leads to nicotine withdrawal symptoms such as somatic withdrawal signs, changes in locomotor activity, anxiety- and depressive-like behavior, learning and memory deficits, attention deficits, hyperalgesia, and dysphoria. These withdrawal symptoms are most pronounced within the first week after cessation of nicotine exposure. Anxiety- and depressive-like behavior, and deficits in learning and memory may persist for several months. Adolescent (4-6 weeks old) rats and mice display fewer nicotine withdrawal symptoms than adults (>8 weeks old). In adult rats and mice, females show fewer nicotine withdrawal symptoms than males. The smoking cessation drugs bupropion and varenicline reduce nicotine withdrawal symptoms in rodents.

CONCLUSION

The nicotine withdrawal symptoms that are observed in rodents are similar to those observed in humans. Tobacco smoke and e-cigarette aerosol contain chemicals and added flavors that enhance the reinforcing properties of nicotine. Therefore, more valid animal models of tobacco and e-cigarette use need to be developed by using tobacco smoke and e-cigarette aerosol exposure methods to induce dependence.

Community- and individual-level risk factors of past month e-cigarette use among adolescents in France

PURPOSE

Studies of adolescent e-cigarette use infrequently consider how environmental effects impact use. Adolescent e-cigarette use in France is also understudied, yet an important contrast since e-cigarette use rarely precedes conventional tobacco use and daily tobacco use is common. We examine whether there is significant variation in e-cigarette use across the geographic unit of départements (n = 95), and whether community factors explain these differences and individual-level probabilities of e-cigarette use.

METHODS

The ESCAPAD survey is a cross-sectional, nationally representative survey collected at a day of civic and military information mandatory for French 17-year-olds. We use the 2014 (n = 22,023) and 2017 (n = 39,115) surveys and geographic information from Eurostat and INSEE. Multilevel, multiple logistic regression models examine any and daily past month e-cigarette use.

RESULTS

We find significant département-level variation in both outcomes, with a considerable proportion of this variation explained by département-level factors. Net of numerous significant individual-level covariates, département-level unemployment (OR = 1.049, p < .05), poverty (OR=0.975, p < .05), age structure (OR=0.720, p < .01), and population growth (OR=0.987 p < .01) were associated with any past month use. The département-level percentage of adolescents using conventional tobacco daily was associated with individual-level any (OR=1.029, p < .001) and daily (OR=1.033, p < .01) e-cigarette use. Predicted probabilities demonstrate that département-level and individual-level tobacco use together were associated with e-cigarette use.

CONCLUSIONS

Researchers should incorporate community effects into studies of e-cigarette use. Particularly, the tobacco use environment contributes to risk of e-cigarette use. For policymakers, resources may be mobilized to address local socioeconomic, demographic, and tobacco use patterns to potentially affect adolescent e-cigarette use.

Snus and Alcohol: Mutually Rewarding Effects in the Brain? A Matched Controlled Population Study

Background:

The use of moist smokeless tobacco (snus) is increasing in the U.S. and other Western countries, and especially among young people. Snus is associated with several health problems, but the relationship between use of snus and alcohol is scarcely explored. Neuro-cognitive and psychological research suggest an association due to possible mutually rewarding effects in the limbic brain. We investigated this issue in a matched controlled population study.

Methods:

Matched control group design where drinking habits and alcohol consumption in a group of users of snus (n = 1043, mean age = 35.20; n men = 749, n women = 294) were compared to a control group of non-users matched on age and gender (n = 1043, mean age = 35.65; n men = 749, n women = 294). In addition, we registered background variables such as level of education, income, self-perceived general, dental health, mental health, current depressive symptoms, and BMI. In estimation of alcohol consumption, the background variables were used as covariates in factorial analyses of variance (ANCOVA).

Results:

Users of snus had lower level of education, lower income, poorer general, dental, and mental health status than non-users, but there were no differences in BMI. Differences in mental health status were related to drinking habits. Users of snus had a higher frequency of drinking, higher frequency of intoxication, and showed more excess drinking. Controlled for background variables users of snus had a 25.2% higher estimated yearly consumption of alcohol in terms of standard units of alcohol on the weekdays, 26.4% higher on weekends and a 60.2% higher yearly excess consumption.

Conclusion:

Users of snus had an elevated alcohol consumption and another drinking style than non-users. The findings are discussed according to neuro-cognitive and psychopharmacological mechanisms, reward learning and conditioning. The results have implications for prevention, treatment and rehabilitation of alcohol and nicotine dependence.

Association of NRG3 and ERBB4 gene polymorphism with nicotine dependence in Turkish population

BACKGROUND

Nicotine dependence (ND) is characterized by regular smoking, anxiety, irritation, difficulty concentrating, impatience, restlessness, tremor, dizziness, hunger, nicotine demand, and the individual's reluctance to quit despite knowing the health risks of smoking. Recently, it has been reported that the Neuregulin 3 (NRG3)/Erb-B2 receptor tyrosine kinase 4 (ERBB4) signaling pathway plays a role in ND. NRG3, which is activated after nicotine intake, binds to ERBB4 and causes GABA release. GABA reduces anxiety and tension, which are one of the nicotine withdrawal symptoms. Therefore we aimed to investigate the relationship between NRG3 and ERBB4 gene polymorphisms and ND.

MATERIALS AND METHODS

The study population was comprised of patients with ND (n = 200) and healthy non-smoker control subjects (n = 200) who were matched for age, sex, and compared for comorbidity factors such as alcohol, smoking, duration, and education (age range 18-60). Genotypes were detected by Real-Time PCR using TaqMan technology. The Fagerström Nicotine Dependence Test (FTND) score was 5 and above for the patient group and 0 for the control group. DNA was obtained from whole peripheral blood and six polymorphisms of Neuregulin 3 (NRG3) (rs1836724, rs7562566, and rs10048757) and Erb-B2 Receptor Tyrosine Kinase 4 (ERBB4) (rs1764072, rs6584400, and rs10883934) genes were analyzed by real-time PCR method.

RESULTS

Our findings show that the six selected SNPs are not significantly associated with ND in the Turkish population and no correlation with dependence levels (p > 0.05).

CONCLUSION

Although our findings do not show a relationship between ND and these polymorphisms, it is the first study to investigate these single nucleotide polymorphisms (SNPs) for the first time in ND and to find some genotypes in the Turkish population when compared to other populations. Also, our findings are important in terms of their contribution to the literature and forensic genetics.

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.

Prevalence and Childhood Precursors of Opioid Use in the Early Decades of Life

IMPORTANCE

Opioid use disorder and opioid deaths have increased dramatically in young adults in the US, but the age-related course or precursors to opioid use among young people are not fully understood.

OBJECTIVE

To document age-related changes in opioid use and study the childhood antecedents of opioid use by age 30 years in 6 domains of childhood risk: sociodemographic characteristics; school or peer problems; parental mental illness, drug problems, or legal involvement; substance use; psychiatric illness; and physical health.

DESIGN, SETTING, AND PARTICIPANTS

This community-representative prospective longitudinal cohort study assessed 1252 non-Hispanic White individuals and American Indian individuals in rural counties in the central Appalachia region of North Carolina from January 1993 to December 2015. Data were analyzed from January 2019 to January 2020.

EXPOSURES

Between ages 9 and 16 years, participants and their parents were interviewed up to 7 times using the Child and Adolescent Psychiatric Assessment and reported risk factors in 6 risk domains.

MAIN OUTCOMES AND MEASURES

Participants were assessed again at ages 19, 21, 25, and 30 years for nonheroin opioid use (any and weekly) and heroin use using the structured Young Adult Psychiatric Assessment.

RESULTS

Of 1252 participants, 342 (27%) were American Indian. By age 30 years, 322 participants had used a nonheroin opioid (24.2%; 95% CI, 21.8-26.5), 155 had used a nonheroin opioid weekly (8.8%; 95% CI, 7.2-10.3), and 95 had used heroin (6.6%; 95% CI, 5.2-7.9). Childhood risk markers for later opioid use included male sex, tobacco use, depression, conduct disorder, cannabis use, having peers exhibiting social deviance, parents with legal involvement, and elevated systemic inflammation. In final models, childhood tobacco use, depression, and cannabis use were most robustly associated with opioid use in young adulthood (ages 19 to 30 years). Chronic depression and dysthymia were strongly associated with any nonheroin opioid use (OR. 5.43; 95% CI, 2.35-12.55 and OR, 7.13; 95% CI, 1.99-25.60, respectively) and with weekly nonheroin opioid use (OR, 8.89; 95% CI, 3.61-21.93 and OR, 11.51; 95% CI, 3.05-42.72, respectively). Among young adults with opioid use, those with heroin use had the highest rates of childhood psychiatric disorders and comorbidities.

CONCLUSIONS AND RELEVANCE

Childhood tobacco use and chronic depression may be associated with impaired reward system functioning, which may increase young adults' vulnerability to opioid-associated euphoria. Preventing and treating early substance use and childhood mental illness may help prevent later opioid use.

Indicators of dependence and efforts to quit vaping and smoking among youth in Canada, England and the USA

OBJECTIVE

The current study examined indicators of dependence among youth cigarette smokers and e-cigarette users in Canada, England and the USA, including changes between 2017 and 2019.

METHODS

Data are from repeated cross-sectional online surveys conducted in 2017, 2018 and 2019 with national samples of youth aged 16-19 years, in Canada (n=12 018), England (n=11 362) and the USA (n=12 110). Measures included perceived addiction to cigarettes/e-cigarettes, frequency of experiencing strong urges to smoke/use an e-cigarette, plans to quit smoking/using e-cigarettes and past attempts to quit. Logistic regression models were fitted to examine differences between countries and changes over time.

RESULTS

The proportion of ever-users who vaped frequently was significantly higher in 2019 compared with 2017 for all outcomes in each country. Between 2017 and 2019, the proportion of past 30-day vapers reporting strong urges to vape on most days or more often increased in each country (Canada: 35.3%, adjusted OR (AOR) 1.69, 95% CI 1.20 to 2.38; England: 32.8%, AOR 1.55, 1.08 to 2.23; USA: 46.1%, AOR 1.88, 1.41 to 2.50), along with perceptions of being 'a little' or 'very addicted' to e-cigarettes (Canada: 48.3%, AOR 1.99, 1.44 to 2.75; England: 40.1%, AOR 1.44, 1.03 to 2.01; USA: 53.1%, AOR 1.99, 1.50 to 2.63). Indicators of dependence among smokers were consistently greater than e-cigarette users, although differences had narrowed by 2019, particularly in Canada and the USA.

CONCLUSIONS

Prevalence of dependence symptoms among young e-cigarette users increased between 2017 and 2019, more so in Canada and the USA compared with England. Dependence symptom prevalence was lower for e-cigarettes than smoking; however, the gap has narrowed over time.

Postnatal Smoke Exposure Further Increases the Hepatic Nicotine Metabolism in Prenatally Smoke Exposed Male Offspring and Is Linked with Aberrant Cyp2a5 Methylation

Prenatal smoke exposure (PreSE) is a risk factor for nicotine dependence, which is further enhanced by postnatal smoke exposure (PostSE). One susceptibility gene to nicotine dependence is Cytochrome P450 (CYP) 2A6, an enzyme responsible for the conversion of nicotine to cotinine in the liver. Higher CYP2A6 activity is associated with nicotine dependence and could be regulated through DNA methylation. In this study we investigated whether PostSE further impaired PreSE-induced effects on nicotine metabolism, along with Cyp2a5, orthologue of CYP2A6, mRNA expression and DNA methylation. Using a mouse model where prenatally smoke-exposed adult offspring were exposed to cigarette smoke for 3 months, enzyme activity, mRNA levels, and promoter methylation of hepatic Cyp2a5 were evaluated. We found that in male offspring, PostSE increased PreSE-induced cotinine levels and Cyp2a5 mRNA expression. In addition, both PostSE and PreSE changed Cyp2a5 DNA methylation in male groups. PreSE however decreased cotinine levels whereas it had no effect on Cyp2a5 mRNA expression or methylation. These adverse outcomes of PreSE and PostSE were most prominent in males. When considered in the context of the human health aspects, the combined effect of prenatal and adolescent smoke exposure could lead to an accelerated risk for nicotine dependence later in life.

Role of genetic background in the effects of adolescent nicotine exposure on mesolimbic dopamine transmission

Smoking during adolescence may increase the likelihood to develop nicotine dependence and to abuse other drugs such as cocaine. Despite great efforts to understand underlying neurobiological mechanisms of this progression, less attention has been paid to the role of genetic factors. Here, we investigated the influence of both genetic background and age at first nicotine exposure in the long-lasting effects on mesolimbic dopamine transmission including the increased cocaine-rewarding effect. Mid-adolescent and adult rats of inbred strains Lewis (addiction prone) and Fischer 344 (addiction resistant) were administered nicotine (0.4 mg/kg) or vehicle once daily for 5 days. Changes in dopamine transmission were investigated by in vivo microdialysis and electrophysiology after 30 days of withdrawal, whereas changes in cocaine-rewarding effect were assessed via conditioned place preference paradigm. Nicotine pre-exposure differentially changed mesolimbic dopamine transmission depending on strain and age of pre-exposure. A potentiation of dopamine response to nicotine was observed in nucleus accumbens (NAc) core of both strains and age groups, whereas dopamine response in NAc shell was enhanced exclusively in Lewis rats exposed to nicotine during adolescence. A similar response was observed following cocaine challenge at adulthood. Changes in VTA dopamine cell population and activity were observed only in adolescent nicotine-pretreated Lewis rats, which also showed an increased cocaine-rewarding effect at adulthood. These results highlight the influence of genetic background in the long-lasting effects of nicotine exposure and suggest that exposure during adolescence might increase nicotine and cocaine-rewarding properties in genetically vulnerable individuals, thereby facilitating progression toward dependence.

Characterizing the polytobacco behaviors of sexual minority young adult college students

INTRODUCTION

Polytobacco use is a growing concern; users are exposed to cumulatively more nicotine, increasing their risk for dependence and long-term use. More sexual minority (SM) young adults report polytobacco use than their heterosexual peers, yet no studies explore how their tobacco patterns vary across the diverse product landscape. The purpose of this study was to characterize SM young adults' patterns of tobacco use and nicotine dependence, and explore co-occurring risk factors for polytobacco use.

METHODS

Participants were 609 SM Texas college students. Latent class analysis identified subgroups of tobacco users based on their tobacco use behaviors and an indicator of nicotine dependence. Multinomial logistic regression identified associations between individual-level variables and the probability of membership in various user classes.

RESULTS

Tobacco use clustered in four classes: non-users, non-addicted cigarette users, non-addicted e-cigarette users, and addicted polytobacco users. Polytobacco users had an increased probability of depressive symptoms and cannabis use relative to non-users, and more binge alcohol use than all other groups. Non-addicted cigarette users had an increased probability of binge alcohol use, cannabis use, and being non-Hispanic White relative to non-users, and an increased likelihood of cannabis use relative to non-addicted e-cigarette users. Non-addicted e-cigarette users had an increased probability of binge alcohol use relative to non-users.

CONCLUSIONS

SM young adults' tobacco use varies across the diverse product landscape. Failing to account for a range of tobacco behaviors and nicotine dependence prevents tailoring interventions that should also address concerns such as depressive symptoms, cannabis use, and binge alcohol use.

Reducing the relative value of cigarettes: Considerations for nicotine and non-nicotine factors

Despite notable progress in recent decades, cigarette smoke persists as a leading cause of premature death and preventable disease. To weaken the link between nicotine reinforcement and the toxicity associated with combusted tobacco, the United States Food and Drug Administration is considering a product standard targeting cigarette nicotine content. In this review, we summarize research assessing the potential impacts of reducing nicotine in cigarettes. Evidence to date suggests cigarette smoking, toxicant exposure and dependence would decline following substantial reductions in nicotine content. However, reduced nicotine content may not eliminate smoking entirely. Regulatory efforts that shape the nicotine and tobacco marketplace should consider that non-nicotine reinforcing factors and decision-making biases can contribute to the value of smoking. The impact of reducing nicotine in cigarettes will likely depend on the alternative nicotine products available to current smokers. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

Flavored Versus Nonflavored Waterpipe Tobacco: A Comparison of Toxicant Exposure, Puff Topography, Subjective Experiences, and Harm Perceptions

INTRODUCTION

Flavored waterpipe (WP) tobacco is the main type of tobacco used by young WP smokers, and a major factor attracting youth to smoke. However, evidence regarding the effect of limiting flavor on WP smokers' experience continues to be lacking. This study aims at evaluating the effect of flavor restriction on WP smokers' toxicant exposure, smoking topography, subjective experiences and harm perception.

METHODS

Thirty-two WP smokers completed two, 45-minute ad libitum smoking sessions (preferred flavor vs non-flavored tobacco) in a crossover design pilot study. Plasma nicotine concentration and exhaled carbon monoxide (eCO) were measured before and after each smoking session. Puff topography was recorded throughout the smoking session. Participants completed survey questionnaires assessing subjective smoking experiences and harm perception.

RESULTS

Significant differences were observed in plasma nicotine concentration between the two WP tobacco conditions, with a higher increase in plasma nicotine concentration following the flavored tobacco session. There were no significant differences between the two WP tobacco conditions for eCO and smoking topography measures. Compared with the non-flavored WP tobacco, we documented enhanced subjective smoking measures of satisfaction, calmness, taste, puff liking and enjoyment following the preferred flavored WP tobacco session. Cigarette harm perception was significantly higher among participants after smoking their preferred flavor compared with non-flavored WP tobacco.

CONCLUSIONS

Limiting tobacco flavor has a substantial effect on WP smokers' nicotine exposure, subjective experience and harm perception. Therefore, eliminating or restricting WP flavors could be an essential element of comprehensive tobacco control policies to reduce the appeal of WP tobacco products for youth.

IMPLICATIONS

This study highlights the important role of flavor in shaping WP smokers' experiences and exposures and the potential impact that regulating flavored WP tobacco may have on curbing WP use among youth in the US. Such regulations may reduce the appeal and the interest in WP smoking initiation and continued use.

The role of negative affect in the persistence of nicotine dependence among alternative high school students: A latent growth curve analysis

BACKGROUND

Previous research has demonstrated how negative affect (i.e., depression, anxiety, stress) is often a correlate of and precursor to nicotine dependence. Although recent evidence shows a gradual decline in tobacco use in the United States, subgroups that report higher levels of negative affect may continue to be at risk of becoming dependent on nicotine. One high-risk subgroup is students who attend alternative high schools. The current longitudinal investigation examined the effect of negative affect on nicotine dependence in this youth population.

METHODS

1060 students from 29 alternative high schools in Southern California completed a series of attitudinal and behavioral measures once per year over a three-year period. The main outcome was nicotine dependence i.e., feeling a strong urge to use nicotine products or experiencing withdrawal symptoms after a period of abstinence, measured using a version of the Fagerstrom Tolerance Questionnaire designed for adolescents. A latent growth curve model was utilized to examine the effect of negative affect on nicotine dependence during this timeframe.

RESULTS

The analysis revealed that negative affect had both a concurrent and prospective relationship with nicotine dependence. Moreover, the association between negative affect and nicotine dependence in the present was not statistically significant once the influence of negative affect reported one year earlier was accounted for.

CONCLUSIONS

Negative affect may play a critical role in the persistence of nicotine dependence among high-risk youth. Providing resources to help manage negative affect may be critical to curtailing nicotine dependence in this population.

The presence and stability of nicotine dependence symptoms among adolescents after the implementation of a smoking prevention program

INTRODUCTION

Symptoms of nicotine dependence among adolescents occur at an early stage in smoking onset and can be present even with low exposure to cigarettes. We aim to examine the early occurrence of symptoms of nicotine dependence and how they predict later smoking behavior.

METHODS

Participants were ninety-four currently smoking 9th-graders attending high school in Targu Mures, Romania. They were followed for 6 months with two assessment points: baseline, and follow-up at 6 months. We assessed the following: 1) the number of smoked cigarettes in the last 30 days, 7 days, and 24 hours using the Minnesota Smoking Index; 2) vulnerability to addiction manifested in cessation difficulties, using the 9-item version of the Hooked On Nicotine Checklist (HONC), 3) loss of autonomy using the endorsement of at least one HONC item, and 4) dependence, using the modified Fagerström Tolerance Questionnaire (mFTQ). We performed statistical analysis with SPSS version 19, using paired-sample t-tests for comparing the differences between baseline and follow-up data. We also conducted linear regression analysis to demonstrate the predictive role of the assessed variables, such as the scores of the mFTQ and the HONC in maintaining smoking and reported smoking status.

RESULTS

Regression models indicated that baseline-measures for symptoms of dependence (β=0.64, p<0.001), vulnerability to addiction (β=0.47, p<0.001), and loss of autonomy (β=0.34, p<0.001) regarding smoking cessation were significant predictors of smoking, explaining 41.7% of the variability of the reported increase in cigarette consumption. At follow-up at 6-months, the three variables were responsible for 14.9% for the variance in cigarette consumption (R2=0.14, F(1,92)=16.05, p<0.01).

CONCLUSIONS

Nicotine dependence at baseline and at follow-up show significant differences in the control group while in the intervention group the scores remained stable. The findings suggest that participation in the Romanian version of ASPIRE was protective against progression towards nicotine addiction.

Youth smoking and anti-smoking policies in North Dakota: a system dynamics simulation study

BACKGROUND

The current study utilizes system dynamics to model the determinants of youth smoking and simulate effects of anti-smoking policies in the context of North Dakota, a state with one of the lowest cigarette tax rates in the USA.

METHODS

An explanatory model was built to replicate historical trends in the youth smoking rate. Three different policies were simulated: 1) an increase in cigarette excise taxes; 2) increased funding for CDC-recommended comprehensive tobacco control programs; and 3) enforcement of increased retailer compliance with age restrictions on cigarette sales.

RESULTS

The explanatory model successfully replicated historical trends in adolescent smoking behavior in North Dakota from 1992 to 2014. The policy model showed that increasing taxes to $2.20 per pack starting in 2015 was the most effective of the three policies, producing a 32.6% reduction in youth smoking rate by 2032. Other policies reduced smoking by a much lesser degree (7.0 and 3.2% for comprehensive tobacco control program funding and retailer compliance, respectively). The effects of each policy were additive.

CONCLUSIONS

System dynamics modeling suggests that increasing cigarette excise taxes are particularly effective at reducing adolescent smoking rates. More generally, system dynamics offers an important complement to conventional analysis of observational data.

Integrative Data Analysis of Gender and Ethnic Measurement Invariance in Nicotine Dependence Symptoms

Little research has evaluated whether conflicting evidence for gender and racial/ethnic differences in nicotine dependence (ND) may be attributed to differences in psychometric properties of ND symptoms, particularly for young Hispanic smokers. Inadequate racial/ethnic diversity and limited smoking exposure variability has hampered research in young smokers. We used integrative data analysis (IDA) to pool DSM-IV ND symptom data for current smokers aged 12-25 (N = 20,328) from three nationally representative surveys (1999, 2000 National Surveys on Drug Use and Health (NSDUH) and Wave 1 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Moderated nonlinear factor analysis (MNLFA) tested symptom measurement invariance in the pooled sample containing greater ethnic and smoking exposure variability. There was study noninvariance for most symptoms. NESARC participants were more likely to report tolerance, using larger amounts or for longer periods, inability to cut down/quit, and more time spent smoking at higher levels of ND severity, but reported emotional/physical health problems at lower ND severity. Four symptoms showed gender or race/ethnicity noninvariance, but observed differences were small. An ND severity factor score adjusting for symptom noninvariance related to study membership, gender, and race/ethnicity did not differ substantively from traditional DSM-IV diagnosis and number of endorsed symptoms in estimated gender and race/ethnicity differences in ND. Results were consistent with studies finding minimal gender and racial/ethnic differences in ND, and suggest that symptom noninvariance is not a major contributor to observed differences. Results support IDA as a potentially promising approach for testing novel ND hypotheses not possible in independent studies.

E-Cigarettes are More Addictive than Traditional Cigarettes-A Study in Highly Educated Young People

E-cigarettes are often considered less addictive than traditional cigarettes. This study aimed to assess patterns of e-cigarette use and to compare nicotine dependence among cigarette and e-cigarette users in a group of highly educated young adults. From 3002 healthy adults, a representative group of 30 cigarette smokers, 30 exclusive e-cigarette users, and 30 dual users were recruited. A 25-item questionnaire was used to collect information related to the patterns and attitudes towards the use of cigarettes and e-cigarettes. The Fagerström test for nicotine dependence (FTND) and its adapted version for e-cigarettes were used to analyze nicotine dependence in each of the groups. The nicotine dependence levels measured with FTND were over two times higher among e-cigarette users (mean 3.5) compared to traditional tobacco smokers (mean 1.6; p<0.001). Similarly, among dual users, nicotine dependence levels were higher when using an e-cigarette (mean 4.7) compared to using traditional cigarettes (mean 3.2; p=0.03). Habits and behaviors associated with the use of e-cigarettes did not differ significantly (p>0.05) between exclusive e-cigarette users and dual users. The findings suggest that e-cigarettes may have a higher addictive potential than smoked cigarettes among young adults.

Early-adolescent male C57BL/6J and DBA/2J mice display reduced sensitivity to acute nicotine administration

BACKGROUND

The initial response to nicotine is an important predictor of subsequent use. Multiple factors may alter this response including genetics and age of first use. Here we investigated the influence of age, genetics, and their interaction on nicotine sensitivity. We then examined whether these factors influence the relationship between initial behavioral responses and voluntary nicotine consumption in adulthood.

METHODS

We measured initial nicotine responses, including nicotine-induced locomotor depression and hypothermia following an acute intraperitoneal injection (0, 0.5, or 1 mg/kg), during early-adolescence, middle-adolescence, late-adolescence, or adulthood. Thirty-five days after the initial testing, mice were assessed for voluntary oral nicotine consumption.

RESULTS

Early-adolescent mice were more resistant to nicotine-induced hypothermia and locomotor depression than later ages, further hypothermia was influenced by genetics. In the DBA/2J  strain, early-adolescent mice were insensitive to nicotine-induced hypothermia, but this response developed at later ages. In contrast, C57BL/6J  mice were sensitive at all ages, but sensitivity increased across developmental age. There was little evidence of a relationship between initial behavioral response and choice nicotine consumption.

CONCLUSION

By understanding how age of exposure and genetics influence initial nicotine behavioral responses, we have a greater understanding of factors that make adolescents differentially sensitive to the effects of this drug.

Nicotine dependence among adolescents in the European Union: How many and who are affected?

Background

Nicotine dependence during adolescence increases the risk of continuing smoking into adulthood. The magnitude of nicotine dependence among adolescents in the European Union (EU) has not been established. We aimed to estimate the number of nicotine dependent 15-year-old adolescents in the EU, and identify high-risk groups.

Methods

The number of nicotine dependent 15-year-olds in the EU was derived combining: (i) total number of 15-year-olds in the EU (2013 Eurostat), (ii) smoking prevalence among 15-year-olds (2013/2014 HBSC survey) and (iii) proportion of nicotine dependent 15-year-olds in six EU countries (2013 SILNE survey). Logistic regression analyses identified high-risk groups in the SILNE dataset.

Results

We estimated 172 636 15-year-olds were moderately to highly nicotine dependent (3.2% of all 15 years old; 35.3% of daily smokers). In the total population, risk of nicotine dependence was higher in males, adolescents with poor academic achievement, and those with smoking parents or friends. Among daily smokers, only lower academic achievement and younger age of smoking onset were associated with nicotine dependence.

Conclusion

According to our conservative estimates, more than 172 000 15-year-old EU adolescents were nicotine dependent in 2013. Prevention of smoking initiation, especially among adolescents with poor academic performance, is necessary to prevent a similar number of adolescents getting addicted to nicotine each consecutive year.

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

Introduction

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

Methods

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

Results

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

Conclusions

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

Implications

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

Nicotine dependence, internalizing symptoms, mood variability and daily tobacco use among young adult smokers

INTRODUCTION

Cigarette use among young adults continues to rise. As young adults transition to college and assume other adult roles and responsibilities, they are at risk for the development of mental health problems and for the progression of substance use problems. Previous studies suggest that individual differences in negative and positive mood contribute to cigarette use in established college-aged smokers, but less is known whether fluctuations in mood influence daily cigarette use, controlling for trait levels of internalizing symptoms and nicotine dependence.

METHODS

Data for this study came from a sample of college students (N=39, 59% female, mean age 20.4years) who reported regular cigarette use and participated in a 21-day ecological momentary assessment (EMA) study assessing within-individual variation in cigarette use and mood.

RESULTS

A three-level hierarchical linear model accounting for the structure of 1896 occasions of cigarette use nested within days and individuals indicated that within-individual variability in positive mood was associated with cigarette use at each occasion, after taking into account baseline levels of nicotine dependence and internalizing problems.

CONCLUSIONS

Daily shifts in positive moods are importantly associated with consuming cigarettes throughout the day.

Sex Differences in Attaining Cigarette Smoking and Nicotine Dependence Milestones Among Novice Smokers

There may be sex differences in the response to nicotine, according to findings of studies in animals; however, sex differences in the natural course of cigarette smoking and nicotine dependence are documented in few studies. Prevalent (n = 240 girls; n = 184 boys) and incident (n = 231 girls; n = 184 boys) cigarette smokers from the Nicotine Dependence in Teens Study were followed up to 5 years after first puff, from age 12 to 18 years (1999-2005). We used Cox proportional hazards models to compare time to development of 3 cigarette-use (i.e., whole cigarette; 100 cigarettes lifetime; regular smoking), and 3 nicotine-dependence symptom (i.e., "really need a cigarette"; mentally addicted; physically addicted) milestones across sex. Girls were at higher risk than boys of attaining all milestones; hazard ratios (95% confidence intervals) ranged from 1.35 (1.06, 1.72) for 100 cigarettes lifetime to 1.74 (1.44, 2.10) for "really need a cigarette." Among nonregular smokers, 26% (8%; 43%) and 25% (6%; 44%) more girls than boys reported "really need a cigarette" 1 and 2 years, respectively, after first puff. Preventive interventions may need adjustment to incorporate these findings. Additional research should clarify the relative contribution of biological and social underpinnings of these sex differences.

Nicotine aversion is mediated by GABAergic interpeduncular nucleus inputs to laterodorsal tegmentum

Nicotine use can lead to dependence through complex processes that are regulated by both its rewarding and aversive effects. Recent studies show that aversive nicotine doses activate excitatory inputs to the interpeduncular nucleus (IPN) from the medial habenula (MHb), but the downstream targets of the IPN that mediate aversion are unknown. Here we show that IPN projections to the laterodorsal tegmentum (LDTg) are GABAergic using optogenetics in tissue slices from mouse brain. Selective stimulation of these IPN axon terminals in LDTg in vivo elicits avoidance behavior, suggesting that these projections contribute to aversion. Nicotine modulates these synapses in a concentration-dependent manner, with strong enhancement only seen at higher concentrations that elicit aversive responses in behavioral tests. Optogenetic inhibition of the IPN-LDTg connection blocks nicotine conditioned place aversion, suggesting that the IPN-LDTg connection is a critical part of the circuitry that mediates the aversive effects of nicotine.

Assessing nicotine dependence in adolescent E-cigarette users: The 4-item Patient-Reported Outcomes Measurement Information System (PROMIS) Nicotine Dependence Item Bank for electronic cigarettes

BACKGROUND

Adolescent e-cigarette use (i.e., "vaping") likely confers risk for developing nicotine dependence. However, there have been no studies assessing e-cigarette nicotine dependence in youth. We evaluated the psychometric properties of the 4-item Patient-Reported Outcomes Measurement Information System Nicotine Dependence Item Bank for E-cigarettes (PROMIS-E) for assessing youth e-cigarette nicotine dependence and examined risk factors for experiencing stronger dependence symptoms.

METHODS

In 2017, 520 adolescent past-month e-cigarette users completed the PROMIS-E during a school-based survey (50.5% female, 84.8% White, 16.22[1.19] years old). Adolescents also reported on sex, grade, race, age at e-cigarette use onset, vaping frequency, nicotine e-liquid use, and past-month cigarette smoking. Analyses included conducting confirmatory factor analysis and examining the internal consistency of the PROMIS-E. Bivariate correlations and independent-samples t-tests were used to examine unadjusted relationships between e-cigarette nicotine dependence and the proposed risk factors. Regression models were run in which all potential risk factors were entered as simultaneous predictors of PROMIS-E scores.

RESULTS

The single-factor structure of the PROMIS-E was confirmed and evidenced good internal consistency. Across models, larger PROMIS-E scores were associated with being in a higher grade, initiating e-cigarette use at an earlier age, vaping more frequently, using nicotine e-liquid (and higher nicotine concentrations), and smoking cigarettes.

CONCLUSION

Adolescent e-cigarette users reported experiencing nicotine dependence, which was assessed using the psychometrically sound PROMIS-E. Experiencing stronger nicotine dependence symptoms was associated with characteristics that previously have been shown to confer risk for frequent vaping and tobacco cigarette dependence.

The Euphoric Sensations of Cigarettes: Exploring How Operant Conditioning May Be the Missing Link in the Theoretical Understanding of Antidrug Policies

This study aims to examine how positive and negative reinforcers during an individual’s first few cigarettes (cigarette initiation experiences) are associated with adulthood smoking behavior. Respondents from the Add Health were asked about subjective feelings during their first few cigarettes. Using ordinary least squares (OLS) and logistic regression, we examine the differential effects of positive and negative cigarette initiation experiences on 30-day cigarette use in adulthood and lifetime nicotine dependence. The results indicate that all measures of positive cigarette initiation experiences are positively associated with both cigarette measures; however, the opposite is not true of negative cigarette initiation experiences. The results highlight the misconceptions of antidrug policies aimed at punishment of users, by indicating that positive experiences influence later cigarette use more than negative experiences. These findings suggest that drug policies and initiatives aimed at punishment may be misguided and could benefit from adopting operant conditioning concepts that emphasize reinforcements.

Waterpipe smoking patterns and symptoms of nicotine dependence: The Waterpipe Dependence in Lebanese Youth Study

INTRODUCTION

Waterpipe typically is smoked intermittently over long smoking sessions. Waterpipe is addictive and its users show symptoms of nicotine dependence (ND). This study examined the risk of developing ND symptoms across waterpipe use patterns among Lebanese youth.

METHODS

Waterpipe use patterns (length of smoking session, smoking a whole waterpipe without sharing, past-30day use frequency, number of waterpipes smoked) were assessed. Symptoms of ND were assessed using the 10-item Hooked on Nicotine Checklist (HONC; endorsement of ≥1 symptom) and the 6 criteria of the International Classification of Diseases-10th revision (ICD-10 ND; presence of ≥3 criteria during 12months).

RESULTS

Both the proportion of participants endorsing ND symptoms and the average number of endorsed ND symptoms increased with increasing waterpipe use frequency, number of waterpipes smoked, and length of smoking session. The risk of endorsing≥1 HONC symptom increased with increasing number of waterpipes smoked in the past 30-days (≥10 vs. <4 waterpipes; Hazard ratio (HR)=2.05, 95% CI: 1.52-2.58, p=0.007), and session length (>60min vs. <30min; HR=2.87, 95% CI: 2.83-2.91, p=0.001). The risk of attaining ICD-10 ND increased with increasing number of waterpipes used in the past 30-days (≥10 vs. <4 waterpipes; HR=2.56, 95% CI: 1.89-3.22, p=0.006), and smoking every day/almost every day vs. less than once weekly (HR=2.86, 95% CI: 2.12-3.60, p=0.007).

CONCLUSIONS

Increasing use frequency, number of waterpipes smoked, and longer smoking sessions were associated with higher risk of ND. The length of smoking session emerged as a novel indicator of ND among waterpipe smokers.

Associations between butane hash oil use and cannabis-related problems

BACKGROUND

High-potency cannabis concentrates are increasingly popular in the United States, and there is concern that use of high-potency cannabis might increase risk for cannabis-related problems. However, little is known about the potential negative consequences of concentrate use. This study reports on associations between past-year use of a high-potency cannabis concentrate, known as butane hash oil (BHO), and cannabis-related problems.

METHODS

A sample of 821 college students were recruited to complete a survey about their health and behavior. Participants who had used cannabis in the past year (33%, n=273) completed questions about their cannabis use, including their use of BHO and cannabis-related problems in eight domains: physical dependence, impaired control, academic-occupational problems, social-interpersonal problems, self-care problems, self-perception, risk behavior, and blackouts.

RESULTS

Approximately 44% (n=121) of past-year cannabis users had used BHO in the past year. More frequent BHO use was associated with higher levels of physical dependence (RR=1.8, p<0.001), impaired control (RR=1.3, p<0.001), cannabis-related academic/occupational problems (RR=1.5, p=0.004), poor self-care (RR=1.3, p=0.002), and cannabis-related risk behavior (RR=1.2, p=0.001). After accounting for sociodemographic factors, age of onset of cannabis use, sensation seeking, overall frequency of cannabis use, and frequency of other substance use, BHO use was still associated with higher levels of physical dependence (RR=1.2, p=0.014).

CONCLUSIONS

BHO use is associated with greater physiological dependence on cannabis, even after accounting for potential confounders. Longitudinal research is needed to determine if cannabis users with higher levels of physiological dependence seek out BHO and/or if BHO use increases risk for physiological dependence.

Association Between Initial Use of e-Cigarettes and Subsequent Cigarette Smoking Among Adolescents and Young Adults: A Systematic Review and Meta-analysis

Importance

The public health implications of e-cigarettes depend, in part, on whether e-cigarette use affects the risk of cigarette smoking.

Objective

To perform a systematic review and meta-analysis of longitudinal studies that assessed initial use of e-cigarettes and subsequent cigarette smoking.

Data Sources

PubMed, EMBASE, Cochrane Library, Web of Science, the 2016 Society for Research on Nicotine and Tobacco 22nd Annual Meeting abstracts, the 2016 Society of Behavioral Medicine 37th Annual Meeting & Scientific Sessions abstracts, and the 2016 National Institutes of Health Tobacco Regulatory Science Program Conference were searched between February 7 and February 17, 2017. The search included indexed terms and text words to capture concepts associated with e-cigarettes and traditional cigarettes in articles published from database inception to the date of the search.

Study Selection

Longitudinal studies reporting odds ratios for cigarette smoking initiation associated with ever use of e-cigarettes or past 30-day cigarette smoking associated with past 30-day e-cigarette use. Searches yielded 6959 unique studies, of which 9 met inclusion criteria (comprising 17 389 adolescents and young adults).

Data Extraction and Synthesis

Study quality and risk of bias were assessed using the Newcastle-Ottawa Scale and the Risk of Bias in Non-randomized Studies of Interventions tool, respectively. Data and estimates were pooled using random-effects meta-analysis.

Main Outcomes and Measures

Among baseline never cigarette smokers, cigarette smoking initiation between baseline and follow-up. Among baseline non-past 30-day cigarette smokers who were past 30-day e-cigarette users, past 30-day cigarette smoking at follow-up.

Results

Among 17 389 adolescents and young adults, the ages ranged between 14 and 30 years at baseline, and 56.0% were female. The pooled probabilities of cigarette smoking initiation were 30.4% for baseline ever e-cigarette users and 7.9% for baseline never e-cigarette users. The pooled probabilities of past 30-day cigarette smoking at follow-up were 21.5% for baseline past 30-day e-cigarette users and 4.6% for baseline non-past 30-day e-cigarette users. Adjusting for known demographic, psychosocial, and behavioral risk factors for cigarette smoking, the pooled odds ratio for subsequent cigarette smoking initiation was 3.62 (95% CI, 2.42-5.41) for ever vs never e-cigarette users, and the pooled odds ratio for past 30-day cigarette smoking at follow-up was 4.28 (95% CI, 2.52-7.27) for past 30-day e-cigarette vs non-past 30-day e-cigarette users at baseline. A moderate level of heterogeneity was observed among studies (I2 = 60.1%).

Conclusions and Relevance

e-Cigarette use was associated with greater risk for subsequent cigarette smoking initiation and past 30-day cigarette smoking. Strong e-cigarette regulation could potentially curb use among youth and possibly limit the future population-level burden of cigarette smoking.

Testing the nicotine dependence measure mFTQ for adolescent smokers: A multinational investigation

BACKGROUND AND OBJECTIVES

As a measure of nicotine dependence among adolescent smokers, the modified Fagerström Tolerance Questionnaire (mFTQ; seven items), has been successfully used in the United States (USA). Nonetheless, the validity and reliability of mFTQ at the international level is still needed. The current study is the first to test the validity and reliability of mFTQ in four countries: Thailand, Spain, the USA, and Russia.

METHODS

In a cross-sectional survey, mFTQ, risk factors of nicotine dependence, and sociodemographic characteristics were assessed. Risk factors included age of first cigarette, frequency of alcohol use, frequency of marijuana use, and number of cigarettes smoked yesterday. Salivary cotinine was also obtained in Thailand and Spain.

RESULTS

For all four countries, mFTQ exhibited a single factor structure, as supported by previous work in the USA. For all studied countries except Thailand, mFTQ presented acceptable internal reliability. Overall, risk factors of nicotine dependence have predicted mFTQ scores across countries. Frequency of alcohol use in the USA and frequency of marijuana use in Thailand and Spain were not associated with mFTQ scores.

DISCUSSION AND CONCLUSIONS

mFTQ is a single-factor measure of nicotine dependence that shows acceptable internal consistency and validity across countries. Further work can advance the scale and tailor it to different cultures.

SCIENTIFIC SIGNIFICANCE

mFTQ can be a clinically practical international measure of nicotine dependence. This study provides initial support for the utility of the mFTQ among Thai, Spanish, American, and Russian adolescents. Further research is needed to test and advance mFTQ across cultures. (Am J Addict 2017;26:689-696).

Preliminary test of cigarette nicotine discrimination threshold in non-dependent versus dependent smokers

BACKGROUND

Despite its potential for understanding tobacco dependence, behavioral discrimination of nicotine via smoking has not been formally examined as a function of nicotine dependence level.

METHODS

Spectrum research cigarettes were used to compare non-dependent with dependent smokers on the lowest content of nicotine they could discriminate (i.e., "threshold"). Dependent (n=21; 16M, 5F) or non-dependent (n=7; 4M, 3F) smokers were tested on ability to discriminate between cigarettes with nicotine contents of 17, 11, 5, 2, and 1mg/g, one per session, from an "ultra-low" cigarette with 0.4mg/g (all had 9-10mg "tar"). All abstained from smoking overnight prior to sessions, and number of sessions was determined by the lowest nicotine content they could reliably discriminate from the ultra-low on >80% of trials (i.e., ≥5 of 6). Subjective perceptions and cigarette choice behavior were also assessed and related to discrimination behavior.

RESULTS

Discrimination thresholds (and most perceptions) did not differ between dependent and non-dependent smokers, with median thresholds of 11mg/g for both subgroups. Yet, "liking" and puff choice for threshold cigarettes were greater in dependent but not non-dependent smokers, while cigarettes with nicotine contents below threshold did not support "liking" or choice in both groups.

CONCLUSIONS

In sum, this preliminary study suggests threshold for discriminating nicotine via smoking may not vary by dependence level, and further study is needed to confirm that cigarettes unable to be discriminated are also not reinforcing.

Prenatal tobacco exposure, maternal postnatal nicotine dependence and adolescent risk for nicotine dependence: Birth cohort study

AIMS

The goals of this study are to determine if there is (a) a threshold effect for prenatal tobacco exposure (PTE) on adolescent risk for nicotine dependence, and (b) an additive effect of PTE and maternal postnatal nicotine dependence on adolescent risk for nicotine dependence.

METHODS

Pregnant women were recruited in their 4th or 5th gestational month and asked about cigarette use during the first trimester. Mothers reported on third trimester cigarette use at delivery. Sixteen years post-partum, mothers and offspring reported on current levels of cigarette use (N=784). Nicotine dependence was assessed in both using a modified Fagerström questionnaire.

RESULTS

Based on the results of a threshold analysis for PTE, four groups were created: threshold PTE only (10+ cigarettes per day), maternal nicotine postnatal dependence with no-low PTE (0-<10 cigarettes per day), threshold PTE+maternal postnatal nicotine dependence, and a referent group with no-low PTE and no maternal postnatal nicotine dependence. Adolescents in the PTE-only group and the PTE+maternal postnatal nicotine dependence group were significantly more likely to be at risk for nicotine dependence than the offspring from the referent group. However, there was no evidence for an additive effect of maternal postnatal nicotine dependence, and maternal nicotine dependence was not a significant predictor of adolescent risk for nicotine dependence in regression models including prenatal tobacco exposure.

CONCLUSIONS

Bivariate analysis revealed a threshold effect for PTE of 10 cigarettes per day. In multivariate analysis, PTE remained significantly related to risk for offspring nicotine dependence, after controlling for maternal postnatal nicotine dependence and other covariates associated with adolescent cigarette use.

Smoking Cessation in Adolescents: targeted approaches that work

Smoking Cessation in adolescents can be considered in a developmental context to enable the clinician to individualise the appropriate assessment and management of the young person they are seeing whether it is in a primary or tertiary care setting. Adolescence is a time of rapid neurocognitive and hormonal change with these factors affected by personality and behavioural factors as well as family, cultural and psychosocial context. Adolescents are uniquely vulnerable to smoking initiation and nicotine addiction throughout these years. Increased awareness of the risks of smoking and using opportunities to assess and intervene regarding smoking cessation are integral to clinical practice for all clinicians seeing young people. This review will discuss the demographics of adolescent smoking, risk factors, assessing smoking and nicotine addiction, the importance of brief interventions, the evidence base for appropriate interventions, particularly in high risk groups and will emphasise innovative training for health professionals in adolescent smoking cessation.

Anxiety Disorders are Associated with Low Socioeconomic Status in Women but Not in Men

OBJECTIVES

We investigated to what extent the lifetime prevalence of anxiety disorders relates to negative economic changes, taking important lifestyle factors and unexpected life events into consideration.

METHODS

We included 3,695 participants recruited in the city of Lausanne (Switzerland), from the population-based CoLaus/PsyCoLaus study. The association between anxiety disorders, lifestyle factors, and life events related to income was investigated using binary logistic regression analyses correcting for demographic and clinical confounders.

RESULTS

Compared with men, women with anxiety disorders showed a significantly lower socioeconomic status (Mann-Whitney U = 56,318; p < .001) and reported a higher negative impact of substantial reduction of income (Mann-Whitney U = 68,531; p = .024). When performing adjusted analyses, low socioeconomic status (odd ratio, 0.87; p = .001) and negative impact of reduction of income (odd ratio, 1.01; p = .004) were associated significantly with anxiety disorders in women but not in men.

CONCLUSION

Our results suggest that anxiety disorders aggravate already existing gender differences in economic conditions, and that women with anxiety need additional support to attain socioeconomic security similar to that of men.

The Association of Cigarette Smoking With Depression and Anxiety: A Systematic Review

BACKGROUND

Many studies report a positive association between smoking and mental illness. However, the literature remains mixed regarding the direction of this association. We therefore conducted a systematic review evaluating the association of smoking and depression and/or anxiety in longitudinal studies.

METHODS

Studies were identified by searching PubMed, Scopus, and Web of Science and were included if they: (1) used human participants, (2) were longitudinal, (3) reported primary data, (4) had smoking as an exposure and depression and/or anxiety as an outcome, or (5) had depression and/or anxiety as the exposure and smoking as an outcome.

RESULTS

Outcomes from 148 studies were categorized into: smoking onset, smoking status, smoking heaviness, tobacco dependence, and smoking trajectory. The results for each category varied substantially, with evidence for positive associations in both directions (smoking to later mental health and mental health to later smoking) as well as null findings. Overall, nearly half the studies reported that baseline depression/anxiety was associated with some type of later smoking behavior, while over a third found evidence that a smoking exposure was associated with later depression/anxiety. However, there were few studies directly supporting a bidirectional model of smoking and anxiety, and very few studies reporting null results.

CONCLUSIONS

The literature on the prospective association between smoking and depression and anxiety is inconsistent in terms of the direction of association most strongly supported. This suggests the need for future studies that employ different methodologies, such as Mendelian randomization (MR), which will allow us to draw stronger causal inferences.

IMPLICATIONS

We systematically reviewed longitudinal studies on the association of different aspects of smoking behavior with depression and anxiety. The results varied considerably, with evidence for smoking both associated with subsequent depression and anxiety, and vice versa. Few studies supported a bidirectional relationship, or reported null results, and no clear patterns by gender, ethnicity, clinical status, length to follow-up, or diagnostic test. Suggesting that despite advantages of longitudinal studies, they cannot alone provide strong evidence of causality. Therefore, future studies investigating this association should employ different methods allowing for stronger causal inferences to be made, such as MR.

Acculturation-related predictors of very light smoking among Latinos in California and nationwide

The prevalence of light smoking has increased among Latinos. The purpose of this study was to identify demographic and acculturation-related factors associated with very light smoking, defined as smoking 1-5 cigarettes per day (CPD), among Latinos in California and nationwide. Latino smokers in the 2007-2008 National Health and Nutrition Examination Survey (NHANES) or the 2009 California Health Interview Survey (CHIS) were analyzed. Logistic regression assessed factors associated with very light smoking. Among NHANES smokers, those born in Mexico or who lived fewer years in the US were more likely to be very light smokers than 6+ CPD smokers. Among CHIS smokers, those born in Mexico, in another Spanish speaking country, or who spent smaller percentages of their life in the US were more likely to be very light smokers. Findings from this study can be used to design tobacco control media campaigns that include very light smokers.

Early symptoms of nicotine dependence among adolescent waterpipe smokers

BACKGROUND

Although waterpipe smoking is increasingly popular among youth and can lead to nicotine dependence (ND), no studies have documented how ND develops in waterpipe smokers. We examined the emerging symptoms of ND among adolescent waterpipe smokers in Lebanon.

METHODS

Individual confidential interviews were used to evaluate ND in 160 waterpipe smokers and 24 cigarette smokers from a sample of 498 students enrolled in 8th and 9th grades in Lebanon.

RESULTS

Among waterpipe smokers, 71.3% endorsed at least one Hooked on Nicotine Checklist (HONC) symptom and 38.1% developed the full syndrome of ND (≥3 criteria using the International Classification of Diseases, 10th revision). The early symptoms of ND among waterpipe smokers were craving (25%), feeling addicted (22.5%), and failed quit attempts (14.3%). Among those who reached the respective milestones, median tobacco use when the first HONC symptom emerged was 7.5 waterpipes/month with smoking frequency of 6 days/month; the median tobacco use for the full syndrome of ND was 15 waterpipes/month with smoking frequency of 15 days/month. Among those who had already reached these milestones, the first HONC symptom appeared 10.9 months after the initiation of waterpipe smoking, and the full syndrome of ND was reached at 13.9 months. In addition, cues such as seeing or smelling waterpipe, and the café environment triggered craving in most waterpipe smokers with symptoms of ND.

CONCLUSIONS

Symptoms of ND develop among adolescent waterpipe smokers at low levels of consumption and frequency of use. Craving for nicotine triggered by waterpipe-specific cues is reported even at this young age. Waterpipe-specific ND prevention and intervention programmes for youth are needed.