Racial differences in heritability of cigarette smoking in adolescents and young adults

Genetics of Smoking Behaviors in American Indians

BACKGROUND

The smoking behavior of American Indians (AI) differs from that of non-Hispanic whites (NHW). Typically light smokers, cessation interventions in AIs are generally less effective. To develop more effective cessation programs for AIs, clinicians, researchers, and public health workers need a better understanding of the genetic factors involved in their smoking behavior. Our aim was to assess whether SNPs associated with smoking behavior in NHWs are also associated with smoking in AIs.

METHODS

We collected questionnaire data on smoking behaviors and analyzed blood and saliva samples from two Tribal populations with dramatically different cultures and smoking prevalence, one in the Northern Plains (n = 323) and the other in the Southwest (n = 176). A total of 384 SNPs were genotyped using an Illumina custom GoldenGate platform. Samples were also assessed for cotinine and 3-hydroxycotinine as markers of nicotine intake and nicotine metabolite ratio.

RESULTS

Among 499 participants, we identified, in the Northern Plains sample only, a variant of the gamma-aminobutyric acid receptor subunit alpha-2 (GABRA2) (rs2119767) on chromosome 4p that was associated with many of the intake biomarkers of smoking we examined, suggesting a role for this gene in modifying smoking behavior in this population. We also identified three SNPs, in the Southwest sample only, as significant correlates of only cigarettes per day: rs4274224, rs4245147 (both dopamine receptor D2 gene), and rs1386493 (tryptophan hydroxylase 2 gene).

CONCLUSIONS

The contribution of many genes known to underlie smoking behaviors in NHWs may differ in AIs.

IMPACT

Once validated, these variants could be useful in developing more effective cessation strategies.

The Type and Timing of Child Maltreatment as Predictors of Adolescent Cigarette Smoking Trajectories

Background: There is limited research examining the association between child maltreatment and cigarette smoking as a specific type of adolescent substance use, and research examining high-risk samples and variations based on maltreatment type and timing remain sparse. Objectives: The primary aim of the study was to examine the relationship between child maltreatment and cigarette smoking trajectories. Methods: Latent class growth analysis and multinomial logistic regression were performed on 903 youth drawn from the Longitudinal Studies of Child Abuse and Neglect (LONGSCAN). Results: Three distinct classes of cigarette smoking trajectories were identified: (1) Stable no/low cigarette use (61%); (2) Gradually increasing cigarette use (30%); and (3) Sharply increasing cigarette use (9%). Physical abuse during early childhood and adolescence predicted membership in the sharply increasing cigarette use class. Neglect during early childhood predicted membership in the gradually increasing cigarette use class. Conclusions: Findings suggest that interventions for adolescent cigarette smoking should integrate trauma-informed approaches. Further, the results highlight early childhood and adolescence as particularly vulnerable periods with respect to the influence of physical abuse and neglect on cigarette smoking, pointing to the need for additional maltreatment prevention efforts during these developmental stages.

Risk Factors Associated With Gambling Involvement among a National Sample of African American and European American Young Adults

In the current research, we examined the association of key risk and protective factors for gambling involvement from the domains of family environment, conduct problems/delinquency, substance use, and depressive psychopathology in a nationally representative sample. The sample was comprised of 13,291 young adults (ages 18-26; Meanage = 22.8) self-identifying as European American (n=9,939) or African American (n=3,335) who participated in Wave III (n = 15,170) of the restricted-use National Longitudinal Study of Adolescent to Adult Health. We used separate logistic regressions to study participation in specific gam bling categories (lottery games, casino-type games, other games). Childhood neglect, physical discipline, and current alcohol use was associated across each of the three gam bling categories. Our results also revealed differences between European American and African American subjects. Current cannabis use was associated with all three categories among African Americans, while current cigarette use was associated among European Americans for lottery games, and depression (female) was associated with other games. We also applied multinomial logistic regression to study gambling involvement based on the number of gam bling categories that the participant engaged in 2 or more (referent), only 1, or none at all. Our results revealed that delinquency/conduct symptoms (AOR=0.83) along with cannabis use (African American; AOR =0.66), cigarette use (European American; AOR =0.83), current alcohol use (AOR=0.66) were associated with gambling in two categories vs. gambling in one category. Childhood physical discipline (AOR=0.75) and childhood neglect (AOR=0.75) were associated with gam bling in two categories vs. no gambling. Further are needed to investigate the developmental pathways leading to increased gam bling involvement among African American and European American adolescents and young adults.

Missing compared to what? Revisiting heritability, genes and culture

Standard models for the determination of phenotypes from genes are grounded in simple assumptions that are inherent in the modern evolutionary synthesis (MES), which was developed in the 1930s, 1940s and 1950s. The MES was framed in the context of Mendelian genetic transmission enhanced by the Fisherian view of the way discretely inherited genes determine continuously quantitative phenotypes. The statistical models that are used to estimate and interpret genetic contributions to human phenotypes-including behavioural traits-are constructed within the framework of the MES. Variance analysis constitutes the main tool and is used under this framework to characterize genetic inheritance, and hence determination of phenotypes. In this essay, we show that cultural inheritance, when incorporated into models for the determination of phenotypes, can sharply reduce estimates of the genetic contribution to these phenotypes. Recognition of the importance of non-genetic transmission of many human traits is becoming ever more necessary to prevent regression to the debates of the 1970s and 1980s concerning policies based on genetic determination of complex human phenotypes.This article is part of the theme issue 'Bridging cultural gaps: interdisciplinary studies in human cultural evolution'.

Familial and Special Twin Influences on Cigarette Use Initiation

BACKGROUND

Shared experiences within families play an important role in the initiation of cigarette use among adolescents. Behavioral genetic studies using various samples have implicated that the shared environment that twins experience is an important source of influence on whether adolescents initiate cigarette use. Whether the special twin environment, in addition to the shared environment, contributes significantly to making twin siblings more similar in cigarette initiation, and whether the influence of the special twin environment persists into adulthood, is less clear.

METHODS

Data for this study came from the National Longitudinal Survey of Adolescent Health. Twin, full-, and half-sibling pairs between the ages of 12 and 33 were separated into three age groups, with about 3,000 individuals in each age group. The proportion of variance in cigarette use initiation explained by genetic, shared, special twin, and unique environmental factors were examined.

RESULTS

The results of separate age-moderated univariate variance decomposition models indicate that the special twin environment does not significantly contribute to the variance in cigarette use initiation in adolescence or young adulthood.

CONCLUSION

Factors shared by individuals in a family, but that are not specific to being a twin, are important in determining whether adolescents will initiate the use of cigarettes.