The role of genetic variation in the causation of mental illness: an evolution-informed framework

Vantage Sensitivity: Environmental Sensitivity to Positive Experiences as a Function of Genetic Differences

A large number of gene-environment interaction studies provide evidence that some people are more likely to be negatively affected by adverse experiences as a function of specific genetic variants. However, such "risk" variants are surprisingly frequent in the population. Evolutionary analysis suggests that genetic variants associated with increased risk for maladaptive development under adverse environmental conditions are maintained in the population because they are also associated with advantages in response to different contextual conditions. These advantages may include (a) coexisting genetic resilience pertaining to other adverse influences, (b) a general genetic susceptibility to both low and high environmental quality, and (c) a coexisting propensity to benefit disproportionately from positive and supportive exposures, as reflected in the recent framework of vantage sensitivity. After introducing the basic properties of vantage sensitivity and highlighting conceptual similarities and differences with diathesis-stress and differential susceptibility patterns of gene-environment interaction, selected and recent empirical evidence for the notion of vantage sensitivity as a function of genetic differences is reviewed. The unique contribution that the new perspective of vantage sensitivity may make to our understanding of social inequality will be discussed after suggesting neurocognitive and molecular mechanisms hypothesized to underlie the propensity to benefit disproportionately from benevolent experiences.

Social support and the serotonin transporter genotype (5-HTTLPR) moderate levels of resilience, sense of coherence, and depression

Gene x environment interactions have mainly been investigated in models of psychopathology. However, the putative interplay between genes and beneficial environmental conditions on positive outcomes has rarely been addressed. We therefore examined the interaction between the serotonin transporter linked polymorphic region (5-HTTLPR) and social support on the sense of coherence (SOC), resilience, and depressive symptoms. Furthermore, we scrutinized our examinations by differentiating between individuals with and without childhood abuse. The sample included 1,811 participants from the general population (Study of Health in Pomerania, Germany). The triallelic genotype of 5-HTTLPR was determined and longitudinal data of social support were used. Among individuals with high social support no significant differences between 5-HTTLPR genotypes regarding all outcome variables were found. However, among those with low social support, carriers of at least one short allele reported significantly increased levels of SOC and resilience, as well as less depressive symptoms than carriers of the l/l genotype. This result was not modified by differentiating between those with childhood abuse and those without. In less supportive social environments the impact of distinct genotypes on behavioral outcomes might be more relevant than in supportive environments where social compensation might take place. Our findings indicate that both alleles of 5-HTTLPR contribute to the adaptability to different environmental conditions.

Epigenetic alterations in depression and antidepressant treatment

Epigenetic modifications control chromatin structure and function, and thus mediate changes in gene expression, ultimately influencing protein levels. Recent research indicates that environmental events can induce epigenetic changes and, by this, contribute to long-term changes in neural circuits and endocrine systems associated with altered risk for stress-related psychiatric disorders such as major depression. In this review, we describe recent approaches investigating epigenetic modifications associated with altered risk for major depression or response to antidepressant drugs, both on the candidate gene levels as well as the genome-wide level. In this review we focus on DNA methylation, as this is the most investigated epigenetic change in depression research.

Developmental differences in early adolescent aggression: a gene × environment × intervention analysis

Aggression-related problems such as assault and homicide among adolescents and young adults exact considerable social and economic costs. Although progress has been made, additional research is needed to help combat this persistent problem. Several lines of research indicate that parental hostility is an especially potent predictor of adolescent aggression, although most longitudinal research has focused on clarifying the direction of effects. In this study, we used longitudinal data from the PROSPER project (N = 580; 54.8% female), a primarily rural Caucasian preventative intervention sample, to examine developmental change in early- to mid-adolescent aggressive behavior problems (age 11-16 years). In addition, we examined maternal hostility as a predictor of developmental change in aggression and the PROSPER preventative intervention, designed to reduce substance use and aggression, as a potential influence on this association. Lastly, several studies indicate that variation in the DRD4 7-repeat gene moderates both parenting and intervention influences on externalizing behavior. Accordingly, we examined the potential moderating role of DRD4. As hypothesized, there was a significant maternal hostility by intervention interaction indicating that the intervention reduced the negative impact of maternal hostility on adolescent change in aggressive behavior problems. DRD4 7-repeat status (7+ vs. 7-) further conditioned this association whereby control group 7+ adolescents with hostile mothers showed increasing aggressive behavior problems. In contrast, aggression decreased for 7+ adolescents with similarly hostile mothers in the intervention. Implications for prevention are discussed as well as current perspectives in candidate gene-by-environment interaction research.

An adaptationist perspective on the etiology of depression

Major depressive disorder (MDD) presents with a variety of symptoms and responds to a wide range of treatment interventions. Diagnostic criteria collapse multiple syndromes with distinct etiologies into the same disorder. MDD is typically understood as a malfunction of neurotransmission or brain circuitry regulating mood, pleasure and reward, or executive function. However, research from an evolutionary perspective suggests that the "normal" functioning of adaptations may also generate symptoms meeting diagnostic criteria. Functioning adaptations may be an underappreciated etiological pathway to MDD. Many adaptive functions for depressive symptoms have been suggested: biasing cognition to avoid losses, conserving energy, disengaging from unobtainable goals, signaling submission, soliciting resources, and promoting analytical thinking. We review the potential role of these adaptive functions and how they can lead to specific clusters of depressive symptoms. Understanding MDD from such a perspective reduces the heterogeneity of cases and may help to select the best intervention for each patient. We discuss the implications of different adaptive and maladaptive etiological pathways for the use of antidepressants and various modes of psychotherapy. In particular, instances of MDD caused by functioning adaptations may benefit most from treatments that support the adaptive function, or that target the precipitating causal stressor. We conclude that an evolutionary approach to the study of MDD may be one of the more promising approaches to reduce its heterogeneity and to better match patients and treatment.

The adaptive and maladaptive continuum of stress responses – a hippocampal perspective

Exposure to stressors elicits a spectrum of responses that span from potentially adaptive to maladaptive consequences at the structural, cellular and physiological level. These responses are particularly pronounced in the hippocampus where they also appear to influence hippocampal-dependent cognitive function and emotionality. The factors that influence the nature of stress-evoked consequences include the chronicity, severity, predictability and controllability of the stressors. In addition to adult-onset stress, early life stress also elicits a wide range of structural and functional responses, which often exhibit life-long persistence. However, the outcome of early stress exposure is often contingent on the environment experienced in adulthood, and could either aid in stress coping or could serve to enhance susceptibility to the negative consequences of adult stress. This review comprehensively examines the consequences of adult and early life stressors on the hippocampus, with a focus on their effects on neurogenesis, neuronal survival, structural and synaptic plasticity and hippocampal-dependent behaviors. Further, we discuss potential factors that may tip stress-evoked consequences from being potentially adaptive to largely maladaptive.

Therapygenetics: 5-HTTLPR genotype predicts the response to exposure therapy for agoraphobia

This study was intended to assess the extent to which the low-expression allele of the serotonin transporter gene promoter predicts better response to exposure-based behavior therapy in patients with panic disorder with agoraphobia (PDA). Ninety-nine patients with PDA underwent a 1-week in vivo exposure-based behavior therapy program and provided saliva samples to extract genomic DNA and classify individuals according to four allelic forms (SA, SG, LA, LG) of the 5-HTT-linked polymorphic region (5-HTTLPR). We determined whether the 5-HTTLPR genotype predicted change in avoidance behavior in PDA following treatment. After controlling for pre-treatment avoidance behavior, the 5-HTTLPR low-expression genotypes showed a more favorable response to exposure therapy two weeks following treatment, compared to the other patients. This study suggests a genetic contribution to treatment outcome following behavior therapy and implicates the serotonergic system in response to exposure-based treatments in PDA.

High social support buffers the effects of 5-HTTLPR genotypes within social anxiety disorder

An interaction between genetic aspects and environmental stressors has been suggested with regard to the etiology of social anxiety disorder (SAD). However, potential protective interplays which might decrease the risk of SAD have not been considered so far. Thus, we analyzed the interaction between 5-HTTLPR and differing levels of social support regarding SAD. The sample was based on participants of the Study of Health in Pomerania, Germany. We used the triallelic genotype of 5-HTTLPR and longitudinal data of social support. Final analyses were conducted in 79 individuals with SAD and 1,708 without. The diagnosis of SAD was derived from diagnostic interviews in accordance with DSM-IV. Considering the risk of SAD, a general protective effect of high social support was shown independent of variation in 5-HTTLPR genotype. In contrast, the risk of SAD was increased for both genotypes within those individuals with low social support. Additionally, the odds ratio for suffering from SAD was about two times higher for carriers of the l/l genotype compared to those with at least one short allele in those perceiving less-supportive social environments. The findings suggest that SAD is influenced by a protective and a contributing gene × environment interaction. High social support might act in a protective and low social support in an increasing manner on the risk of SAD especially within carriers of the l/l genotype. Therefore, effects of 5-HTTLPR might be buffered by high social support with respect to the risk of SAD.

5-HTTLPR modulates the recognition accuracy and exploration of emotional facial expressions

Individual genetic differences in the serotonin transporter-linked polymorphic region (5-HTTLPR) have been associated with variations in the sensitivity to social and emotional cues as well as altered amygdala reactivity to facial expressions of emotion. Amygdala activation has further been shown to trigger gaze changes toward diagnostically relevant facial features. The current study examined whether altered socio-emotional reactivity in variants of the 5-HTTLPR promoter polymorphism reflects individual differences in attending to diagnostic features of facial expressions. For this purpose, visual exploration of emotional facial expressions was compared between a low (n = 39) and a high (n = 40) 5-HTT expressing group of healthy human volunteers in an eye tracking paradigm. Emotional faces were presented while manipulating the initial fixation such that saccadic changes toward the eyes and toward the mouth could be identified. We found that the low vs. the high 5-HTT group demonstrated greater accuracy with regard to emotion classifications, particularly when faces were presented for a longer duration. No group differences in gaze orientation toward diagnostic facial features could be observed. However, participants in the low 5-HTT group exhibited more and faster fixation changes for certain emotions when faces were presented for a longer duration and overall face fixation times were reduced for this genotype group. These results suggest that the 5-HTT gene influences social perception by modulating the general vigilance to social cues rather than selectively affecting the pre-attentive detection of diagnostic facial features.

Functional polymorphism in the brain-derived neurotrophic factor gene interacts with stressful life events but not childhood maltreatment in the etiology of depression

BACKGROUND

We test the hypothesis that the functional Val66Met polymorphism of BDNF interacts with recent life events to produce onset of new depressive episodes. We also explore the possibility that the Met allele of this polymorphism interacts with childhood maltreatment to increase the risk of chronic depression.

METHODS

In a risk-enriched combined sample of unrelated women, childhood maltreatment and current life events were measured with the Childhood Experience of Care and Abuse, and Life Events and Difficulties Schedule interviews. Chronic episodes of depression (12 months or longer) during adulthood and onset of a major depressive episode during a 12-month follow-up were established with the Schedules for Clinical Assessment in Neuropsychiatry interview.

RESULTS

Met alleles of BDNF moderated the relationship between recent life events and adult onsets of depression in a significant gene-environment interaction (interaction risk difference 0.216, 95% CI 0.090-0.342; P =.0008). BDNF did not significantly influence the effect of childhood maltreatment on chronic depression in the present sample.

CONCLUSIONS

The Met allele of BDNF increases the risk of a new depressive episode following a severe life event. The BDNF and the serotonin transporter gene length polymorphism (5-HTTLPR) and BDNF may contribute to depression through distinct mechanisms involving interactions with childhood and adulthood adversity respectively, which may, in combination, be responsible for a substantial proportion of depression burden in the general population.

The effect of paternal age on offspring intelligence and personality when controlling for paternal trait level

Paternal age at conception has been found to predict the number of new genetic mutations. We examined the effect of father’s age at birth on offspring intelligence, head circumference and personality traits. Using the Minnesota Twin Family Study sample we tested paternal age effects while controlling for parents’ trait levels measured with the same precision as offspring’s. From evolutionary genetic considerations we predicted a negative effect of paternal age on offspring intelligence, but not on other traits. Controlling for parental intelligence (IQ) had the effect of turning an initially positive association non-significantly negative. We found paternal age effects on offspring IQ and Multidimensional Personality Questionnaire Absorption, but they were not robustly significant, nor replicable with additional covariates. No other noteworthy effects were found. Parents’ intelligence and personality correlated with their ages at twin birth, which may have obscured a small negative effect of advanced paternal age (<1% of variance explained) on intelligence. We discuss future avenues for studies of paternal age effects and suggest that stronger research designs are needed to rule out confounding factors involving birth order and the Flynn effect.

The emerging molecular architecture of schizophrenia, polygenic risk scores and the clinical implications for GxE research

Schizophrenia is a devastating mental disorder. The level of risk in the general population is sustained by the persistence of social, environmental and biological factors, as well as their interactions. Socio-environmental risk factors for schizophrenia are well established and robust. The same can belatedly be said of genetic risk factors for the disorder. Recent progress in schizophrenia genetics is primarily fuelled by genome-wide association, which is able to leverage substantial proportions of additional explained variance previously classified as 'missing'. Here, we provide an outline of the emerging genetic landscape of schizophrenia and demonstrate how this knowledge can be turned into a simple empirical measure of genetic risk, known as a polygenic risk score. We highlight the statistical framework used to assess the clinical potential of the new score and finally, draw relevance to and discuss the clinical implications for the study of gene-environment interaction.

Pharmacogenetics of addiction therapy

Drug addiction is a serious relapsing disease that has high costs to society and to the individual addicts. Treatment of these addictions is still in its nascency, with only a few examples of successful therapies. Therapeutic response depends upon genetic, biological, social, and environmental components. A role for genetic makeup in the response to treatment has been shown for several addiction pharmacotherapies. For several addiction pharmacotherapies, response to treatment varies based on individual genetic makeup. In this chapter, we discuss the role of genetics in pharmacotherapies, specifically for cocaine, alcohol, and opioid dependences. The elucidation of the role of genetics should aid in the development of new treatments and increase the efficacy of existing treatments.

Gene-environment interactions in common mental disorders: an update and strategy for a genome-wide search

A decade of research has demonstrated the explanatory potential of interplay between genetic variants and environmental factors in the development of common mental disorders. Initial findings have undergone tests of replicability and specificity. Some gene-environment interactions have been confirmed, some have not replicated and yet other turned out to be more specific than initially thought. Specific and complementary roles of genetic factors have been delineated: a common functional length polymorphism in the serotonin transporter gene (5-HTTLPR) moderated the effect of childhood maltreatment on chronic depression in adulthood, but did not substantially influence the effects of adult stressful life events on the onset of new depressive episodes; in contrast, a common functional polymorphism in the brain-derived neurotrophic factor gene (BDNF) moderated the effect of stressful life events in adulthood in triggering new depressive episodes, but did not influence the effects of childhood maltreatment. Molecular mechanisms underlying gene-environment interactions are being uncovered, including DNA methylation and other epigenetic modifications. New gene-environment interactions continue to be reported, still largely from hypothesis-driven research. Statistical and biological prioritization strategies are proposed to facilitate a systematic discovery of novel gene-environment interactions in genome-wide analyses.

Gene-environment interactions in severe mental illness

Severe mental illness (SMI) is a broad category that includes schizophrenia, bipolar disorder, and severe depression. Both genetic disposition and environmental exposures play important roles in the development of SMI. Multiple lines of evidence suggest that the roles of genetic and environmental factors depend on each other. Gene-environment interactions may underlie the paradox of strong environmental factors for highly heritable disorders, the low estimates of shared environmental influences in twin studies of SMI, and the heritability gap between twin and molecular heritability estimates. Sons and daughters of parents with SMI are more vulnerable to the effects of prenatal and postnatal environmental exposures, suggesting that the expression of genetic liability depends on environment. In the last decade, gene-environment interactions involving specific molecular variants in candidate genes have been identified. Replicated findings include an interaction between a polymorphism in the AKT1 gene and cannabis use in the development of psychosis and an interaction between the length polymorphism of the serotonin transporter gene and childhood maltreatment in the development of persistent depressive disorder. Bipolar disorder has been underinvestigated, with only a single study showing an interaction between a functional polymorphism in the BDNF gene and stressful life events triggering bipolar depressive episodes. The first systematic search for gene-environment interactions has found that a polymorphism in CTNNA3 may sensitize the developing brain to the pathogenic effect of cytomegalovirus in utero, leading to schizophrenia in adulthood. Strategies for genome-wide investigations will likely include coordination between epidemiological and genetic research efforts, systematic assessment of multiple environmental factors in large samples, and prioritization of genetic variants.

The roles of FMRP-regulated genes in autism spectrum disorder: single- and multiple-hit genetic etiologies

Autism spectrum disorder (ASD) is a highly heritable complex neurodevelopmental condition characterized by impairments in social interaction and communication and restricted and repetitive behaviors. Although roles for both de novo and familial genetic variation have been documented, the underlying disease mechanisms remain poorly elucidated. In this study, we defined and explored distinct etiologies of genetic variants that affect genes regulated by Fragile-X mental retardation protein (FMRP), thought to play a key role in neuroplasticity and neuronal translation, in ASD-affected individuals. In particular, we developed the Trend test, a pathway-association test that is able to robustly detect multiple-hit etiologies and is more powerful than existing approaches. Exploiting detailed spatiotemporal maps of gene expression within the human brain, we identified four discrete FMRP-target subpopulations that exhibit distinct functional biases and contribute to ASD via different types of genetic variation. We also demonstrated that FMRP target genes are more likely than other genes with similar expression patterns to contribute to disease. We developed the hypothesis that FMRP targets contribute to ASD via two distinct etiologies: (1) ultra-rare and highly penetrant single disruptions of embryonically upregulated FMRP targets ("single-hit etiology") or (2) the combination of multiple less penetrant disruptions of nonembryonic, synaptic FMRP targets ("multiple-hit etiology"). The Trend test provides rigorous support for a multiple-hit genetic etiology in a subset of autism cases and is easily extendible to combining information from multiple types of genetic variation (i.e., copy-number and exome variants), increasing its value to next-generation sequencing approaches.

Genomics and the classification of mental illness: focus on broader categories

Coinciding with the release of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, two recently published molecular genetics analyses suggest large overlaps in genetic liability to schizophrenia, bipolar disorder and major depressive disorder. This indicates that a broader category of severe mental illness may be an important target for future large-scale etiological and therapeutic investigations. Studies of patient groups not restricted to current diagnostic categories may lead to a genetically informed nosology.

Gene expression: biomarker of antidepressant therapy?

While antidepressant therapy is an essential treatment of major depression, a substantial group of treated patients do not respond to therapy, or suffer from severe side effects. Moreover, the time of onset of the clinical improvement is often delayed. Antidepressants as currently available usually enhance serotonergic, noradrenergic and dopaminergic neurotransmission and may contribute to the inadequate remission rates for major depression. Therefore biomarkers enabling the identification of subgroups of patients and also finding unprecedented targets would provide the basis for personalized medication and thus improve treatment efficacy and reduce side effects. Several pharmacogenetic studies on antidepressant treatment response using single nucleotide polymorphism (SNPs) mapping have been performed but provided only modest findings. Therefore the analysis of gene expression to integrate genomic activity and environmental effects promises a new approach to cope with the complexity of factors influencing antidepressant treatment. Here gene expression studies focusing on candidate genes and genome-wide approaches using RNA derived from peripheral blood cells are reviewed. The most promising findings exist for hypothalamic-pituitary-adrenal (HPA) axis, inflammation and neuroplasticity related genes. However, straightforward translation into tailored treatment is still unlikely. Contradictory results limit the clinical use of the findings. Future studies are necessary, which could include functional analysis and consider gene-environment interactions.

Negative life events and corticotropin-releasing-hormone receptor1 gene in recurrent major depressive disorder

Major depressive disorder (MDD) is a long-term, recurrent condition that often takes a chronic course. It seems imperative that research should be focused on gaining a better understanding of what predicts recurrent MDD. As a major mediator of the stress response, corticotropin-releasing-hormone receptor 1 (CRHR1) has been demonstrated to be an important contributor to the pathogenesis of MDD. In this study, we show a significant increase in the G-allele (rs242939) of the CRHR1 gene in the recurrent MDD group compared with the control group, and an overrepresentation of G-G-T hyplotype of the CRHR1 gene in recurrent MDD. We also demonstrate the interaction of the CRHR1 gene and negative life events in recurrent MDD. These results suggest that the CRHR1 gene could modify the susceptibility to developing recurrent MDD following negative life events in adulthood.

The Val66Met polymorphism of the BDNF gene in anorexia nervosa: new data and a meta-analysis

OBJECTIVES

The Val66Met polymorphism (rs6265) of the BDNF gene is a non-synonymous polymorphism, previously associated with anorexia nervosa (AN).

METHODS

We genotyped rs6265 in 235 patients with AN and 643 controls. Furthermore, we performed a systematic review of all case-control and family-based studies testing this SNP in AN, and combined the results in a meta-analysis.

RESULTS

The results of the case-control study were non-significant. For the meta-analysis, nine studies were identified (ncases = 2,767; ncontrols = 3,322, ntrios = 53) and included. Primarily, the analyses indicated an association with OR of 1.11 (P = 0.024) in the allelic contrast, and OR of 1.14 (P = 0.025) for the dominant effect of the Met allele. However, additional analyses revealed that the first published study (from those included in the meta-analysis) overly influenced the pooled effect size (possibly due to a phenomenon known as a winner's curse). When this case-control study was replaced by a trio study (ntrios = 293) performed on a largely overlapping sample, the effect size became smaller and non-significant, both for the allelic contrast (OR = 1.07, P = 0.156) and the dominant effect (OR = 1.07, P = 0.319). The quality of included studies was good and there was no significant heterogeneity across the effect sizes.

CONCLUSIONS

Our analyses indicate that the BDNF Val66Met variant is not associated with AN at detectable levels.

Biomarkers for personalised treatment in psychiatric diseases

Biomarker research of psychiatric disorders is delayed by symptom pattern-related diagnostic categories that are only distantly associated with biological mechanisms. In neuropsychiatric disorders that have high heritability (schizophrenia, autism, Alzheimer's disease), genomic research led to significant genome-wide association study (GWAS) results by increasing the number of subjects in case–control studies, and thus provided new hypotheses regarding the aetiology of these disorders and possible targets for research of new treatment approaches. In contrast, in moderately heritable psychiatric disorders (anxiety disorders, unipolar major depression), the development of symptoms, in addition to risk genes, is more dependent on the presence of specific environmental risk factors. Thus, controlling for heterogeneity, and not simply increasing the number of subjects, is crucial for further significant psychiatric GWAS findings that warrant the collection of more detailed individual phenotypic data and information about relevant previous environmental exposures. Gene–gene interactions (epistasis) and intermediate phenotypes or psychiatric and somatic co-morbidities, by identifying similar cases within a diagnostic category, could further increase the generally weak effects of individual genes that limit their usefulness as biomarkers. In conclusion, we argue that methods that are suitable to identify biologically more homogeneous subgroups within a given psychiatric disorder are necessary to advance biomarker research.

Mouse models of gene-environment interactions in schizophrenia

Gene-environment interactions (GEIs) likely play significant roles in the pathogenesis of schizophrenia and underlie differences in pathological, behavioral, and clinical presentations of the disease. Findings from epidemiology and psychiatric genetics have assisted in the generation of animal models of GEI relevant to schizophrenia. These models may provide a foundation for elucidating the molecular, cellular, and circuitry mechanisms that mediate GEI in schizophrenia. Here we critically review current mouse models of GEI related to schizophrenia, describe directions for their improvement, and propose endophenotypes to provide a more tangible basis for molecular studies of pathways of GEI and facilitate the identification of novel therapeutic targets.

Serotonin transporter genotype and mild traumatic brain injury independently influence resilience and perception of limitations in veterans

Evidence indicates that individuals with the 5-HTTLPR variant short/short genotype have increased sensitivity to both positive and negative perceptions of perceived social support. The aim of this study was to evaluate this association among Veterans in the context of mild traumatic brain injury (TBI). As part of a larger TBI center, we performed a cross-sectional study of 67 OEF/OIF/OND Veterans (41 with TBI and 26 controls without TBI) who completed the questionnaires and consented to genetic testing. The primary measures included the Connor-Davidson Resilience Scale (CDRISC) and the Perceived Limitations in community participation subscale of the Community Reintegration of Service Members Instrument (CRIS-PL). Both 5-HTTLPR genotype and TBI status were independently associated with the CRIS-PL (p = .009 for genotype, p = .001 for TBI) and the CDRISC (p = .015 for genotype, p = .003 for TBI) scores. This study suggests that both the 5-HTTLPR genotype and TBI status independently, in an almost equal but opposite direction, influence resilience and perceived limitations to social participation. Further, resilience appears more sensitive to perceived limitations in Veterans carrying an S'S' genotype than in L' carriers, but only in the context of having sustained a TBI. While having a TBI appeared to increase a Veteran's sensitivity to social stress, the Veteran's who were L' allele carriers with a TBI fared the worst, with lower resilience and more perceived limitations for community participation compared to L' carrier Veterans without a TBI or Veterans with the S'S' genotype regardless of TBI status.

Autism risk across generations: a population-based study of advancing grandpaternal and paternal age

IMPORTANCE

Advancing paternal age has been linked to autism.

OBJECTIVE

To further expand knowledge about the association between paternal age and autism by studying the effect of grandfathers' age on childhood autism.

DESIGN

Population-based, multigenerational, case-control study.

SETTING

Nationwide multigeneration and patient registers in Sweden.

PARTICIPANTS

We conducted a study of individuals born in Sweden since 1932. Parental age at birth was obtained for more than 90% of the cohort. Grandparental age at the time of birth of the parent was obtained for a smaller subset (5936 cases and 30 923 controls).

MAIN OUTCOME AND MEASURE

International Classification of Diseases diagnosis of childhood autism in the patient registry.

RESULTS

A statistically significant monotonic association was found between advancing grandpaternal age at the time of birth of the parent and risk of autism in grandchildren. Men who had fathered a daughter when they were 50 years or older were 1.79 times (95% CI, 1.35-2.37; P < .001) more likely to have a grandchild with autism, and men who had fathered a son when they were 50 years or older were 1.67 times (95% CI, 1.35-2.37; P < .001) more likely to have a grandchild with autism, compared with men who had fathered children when they were 20 to 24 years old, after controlling for birth year and sex of the child, age of the spouse, family history of psychiatric disorders, highest family educational level, and residential county. A statistically significant monotonic association was also found between advancing paternal age and risk of autism in the offspring. Sensitivity analyses indicated that these findings were not the result of bias due to missing data on grandparental age.

CONCLUSIONS AND RELEVANCE

Advanced grandparental age was associated with increased risk of autism, suggesting that risk of autism could develop over generations. The results are consistent with mutations and/or epigenetic alterations associated with advancing paternal age.

Updating the mild encephalitis hypothesis of schizophrenia

Schizophrenia seems to be a heterogeneous disorder. Emerging evidence indicates that low level neuroinflammation (LLNI) may not occur infrequently. Many infectious agents with low overall pathogenicity are risk factors for psychoses including schizophrenia and for autoimmune disorders. According to the mild encephalitis (ME) hypothesis, LLNI represents the core pathogenetic mechanism in a schizophrenia subgroup that has syndromal overlap with other psychiatric disorders. ME may be triggered by infections, autoimmunity, toxicity, or trauma. A 'late hit' and gene-environment interaction are required to explain major findings about schizophrenia, and both aspects would be consistent with the ME hypothesis. Schizophrenia risk genes stay rather constant within populations despite a resulting low number of progeny; this may result from advantages associated with risk genes, e.g., an improved immune response, which may act protectively within changing environments, although they are associated with the disadvantage of increased susceptibility to psychotic disorders. Specific schizophrenic symptoms may arise with instances of LLNI when certain brain functional systems are involved, in addition to being shaped by pre-existing liability factors. Prodrome phase and the transition to a diseased status may be related to LLNI processes emerging and varying over time. The variability in the course of schizophrenia resembles the varying courses of autoimmune disorders, which result from three required factors: genes, the environment, and the immune system. Preliminary criteria for subgrouping neurodevelopmental, genetic, ME, and other types of schizophrenias are provided. A rare example of ME schizophrenia may be observed in Borna disease virus infection. Neurodevelopmental schizophrenia due to early infections has been estimated by others to explain approximately 30% of cases, but the underlying pathomechanisms of transition to disease remain in question. LLNI (e.g. from reactivation related to persistent infection) may be involved and other pathomechanisms including dysfunction of the blood-brain barrier or the blood-CSF barrier, CNS-endogenous immunity and the volume transmission mode balancing wiring transmission (the latter represented mainly by synaptic transmission, which is often described as being disturbed in schizophrenia). Volume transmission is linked to CSF signaling; and together could represent a common pathogenetic link for the distributed brain dysfunction, dysconnectivity, and brain structural abnormalities observed in schizophrenia. In addition, CSF signaling may extend into peripheral tissues via the CSF outflow pathway along brain nerves and peripheral nerves, and it may explain the peripheral topology of neuronal dysfunctions found, like in olfactory dysfunction, dysautonomia, and even in peripheral tissues, i.e., the muscle lesions that were found in 50% of cases. Modulating factors in schizophrenia, such as stress, hormones, and diet, are also modulating factors in the immune response. Considering recent investigations of CSF, the ME schizophrenia subgroup may constitute approximately 40% of cases.

Gene × environment interactions in the prediction of response to antidepressant treatment

Major depressive disorder (MDD) is responsible for an increasing individual and global health burden. Extensive research on the genetic disposition to develop MDD and to predict the response to antidepressant treatment has yet failed to identify strong genetic effects. The concept of gene × environment interaction takes into account that environmental factors have been identified as important components in the development of MDD and combines both, genetic predisposition and environmental exposure, to elucidate complex traits such as MDD. Here, we review the current research on gene × environment interactions with regard to the development of MDD as well as response to antidepressant treatment. We hypothesize that gene × environment interactions delineate specific biological subtypes of depression and that individuals with such pathophysiological distinct types of depression will likely respond to different treatments. The elucidation of gene × environment interactions may thus not only help to understand the pathophysiology of MDD but could also provide markers for a personalized antidepressant therapy.

The evolutionary paradox and the missing heritability of schizophrenia

Schizophrenia is one of the most detrimental common psychiatric disorders, occurring at a prevalence of approximately 1%, and characterized by increased mortality and reduced reproduction, especially in men. The heritability has been estimated around 70% and the genome-wide association meta-analyses conducted by the Psychiatric Genomics Consortium have been successful at identifying an increasing number of risk loci. Various theories have been proposed to explain why genetic variants that predispose to schizophrenia persist in the population, despite the fitness reduction in affected individuals, a question known as the evolutionary paradox. In this review, we consider evolutionary perspectives of schizophrenia and of the empirical evidence that may support these perspectives. Proposed evolutionary explanations include balancing selection, fitness trade-offs, fluctuating environments, sexual selection, mutation-selection balance and genomic conflicts. We address the expectations about the genetic architecture of schizophrenia that are predicted by different evolutionary scenarios and discuss the implications for genetic studies. Several potential sources of "missing" heritability, including gene-environment interactions, epigenetic variation, and rare genetic variation are examined from an evolutionary perspective. A better understanding of evolutionary history may provide valuable clues to the genetic architecture of schizophrenia and other psychiatric disorders, which is highly relevant to genetic studies that aim to detect genetic risk variants.

Whole-genome sequencing in autism identifies hot spots for de novo germline mutation

De novo mutation plays an important role in autism spectrum disorders (ASDs). Notably, pathogenic copy number variants (CNVs) are characterized by high mutation rates. We hypothesize that hypermutability is a property of ASD genes and may also include nucleotide-substitution hot spots. We investigated global patterns of germline mutation by whole-genome sequencing of monozygotic twins concordant for ASD and their parents. Mutation rates varied widely throughout the genome (by 100-fold) and could be explained by intrinsic characteristics of DNA sequence and chromatin structure. Dense clusters of mutations within individual genomes were attributable to compound mutation or gene conversion. Hypermutability was a characteristic of genes involved in ASD and other diseases. In addition, genes impacted by mutations in this study were associated with ASD in independent exome-sequencing data sets. Our findings suggest that regional hypermutation is a significant factor shaping patterns of genetic variation and disease risk in humans.

Genome-wide association analysis of copy number variation in recurrent depressive disorder

Large, rare copy number variants (CNVs) have been implicated in a variety of psychiatric disorders, but the role of CNVs in recurrent depression is unclear. We performed a genome-wide analysis of large, rare CNVs in 3106 cases of recurrent depression, 459 controls screened for lifetime-absence of psychiatric disorder and 5619 unscreened controls from phase 2 of the Wellcome Trust Case Control Consortium (WTCCC2). We compared the frequency of cases with CNVs against the frequency observed in each control group, analysing CNVs over the whole genome, genic, intergenic, intronic and exonic regions. We found that deletion CNVs were associated with recurrent depression, whereas duplications were not. The effect was significant when comparing cases with WTCCC2 controls (P=7.7 × 10(-6), odds ratio (OR) =1.25 (95% confidence interval (CI) 1.13-1.37)) and to screened controls (P=5.6 × 10(-4), OR=1.52 (95% CI 1.20-1.93). Further analysis showed that CNVs deleting protein coding regions were largely responsible for the association. Within an analysis of regions previously implicated in schizophrenia, we found an overall enrichment of CNVs in our cases when compared with screened controls (P=0.019). We observe an ordered increase of samples with deletion CNVs, with the lowest proportion seen in screened controls, the next highest in unscreened controls and the highest in cases. This may suggest that the absence of deletion CNVs, especially in genes, is associated with resilience to recurrent depression.

Gene-environment interaction in panic disorder and posttraumatic stress disorder

Gene-environment interaction is a form of causal interplay, whereby genetic effects on phenotypic variation change as a function of environmental exposure. While conceptually appealing, there is still much debate on the veracity and the relevance of this form of etiological interdependence for psychiatric disorders. By focusing on panic disorder (PD) and posttraumatic stress disorder (PTSD), this article outlines why gene-environment interaction is controversial, why it can be important for both researchers and clinicians, and how it is investigated by quantitative genetic, molecular genetic, and genomic strategies. It is suggested that gene-environment interaction effects are more reliable and meaningful when they can be harnessed to pinpoint specific biological pathways and mechanisms. In psychiatry, this can be guided by phenotypic dissection and realized by adopting intermediate phenotypes of a physiological nature, such as carbon dioxide sensitivity for PD, or gene expression profiling after stress for PTSD. A developmental framework of reference and the possibility of transferring the investigation to animal models are additional key elements in this debate.

Mental illness, suicide and creativity: 40-year prospective total population study

We previously demonstrated that patients with schizophrenia or bipolar disorder and their relatives are overrepresented in creative occupations. Here, we use a new dataset with a considerably larger sample of patients (n = 1,173,763) to survey other psychiatric diagnoses and to validate previous findings. The specific aims of this study were to i) investigate if creativity is associated with all psychiatric disorders or restricted to those with psychotic features, and ii) to specifically investigate authors in relationship to psychopathology. We conducted a nested case-control study using longitudinal Swedish total population registries, where the occurrence of creative occupations in patients and their non-diagnosed relatives was compared to that of matched population controls. Diagnoses included were schizophrenia, schizoaffective disorder, bipolar disorder, unipolar depression, anxiety disorders, alcohol abuse, drug abuse, autism, ADHD, anorexia nervosa, and completed suicide. Creative professions were defined as scientific and artistic occupations. Data were analyzed using conditional logistic regression. Except for bipolar disorder, individuals with overall creative professions were not more likely to suffer from investigated psychiatric disorders than controls. However, being an author was specifically associated with increased likelihood of schizophrenia, bipolar disorder, unipolar depression, anxiety disorders, substance abuse, and suicide. In addition, we found an association between creative professions and first-degree relatives of patients with schizophrenia, bipolar disorder, anorexia nervosa, and for siblings of patients with autism. We discuss the findings in relationship to some of the major components of creativity.

Serotonin transporter length polymorphism, childhood maltreatment, and chronic depression: a specific gene-environment interaction

BACKGROUND

Key questions about the interaction between the serotonin transporter length polymorphism (5-HTTLPR) and stress in the etiology of depression remain unresolved. We test the hypotheses that the interaction is restricted to childhood maltreatment (as opposed to stressful events in adulthood), and leads to chronic depressive episodes (as opposed to any onset of depression), using gold-standard assessments of childhood maltreatment, severe life events, chronic depression, and new depressive onsets.

METHOD

In a risk-enriched sample of 273 unrelated women, childhood maltreatment was retrospectively assessed with the Childhood Experience of Care and Abuse (CECA) interview and 5-HTTLPR was genotyped. A subset of 220 women was followed prospectively for 12 months with life events assessed with the Life Events and Difficulties (LEDS) interview. Any chronic episode of depression (12 months or longer) during adulthood and onset of a major depressive episode during a 12-month follow-up were established with the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) interview.

RESULTS

The short alleles of 5-HTTLPR moderated the relationship between childhood maltreatment and chronic depression in adulthood, reflected in a significant gene-environment interaction (RD = 0.226, 95% CI: 0.076-0.376, P = .0032). 5-HTTLPR did not moderate the effects of either childhood maltreatment or severe life events on new depressive onsets.

CONCLUSIONS

The short variant of the serotonin transporter gene specifically sensitizes to the effect of early-life experience of abuse or neglect on whether an adult depressive episode takes a chronic course. This interaction may be responsible for a substantial proportion of cases of chronic depression in the general population.

The role of serotonergic genes and environmental stress on the development of depressive symptoms and neuroticism

BACKGROUND

Depression is considered to be the result of a complicated synergy between genetic and environmental factors. Several genes of the serotonergic neurotransmission have been related to depression phenotypes, however results are inconsistent, possibly due to the oversight of the role of environmental stress.

METHODS

We examined gene-environment (GxE) interactions with serotonergic genes on depressive symptoms and neuroticism in a homogeneous population-based sample of 415 females. We chose several genetic variants within candidate genes (SLC6A4, TPH2, HTR1A) that have been previously found to provide some evidence of association with depression outcomes.

RESULTS

Single marker analyses showed a significant GxE interaction with several TPH2 variants, including rs4570625, on depressive symptoms. Significant GxE interactions were also observed with TPH2 haplotypes. No reliable associations were observed with SLC6A4 and HTR1A genes. We did not find any robust evidence of a direct impact of serotonergic genes on depressive symptoms or neuroticism.

LIMITATIONS

Due to the high number of analyses conducted, results must be interpreted with caution.

CONCLUSIONS

The present study indicates an association between TPH2 and depressive symptoms that is conditional on prior experience of stressful life events. Further evidence is provided about the role of the environment in genetic vulnerability to depression.

The 3111T/C polymorphism interacts with stressful life events to influence patterns of sleep in females

Genetic variations in clock-relevant genes have been investigated in relation to sleep abnormalities, both in healthy populations and in mood-disorder patients with inconsistent results. Environmental influences may moderate associations between genes and phenotype. The authors examined the CLOCK 3111T/C polymorphism and several variants within the PER3 gene and their possible interaction with stressful life events in a group of female volunteers (n = 415). Gene-environment (G × E) interactions and gene main effects were investigated on depressive symptoms using the Beck Depression Inventory and on change of sleep patterns (Item 16). Results showed a G × E interaction on alteration of sleeping pattern: the 3111C homozygous genotype reported greater disruption in sleep pattern after the experience of stressful life events. Within the PER3 gene, one G × E interaction was observed with rs228642 on sleep change. These findings show that the 3111T/C polymorphism is not associated with depressive symptoms, but only with symptoms of sleep change in the case of prior stressful life experiences. The combination of a sensitive genotype (3111C/C) and environmental stress increases vulnerability to circadian rhythm disruption in females.

Basing psychiatric classification on scientific foundation: problems and prospects

To examine whether and how the classification of mental disorders can be based on research, we evaluate the relevance of psychiatric science to the major questions in classification. We conclude that most studies cannot inform the validity of diagnostic categories because they are constrained by the classification through a top-down diagnostic approach. Analyses of relationships between diagnostic categories suggest that most interdiagnostic boundaries in current classifications lack validity. Likewise, genetic studies show that the susceptibility to mental illness is at most partly disorder-specific. Neuroimaging research is uninformative due to unsystematic single-diagnosis studies, use of super-healthy controls, and publication bias. Treatment research suggests moderate specificity in several areas of psychopathology (e.g. lithium for bipolar disorder), but lack of specificity is the rule (e.g. the broad indications of serotonin-reuptake inhibitors). In summary, evidence from multiple lines of research converges to indicate that current classifications contain excessively large numbers of categories of limited validity. Dimensional classification will not solve the problem because the number of dimensions is as uncertain as the number of categories. Psychiatric research should discard the assumption that current classification is valid. Instead of diagnosis-specific investigations, studies of unselected groups assessed with bottom-up approaches are needed to advance psychiatry.

Genomic structural variation in psychiatric disorders

Copy number variants (CNVs) are submicroscopic deletions and duplications of genomic material that were previously thought to be rare phenomena. They have now been robustly associated with a variety of disorders such as autism, schizophrenia, and attention-deficit/hyperactivity disorder through an emerging research base in affective disorders. A complex picture is emerging of a polygenic, heterogeneous model of disease, with CNVs conferring broad susceptibility to a variety of neurodevelopmental disorders, rather than specific disorders per se. Although the insights gleaned thus far only represent a small piece of a much larger puzzle, progress has been rapid and new technologies promise even more insights into these hitherto opaque brain disorders. We will discuss CNVs, the current state of evidence for their role in the pathogenesis of classical psychiatric disorders, and the application of such knowledge in clinical settings.

Genome-wide association analysis of eating disorder-related symptoms, behaviors, and personality traits

Eating disorders (EDs) are common, complex psychiatric disorders thought to be caused by both genetic and environmental factors. They share many symptoms, behaviors, and personality traits, which may have overlapping heritability. The aim of the present study is to perform a genome-wide association scan (GWAS) of six ED phenotypes comprising three symptom traits from the Eating Disorders Inventory 2 [Drive for Thinness (DT), Body Dissatisfaction (BD), and Bulimia], Weight Fluctuation symptom, Breakfast Skipping behavior and Childhood Obsessive-Compulsive Personality Disorder trait (CHIRP). Investigated traits were derived from standardized self-report questionnaires completed by the TwinsUK population-based cohort. We tested 283,744 directly typed SNPs across six phenotypes of interest in the TwinsUK discovery dataset and followed-up signals from various strata using a two-stage replication strategy in two independent cohorts of European ancestry. We meta-analyzed a total of 2,698 individuals for DT, 2,680 for BD, 2,789 (821 cases/1,968 controls) for Bulimia, 1,360 (633 cases/727 controls) for Childhood Obsessive-Compulsive Personality Disorder trait, 2,773 (761 cases/2,012 controls) for Breakfast Skipping, and 2,967 (798 cases/2,169 controls) for Weight Fluctuation symptom. In this GWAS analysis of six ED-related phenotypes, we detected association of eight genetic variants with P < 10(-5) . Genetic variants that showed suggestive evidence of association were previously associated with several psychiatric disorders and ED-related phenotypes. Our study indicates that larger-scale collaborative studies will be needed to achieve the necessary power to detect loci underlying ED-related traits.

Variation in the glucocorticoid receptor gene at rs41423247 moderates the effect of prenatal maternal psychological symptoms on child cortisol reactivity and behavior

Prenatal maternal psychopathology affects child development, but some children seem more vulnerable than others. Genetic variance in hypothalamic-pituitary-adrenal axis genes may influence the effect of prenatal maternal psychological symptoms on child emotional and behavioral problems. This hypothesis was tested in the Generation R Study, a population-based cohort from fetal life onward. In total, 1727 children of Northern European descent and their mothers participated in this study and were genotyped for variants in the glucocorticoid receptor (GR) gene (rs6189/rs6190, rs10052957, rs41423247, rs6195, and rs6198) and the FK506-binding protein 5 (FKBP5) gene (rs1360780). Prenatal maternal psychological symptoms were assessed at 20 weeks pregnancy and child behavior was assessed by both parents at 3 years. In a subsample of 331 children, data about cortisol reactivity were available. Based on power calculations, only those genetic variants with sufficient minor allele frequencies (rs41423247, rs10052957, and rs1360780) were included in the interaction analyses. We found that variation in GR at rs41423247 moderates the effect of prenatal maternal psychological symptoms on child emotional and behavioral problems (beta 0.41, SE 0.16, p=0.009). This prenatal interaction effect was independent of mother's genotype and maternal postnatal psychopathology, and not found for prenatal psychological symptoms of the father. Moreover, the interaction between rs41423247 and prenatal psychological symptoms was also associated with decreased child cortisol reactivity (beta -2.30, p-value 0.05). These findings emphasize the potential effect of prenatal gene-environment interaction, and give insight in possible mechanisms accounting for children's individual vulnerability to develop emotional and behavioral problems.

Advanced paternal age increases the risk of schizophrenia and obsessive-compulsive disorder in a Chinese Han population

Using the Structured Clinical Interview for DSM-IV, patient and non-patient version (SCID-P/NP), this study investigated 351 patients with schizophrenia, 122 with obsessive-compulsive disorder (OCD), and 238 unrelated healthy volunteers in a Chinese Han population. The relative risks posed by advanced paternal age for schizophrenia and OCD in offspring were computed under logistic regression analyses and adjusted for the participant's sex, age and co-parent age at birth. Compared to the offspring with paternal age of 25-29 years old, the relative risks rose from 2.660 to 10.183 in the paternal age range of 30-34 and ≥35. The relative risks for OCD increased from 2.225 to 5.413 in 30-34 and ≥35. For offspring with paternal age of <25, the odds ratios of developing schizophrenia and OCD were 0.628 and 0.289 respectively, whereas an association between increased maternal age and risk for schizophrenia/OCD was not seen. Interaction analysis showed an interaction effect between paternal age and maternal age at birth. Such a tendency of risk affected by parental age for schizophrenia and OCD existed after splitting out the data of early onset patients. Sex-specific analyses found that the relative risks for schizophrenia with paternal age of 30-34 and ≥35 in male offspring were 2.407 and 10.893, and in female offspring were 3.080 and 9.659. The relative risks for OCD with paternal age of 30-34 and ≥35 in male offspring were 3.493 and 7.373, and in female offspring 2.005 and 4.404. The mean paternal age of schizophrenia/OCD patients born before the early 1980s was much greater than that of patients who were born after then. The findings illustrated that advanced paternal age is associated with increased risk for both schizophrenia and OCD in a Chinese Han population, prominently when paternal age is over 35. Biological and non-biological mechanisms may both be involved in the effects of advanced paternal age on schizophrenia and OCD.

Reduced fractional anisotropy in the uncinate fasciculus in patients with major depression carrying the met-allele of the Val66Met brain-derived neurotrophic factor genotype

Experimental studies support a neurotrophic hypothesis of major depressive disorder (MDD). The aim of this study was to determine the effect of Val66Met brain-derived neurotrophic factor (BDNF) polymorphism on the white matter fiber tracts connecting hippocampus and amygdala with the prefrontal lobe in a sample of patients with MDD and healthy controls. Thirty-seven patients with MDD and 42 healthy volunteers were recruited. Diffusion tensor imaging (DTI) data with 61 diffusion directions were obtained with MRI 3 Tesla scanner. Deterministic tractography was applied with ExploreDTI and Val66Met BDNF SNP (rs6265) was genotyped. Fiber tracts connecting the hippocampus and amygdala with the prefrontal lobe, namely uncinate fasciculus (UF), fornix, and cingulum were analyzed. A significant interaction was found in the UF between BDNF alleles and diagnosis. Patients carrying the BDNF met-allele had smaller fractional anisotropy (FA) in the UF compared to those patients homozygous for val-allele and compared to healthy subjects carrying the met-allele. A significant three-way interaction was detected between region of the cingulum (dorsal, rostral, and parahippocampal regions), brain hemisphere and BDNF genotype. Larger FA was detectable in the left rostral cingulum for met-allele carriers when compared to val/val alelle carriers. We provide evidence for the importance of the neurotrophic involvement in limbic and prefrontal connections. The met-allele of the BDNF polymorphism seems to render subjects more vulnerable for dysfunctions associated with the UF, a tract known to be related to negative emotional-cognitive processing bias, declarative memory problems, and autonoetic self awareness.

The genetic basis of addictive disorders

Addictions are common, chronic, and relapsing diseases that develop through a multistep process. The impact of addictions on morbidity and mortality is high worldwide. Twin studies have shown that the heritability of addictions ranges from 0.39 (hallucinogens) to 0.72 (cocaine). Twin studies indicate that genes influence each stage from initiation to addiction, although the genetic determinants may differ. Addictions are by definition the result of gene × environment interaction. These disorders, which are in part volitional, in part inborn, and in part determined by environmental experience, pose the full range of medical, genetic, policy, and moral challenges. Gene discovery is being facilitated by a variety of powerful approaches, but is in its infancy. It is not surprising that the genes discovered so far act in a variety of ways: via altered metabolism of drug (the alcohol and nicotine metabolic gene variants), via altered function of a drug receptor (the nicotinic receptor, which may alter affinity for nicotine but as discussed may also alter circuitry of reward), and via general mechanisms of addiction (genes such as monoamine oxidase A and the serotonin transporter that modulate stress response, emotion, and behavioral control). Addiction medicine today benefits from genetic studies that buttress the case for a neurobiologic origin of addictive behavior, and some general information on familially transmitted propensity that can be used to guide prevention. A few well-validated, specific predictors such as OPRM1, ADH1B, ALDH2, CHRNA5, and CYP26 have been identified and can provide some specific guidance, for example, to understand alcohol-related flushing and upper GI cancer risk (ADH1B and AKLDH2), variation in nicotine metabolism (CYP26), and, potentially, naltrexone treatment response (OPRM1). However, the genetic predictors available are few in number and account for only a small portion of the genetic variance in liability, and have not been integrated into clinical nosology or care.