Imputation of behavioral candidate gene repeat variants in 486,551 publicly-available UK Biobank individuals.

Some of the most widely studied variants in psychiatric genetics include variable number tandem repeat variants (VNTRs) in SLC6A3, DRD4, SLC6A4, and MAOA. While initial findings suggested large effects, their importance with respect to psychiatric phenotypes is the subject of much debate with broadly conflicting results. Despite broad interest, these loci remain absent from the largest available samples, such as the UK Biobank, limiting researchers' ability to test these contentious hypotheses rigorously in large samples. Here, using two independent reference datasets, we report out-of-sample imputation accuracy estimates of >0.96 for all four VNTR variants and one modifying SNP, depending on the reference and target dataset. We describe the imputation procedures of these candidate variants in 486,551 UK Biobank individuals, and have made the imputed variant data available to UK Biobank researchers. This resource, provided to the scientific community, will allow the most rigorous tests to-date of the roles of these variants in behavioral and psychiatric phenotypes.

The role of genetic and environmental influences on the association between childhood ADHD symptoms and BMI.

BACKGROUND/OBJECTIVES: Although childhood attention deficit hyperactivity disorder (ADHD) has been previously associated with concurrent and later obesity in adulthood, the etiology of this association remains unclear. The objective of this study is to determine the shared genetic effects of ADHD symptoms and BMI in a large sample of sibling pairs, consider how these shared effects may vary over time, and examine potential sex differences. SUBJECT/METHODS: Sibling pair data were obtained from the National Longitudinal Study of Adolescent to Adult Health (Add Health); childhood ADHD symptoms were reported retrospectively during young adulthood, while three prospective measurements of BMI were available from young adulthood to later adulthood. Cholesky decomposition models were fit to this data using Mx and maximum-likelihood estimation. The twin and sibling sample for these analyses included: 221 monozygotic (MZ) pairs (92 male-male, 139 female-female), 228 dizygotic (DZ) pairs (123 male-male, 105 female-female), 471 full-sibling (FS) pairs (289 male-male, 182 female-female), 106 male-female DZ twin pairs, and 234 male-female FS pairs. RESULTS: The magnitude of the association between childhood ADHD symptoms and BMI changed over time and by sex. The etiological relationship between childhood ADHD symptoms and the three prospective measurements of BMI differed for males and females, such that unique or non-shared environmental influences contributed to the relationship within males and genetic factors contributed to the relationship within females. Specifically, among females, genetic influences on childhood ADHD symptoms were partially shared with those effecting BMI and increased from adolescence to later adulthood (genetic correlation = 0.20 (95% CI: 0.07-0.36) in adolescence and 0.24 (95% CI: 0.10, 0.41) in adulthood). CONCLUSION: Genetic influences on ADHD symptoms in childhood are partially shared with those effecting obesity. However, future research is needed to determine why this association is limited to females.

Population differences in associations of serotonin transporter promoter polymorphism (5HTTLPR) di- and triallelic genotypes with blood pressure and hypertension prevalence.

Based on prior research finding the 5HTTLPR L allele associated with increased cardiovascular reactivity to laboratory stressors and increased risk of myocardial infarction, we hypothesized that the 5HTTLPR L allele will be associated with increased blood pressure (BP) and increased hypertension prevalence in 2 large nationally representative samples in the United States and Singapore. METHODS: Logistic regression and linear models tested associations between triallelic (L'S', based on rs25531) 5HTTLPR genotypes and hypertension severity and mean systolic and diastolic blood pressure (SBP and DBP) collected during the Wave IV survey of the National Longitudinal Study of Adolescent to Adult Health (Add Health, N=11,815) in 2008-09 and during 2004-07 in 4196 Singaporeans. RESULTS: In US Whites, L' allele carriers had higher SBP (0.9 mm Hg, 95% CI=0.26-1.56) and greater odds (OR=1.23, 95% CI=1.10-1.38) of more severe hypertension than those with S'S' genotypes. In African Americans, L' carriers had lower mean SBP (-1.27mm Hg, 95% CI=-2.53 to -0.01) and lower odds (OR = 0.78, 95% CI=0.65-0.94) of more severe hypertension than those with the S'S' genotype. In African Americans, those with L'L' genotypes had lower DBP (-1.13mm Hg, 95% CI=-2.09 to -0.16) than S' carriers. In Native Americans, L' carriers had lower SBP (-6.05mm Hg, 95% CI=-9.59 to -2.51) and lower odds of hypertension (OR = 0.34, 95% CI=0.13-0.89) than those with the S'S' genotype. In Asian/Pacific Islanders those carrying the L' allele had lower DBP (-1.77mm Hg, 95% CI=-3.16 to -0.38) and lower odds of hypertension (OR = 0.68, 95% CI=0.48-0.96) than those with S'S'. In the Singapore sample S' carriers had higher SBP (3.02mm Hg, 95% CI=0.54-5.51) and DBP (1.90mm Hg, 95% CI=0.49-3.31) than those with the L'L' genotype. CONCLUSIONS: These findings suggest that Whites carrying the L' allele, African Americans and Native Americans with the S'S' genotype, and Asians carrying the S' allele will be found to be at higher risk of developing cardiovascular disease and may benefit from preventive measures.

Perceived Family Cohesion Moderates Environmental Influences on Prosocial Behavior in Nigerian Adolescent Twins.

Research shows that perceived family cohesion is positively related to prosocial behavior in adolescents. In this study, we investigated heritability of prosocial behavior (PB) and perceived family cohesion (FC) among Nigerian twins attending public schools in Lagos State, Nigeria (mean age = 14.7 years, SD = 1.7 years), and explored the issue of whether children's perception of cohesive family environment moderated genetic and environmental influences on (PB). The PB scale of the Strengths and Difficulties Questionnaire and the FC scale of the Family Adaptability and Cohesion Evaluation Scale III were completed by 2,376 twins (241 monozygotic (MZ) male, 354 MZ female, 440 dizygotic (DZ) male, 553 DZ female, and 788 opposite-sex DZ twins). A general sex-limitation and the bivariate genotype by environment interaction (G×E) models were applied to the data. The general sex-limitation model showed no significant sex differences, indicating that additive genetic and non-shared environmental influences were, 38% (95% CI = 31, 46) and 62% (95% CI = 54, 69) for PB and 33% (95% CI = 24, 40) and 67% (95% CI = 60, 76) for FC in both sexes. These estimates were similar to those found in Western and Asian twin studies to date. The correlation between PB and FC was 0.36. The best-fitting bivariate G×E model indicated that FC significantly moderated non-shared environmental influence unique to PB (E×E interaction). Specifically, non-shared environmental contributions to PB were highest when FC was lowest, and decreased as the levels of FC increased. However, genetic variances in PB were stable across all levels of FC. These findings suggest that FC reduces individual differences in PB by changing non-shared environmental experiences rather than genetic factors in PB.

Depression, Stressful Life Events, and the Impact of Variation in the Serotonin Transporter: Findings from the National Longitudinal Study of Adolescent to Adult Health (Add Health).

BACKGROUND: The low transcriptionally efficient short-allele of the 5HTTLPR serotonin transporter polymorphism has been implicated to moderate the relationship between the experience of stressful life events (SLEs) and depression. Despite numerous attempts at replicating this observation, results remain inconclusive. METHODS: We examined this relationship in young-adult Non-Hispanic white males and females between the ages of 22 and 26 (n = 4724) participating in the National Longitudinal Study of Adolescent to Adult Health (Add Health) with follow-up information every six years since 1995. RESULTS: Linear and logistic regression models, corrected for multiple testing, indicated that carriers of one or more of the S-alleles were more sensitive to stress than those with two L-alleles and at a higher risk for depression. This relationship behaved in a dose-response manner such that the risk for depression was greatest among those who reported experiencing higher numbers of SLEs. In post-hoc analyses we were not able to replicate an interaction effect for suicide ideation but did find suggestive evidence that the effects of SLEs and 5HTTLPR on suicide ideation differed for males and females. There were no effects of childhood maltreatment. DISCUSSION: Our results provide partial support for the original hypothesis that 5-HTTLPR genotype interacts with the experience of stressful life events in the etiology of depression during young adulthood. However, even with this large sample, and a carefully constructed a priori analysis plan, the results were still not definitive. For the purposes of replication, characterizing the 5HTTLPR in other large data sets with extensive environmental and depression measures is needed.

Life events, genetic susceptibility, and smoking among adolescents.

Although stressful life events during adolescence are associated with the adoption of unhealthy behaviors such as smoking, both social circumstances and physical traits can moderate the relationship. This study builds on the stress paradigm and gene-environment approach to social behavior by examining how a polymorphism in the serotonin transporter gene 5-HTTLPR moderates the effect of life events on adolescent smoking. Tests of interaction hypotheses use data from the Family Transitions Project, a longitudinal study of 7th graders followed for 5years. A sibling-pair design with separate models for the gender composition of pairs (brothers, sisters, or brother/sister) controls for unmeasured family background. The results show that negative life events are significantly and positively associated with smoking. Among brother pairs but not other pairs, the results provide evidence of gene-environment interaction by showing that life events more strongly influence smoking behavior for those with more copies of the 5-HTTLPR S allele.

Molecular Genetic Testing in Reward Deficiency Syndrome (RDS): Facts and Fiction.

BACKGROUND: The Brain Reward Cascade (BRC) is an interaction of neurotransmitters and their respective genes to control the amount of dopamine released within the brain. Any variations within this pathway, whether genetic or environmental (epigenetic), may result in addictive behaviors or RDS, which was coined to define addictive behaviors and their genetic components. METHODS: To carry out this review we searched a number of important databases including: Filtered: Cochrane Systematic reviews; DARE; Pubmed Central Clinical Quaries; National Guideline Clearinghouse and unfiltered resources: PsychINFO; ACP PIER; PsychSage; Pubmed/Medline. The major search terms included: dopamine agonist therapy for Addiction; dopamine agonist therapy for Reward dependence; dopamine antagonistic therapy for addiction; dopamine antagonistic therapy for reward dependence and neurogenetics of RDS. RESULTS: While there are many studies claiming a genetic association with RDS behavior, not all are scientifically accurate. CONCLUSION: Albeit our bias, this Clinical Pearl discusses the facts and fictions behind molecular genetic testing in RDS and the significance behind the development of the Genetic Addiction Risk Score (GARSPREDX™), the first test to accurately predict one's genetic risk for RDS.

Genome-Wide Association Study of Behavioral Disinhibition in a Selected Adolescent Sample.

Behavioral disinhibition (BD) is a quantitative measure designed to capture the heritable variation encompassing risky and impulsive behaviors. As a result, BD represents an ideal target for discovering genetic loci that predispose individuals to a wide range of antisocial behaviors and substance misuse that together represent a large cost to society as a whole. Published genome-wide association studies (GWAS) have examined specific phenotypes that fall under the umbrella of BD (e.g. alcohol dependence, conduct disorder); however no GWAS has specifically examined the overall BD construct. We conducted a GWAS of BD using a sample of 1,901 adolescents over-selected for characteristics that define high BD, such as substance and antisocial behavior problems, finding no individual locus that surpassed genome-wide significance. Although no single SNP was significantly associated with BD, restricted maximum likelihood analysis estimated that 49.3 % of the variance in BD within the Caucasian sub-sample was accounted for by the genotyped SNPs (p = 0.06). Gene-based tests identified seven genes associated with BD (p ≤ 2.0 × 10(-6)). Although the current study was unable to identify specific SNPs or pathways with replicable effects on BD, the substantial sample variance that could be explained by all genotyped SNPs suggests that larger studies could successfully identify common variants associated with BD.

Population frequencies of the Triallelic 5HTTLPR in six Ethnicially diverse samples from North America, Southeast Asia, and Africa.

Genetic differences between populations are potentially an important contributor to health disparities around the globe. As differences in gene frequencies influence study design, it is important to have a thorough understanding of the natural variation of the genetic variant(s) of interest. Along these lines, we characterized the variation of the 5HTTLPR and rs25531 polymorphisms in six samples from North America, Southeast Asia, and Africa (Cameroon) that differ in their racial and ethnic composition. Allele and genotype frequencies were determined for 24,066 participants. Results indicated higher frequencies of the rs25531 G-allele among Black and African populations as compared with White, Hispanic and Asian populations. Further, we observed a greater number of 'extra-long' ('XL') 5HTTLPR alleles than have previously been reported. Extra-long alleles occurred almost entirely among Asian, Black and Non-White Hispanic populations as compared with White and Native American populations where they were completely absent. Lastly, when considered jointly, we observed between sample differences in the genotype frequencies within racial and ethnic populations. Taken together, these data underscore the importance of characterizing the L-G allele to avoid misclassification of participants by genotype and for further studies of the impact XL alleles may have on the transcriptional efficiency of SLC6A4.

Dopamine in the Brain: Hypothesizing Surfeit or Deficit Links to Reward and Addiction.

Recently there has been debate concerning the role of brain dopamine in reward and addiction. David Nutt and associates eloquently proposed that dopamine (DA) may be central to psycho stimulant dependence and some what important for alcohol, but not important for opiates, nicotine or even cannabis. Others have also argued that surfeit theories can explain for example cocaine seeking behavior as well as non-substance-related addictive behaviors. It seems prudent to distinguish between what constitutes "surfeit" compared to" deficit" in terms of short-term (acute) and long-term (chronic) brain reward circuitry responsivity. In an attempt to resolve controversy regarding the contributions of mesolimbic DA systems to reward, we review the three main competing explanatory categories: "liking", "learning", and "wanting". They are (a) the hedonic impact -liking reward, (b) the ability to predict rewarding effects-learning and (c) the incentive salience of reward-related stimuli -wanting. In terms of acute effects, most of the evidence seems to favor the "surfeit theory". Due to preferential dopamine release at mesolimbic-VTA-caudate-accumbens loci most drugs of abuse and Reward Deficiency Syndrome (RDS) behaviors have been linked to heightened feelings of well-being and hyperdopaminergic states.The "dopamine hypotheses" originally thought to be simple, is now believed to be quite complex and involves encoding the set point of hedonic tone, encoding attention, reward expectancy, and incentive motivation. Importantly, Willuhn et al. shows that in a self-administration paradigm, (chronic) excessive use of cocaine is caused by decreased phasic dopamine signaling in the striatum. In terms of chronic addictions, others have shown a blunted responsivity at brain reward sites with food, nicotine, and even gambling behavior. Finally, we are cognizant of the differences in dopaminergic function as addiction progresses and argue that relapse may be tied to dopamine deficiency. Vulnerability to addiction and relapse may be the result of the cumulative effects of dopaminergic and other neurotransmitter genetic variants and elevated stress levels. We therefore propose that dopamine homeostasis may be a preferred goal to combat relapse.

Self-regulatory failure and the perpetration of adolescent dating violence: Examining an alcohol use by gene explanation.

Studies report that alcohol use is related to partner violence, but for many, alcohol use does not culminate in violence against partners. Guided by a self-regulatory failure framework, we predicted that alcohol use would be more strongly associated with dating violence perpetration among adolescents with genotypes linked to impulsivity and emotional reactivity. The hypothesis was tested using random coefficient modeling of data from a multi-wave longitudinal study spanning grades 8-12 (ages 13-18) (n = 1,475). Analyses adjusted for multiple testing and race, and the potential for gene by environment correlation was examined. As predicted, alcohol use was more strongly associated with dating violence among adolescents who had a high rather than a low multilocus genetic profile composed of five genetic markers that influence dopamine signaling. Alcohol use was more strongly related to dating violence among boys with long rather than short 5-HTTLPR alleles, the opposite of the prediction. MAOA-uVNTR did not interact with alcohol, but it had a main effect on dating violence by boys in later grades in the expected direction: boys with more low activity alleles perpetrated more dating violence. Exploratory analyses found variation in findings by race. Our findings demonstrate the importance of incorporating genes into etiological studies of adolescent dating violence, which to date has not been done. Aggr. Behav. Aggr. Behav. 42:189-203, 2015. © 2014 Wiley Periodicals, Inc.

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.

Genetic and environmental influences on the allocation of adolescent leisure time activities.

There is a growing recognition of the importance of the out-of-school activities in which adolescents choose to participate. Youth activities vary widely in terms of specific activities and in time devoted to them but can generally be grouped by the type and total duration spent per type. We collected leisure time information using a 17-item leisure time questionnaire in a large sample of same- and opposite-sex adolescent twin pairs (N = 2847). Using both univariate and multivariate genetic models, we sought to determine the type and magnitude of genetic and environmental influences on the allocation of time toward different leisure times. Results indicated that both genetic and shared and nonshared environmental influences were important contributors to individual differences in physical, social, intellectual, family, and passive activities such as watching television. The magnitude of these influences differed between males and females. Environmental influences were the primary factors contributing to the covariation of different leisure time activities. Our results suggest the importance of heritable influences on the allocation of leisure time activity by adolescents and highlight the importance of environmental experiences in these choices.

Simple sequence repeats in the national longitudinal study of adolescent health: an ethnically diverse resource for genetic analysis of health and behavior.

Simple sequence repeats (SSRs) are one of the earliest available forms of genetic variation available for analysis and have been utilized in studies of neurological, behavioral, and health phenotypes. Although findings from these studies have been suggestive, their interpretation has been complicated by a variety of factors including, among others, limited power due to small sample sizes. The current report details the availability, diversity, and allele and genotype frequencies of six commonly examined SSRs in the ethnically diverse, population-based National Longitudinal Study of Adolescent Health. A total of 106,743 genotypes were generated across 15,140 participants that included four microsatellites and two di-nucleotide repeats in three dopamine genes (DAT1, DRD4, DRD5), the serotonin transporter, and monoamine oxidase A. Allele and genotype frequencies showed a complex pattern and differed significantly between populations. For both di-nucleotide repeats we observed a greater allelic diversity than previously reported. The availability of these six SSRs in a large, ethnically diverse sample with extensive environmental measures assessed longitudinally offers a unique resource for researchers interested in health and behavior.

Prevalence and correlates of alcohol and cannabis use disorders in the United States: results from the national longitudinal study of adolescent health.

BACKGROUND: Limited current information on the epidemiology of lifetime alcohol and cannabis use disorders in the United States is available. AIMS: To present detailed information about the prevalence and sociodemographic correlates of lifetime alcohol and cannabis use disorders rates in the United States. To examine gender differences in hazard ratios for the onset of alcohol and cannabis dependence. METHODS: Participants in Wave IV of the National Longitudinal Study of Adolescent Health (N=15,500, age range: 24-32) were interviewed between 2008 and 2009. Participants who exceeded screening thresholds were queried about lifetime DSM-IV alcohol and marijuana abuse and dependence symptoms. Age of substance dependence onset was queried. RESULTS: Lifetime rates of alcohol abuse and dependence were 11.8 and 13.2%. Lifetime rates of cannabis abuse and dependence were 3.9 and 8.3%. Lifetime alcohol and cannabis dependence onset peaks were 23 and 20. Correlates of lifetime alcohol abuse included being male (OR 1.4), African-American (OR 0.7), income in the 2nd or 3rd quartile (OR 0.7 and 0.6). Correlates of lifetime alcohol dependence were: being male (OR 1.8), African-American (OR 0.5), and never being married (OR 1.5), and regions outside of the west (Midwest OR 0.7, South OR 0.6, Northeast OR 0.6). Correlates of cannabis abuse and dependence were being male (OR 1.8 and 1.4). CONCLUSIONS: Lifetime alcohol and cannabis use disorders are highly prevalent in the US population. Men are at higher risk for alcohol and cannabis use disorders. Alcohol use disorders demonstrated specific sociodemographic correlates while marijuana use disorders did not.

Is the gene-environment interaction paradigm relevant to genome-wide studies? The case of education and body mass index.

This study uses data from the Framingham Heart Study to examine the relevance of the gene-environment interaction paradigm for genome-wide association studies (GWAS). We use completed college education as our environmental measure and estimate the interactive effect of genotype and education on body mass index (BMI) using 260,402 single-nucleotide polymorphisms (SNPs). Our results highlight the sensitivity of parameter estimates obtained from GWAS models and the difficulty of framing genome-wide results using the existing gene-environment interaction typology. We argue that SNP-environment interactions across the human genome are not likely to provide consistent evidence regarding genetic influences on health that differ by environment. Nevertheless, genome-wide data contain rich information about individual respondents, and we demonstrate the utility of this type of data. We highlight the fact that GWAS is just one use of genome-wide data, and we encourage demographers to develop methods that incorporate this vast amount of information from respondents into their analyses.

MAOA genotype, childhood maltreatment, and their interaction in the etiology of adult antisocial behaviors.

BACKGROUND: Maltreatment by an adult or caregiver during childhood is a prevalent and important predictor of antisocial behaviors in adulthood. A functional promoter polymorphism in the monoamine oxidase A (MAOA) gene has been implicated as a moderating factor in the relationship between childhood maltreatment and antisocial behaviors. Although there have been numerous attempts at replicating this observation, results remain inconclusive. METHODS: We examined this gene-environment interaction hypothesis in a sample of 3356 white and 960 black men (aged 24-34) participating in the National Longitudinal Study of Adolescent Health. RESULTS: Primary analysis indicated that childhood maltreatment was a significant risk factor for later behaviors that violate rules and the rights of others (p < .05), there were no main effects of MAOA genotype, and MAOA genotype was not a significant moderator of the relationship between maltreatment and antisocial behaviors in our white sample. Post hoc analyses identified a similar pattern of results among our black sample in which maltreatment was not a significant predictor of antisocial behavior. Post hoc analyses also revealed a main effect of MAOA genotype on having a disposition toward violence in both samples and for violent convictions among our black sample. None of these post hoc findings, however, survived correction for multiple testing (p > .05). Power analyses indicated that these results were not due to insufficient statistical power. CONCLUSIONS: We could not confirm the hypothesis that MAOA genotype moderates the relationship between childhood maltreatment and adult antisocial behaviors.

Behavioral disinhibition and sexual risk behavior among adolescents and young adults in Malawi.

BACKGROUND: While behavioral factors such as early age of sexual debut, inconsistent use of condoms and multiple sexual partners have been studied in Africa, less is known about how characteristics such as impulsivity and externalizing behaviors relate to HIV-related sexual risk-taking in that region. The purpose of this study was to develop a culturally adapted behavioral disinhibition index in a sample of adolescents and young adults in Malawi. We then sought to examine the relationship between the index and sexual risk behavior as measured by multiple sexual partners and number of lifetime sexual partners. METHODS: Cross-sectional data were collected from 2342 participants in rural Malawi aged 15 to 29 years. We constructed a disinhibitory behavior score (DBS) using questions assessing disinhibitory behaviors. Bivariate analyses were conducted to assess the relationships among the individual DBS component behaviors. We utilized multivariable logistic regression to determine the association of the DBS with multiple sexual partners, and negative binomial regression to model the relationship between the DBS and number of lifetime sexual partners. FINDINGS: Nearly all the DBS component behaviors were significantly associated in the bivariate analyses. The DBS was associated with having multiple sexual partners (OR 1.97; 95% CI 1.57-2.48) in the multivariable logistic regression analysis. Further, negative binomial regression results demonstrated that the DBS was associated with an increased number of lifetime sexual partners (OR 1.11; 95% CI 1.07-1.16). CONCLUSIONS: HIV preventive programs in Africa should take into consideration disinhibitory behaviors that may be associated with sexual risk-taking. The DBS can be used as a simple tool to identify those who may be more likely to engage in these behaviors and provide useful information regarding which groups of individuals particularly need to be targeted for behavior change interventions.

Frequency of alcohol use in adolescence as a marker for subsequent sexual risk behavior in adulthood.

PURPOSE: Although a number of studies have demonstrated an association between alcohol use frequency and sexual risk behavior, few have used longitudinal data. This study examined alcohol use frequency in adolescence as a predictor of HIV sexual risk behavior in adulthood. METHODS: We collected data among 1,368 participants in Colorado. During adolescence (time 1), respondents were asked about the frequency of using alcohol during the previous 12 months. In adulthood (time 2), the same respondents were asked about their sexual risk behavior during the previous 12 months. Sexual risk behavior items were used to construct an index, which was categorized to indicate low-, medium-, and high-risk study participants. The relationship between alcohol use patterns and risky sexual behavior was modeled using ordinal regression. RESULTS: Compared with individuals who drank no alcohol in the past 12 months at time 1, the odds of being in a higher risk group of sexual behavior as opposed to a lower one at time 2 were 1.56 (95% CI, 1.04-2.35) among those who drank 6-19 times. Similarly, the odds of being in a higher risk group relative to a lower one among those who drank ≥20 times or were 1.78 (95% CI, 1.05-3.02). CONCLUSIONS: Alcohol use patterns in adolescence may be useful markers for programs that aim to prevent risky sexual behavior. Based on alcohol intake patterns, it may be possible to identify frequent alcohol users that need to be targeted with appropriate alcohol use and HIV risk reduction messages.

Colorado Twin Registry: an update.

The Colorado Twin Registry (CTR) is a population-based registry housed at the Institute for Behavioral Genetics at the University of Colorado. Recruitment began in 1982 and includes twins born from 1968 to the present. Four samples are currently drawn from the CTR: The Community Twin Sample, the Longitudinal Twin Sample, the Early Reading Development Sample, and the Colorado Learning Sample. Criteria for enrollment, recruitment strategies, demographic information, and zygosity assignment are explained for each sample. In addition, five studies in which CTR twins are now participating are highlighted. These include studies of cognition, learning ability, and vulnerability to substance abuse and antisocial behavior. The development of the CTR is an ongoing and evolving process, and it has proven to be a valuable registry, relatively representative of the population from which it was drawn.