The next challenge for psychiatric genetics: characterizing the risk associated with identified genes

Psychopathology research in the RDoC era: Unanswered questions and the importance of the psychophysiological unit of analysis

The NIMH Research Domain Criteria (RDoC) initiative seeks to re-conceptualize psychopathology by identifying transdiagnostic constructs that reflect core mechanisms of psychopathology. Although the RDoC framework has been discussed in many prior papers, there are several methodological and conceptual points that have yet to be fully specified. For example, little discussion exists on the importance of distinguishing each construct's nomological network and linking it to risk for psychopathology. It has also been unclear the extent to which RDoC constructs (within and across systems) should relate to one another and how these associations may differ as a function of developmental period. These are important questions as we enter the RDoC era and psychophysiological measures represent an exciting tool to address these issues. In this paper, we discuss the currently un- (or under-)specified aspects of the RDoC initiative and highlight the advantages of the psychophysiological 'unit of analysis.' We also briefly review existing psychophysiological studies, within the positive and negative valence systems, that exemplify the RDoC approach and make recommendations for how future studies can help the field progress in this mission.

Anxiety disorders and risk for alcohol use disorders: the moderating effect of parental support

BACKGROUND

There have been mixed findings on the temporal relation between anxiety disorders and alcohol use disorders (AUDs), suggesting that the pathway to AUDs may differ among individuals. The aim of the current study was to test whether parental support moderated the association between anxiety disorders and the development of AUDs. We also tested whether our effects differed as a function of age of AUD onset.

METHODS

817 individuals were assessed for lifetime diagnoses of psychopathology during 4-waves between adolescence (mean age=16) and adulthood (mean age=30).

RESULTS

Proportional hazards model analyses indicated that baseline anxiety disorders interacted with baseline perceived maternal support to prospectively predict onset of AUDs. At high levels of maternal support, anxiety disorders were associated with a reduced risk for AUD onset (HR=0.74, 95% CI=0.55-1.00). However, this effect was more robust for AUDs that developed prior to age 20. At low levels of maternal support, anxiety disorders were associated with an increased risk for AUD onset (HR=1.65, 95% CI=1.21-2.26). This effect was present for AUDs that developed across adolescence and adulthood. Paternal support was not associated with AUDs and did not interact with anxiety disorders.

CONCLUSIONS

Prevention and intervention efforts targeted at maternal support in adolescents with anxiety disorders may be valuable, as this may represent a factor that has a significant impact on the developmental course of AUDs.

Evocative gene-parenting correlations and academic performance at first grade: an exploratory study

Academic performance during the first years of school lays the groundwork for subsequent trajectories of academic success throughout childhood and adolescence. The current study tests a model according to which a gene-parenting correlation in the first 3 years of life is associated with subsequent psychosocial adjustment and then academic performance in the first grade (as indicated by teachers' assessment of academic behavior and two subscales of the Woodcock-Johnson Test of Achievement, Third Edition). Drawing on multiple waves of data from the Durham Child Health and Development Study, we find that risk alleles for dopamine receptor genes (dopamine receptor D4 for girls, dopamine receptor D2 for boys) are associated with less sensitive parenting. For girls, parenting mediates the link between dopamine receptor D4 and all academic outcomes. There is some indication that parenting also influences girls' withdrawn behavior in the classroom, which in turn influences teachers' assessments of academic performance. For boys, some evidence suggests that parenting is associated with emotion regulation, which is associated with teachers' assessments of academic behavior and both subscales of the Woodcock-Johnson. Replications of this exploratory study are necessary, but these findings provide a first step in understanding how evocative correlations in the home may predict indicators of psychosocial adjustment that in turn influence performance and achievement at school.

Multi-species data integration and gene ranking enrich significant results in an alcoholism genome-wide association study

BACKGROUND

A variety of species and experimental designs have been used to study genetic influences on alcohol dependence, ethanol response, and related traits. Integration of these heterogeneous data can be used to produce a ranked target gene list for additional investigation.

RESULTS

In this study, we performed a unique multi-species evidence-based data integration using three microarray experiments in mice or humans that generated an initial alcohol dependence (AD) related genes list, human linkage and association results, and gene sets implicated in C. elegans and Drosophila. We then used permutation and false discovery rate (FDR) analyses on the genome-wide association studies (GWAS) dataset from the Collaborative Study on the Genetics of Alcoholism (COGA) to evaluate the ranking results and weighting matrices. We found one weighting score matrix could increase FDR based q-values for a list of 47 genes with a score greater than 2. Our follow up functional enrichment tests revealed these genes were primarily involved in brain responses to ethanol and neural adaptations occurring with alcoholism.

CONCLUSIONS

These results, along with our experimental validation of specific genes in mice, C. elegans and Drosophila, suggest that a cross-species evidence-based approach is useful to identify candidate genes contributing to alcoholism.

Interaction between the DRD4 VNTR polymorphism and proximal and distal environments in alcohol dependence during emerging and young adulthood

The manifestation of alcohol dependence at different developmental stages may be associated with different genetic and environmental factors. Taking a developmental approach, we characterized interaction between the dopamine receptor 4 variable number tandem repeat (DRD4 VNTR) polymorphism and developmentally specific environmental factors (childhood adversity, college/Greek organization involvement, and delayed adult role transition) on alcohol dependence during emerging and young adulthood. Prospective data were obtained from a cohort of 234 White individuals (56% women, 44% men) who were followed up at ages 18 through 34. A longitudinal hierarchical factor model was estimated to model a traitlike persistent alcohol dependence factor throughout emerging and young adulthood and 2 residual statelike alcohol dependence factors limited to emerging adulthood and young adulthood, respectively. We accounted for those alcohol dependence factors by modeling 3 two-way interaction effects between the DRD4 VNTR polymorphism and the 3 developmentally specific environment factors. Carriers of the DRD4 long allele showed greater susceptibility to environmental effects; they showed more persistent symptoms of alcohol dependence as childhood adversity increased and more alcohol dependence symptoms limited to emerging adulthood as college/Greek organization involvement increased. Alcohol dependence among noncarriers of the long allele, however, did not differ as a function of those environments. Although replication is necessary, these findings highlight the importance of repeated phenotypic assessments across development and modeling both distal and proximal environments and their interaction with genetic susceptibility at specific developmental stages.

Use of genomic assessments and interventions in psychiatric nursing practice

The purpose of this study was to determine the impact of a genomic educational session by measuring participants' application of the class content to their nursing care. A sample of 65 psychiatric nurses participated in a staff development activity and completed a survey. Every respondent reported use of a genomic assessment or intervention with a patient from their clinical practice. The mean use of genomic assessment and intervention items was 5.5 out of the possible 10 which were identified and described in the educational session, providing evidence that nurses are able to include genomic assessments and interventions when caring for a patient with a psychiatric disorder.

Complexity and accountability: the witches' brew of psychiatric genetics

This paper examines the role of complexity in descriptions of the aetiology of common psychiatric disorders. While scientists attest to the discovery of an underlying reality of complex inheritance--the so-called 'witches' brew' of genetic and non-genetic factors--we argue that 'complexity' also performs rhetorical work. In our analysis of scientific review papers (1999-2008), we find a relatively stable genre of accountability in which descriptions of complexity appear to neutralize past failures by incorporating different and sometimes competing methodological perspectives. We identify two temporal strategies: retrospective accounting, which reconstructs a history of psychiatric genetics that deals with the recent failures, citing earlier twin studies as proof of the heritability of common psychiatric disorders; and prospective accounting, which engages in the careful reconstruction of expectations by balancing methodological limitations with moderated optimism. Together, these strategies produce a simple-to-complex narrative that belies the ambivalent nature of complexity. We show that the rhetorical construction of complexity in scientific review papers is oriented to bridging disciplinary boundaries, marshalling new resources and reconstructing expectations that justify delays in gene discovery and risk prediction.

A comparison of selected quantitative trait loci associated with alcohol use phenotypes in humans and mouse models

Evidence for genetic linkage to alcohol and other substance dependence phenotypes in areas of the human and mouse genome have now been reported with some consistency across studies. However, the question remains as to whether the genes that underlie the alcohol-related behaviors seen in mice are the same as those that underlie the behaviors observed in human alcoholics. The aims of the current set of analyses were to identify a small set of alcohol-related phenotypes in human and in mouse by which to compare quantitative trait locus (QTL) data between the species using syntenic mapping. These analyses identified that QTLs for alcohol consumption and acute and chronic alcohol withdrawal on distal mouse chromosome 1 are syntenic to a region on human chromosome 1q where a number of studies have identified QTLs for alcohol-related phenotypes. Additionally, a QTL on human chromosome 15 for alcohol dependence severity/withdrawal identified in two human studies was found to be largely syntenic with a region on mouse chromosome 9, where two groups have found QTLs for alcohol preference. In both of these cases, while the QTLs were found to be syntenic, the exact phenotypes between humans and mice did not necessarily overlap. These studies demonstrate how this technique might be useful in the search for genes underlying alcohol-related phenotypes in multiple species. However, these findings also suggest that trying to match exact phenotypes in humans and mice may not be necessary or even optimal for determining whether similar genes influence a range of alcohol-related behaviors between the two species.

Dopamine D2 receptor polymorphisms and susceptibility to alcohol dependence in Indian males: a preliminary study

Background

Dopamine is an important neurotransmitter involved in reward mechanism in the brain and thereby influences development and relapse of alcohol dependence. The dopamine D2 receptor (DRD2) gene on chromosome 11 (q22-q23) has been found to be associated with increased alcohol consumption through mechanisms involving incentive salience attributions and craving in alcoholic patients. Therefore, we investigated the association of three single nucleotide polymorphisms (SNP) in DRD2 gene with alcohol dependence in the north Indian subjects.

Methods

In a retrospective analysis, genetic association of three polymorphisms from DRD2 gene with alcohol dependence was investigated using a case-control approach. Alcohol dependence was determined by DSM-IV criteria and a total of 90 alcoholics and 60 healthy unrelated age-matched control subjects were recruited. Odds ratio and confidence interval was calculated to determine risk conferred by a predisposing allele/genotype/haplotype. Logistic regression analysis was carried out to correlate various clinical parameters with genotypes, and to study pair-wise interactions between SNPs.

Results

The study showed a significant association of -141C Ins allele and a trend of association of TaqI A1 allele of DRD2 with alcohol dependence. Haplotype with the predisposing -141C Ins and TaqI A1 alleles (-141C Ins-A-A1) seems to confer ≈ 2.5 times more risk to develop alcohol dependence.

Conclusions

The study provides preliminary insight into genetic risk to alcohol dependence in Indian males. Two polymorphisms namely, -141C Ins/Del and TaqI A in DRD2 gene may have clinical implications among Indian alcoholic subjects.

Family history of alcoholism mediates the frontal response to alcoholic drink odors and alcohol in at-risk drinkers

Although a family history of alcoholism is the strongest risk factor for developing alcohol dependence, there are few studies of the association between familial alcoholism and the human brain's reward system activity. We used functional magnetic resonance imaging (fMRI) to determine how family history affects the brain's response to subjects' preferred alcoholic drink odors (AO) as compared to appetitive control odors (ApCO). Fourteen non-dependent heavy drinkers (HD) who were family history positive (FHP) participated, as did 12 HD who were family history negative (FHN). Subjects were imaged under both alcohol intoxication and placebo, using intravenous infusion and pharmacokinetic modeling to target a blood alcohol level of 50 mg%. Under placebo, HD-FHP had a larger medial frontal [AO>ApCO] effect than did HD-FHN. Alcohol intoxication dampened this response in the HD-FHP but potentiated it in the HD-FHN. This suggests that a family history of alcoholism and brain exposure to alcohol interact in heavy drinkers to differentially affect how the brain responds to alcohol cues.

Role of GABRA2 in trajectories of externalizing behavior across development and evidence of moderation by parental monitoring

CONTEXT

As we identify genes involved in psychiatric disorders, the next step will be to study how the risk associated with susceptibility genes manifests across development and in conjunction with the environment. We describe analyses aimed at characterizing the pathway of risk associated with GABRA2, a gene previously associated with adult alcohol dependence, in a community sample of children followed longitudinally from childhood through young adulthood.

OBJECTIVE

To test for an association between GABRA2 and trajectories of externalizing behavior from adolescence to young adulthood and for moderation of genetic effects by parental monitoring.

DESIGN

Data were analyzed from the Child Development Project, with yearly assessments conducted since that time. A saliva sample was collected for DNA at the 2006 follow-up, with a 93% response rate in the target sample. Growth mixture modeling was conducted using Mplus to identify trajectories of externalizing behavior and to test for effects of GABRA2 sequence variants and parental monitoring.

SETTING

Nashville and Knoxville, Tennessee, and Bloomington, Indiana.

PARTICIPANTS

A community-based sample of families enrolled at 3 sites as children entered kindergarten in 1987 and 1988. Analyses for the white subset of the sample (n = 378) are reported here.

MAIN OUTCOME MEASURES

Parental monitoring measured at 11 years of age; Child Behavior Checklist youth reports of externalizing behavior at ages 12, 14, 15, 16, 17, 19, 20, 21, and 22 years.

RESULTS

Two classes of externalizing behavior emerged: a stable high externalizing class and a moderate decreasing externalizing behavior class. The GABRA2 gene was associated with class membership, with subjects who showed persistent elevated trajectories of externalizing behavior more likely to carry the genotype previously associated with increased risk of adult alcohol dependence. A significant interaction with parental monitoring emerged; the association of GABRA2 with externalizing trajectories diminished with high levels of parental monitoring.

CONCLUSIONS

These analyses underscore the importance of studying genetic effects across development and of identifying environmental factors that moderate risk.

Associations among GABRG1, level of response to alcohol, and drinking behaviors

BACKGROUND

Recent studies of the genetics of alcoholism have focused on a cluster of genes encoding for gamma-aminobutyric acid (GABA(A)) receptor subunits, which is thought to play a role in the expression of addiction phenotypes. This study examined allelic associations between 2 single nucleotide polymorphisms (SNPs) of the GABRG1 gene (rs1391166 and rs1497571) and alcohol phenotypes, namely level of response to alcohol, alcohol use patterns, and alcohol-related problems.

METHOD

Participants were non-treatment-seeking seeking hazardous drinkers (n = 124) who provided DNA samples, participated in a face-to-face interview for level of response to alcohol, and completed a series of drinking and individual differences measures.

RESULTS

Analyses revealed that a SNP of the GABRG1 gene (rs1497571) was associated with level of response to alcohol and drinking patterns in this subclinical sample. Follow-up mediational analyses were also conducted to examine putative mechanisms underlying these associations.

DISCUSSION

These findings replicate and extend recent research suggesting that genetic variation at the GABRG1 locus may underlie the expression of alcohol phenotypes, including level of response to alcohol.

Parent Depression and Child Anxiety: An Overview of the Literature with Clinical Implications

The association of parental depression with child anxiety has received relatively little attention in the literature. In this paper we initially present several reasons for examining this relationship. We then summarize the empirical support for a link between these two variables. Finally, we discuss directions for future research and clinical implications of an association of parental depression with child anxiety.

The dopamine D Receptor (DRD4) gene exon III polymorphism, problematic alcohol use and novelty seeking: direct and mediated genetic effects

The present study sought to integrate convergent lines of research on the associations among the dopamine D(4) receptor (DRD4) gene, novelty seeking and drinking behaviors with the overall goal of elucidating genetic influences on problematic drinking in young adulthood. Specifically, this study tested a model in which novelty seeking mediated the relationship between DRD4 variable number of tandem repeats (VNTR) genotype and problematic alcohol use. Participants (n = 90, 40 females) were heavy-drinking college students. Analyses using a structural equation modeling framework suggested that the significant direct path between DRD4 VNTR genotype and problematic alcohol use was reduced to a trend level in the context of a model that included novelty seeking as a mediator, thereby suggesting that the effects of DRD4 VNTR genotype on problematic alcohol use among heavy-drinking young adults were partially mediated by novelty seeking. Cross-group comparisons indicated that the relationships among the model variables were not significantly different in models for men versus women. These results extend recent findings of the association between this polymorphism of the DRD4 receptor gene, problematic alcohol use and novelty seeking. These findings may also help elucidate the specific pathways of risk associated with genetic influences on alcohol use and abuse phenotypes.

Dopamine receptor D4 gene -521C/T polymorphism is associated with opioid dependence through cold-pain responses

Heroin users exhibit abnormal pain sensitivity called opioid-induced hyperalgesia that may weaken their determination to abstain. The dopamine receptor D4 gene (DRD4) is associated with heroin dependence; one of its polymorphisms is a C/T variation 521 bp upstream to the gene (-521C/T). We investigated whether this polymorphism was related to opioid dependence through modulation of cold-pain responses. We recruited 84 heroin-dependent Chinese male subjects and 168 healthy male Chinese controls. Genotyping was performed by PCR-RFLP. A significantly higher T allele frequency was observed in the heroin group (P= 0.041). Of the cohort recruited, 43 current heroin users and 66 controls were further subjected to a cold-pressor test (CPT) to determine their pain threshold and tolerance. TT controls demonstrated a significantly lower pain threshold than did their CC/CT counterparts (P= 0.022) and TT opioid users (P= 0.006). Moreover, CC/CT controls had a significantly higher pain tolerance than TT controls (P= 0.042) and CC/CT opioid users (P= 0.010). The data suggest that DRD4-521C/T plays an important role in opioid dependence through modulating cold-pain responses. TT individuals might have a higher tendency to use opioids because they experience pain less strongly after chronic opioid use.

Will we ever find the genes for addiction?

AIM

To assess the likelihood of finding genes which predispose to addiction and to present this information in a form accessible to the general readership of Addiction.

METHODS

Review of the evidence that genetic factors play a significant role in the process of addiction and the proximity of the identification of these factors.

RESULTS

The search for the genetic susceptibility variants for many complex illnesses has been ongoing for decades, with increased pace in the last 20 years. However, until very recently only a small number of such variants have been found. Recent studies have used several thousand samples in genome-wide association studies and the latest genotyping technology and have reported a growing number of successes, but have highlighted the need for even larger samples and new statistical methods or new experimental approaches to identify fully the genes involved in the disease process. The phenotype for addiction to drugs is not well defined, and the heritability of addiction to drugs of abuse is far from clear and may be small compared to that of many other complex disorders. The absolute requirement for the administration of drugs before addiction can occur, and other environmental factors known to have a major effect, makes the selection of both probands and controls challenging for genetic studies. Many candidate genes put forward so far as susceptibility genes may be unrelated to the underlying process referred to as addiction but, rather, are related to the propensity to take drugs in the first place.

CONCLUSIONS

It is the underlying biological process which changes to an alternative state following addiction, which is the target of investigation, and it is not clear that even genome-wide association studies with sample sizes a magnitude greater than those reported so far would identify the genes involved which have the largest effect. Ultimately, modern neurobiological approaches may identify this process and the genes involved, and even at this stage identifying the susceptibility variants will require both biological as well as genetic analysis.

Association between the Stin2 VNTR polymorphism of the serotonin transporter gene and treatment outcome in alcohol-dependent patients

AIMS

The aim of this study was to investigate the potential association between functional polymorphisms of dopaminergic [dopamine receptor D2 (DRD2), dopamine receptor D3 (DRD3) and dopamine transporter (SLC6A3)] and serotonergic [serotonin 2A receptor (HTR2A) and serotonin transporter (SLC6A4)] genes and treatment outcome in alcohol-dependent patients.

METHODS

A total of 90 Spanish Caucasian alcohol-dependent outpatients (ICD-10 criteria) were enrolled in the study. The association between genotypes and drinking outcomes was measured over 6 months of treatment. Biomarkers of alcohol consumption, as well as alcohol consumption and its consequences, craving, disability and quality of life, were assessed. Based on those measures, we created a composite secondary measure to globally assess treatment outcome in alcoholism.

RESULTS

No association was found between DRD2, DRD3, SLC6A3 or HTR2A gene variants and treatment outcome. However, SLC6A4 STin2 12/12 carriers showed poor 6-month time point treatment outcome [32.8% in the good outcome group versus 64.0% in the poor outcome group, chi(2) (df) = 7.20 (1), corrected P = 0.042, OR (95% CI) = 0.27 (0.10-0.72)]. Nevertheless, independent analysis of each treatment group reveals that the excess of 12/12 carriers in the poor outcome group was only found in the naltrexone-treated group [24.1% versus 64.7% chi(2) (df) = 7.41 (1), corrected P = 0.042, OR (95% CI) = 0.17 (0.05-0.64)]. In the whole sample, the L-10 repeats haplotype (5-HTTLPR-STin2 VNTR) is associated with good outcome (LRT = 3.88, df = 1, P = 0.049).

CONCLUSIONS

Our findings suggest that functional polymorphism of the SLC6A4 gene may have an influence on treatment outcome in alcohol-dependent patients.

Childhood and adolescent predictors of heavy drinking and alcohol use disorders in early adulthood: a longitudinal developmental analysis

AIMS

To identify childhood and adolescent factors differentiating heavy alcohol users in early adulthood from more moderate users or abstainers.

DESIGN

Low-income participants followed from birth to age 28 years.

PARTICIPANTS

A total of 178 adults (95 males) who were first-born children of low-income mothers recruited in Minneapolis, Minnesota, during their third trimester of pregnancy.

MEASUREMENTS

Maternal hostility (24/42 months), externalizing and internalizing behavior problems (9 years), peer acceptance and academic achievement (12 years), maternal alcohol use and participants' drinking behavior (16 years), quantity of alcohol use per occasion (19, 23 and 26 years), alcohol use disorders (28 years).

FINDINGS

For men: (i) higher amounts of alcohol consumption at age 16 increased the odds of being a heavy drinker compared to an abstainer (age 19) and a moderate drinker (ages 23 and 26); (ii) lower achievement scores at age 12 and having a mother who drank more when the participant was age 16 increased the odds of being a heavy drinker compared to moderate drinker (age 26). Higher levels of externalizing behavior problems at age 9 and drinking more when the participants were age 16 increased the odds that men would have a current alcohol use disorder at age 28. For women: (i) drinking more at age 16 increased the odds of being a heavy drinker compared to being either an abstainer or a moderate drinker (age 26); (ii) having higher levels of achievement at age 12 increased the odds of being a heavy drinker compared to an abstainer at age 23. Adolescent alcohol use mediated the relation between externalizing behavior at age 9 and alcohol use at age 26 for women.

CONCLUSIONS

Problem drinking may be the result of a long-term developmental process wherein childhood externalizing behavior problems sets a pathway leading to heavy drinking during and after adolescence.

The Alcohol Dependence Syndrome, 30 years later: a commentary. the 2006 H. David Archibald lecture

AIMS

Major classification systems for alcohol use disorders (DSM-IV and ICD-10) contain elements of the 1976 Edwards and Gross formulation of the Alcohol Dependence Syndrome (ADS). However, issues remain about the criteria that identify Alcohol Dependence (AD) as distinct from Alcohol Abuse (AA) in DSM-IV and Harmful Use in ICD-10. These issues, in part, have their roots in changing historical perceptions of alcohol use and its problems. We discuss current diagnostic criteria for AA and AD, collectively called Alcohol Use Disorders (AUDs), in the context of their historical evolution; research progress in understanding alcohol problems, including alcohol dependence; new findings on the severity of AUDs as classified by DSM-IV; and the role of alcohol consumption patterns in future classifications of AUDs.

METHODS

This paper is based largely on the 2006 H. David Archibald Lecture. Parts of the original lecture have been modified to reflect more recent findings from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) of the US National Institute on Alcohol Abuse and Alcoholism (NIAAA).

RESULTS

The original Edwards and Gross ADS construct is supported by advances in biological and behavioral science over the past 30 years. New findings indicate that DSM-IV AA and AD are not diagnostically distinct entities, but represent a continuum of severity of AUDs. The ADS criteria may best represent one quantifiable dimension of alcohol use problems and this scale can be related to that of the frequency of harmful patterns of drinking.

CONCLUSION

The Edwards and Gross ADS criteria can be used as the basis for beginning the development of scalable multi-dimensional criteria for diagnosing AUDs in new initiatives to revise DSM-IV and ICD-10.