Association between adolescent substance use and obesity in young adulthood: A group-based dual trajectory analysis

Purpose

This study investigated whether and how trajectories of substance use in adolescence were associated with obesity trajectories in young adulthood. We hypothesized that: (1) exposure to persistent substance use throughout adolescence may heighten obesity risk in young adulthood; and (2) such associations may differ once gender, ethnicity, socioeconomic status, and obesity status in adolescence, are considered.

Methods

The study included 5141 adolescents from the child sample of the 1979 National Longitudinal Survey of Youth and utilized biennial data across the 12 assessments (1986–2008) to examine trajectories of substance use behaviors (i.e., cigarette smoking, alcohol use, and marijuana use) from ages 12 to 18 and obesity trajectories from ages 20 to 24. Group-based dual trajectory modeling was applied to examine sequential associations of trajectories of each type of substance use behavior with obesity trajectories.

Results

Three distinctive trajectory patterns were respectively identified for cigarette smoking, alcohol use, and marijuana use from ages 12 to 18, as well as for obesity status (BMI ≥ 30) from ages 20 to 24. Taking into account gender, ethnicity, socioeconomic status, and obesity status in adolescence, adolescents with the most problematic smoking trajectory (High-decreasing) were more likely to exhibit a High-obesity trajectory from ages 20 to 24. Also, adolescents with an Increasing marijuana use trajectory were more likely to exhibit an Increased obesity trajectory in young adulthood.

Conclusions

The current study demonstrates that adolescent substance use is associated with subsequent obesity in young adulthood. The associations appear to differ based on the type of substance use and patterns of use.     

Trajectories of criteria of nicotine dependence from adolescence to early adulthood

Background

To identify patterns and correlates of developmental trajectories of DSM-IV nicotine dependence criteria from adolescence to early adulthood.

Methods

The analytical sample of lifetime smokers (N = 877) is from a longitudinal cohort of 6th–10th graders drawn from an urban school system. Subjects were interviewed 5 times at 6-month intervals and once 4.5 years later. Growth mixture models were estimated to identify trajectories of DSM-IV nicotine dependence criteria over ages 12–23.

Results

A four-class solution fitted the data best: No dependence criteria (Class 1, 32.0%); Early onset/Chronic course (Class 2, 26.1%); Early onset/Remission (Class 3, 15.4%); Late onset (Class 4, 26.5%). There appeared to be three critical periods. At ages 12–15, symptoms increased rapidly. As of age 16, the Early onset/Chronic class stabilized at high levels of symptoms, the Early onset/Remission class started its symptomatic decline, and the Late onset class experienced a sharp increase in symptoms. At age 20, there was a convergence in the prevalence of symptoms experienced at high (Classes 2 and 4) and low levels (Classes 1 and 3). Extensiveness of smoking and marijuana use were associated with higher baseline levels of nicotine dependence criteria. Anxiety disorders were associated with all three symptomatic trajectories. Parental smoking and nicotine dependence were associated specifically with the Early/Chronic class, while pleasant initial sensitivity and earlier onset ages of cigarette and marijuana use characterized the two early onset classes (2 and 3).

Conclusions

Trajectories of dependence criteria constitute an advantageous phenotype for research and intervention over static summaries of smoking behaviors.     

The association between CHRN genetic variants and dizziness at first inhalation of cigarette smoke

Numerous single nucleotide polymorphisms (SNPs) in multiple nicotinic receptor genes (CHRN) are associated with smoking. However few studies have examined the association between CHRN SNPs and subjective responses to smoking in adolescents which may relate to sustained smoking, such as dizziness at first inhalation. The objective of this study was to investigate the association between 61 SNPs in eight CHRN genes (CHRNA3, CHRNA4, CHRNA5, CHRNA6, CHRNA7, CHRNB2, CHRNB3, CHRNB4) and dizziness at first inhalation. Data were available from a longitudinal cohort investigation of 1293 students 12–13 year-old at baseline. Students completed self-report questionnaires at school every 3 months for 5 years during secondary school, and a mailed questionnaire three years later. DNA extracted from blood or saliva was genotyped for 61 CHRN SNPs selected using a gene tagging approach. Associations were modeled using logistic regression controlling for sex, race and age at first cigarette. Complete data were available for 356 of 475 participants (75%) who initiated smoking. The minor alleles of three SNPs in CHRNA6 (rs7812298, rs2304297, rs7828365) were associated with a decreased probability of dizziness (OR(95% CI) = 0.54 (0.36, 0.81), 0.59 (0.40, 0.86) and 0.58 (0.36, 0.95), respectively), while one SNP in each of three other genes (rs3743077 (CHRNA3), rs755204 (CHRNA4), rs7178176 (CHRNA7)) was associated with an increased probability of dizziness (OR(95% CI) = 1.40 (1.02, 1.90), 1.85 (1.05, 3.27) and 1.51 (1.06, 2.15), respectively). Thus, several SNPs located in CHRN genes are associated with dizziness at first inhalation, a smoking initiation phenotype that may relate to sustained smoking.     

Attention-deficit/hyperactivity disorder (ADHD) symptoms, craving to smoke, and tobacco withdrawal symptoms in adult smokers with ADHD

Background

Tobacco withdrawal symptoms may be confounded with attention-deficit/hyperactivity disorder (ADHD) symptoms among smokers with ADHD.

Objective

(1) To assess overlap between ADHD symptoms and tobacco/nicotine withdrawal symptoms and craving; (2) to assess the relationship between craving or withdrawal symptoms and the effect of osmotic-release oral system methylphenidate (OROS-MPH) on ADHD symptoms; (3) to assess the association of ADHD symptoms, craving, and withdrawal symptoms with abstinence.

Methods

Secondary analysis of a randomized, placebo controlled smoking cessation trial assessing the efficacy of OROS-MPH taken in addition to nicotine patch among individuals with ADHD. ADHD symptoms, withdrawal symptoms, and craving were assessed at baseline and 2, 4 and 6 weeks after a target quit day.

Results

Withdrawal symptoms and craving showed limited and modest overlap with ADHD symptoms prior to abstinence but more extensive and stronger correlation after quit day. Compared to placebo, OROS-MPH reduced ADHD symptoms; this effect was attenuated by controlling for withdrawal symptoms, but not by craving. Craving, but not ADHD symptoms and withdrawal symptoms, was associated with abstinence during the trial.

Conclusion

When treating smokers with ADHD (1) craving, rather than tobacco withdrawal symptoms or ADHD symptoms may be the more effective therapeutic smoking cessation targets; (2) careful distinction of craving, withdrawal symptoms, and ADHD symptoms when assessing withdrawal phenomena is needed.     

Nondaily smoking patterns in young adulthood

Purpose

Many young adult smokers routinely smoke less than daily. Prospective, longitudinal data are needed to describe and predict the influences on smoking patterns among nondaily young adult smokers.

Methods

Latent class growth analysis was used to examine developmental trajectories and predictors of nondaily cigarette smoking among young adults aged 18 to 21 in the Upper Midwestern United States.

Results

There were three distinct groups of nondaily smokers during young adulthood (n = 519). College status, previous quit attempts, attitudes toward the meanings of cigarettes, and situational factors influencing smoking were significant predictors of group membership.

Conclusions

Nondaily smoking in young adulthood may result in several discrete patterns of smoking between age 18 and 21. Predictors that differentiate smoking trajectories may be useful to promote cessation or reduction in young adult smoking.     

Racial/ethnic differences in the longitudinal progression of co-occurring negative affect and cigarette use: from adolescence to young adulthood

Aims

This study examined the longitudinal progression of the co-occurrence of cigarette use and negative affect among the general population of U.S. adolescents and young adults and between racial/ethnic groups.

Methods

Data for this study consisted of Waves 4, 6, and 8 of the NLSY97 longitudinal study containing a nationally representative sample of U.S. adolescents and young adults. A total of 7979 adolescents (Mean age at Wave 4 = 17.98, SD = 1.44, 49% female) were included in the analyses. To investigate the co-morbidity between negative affect and cigarette use, a latent factor of negative affect and single indicator of cigarette consumption were examined at each wave. A three wave Bivariate Autoregressive Cross-Lagged Effect Model was estimated to test the conjoint trajectory of negative affect and smoking.

Results

For all racial/ethnic groups prior negative affect status influenced future negative affect between waves and prior negative affect was positively related to increases in smoking in subsequent waves. The longitudinal trajectory of negative affect for the three racial/ethnic groups was the same, but racial/ethnic group differences were observed in the strength of the longitudinal relationship between previous and future cigarette use. Specifically, the following racial/ethnic differences were observed, even after controlling for the effect of SES; White young adults were found to exhibit the strongest association between cigarette use in the first two waves, followed by Hispanic individuals and lastly by African Americans. In the last two waves, African American young adults were found to have the strongest association between cigarette use at the latter two waves, followed by White individuals.

Conclusions

Both negative affect and cigarette consumption influence each other during the transition between late adolescence and young adulthood but the magnitude of the associations between cigarettes use across waves differed between racial/ethnic groups. Implications for prevention and treatment programs include considering both cigarette use and negative affect as two factors that jointly impact each other and that should be targeted simultaneously.     

Sex specific trajectories in cigarette smoking behaviors among students participating in the unplugged school-based randomized control trial for substance use prevention

Objectives

Understanding the developmental pathways and sex differences in cigarette smoking behaviors in adolescents has the potential to positively impact substance abuse prevention and to reduce smoking-related health problems. Using data from the Unplugged school-based prevention trial, we investigated different patterns of smoking behavior development among secondary school students in the Czech Republic.

Methods

Growth mixture modeling was used to examine different trajectories in cigarette smoking behaviors among male and female students (N = 1874 6th graders; 50.4% male, mean age 11.8 years at baseline) participating in the Unplugged school-based randomized control trial for substance use prevention.

Results

A two-class model characterized cigarette use as a function of sex and Unplugged intervention status. More rapid cigarette use increases were observed in females (OR = 1.17, p = 0.01 in both rapid/moderate and slow smoking escalator classes) as compared to males. Further, in both classes, more rapid increases in smoking were observed for the control group as compared to the intervention group (OR = 1.22, p < 0.01 slow escalators; OR = 1.54, p = 0.08 rapid/moderate escalators). There was no difference in sex distribution when comparing the two classes (OR = 1.02, p = 0.98).

Conclusions

This study adds to a growing literature on developmental and sex differences in cigarette use among adolescents. This research supports additional multi-year prevention strategies aimed at adolescent females and early treatment programs for adolescent smokers to prevent increasing cigarette use with age.     

Ten-year stability and variability, drinking patterns, and impairment in community youth with diagnostic orphan status of alcohol dependence

Objective

Some adolescents and young adults who do not fulfill criteria for DSM-IV alcohol abuse (AA) report symptoms of DSM-IV alcohol dependence (AD) below the diagnostic threshold (diagnostic orphans, DOs; 1 or 2 symptoms). Contemporarily, little is known on the long-term stability, risk of progression to AD, impairment, and drinking patterns possibly associated with this status in the first decades of life.

Aim

(1) To identify prevalence rates of the DO status from adolescence to early adulthood. To investigate (2) stability and variability of the DO status over time and (3) associations between DO status, drinking patterns and impairment in comparison to subjects with AA, with AD, or without any symptoms.

Method

N = 2039 community subjects (aged 14–24 years at baseline) were assessed at baseline and at about four and ten years after baseline. DSM-IV AUD diagnoses were obtained with the DIA-X/M-CIDI.

Results

About 11–12% of the sample was classified as DOs at all waves. Over a period of ten years, 18% of DOs were stable in their diagnosis and additional 10% progressed to AD. DOs were comparable to subjects with AA in drinking patterns, impairment and stability of diagnostic status. DOs progressed to AD significantly more often than AA. AD was associated with highest levels in all outcomes of interest.

Conclusions

The DO status in adolescence and early adulthood is associated with considerable stability, risk of progression and problematic alcohol intake. In consequence, it can be meaningful for the timely identification of early stages of clinically relevant alcohol problems. For subjects with DO status early specific interventions are required.     

Adolescent exposure to nicotine results in reinforcement enhancement but does not affect adult responding in rats

Background

Adolescence is a period of development associated with a peak in an organism's responsiveness to reward. Epidemiological data indicate that the initiation of smoking is high during adolescence and that earlier age of onset is associated with increased incidence of dependence as adults. In rats, nicotine is known to have primary reinforcing and reinforcement enhancing effects. Although the primary reinforcing effects of nicotine have been demonstrated in adolescent rats (self-administration), less is known about its reinforcement enhancing effects during this period. Moreover, the impact of adolescent nicotine exposure on its reinforcement enhancing effects during adulthood has not yet been examined. The objectives of this study were to assess whether (1) nicotine enhances operant responding for an unconditioned visual reinforcer (VS) in adolescent rats, and (2) exposure to nicotine during adolescence affects responsiveness to the VS in adulthood.

Methods

Rats were exposed to nicotine (0.32 mg/kg, subcutaneous injection) or saline during adolescence (postnatal day 29–42) and adulthood. Nose-poking for the VS was assessed under fixed and progressive ratio schedules.

Results

Nicotine increased responding for the VS during adolescence. Adolescent nicotine exposure failed to significantly affect adult responsiveness for the VS, regardless of adult nicotine exposure, but early exposure to the VS affected responsiveness to the VS in adulthood.

Conclusions

Nicotine exhibits reinforcement enhancing effects in adolescent rats. Long-term effects of adolescent nicotine on reinforcement enhancement are minimal, but the impact of early exposure to the VS and/or the primary reinforcing effects of nicotine requires further investigation.     

Temporal changes of smoking status and motivation among Chinese heroin-dependent,methadone-maintained smokers

Introduction

The rates of cigarette smoking remain extremely high in active heroin users and methadone-maintained patients. It remains undetermined whether smoking status and motivation would be differentially affected by heroin and methadone administration.

Methods

Heroin-dependent, methadone-maintained patients were recruited in the present studies. A battery of self-report questionnaires was used in the current study, in order to assess smoking status and motivations before first heroin use, during active heroin use and after Methadone Maintenance Treatment (MMT) admission.

Results

An extremely high portion of participants started smoking before first heroin use. The highest level of cigarette smoking was found during the period of active heroin use, and cigarette consumption was reported to decrease after MMT admission. A wide range of smoking motivations were found before first heroin use. Moreover, “maintaining heroin pleasure” was the primary motivation for the increase in cigarette consumption during the period of active heroin use and 1 h after heroin administration, while “habitual smoking” was the primary smoking motivation before first heroin use and after MMT admission respectively.

Conclusions

The present study first demonstrated that the prolonged rewarding effect of heroin following cigarette smoking may account for the increase of nicotine consumption found in the heroin-dependent patients. It appears that heroin and methadone differentially influenced smoking status and motivation among heroin-dependent, methadone-maintained patients.     

Symptoms of alcohol dependence and smoking initiation and persistence: A longitudinal study among US adults

Background

A large number of adults report symptoms of, but do not meet diagnostic criteria for, an alcohol use disorder. Yet, little is known about the relationship between symptoms of alcohol use disorders and the initiation and persistence of smoking. This study prospectively examines the relationship between having 1–2 symptoms of alcohol dependence (without abuse) and smoking initiation and persistence as well as nicotine dependence over a 3-year period among adults in the United States.

Methods

Data were drawn from Wave 1 (2001–2002) and Wave 2 (2004–2005) of the National Epidemiologic Survey on Alcohol and Related Conditions. Relationships between Wave 1 symptoms of alcohol dependence, alcohol abuse, and alcohol dependence and initiation and persistence of cigarette smoking and nicotine dependence at Wave 2 were examined using logistic regression analyses. Analyses were adjusted for demographics, mood and anxiety disorders.

Results

Symptoms of alcohol dependence were associated with smoking initiation at Wave 2. There was no association between symptoms of alcohol dependence and smoking persistence. Symptoms of alcohol dependence predicted incident and persistent nicotine dependence. Findings persisted after adjusting for demographic characteristics and mood/anxiety disorders.

Conclusions

Even 1–2 symptoms of alcohol dependence are associated with increased vulnerability to smoking initiation and onset and persistence of nicotine dependence at a similar strength as alcohol use disorders. Efforts at smoking cessation must address problematic alcohol use, even at the subclinical level, in order to improve efficacy.     

Alcohol use as a signal for sensitivity to nicotine dependence among recent onset smokers

Objective

This study evaluated the association between alcohol use, abuse and dependence and cigarette smoking to determine whether alcohol may signal greater sensitivity to nicotine dependence at very low levels of smoking.

Method

Data were drawn from five annual National Surveys on Drug Use and Health and included individuals age 12 to 21 who reported first exposure to smoking within the past two years and smoking at least once in the past month.

Results

Both alcohol abuse and alcohol dependence were associated with increased likelihood of symptoms that seem to tap tolerance for nicotine. These included items such as “the amount you smoke has increased”; “needing to smoke a lot more now in order to be satisfied”; and “smoking much more before starting to feel anything”. Alcohol dependence, but not abuse was associated with the remaining symptoms, “after not smoking for a while, needing to smoke to feel less restless and irritable”; “craving cigarettes after not smoking for a while”; and “worrying about running out of cigarettes”. All associations were not better accounted for by either alcohol use or amount smoked.

Conclusion

If causally associated, treatment of alcohol-use disorders may prevent or reduce the early emergence of nicotine dependence symptoms among new smokers, very early in the smoking uptake process. If instead alcohol disorders are a signal of sensitivity for nicotine dependence best accounted for by a third variable, then adolescents with alcohol dependence and/or abuse during early exposures to smoking represents an important subgroup that may benefit from interventions directly targeting this association.     

Do early experiences with cannabis vary in cigarette smokers?

Introduction

We examine whether regular cigarette smokers were more likely to be exposed to and use cannabis at an earlier age, and further, upon initiation, whether their initial experiences with cannabis varied from those reported by never/non-regular cigarette smokers.

Method

A sample of 3797 Australian twins and siblings aged 21–46 years was used. Survival analyses examined whether cigarette smokers were at increased likelihood of early opportunity to use cannabis and early onset of cannabis use. Logistic regression examined whether cigarette smokers reported greater enjoyment of their cannabis experience, inhaling on the first try, differing positive and negative initial subjective reactions, smoked cigarettes with cannabis the first time and were more likely to try cannabis again within a week.

Results

Regular cigarette smokers were more likely to report an earlier opportunity to use cannabis and early onset of cannabis use. Regular cigarette smokers were also considerably more likely to have enjoyed their first experience with cannabis and reported higher rates of positive initial reactions. They were more likely to report inhaling on the first try and smoking cigarettes with cannabis. Potentially negative subjective reactions were also elevated in regular cigarette smokers. Importantly, cigarette smokers were at 1.87 increased odds of smoking cannabis within a week of their initial use.

Conclusion

These findings indicate that the well-known overlap in cannabis and cigarette smoking behaviors may evolve as early as opportunity to use and extend through the course of the substance use trajectory.     

The effects of general and alcohol-specific peer factors in adolescence on trajectories of alcohol abuse disorder symptoms from 21 to 33 years

Background

The present study examines whether general and alcohol-specific peer risk factors from age 10 to 18 are associated with longitudinal patterns of adult alcohol abuse disorder symptoms from age 21 to 33.

Methods

Using growth mixture modeling, trajectory groups of alcohol abuse disorder symptoms from age 21 to 33 were identified. We then examined the relationships between the identified trajectory groups of alcohol abuse disorder symptoms and respondents’ own adolescent binge drinking, a general negative peer factor, and an alcohol-specific peer factor (having drinking peers) in adolescence using pseudo-class Wald Chi-square tests, and multinomial logistic regressions.

Results

Four different trajectory groups of alcohol abuse disorder symptoms were identified: persistor group (3%), decreaser group (23%), escalator group (3%), and a no-disorder group (71%). Bivariate Wald Chi-square tests indicated that adolescent binge drinking behavior and general and alcohol-specific peer factors differentiated the adult alcohol abuse trajectory groups. Multivariate multinomial logistic regression showed that the general negative peer factors distinguished those who later persisted in alcohol abuse from those who desisted (i.e., persistor group vs. decreaser group) during young adulthood, even after adjusting for respondents’ adolescent binge drinking. On the other hand, associating with drinking peers did not distinguish these trajectories.

Conclusion

Alcohol-specific peer influences appear to influence alcohol abuse disorder symptoms in the early 20s, while general negative peer exposure in adolescence increases in importance as a risk factor for alcohol abuse disorder symptom persistence in the late 20s and the early 30s.     

Substance use disorder trajectory classes: diachronic integration of onset age, severity, and course

Background

Substance use disorders (SUDs) may be characterized by onset age, severity, substance type, course, and outcomes. SUD phenotypes in the literature typically consider each of these features in isolation. Conceptual frameworks and data collection procedures for assessing SUD phenotypes are increasingly “diachronic” in approach, providing for characterizations “throughout time”. The recent availability of statistical procedures for the identification of latent classes offers the possibility of developing SUD phenotypes integrating these developmental features. This article illustrates the utilization of SAS-TRAJ mixture modeling to characterize variations in SUD symptom trajectories to define phenotypes.

Methods

The subjects were 332 adult males with SUDs. Their course of symptoms from early adolescence through middle adulthood was retrospectively determined. Symptom trajectories were defined by the number of DSM-IV SUD symptoms by year of age. SAS-TRAJ mixture models identified trajectory classes. Model development, evaluation, and selection using this approach are discussed.

Results

Among these men with SUDs, six trajectory classes were identified, including groups characterized by early-onset and severe SUD symptoms persisting into adulthood, an early-onset group similar in adolescence but improving in adulthood, and other groups with symptoms emerging later with varying degrees of severity and persistence. The SUD trajectory classes were significantly different on comorbid psychopathology, particularly childhood disruptive behavior disorders.

Conclusion

The results present a new method for the comprehensive depiction of heterogeneity in SUD symptoms. Future studies may determine the extent to which SUDs phenotypes based on the course of symptom development inform etiology, prevention and treatment research.     

Depressed mood and the effect of two universal first grade preventive interventions on survival to the first tobacco cigarette smoked among urban youth

Introduction

As part of an evaluation of two first-grade, universal preventive interventions whose proximal targets were early learning and behavior, we investigated the influence of depressed mood, the interventions, and their interaction on survival to the first tobacco cigarette smoked through age 19. One intervention focused on improving teacher behavior management and instructional skills (Classroom-Centered, CC) as a means of improving student behavior and learning and the other on the family–school partnership (FSP). Variation in the relationship between depressed mood and first cigarette smoked by gender and grade was also examined.

Methods

Self-reports of smoking behavior and depressed mood were collected on an annual basis from grade 6 through age 19. The present analyses were restricted to the 563 youth who had never smoked by grade 6, or 83% of the original sample of first grade participants. Discrete-time survival analysis was used to examine the effects of depressed mood and the interventions on survival to the first tobacco cigarette smoked.

Results

Depressed mood was associated with reduced survival time to the first cigarette smoked (adjusted hazard ratio, aHR: 1.4; 95% CI: 1.1–1.9), whereas the CC intervention prolonged survival time (aHR: 0.8; 95% CI: 0.7–0.9). No significant variation in the effect of depressed mood on survival was found by gender or grade, nor was the effect of the CC intervention moderated by depressed mood.

Conclusions

Strategies to prevent tobacco cigarette smoking should include both a focus on depressed mood in adolescence as well as on early success in elementary school.     

Neighborhood safety as a correlate of tobacco use in a sample of urban, pregnant women

Objectives

Environmental context has been increasingly recognized as an important determinant of health behavior. This study examined the effects of self-reported neighborhood violence and perceived safety on tobacco use in a sample of low-income, pregnant women.

Methods

Pregnant women (N = 1521) being treated at an urban emergency room completed a baseline interview where neighborhood safety (self-reported neighborhood violence and perceived safety) as well as individual (demographics, depression symptoms, stress, tobacco use, substance abuse) and social variables (prenatal social environment and number of close friends) were evaluated cross-sectionally. Tobacco use was measured again in a telephone interview at 22 weeks gestation.

Results

In a logistic regression model of baseline smoking status, self-reported neighborhood violence was significantly associated with being a smoker independent of age, education status, attendance to prenatal care, gestational age and lifetime use of cocaine and marijuana. In a regression model estimating the relationship between these baseline variables and continued prenatal smoking, baseline smoking emerged as the strongest correlate of continued smoking during pregnancy.

Conclusions

These findings suggest that self-reported neighborhood violence had a stronger association with early pregnancy cigarette use compared to ongoing cigarette use in a sample of low-income, pregnant women. Prospective trials are needed to fully elucidate the relationship between individual and social-environmental determinants of tobacco use in this high-risk population.     

The interactive effect of neighborhood peer cigarette use and 5HTTLPR genotype on individual cigarette use

Background

Previous cross-sectional research has shown that adolescents' cigarette use is interactively associated with that of their school peers and their 5HTTLPR genotype, such that the cigarette use of persons with more copies of the 5HTTLPR*S′ allele is more dependent on school peers' cigarette use behaviors than their counterparts. This analysis seeks to extend this novel finding by examining whether the same conclusion can be reached when substituting neighborhood peers for school peers and examining the timing of the initiation of any and regular smoking in adolescence.

Methods

This analysis employs an independent sample with longitudinal measures of cigarette use among 6th through 8th graders clustered in 82 neighborhoods, of whom 1098 contributed genetic data. The proportion of respondents who had ever smoked cigarettes by the first wave was calculated for each census block group in the study. 5HTTLPR genotype was assayed using the method of Whisman et al. (2011). The timing of any or regular smoking initiation and over four years were modeled as dependent variables using Cox proportional hazard models.

Results

The interaction of neighborhood peer smoking behavior in the first wave and 5HTTLPR genotype statistically significantly predicted any smoking initiation (hazard ratio: 3.532; p-value = 0.002) and regular smoking initiation (hazard ratio: 5.686; p-value = 0.000), net of controls for sex, race/ethnicity, grade in the first wave of data, and parental educational attainment. These findings reach the same conclusions as previous cross-sectional research.

Conclusions

These results differ in the model of gene–environment interaction that they support. The findings for any smoking initiation are consistent with the diathesis–stress model of gene–environment interaction; the findings for regular smoking initiation are consistent with the differential susceptibility model.     

Electronic cigarette use by college students

Background

Electronic cigarettes, or e-cigarettes, are battery operated devices that deliver nicotine via inhaled vapor. There is considerable controversy about the disease risk and toxicity of e-cigarettes and empirical evidence on short- and long-term health effects is minimal. Limited data on e-cigarette use and correlates exist, and to our knowledge, no prevalence rates among U.S. college students have been reported. This study aimed to estimate the prevalence of e-cigarette use and identify correlates of use among a large, multi-institution, random sample of college students.

Methods

4444 students from 8 colleges in North Carolina completed a Web-based survey in fall 2009.

Results

Ever use of e-cigarettes was reported by 4.9% of students, with 1.5% reporting past month use. Correlates of ever use included male gender, Hispanic or “Other race” (compared to non-Hispanic Whites), Greek affiliation, conventional cigarette smoking and e-cigarette harm perceptions. Although e-cigarette use was more common among conventional cigarette smokers, 12% of ever e-cigarette users had never smoked a conventional cigarette. Among current cigarette smokers, e-cigarette use was negatively associated with lack of knowledge about e-cigarette harm, but was not associated with intentions to quit.

Conclusions

Although e-cigarette use was more common among conventional cigarette smokers, it was not exclusive to them. E-cigarette use was not associated with intentions to quit smoking among a sub-sample of conventional cigarette smokers. Unlike older, more established cigarette smokers, e-cigarette use by college students does not appear to be motivated by the desire to quit cigarette smoking.     

Serotonin transporter and receptor genes significantly impact nicotine dependence through genetic interactions in both European American and African American smokers

Background

Pharmacologic studies implicate a significant role of genes encoding the serotonin transporter (SLC6A4) and the 5-HT_3AB subunits HTR3A and HTR3B in nicotine dependence (ND). However, whether they are involved in ND remains largely unknown.

Methods

Here, we examined the impact of variations in the three genes on ND in 1366 individuals from 402 African American (AA) and 671 individuals from 200 European American (EA) families. The ND of each smoker was assessed with smoking quantity (SQ), heaviness of smoking index (HSI), and Fagerström test for nicotine dependence (FTND).

Results

Association analysis revealed marginal association of rs10160548 in HTR3A with SQ and HSI in AA, 5-HTTLPR in SLC6A4 with FTND in EA, and rs11606194 in HTR3B with SQ and FTND in the pooled sample. Haplotype-based association analysis revealed a few major haplotypes in HTR3A that were significantly associated with ND in the AA, EA, and pooled samples. However, none of these associations remained significant after correcting for multiple testing except for a haplotype G-C-C-T-A-T formed by SNPs rs1150226, rs1062613, rs33940208, rs1985242, rs2276302, and rs10160548 in HTR3A for the AA sample. Considering biological functions of the three genes, we examined interactive effects of variants in the three genes, which revealed significant interactions among rs1062613 and rs10160548 in HTR3A, rs1176744 in HTR3B, and 5-HTTLPR and rs1042173 in SLC6A4 in affecting ND in the three samples.

Conclusions

We conclude that SLC6A4, HTR3A and HTR3B play a significant role in ND through genetic interactions.