Basic concepts in the study of diseases with complex genetics

Does Young Adults' Neighborhood Environment Affect Their Depressive Mood? Insights from the 2019 Korean Community Health Survey

The rates of depression among young adults have been increasing in high-income countries and have emerged as a social problem in South Koreans aged 19–34. However, the literature is unclear on whether the neighborhood environment that young adults live in affects the onset and severity of their depressive symptoms. This study analyzed data from the 2019 Korean Community Health Survey (KCHS) using the Tobit model to identify the effect of the neighborhood environment on young adults’ depressive moods. Controlling for other corresponding factors, young adults’ neighborhood environment satisfaction affected their depression, and natural environment satisfaction (32.5%), safety level satisfaction (31.0%), social overhead capital (SOC), environment satisfaction (30.2%), trust between neighbors satisfaction (20.1%), and public transportation environmental satisfaction (12.2%) affected young adults’ depressive moods. Of these, natural environment satisfaction (32.5%), safety level environment satisfaction (31.0%), and SOC environment satisfaction (30.2%) affected young adults’ depressive mood to a similar extent. This implies that many young adults in South Korea live in inadequate neighborhood conditions. This research contributes to the literature by identifying the specific environmental factors that affect young adults’ depressive moods.

Molecular and biological functions of resveratrol in psychiatric disorders: a review of recent evidence

Mental disorders including depression, anxiety, schizophrenia, autism spectrum disorders, bipolar and etc. have a considerable proportion of global disorder burden. Many nutritional psychiatry investigations have been conducted to evaluate the relationship between several individual nutrients such as herbal compounds with mental health. Resveratrol, a famous polyphenol compound, is known as an antioxidant, anti-inflammatory, anti-apoptotic, and neuroprotective agent regulating the function of brain and improves the behavioral factors associated with learning, anxiety, depression, and memory. In addition, this natural compound can cross the blood–brain barrier representing neurological influences. The pharmacological interest of utilizing resveratrol in mental disorders is due to its anti-inflammatory and antioxidant features. The aim of this paper was to review the studies evaluated the potential effects of resveratrol on mental disorders.

Resilience Dysregulation in Major Depressive Disorder: Focus on Glutamatergic Imbalance and Microglial Activation

BACKGROUND

Many studies have been shown an important role of glutamatergic system as well microglial activation in the pathophysiology of major depressive disorder (MDD). In humans most resistant to the development of psychiatric disorders, including MDD, are observed a greater degree of resilience resulting from stress. Less resilience is associated with neuroendocrine and neuroinflammatory markers, as well as with glutamatergic system dysregulation. Thus, this review we highlighted findings from literature identifying the function of glutamatergic system, microglial activation and inflammation in resilience.

METHODS

We conducted a review of computerized databases from 1970 to 2017.

RESULTS

There is an association between microglial activation and glutamatergic system activation with stress vulnerability and resilience.

CONCLUSIONS

Glutamate neurotransmission, including neurotransmitter synthesis, signalling, and glutamate receptor functions and expression all seem to be involved with both stress vulnerability and resilience. Moreover, inflammation and microglial activation mediate individual differences in resilience and the risk of stress-induced MDD.

Molecular Mechanisms Underlying the Anti-depressant Effects of Resveratrol: a Review

Major depression is a public health problem, affecting 121 million people worldwide. Patients suffering from depression present high rates of morbidity, causing profound economic and social impacts. Furthermore, patients with depression present cognitive impairments, which could influence on treatment adherence and long-term outcomes. The pathophysiology of major depression is not completely understood yet but involves reduced levels of monoamine neurotransmitters, bioenergetics, and redox disturbances, as well as inflammation and neuronal loss. Treatment with anti-depressants provides a complete remission of symptoms in approximately 50% of patients with major depression. However, these drugs may cause side effects, as sedation and weight gain. In this context, there is increasing interest in studies focusing on the anti-depressant effects of natural compounds found in the diet. Resveratrol is a polyphenolic phytoalexin (3,4',5-trihydroxystilbene; C₁₄H₁₂O₃; MW 228.247 g/mol) and has been found in peanuts, berries, grapes, and wine and induces anti-oxidant, anti-inflammatory, and anti-apoptotic effects in several mammalian cell types. Resveratrol also elicits anti-depressant effects, as observed in experimental models using animals. Therefore, resveratrol may be viewed as a potential anti-depressant agent, as well as may serve as a model of molecule to be modified aiming to ameliorate depressive symptoms in humans. In the present review, we describe and discuss the anti-depressant effects of resveratrol focusing on the mechanism of action of this phytoalexin in different experimental models.

Gene × Environment Interactions in Schizophrenia: Evidence from Genetic Mouse Models

The study of gene × environment, as well as epistatic interactions in schizophrenia, has provided important insight into the complex etiopathologic basis of schizophrenia. It has also increased our understanding of the role of susceptibility genes in the disorder and is an important consideration as we seek to translate genetic advances into novel antipsychotic treatment targets. This review summarises data arising from research involving the modelling of gene × environment interactions in schizophrenia using preclinical genetic models. Evidence for synergistic effects on the expression of schizophrenia-relevant endophenotypes will be discussed. It is proposed that valid and multifactorial preclinical models are important tools for identifying critical areas, as well as underlying mechanisms, of convergence of genetic and environmental risk factors, and their interaction in schizophrenia.

Initial subjective reward: single-exposure conditioned place preference to alcohol in mice

Most adults consume alcohol with relative impunity, but about 10–20% of users persist (or progress) in their consumption, despite mounting and serious repercussions. Identifying at-risk individuals before neuroadaptative changes associated with chronic use become well ingrained is thus a key step in mitigating and preventing the end stage disease and its devastating impacts. Explaining liability has been impeded, in part, by the absence of animal models for assessing initial sensitivity to the drug's reinforcing properties, an important endophenotype in the trajectory toward excessive drinking. Here we assess the initial rewarding effects of the drug in a novel application of the conditioned place preference paradigm. In contrast to previous studies that have all employed repeated drug administration, we demonstrated a robust preference for a context paired with a single exposure to 1.5 g/kg EtOH in male and female subjects of three strains. This model validates an assay of initial sensitivity to the subjective rewarding effects of alcohol, a widely used drug with multifarious impacts on both brain and society, and provides a new tool for theory-driven endophenotypic pharmacogenetic approaches to understanding and treating addiction.

Speech-language pathology insights into genetics and neuroscience: beyond surface behaviour

For almost a century, speech-language pathologists (SLPs) have worked at refining communication disorder phenotypes. Yet a hundred years of mastering the characterization of surface behaviours has provided only limited understanding of the neurobiological underpinnings of communication disorder. Arguably, the most momentous aetiological findings in speech-language pathology have been made relatively recently and by cross-disciplinary colleagues in the fields of molecular genetics and neuroimaging. Such findings include discovery of FOXP2, for example, the first gene found to be associated with a primary speech disorder. New gene-brain-behaviour discoveries in communication disorder are occurring on an almost weekly basis and it is challenging for clinical SLPs to engage with, interpret, and keep abreast of this literature. This paper aims to provide a brief overview of genetic and neuroimaging approaches to the study of communication disorders. Further examples of key findings in these fields are presented, with a discussion of the impacts on core SLP practice. Future research directions for further illuminating gene-brain-behaviour relationships in communication disorder are identified.

Polymorphic variation in choline transporter gene (CHT1) is associated with early, subclinical measures of carotid atherosclerosis in humans

Atherosclerosis is a heritable trait with little known about specific genetic influences on preclinical measures of plaque formation. Based on relations of parasympathetic-cholinergic function to atherosclerosis and to a choline transporter gene [CHT1 (G/T)] polymorphism, we investigated whether the same allelic variant predicts variation in carotid intima-media thickness (IMT) and plaque formation. Carotid IMT and plaque occurrence as well as genotyping for the CHT1 (G/T) variant were measured in a sample (N = 264) of generally healthy adults (age 30-55) of European ancestry. CHT1 GG homozygotes had greater IMT (P < 0.005) and plaque occurrence (P < 0.020) than T allele carriers. This is the first study showing polymorphic variation in the CHT1 gene to predict early, subclinical measures of carotid atherosclerosis which may aid in understanding cholinergic-vagal processes potentially underlying atherosclerotic risk.

Susceptibility genes for schizophrenia: mutant models, endophenotypes and psychobiology

Schizophrenia is characterised by a multifactorial aetiology that involves genetic liability interacting with epigenetic and environmental factors to increase risk for developing the disorder. A consensus view is that the genetic component involves several common risk alleles of small effect and/or rare but penetrant copy number variations. Furthermore, there is increasing evidence for broader, overlapping genetic-phenotypic relationships in psychosis; for example, the same susceptibility genes also confer risk for bipolar disorder. Phenotypic characterisation of genetic models of candidate risk genes and/or putative pathophysiological processes implicated in schizophrenia, as well as examination of epidemiologically relevant gene × environment interactions in these models, can illuminate molecular and pathobiological mechanisms involved in schizophrenia. The present chapter outlines both the evidence from phenotypic studies in mutant mouse models related to schizophrenia and recently described mutant models addressing such gene × environment interactions. Emphasis is placed on evaluating the extent to which mutant phenotypes recapitulate the totality of the disease phenotype or model selective endophenotypes. We also discuss new developments and trends in relation to the functional genomics of psychosis which might help to inform on the construct validity of mutant models of schizophrenia and highlight methodological challenges in phenotypic evaluation that relate to such models.

The role of BDNF in depression on the basis of its location in the neural circuitry

Depression is one of the most prevalent and life-threatening forms of mental illnesses and the neural circuitry underlying depression remains incompletely understood. Most attention in the field has focused on hippocampal and frontal cortical regions for their roles in depression and antidepressant action. While these regions no doubt play important roles in the mental illness, there is compelling evidence that other brain regions are also involved. Brain-derived neurotrophic factor (BDNF) is broadly expressed in the developing and adult mammalian brain and has been implicated in development, neural regeneration, synaptic transmission, synaptic plasticity and neurogenesis. Recently BDNF has been shown to play an important role in the pathophysiology of depression, however there are controversial reports about the effects of BDNF on depression. Here, we present an overview of the current knowledge concerning BDNF actions and associated intracellular signaling in hippocampus, prefrontal cortex, nucleus accumbens (NAc) and amygdala as their relation to depression.

Phenotypic characterization of a genetically diverse panel of mice for behavioral despair and anxiety

Background

Animal models of human behavioral endophenotypes, such as the Tail Suspension Test (TST) and the Open Field assay (OF), have proven to be essential tools in revealing the genetics and mechanisms of psychiatric diseases. As in the human disorders they model, the measurements generated in these behavioral assays are significantly impacted by the genetic background of the animals tested. In order to better understand the strain-dependent phenotypic variability endemic to this type of work, and better inform future studies that rely on the data generated by these models, we phenotyped 33 inbred mouse strains for immobility in the TST, a mouse model of behavioral despair, and for activity in the OF, a model of general anxiety and locomotor activity.

Results

We identified significant strain-dependent differences in TST immobility, and in thigmotaxis and distance traveled in the OF. These results were replicable over multiple testing sessions and exhibited high heritability. We exploited the heritability of these behavioral traits by using in silico haplotype-based association mapping to identify candidate genes for regulating TST behavior. Two significant loci (-logp >7.0, gFWER adjusted p value <0.05) of approximately 300 kb each on MMU9 and MMU10 were identified. The MMU10 locus is syntenic to a major human depressive disorder QTL on human chromosome 12 and contains several genes that are expressed in brain regions associated with behavioral despair.

Conclusions

We report the results of phenotyping a large panel of inbred mouse strains for depression and anxiety-associated behaviors. These results show significant, heritable strain-specific differences in behavior, and should prove to be a valuable resource for the behavioral and genetics communities. Additionally, we used haplotype mapping to identify several loci that may contain genes that regulate behavioral despair.

Subjective responses to alcohol consumption as endophenotypes: advancing behavioral genetics in etiological and treatment models of alcoholism

Individual differences in subjective responses to alcohol consumption represent genetically mediated biobehavioral mechanisms of alcoholism risk (i.e., endophenotype). The objective of this review is three-fold: (1) to provide a critical review the literature on subjective response to alcohol and to discuss the rationale for its conceptualization as an endophenotype for alcoholism; (2) to examine the literature on the neurobiological substrates and associated genetic factors subserving individual differences in subjective response to alcohol; and (3) to discuss the treatment implications of this approach and to propose a framework for conceptualizing, and systematically integrating, endophenotypes into alcoholism treatment.

MicroRNA dysregulation in psychiatric disease

MicroRNAs (miRNAs) are small regulatory RNAs that individually regulate up to several hundred genes, and collectively may regulate as much as two-thirds of the transcriptome. Recent evidence supports a role for miRNA dysregulation in psychiatric and neurological disorders, including schizophrenia, bipolar disorder, and autism. Small changes in miRNA expression can fine-tune the expression of multiple genes within a biological network, suggesting that miRNA dysregulation may underlie many of the molecular changes observed in psychiatric disease, and that therapeutic regulation of miRNA levels may represent a novel treatment option.

Depression research: where are we now?

Extensive studies have led to a variety of hypotheses for the molecular basis of depression and related mood disorders, but a definite pathogenic mechanism has yet to be defined. The monoamine hypothesis, in conjunction with the efficacy of antidepressants targeting monoamine systems, has long been the central topic of depression research. While it is widely embraced that the initiation of antidepressant efficacy may involve acute changes in monoamine systems, apparently, the focus of current research is moving toward molecular mechanisms that underlie long-lasting downstream changes in the brain after chronic antidepressant treatment, thereby reaching for a detailed view of the pathophysiology of depression and related mood disorders. In this minireview, we briefly summarize major themes in current approaches to understanding mood disorders focusing on molecular views of depression and antidepressant action.

AKAP10 (I646V) functional polymorphism predicts heart rate and heart rate variability in apparently healthy, middle-aged European-Americans

Previous evidence suggests that the dual-specific A kinase-anchoring protein 2 functional polymorphism (AKAP10 (A/G) I646V) influences heart rate (HR) and heart rate variability (HRV) in mice and humans (N=122) with cardiovascular disease. Here, we asked whether this AKAP10 variant predicts HR and HRV in a large sample of healthy humans. Resting HR and short-term time and frequency domain measures of HRV (5 min during paced and unpaced respiration conditions) were assessed in a U.S. community sample (N=1,033) of generally healthy men and women (age 30-54) of European ancestry. Each person was genotyped for the AKAP10 variant. As with previous work, the AKAP10 Val allele predicted greater resting HR (Paced p<.01; Unpaced p<.03) and diminished HRV (Paced ps <.05) suggesting that this variant may modulate the sensitivity of cardiac pacemaker cells to autonomic inputs, possibly conferring risk for arrhythmias and sudden cardiac death.

Associations of ADH and ALDH2 gene variation with self report alcohol reactions, consumption and dependence: an integrated analysis

Alcohol dependence (AD) is a complex disorder with environmental and genetic origins. The role of two genetic variants in ALDH2 and ADH1B in AD risk has been extensively investigated. This study tested for associations between nine polymorphisms in ALDH2 and 41 in the seven ADH genes, and alcohol-related flushing, alcohol use and dependence symptom scores in 4597 Australian twins. The vast majority (4296) had consumed alcohol in the previous year, with 547 meeting DSM-IIIR criteria for AD. There were study-wide significant associations (P<2.3 x 10(-4)) between ADH1B-Arg48His (rs1229984) and flushing and consumption, but only nominally significant associations (P<0.01) with dependence. Individuals carrying the rs1229984 G-allele (48Arg) reported a lower prevalence of flushing after alcohol (P=8.2 x 10(-7)), consumed alcohol on more occasions (P=2.7 x 10(-6)), had a higher maximum number of alcoholic drinks in a single day (P=2.7 x 10(-6)) and a higher overall alcohol consumption (P=8.9 x 10(-8)) in the previous year than those with the less common A-allele (48His). After controlling for rs1229984, an independent association was observed between rs1042026 (ADH1B) and alcohol intake (P=4.7 x 10(-5)) and suggestive associations (P<0.001) between alcohol consumption phenotypes and rs1693482 (ADH1C), rs1230165 (ADH5) and rs3762894 (ADH4). ALDH2 variation was not associated with flushing or alcohol consumption, but was weakly associated with AD measures. These results bridge the gap between DNA sequence variation and alcohol-related behavior, confirming that the ADH1B-Arg48His polymorphism affects both alcohol-related flushing in Europeans and alcohol intake. The absence of study-wide significant effects on AD results from the low P-value required when testing multiple single nucleotide polymorphisms and phenotypes.

Examining the heritability of a laboratory-based smoking endophenotype: initial results from an experimental twin study

The objective of this study was to examine the heritability of an endophenotype relevant to nicotine dependence, namely tension reduction after smoking. This study also examined whether common genetic, shared environmental, and nonshared environmental factors influence this endophenotype measured repeatedly during an experimental paradigm. Twin and sibling pairs, all of whom were regular smokers, completed a laboratory paradigm in which they reported on levels of tension at baseline and after smoking each of 3 cigarettes. Univariate twin analyses suggested a sizeable role of additive genetic effects on tension reduction, with heritability estimates ranging between 47 and 68%. Result of multivariate Cholesky analyses indicated that there were additive genetic influences common to tension reduction assessed after cigarettes 1, 2, and 3. Multivariate models including genetic and nonshared environmental effects provided the best fit to the data. To the best of our knowledge, this is the first study to examine the genetic basis of a laboratory smoking endophenotype, in this case tension reduction after smoking. Implications for genetic association studies are discussed.

Multi-locus association study of schizophrenia susceptibility genes with a posterior probability method

Schizophrenia is a serious neuropsychiatric illness affecting about 1% of the world's population. It is considered a complex inheritance disorder. A number of genes are involved in combination in the etiology of the disorder. Evidence implicates the altered dopaminergic transmission in schizophrenia. In the present study, in order to identify susceptibility genes for schizophrenia in dopaminergic metabolism, we analyzed 59 single nucleotide polymorphisms (SNPs) in 24 genes of the dopaminergic pathway among 82 unrelated patients with schizophrenia and 108 matched normal controls. Considering that traditional single-locus association studies ignore the multigenic nature of complex diseases and do not take into account possible interactions between susceptibility genes, we proposed a multi-locus analysis method, using the posterior probability of morbidity as a measure of absolute disease risk for a multi-locus genotype combination, and developed an algorithm based on perturbation and average to detect the susceptibility multi-locus genotype combinations, as well as to repress noise and avoid false positive results at our best. A three-locus SNP genotype combination involved in the interactions of COMT and ALDH3B1 genes was detected to be significantly susceptible to schizophrenia.

Chronic stress, depression and antidepressants: effects on gene transcription in the hippocampus

Depressive disorders are among the most frequent forms of mental illness. Both genetic and environmental factors, such as stress, are involved in the etiology of depression. Therefore, chronic stress paradigms in laboratory animals constitute an important tool for research in this field. The molecular bases of chronic stress/depression are largely unknown, although a large amount of information has been accumulated during recent years. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis as well as structural and physiological alterations in the hippocampus and neocortex are known to occur. Modifications in the expression level of some genes, such as brain-derived neurotrophic factor, cAMP-response-element binding protein, serotonin receptors and HPA axis components were consistently associated in a number of experimental models. However, recent results suggest that several synaptic proteins, transcription factors and proteins involved in neuronal growth/differentiation, are also modified in their expression in experimental models of chronic stress. In general, these alterations can be reversed by treatment with antidepressants. Thus, a complex pattern of gene expression leading to stress/depression is starting to emerge. We summarize here recent findings on the alterations of gene expression in the hippocampus of chronically stressed and antidepressant treated animals.

Cue-elicited craving for food: a fresh approach to the study of binge eating

Recent research has indicated that craving for food can be elicited by exposure to food cues, suggesting that exposure to food cues may represent a useful experimental paradigm to investigate mechanisms related to binge eating. The first objective of the present research was to replicate previous reports that exposure to food cues elicits craving for food. In addition, this investigation was designed to extend the extant literature by testing the effects of 'priming' portions of food, by examining the association between reactivity to food cues and indicators of binge eating, and to examine the role of a putative genetic factor previously found to be associated with cue-elicited craving for alcohol and tobacco. In Study 1, 48 individuals completed measures of craving and mood after exposure to control cues, after exposure to food cues, and after consuming each of three small portions of food. In Study 2, 31 individuals with subclinical symptoms of binge eating completed the same procedures. The results suggested that food cues reliably elicited craving, increased attention to the cues, and decreased positive affect in both samples, although reactivity was greater among the sample with greater eating pathology. Correlational analyses suggested that reactivity to food cues was correlated with binge eating and body mass index among women but not men. Results also suggest that the DRD4 VNTR polymorphism influences cue-elicited craving for food, although the influence of the DRD4 may depend on the population under study.

Heart rate variability is associated with polymorphic variation in the choline transporter gene

OBJECTIVE

The objective of this study was to determine whether interindividual variation in parasympathetic (cholinergic) and sympathetic (adrenergic) regulation of heart rate (as estimated by frequency components of heart rate variability [HRV]) may be accounted for, in part, by genetic variation in the choline transporter, a component of acetylcholine neurotransmission.

METHODS

Resting HRV estimates of high- (HF) and low-frequency (LF) power and LF/HF ratio were determined from electrocardiogram recordings collected continuously over 5 minutes in 413 white individuals of European ancestry (49% men; aged 30-54 years [mean, 44 years]). Subjects were genotyped for a single nucleotide polymorphism (SNP) located in the 3' untranslated region of the choline transporter gene (CHT1). Frequencies of the alternate CHT1 alleles, labeled G and T, were 76% and 24%.

RESULTS

Compared with GG homozygotes, participants having any T allele had greater HF power (p <.02), lower LF power (p <.02), and lower LF/HF ratios (p <.005). Relative to men, women had lower LF power (p <.001) and lower LF/HF ratios (p <.005).

CONCLUSIONS

These findings show that polymorphic variation in the CHT1 gene is associated significantly with interindividual variability in HRV indices related to parasympathetic (cholinergic) activity.

An Expanded Evaluation of the Relationship of Four Alleles to the Level of Response to Alcohol and the Alcoholism Risk

BACKGROUND

Alcoholism is a complex, genetically influenced disorder the cause of which may be better understood through the study of genetically influenced phenotypes that mediate the risk. One such intermediate phenotype is the low level of response (LR) to alcohol. This project used a case-control approach to search for genes that may contribute to LR.

METHODS

Data were available from alcohol challenges at approximately age 20 and regarding the development of alcohol use disorders over the subsequent 20 years for 85 men, including 40 reported in a previous genetic analysis. LR was evaluated using oral consumption of 0.75 ml/kg of alcohol, after which changes in subjective feelings of intoxication and body sway were measured. Alcohol abuse and dependence were diagnosed by DSM-III-R criteria through structured interviews administered to both the participant and an informant (usually the spouse) 10, 15, and 20 years after initial testing. Four polymorphisms were evaluated, including the serotonin transporter HTTLPR promoter ins/del, GABAAalpha6 Pro385Ser, NPY Leu7Pro, and catalase 262C>T. Two of these, HTTLPR and GABAAalpha6 Pro385Ser, had been previously associated with LR and alcoholism in a preliminary study.

RESULTS

The HTTLPR L allele was significantly related to both the LR and alcoholism in an allele-dosage (stepwise) manner. Furthermore, the association remained when L alleles were subdivided into recently reported functional subtypes: the lowest LR was associated with genotypes correlated with the highest serotonin transporter expression. The GABAAalpha6 Ser385 allele showed a nonsignificant trend for association to a low LR, as had been previously observed, although the Ser385 allele is uncommon, and only 18 heterozygotes were in the current group. However, the six men with both LL and Pro385/Ser385 genotypes had the lowest LR, and each had developed alcoholism during follow-up. Neither NPY nor catalase was associated with either LR or alcoholic outcomes, although the sample did not have sufficient power for definitive conclusions.

CONCLUSIONS

This report strengthens the support for a relationship between the HTTLPR L and GABAAalpha6 Ser385 alleles to low alcohol LR and to alcoholism in a prospectively studied cohort evaluated for LR in young adulthood and before the onset of alcohol dependence.

Advances in molecular genetics and the prevention and treatment of substance misuse: Implications of association studies of the A1 allele of the D2 dopamine receptor gene

Substance misuse is influenced by multiple genetic and environmental factors. Recent research has identified a number of potential genetic markers of risk and those associated with drug reward substrates show particular promise. The current study reexamines the extant published data of the association between the D2 dopamine receptor (DRD2) gene minor Taq 1A (A1) allele and substance misuse risk. A series of meta-analyses was performed on 64 studies examining DRD2 A1+ allelic status and substance misuse. In addition, personality was examined as a possible endophenotype. Significant association was found between the A1 allele and severe substance dependence in both Caucasian and non-Caucasian groups. The data did not support a significant association between the A1 allele and personality features. While the specific mechanism underlying these associations requires further elucidation, this genetic marker shows promise as a marker of brain reinforcement processes. Possible ways of utilising the A1 allele to inform prevention and treatment initiatives are discussed.

Socio-economic status covaries with central nervous system serotonergic responsivity as a function of allelic variation in the serotonin transporter gene-linked polymorphic region

It was reported recently that exposure to an adverse rearing environment lowers central nervous system (CNS) serotonergic activity in a nonhuman primate (rhesus monkeys), but only among animals having the shorter variant of a functional, biallelic repeat polymorphism in the regulatory region of the serotonin transporter (5-HTT) gene. Because repeat variants of the same core sequence affect transcriptional efficiency of the 5-HTT gene in humans, we examined whether biallelic variation in the 5-HTT gene-linked polymorphic region (5-HTTLPR) acts analogously to modulate a previously described association between socio-economic status (SES) and CNS serotonergic function. The 5-HTTLPR was genotyped in 139 adult men and women (n = 75 and 64) who were administered a standard neuroendocrine challenge to assess central serotonergic responsivity (plasma prolactin (PRL) response to the serotonin releasing agent, fenfluramine). Socio-economic status was estimated from reported income and years of education. Hierarchical linear regression showed serotonergic responsivity to be predicted by the interaction of 5-HTTLPR genotype and SES (p = 0.018). Individuals of lower income and less education had lower peak PRL concentrations following administration of fenfluramine than did subjects ranking higher on these dimensions, but only among persons possessing at least one 5-HTTLPR short allele. Within genotype, SES covaried moderately with the PRL response to fenfluramine among subjects who were homozygous for the short allele (r18 = 0.50, p < 0.03). A similar association was present at lesser magnitude in heterozygotes (r70 = 0.24, p < 0.05) and absent among subjects homozygous for the long allele (r45 = -0.04, n.s.). Findings were comparable for men and women and persisted on re-analysis restricted to persons without current Axis I psychopathology. We conclude that allelic variation at 5-HTTLPR moderates the influence of social position on CNS serotonergic responsivity.

Population stratification in the candidate gene study: fatal threat or red herring?

Advances in molecular genetics have provided behavioral scientists with a means of investigating the influence of genetic factors on human behavior. Unfortunately, recent candidate gene studies have produced inconsistent results, and a frequent scapegoat for the lack of replication across studies is the threat of population stratification. This review of the literature on population stratification suggests that the threat may be a red herring. Reliable findings will require improved specification and measurement of the behavioral phenotypes in question, a renewed focus on internal validity, and the specification and testing of genetic factors in the context of longitudinal multivariate models. In this respect, behavioral scientists are well suited to investigating genetic factors that influence psychological mechanisms.

The policy and ethical implications of genetic research on attention deficit hyperactivity disorder

OBJECTIVE

To review the policy and ethical implications of recent research on the molecular genetics of attention deficit hyperactivity disorder (ADHD).

METHOD

MEDLINE and psycINFO database searches were used to identify studies on the genetics of ADHD. The implications of replicated candidate genes are discussed.

RESULTS

The findings for most genes have been inconsistent but several studies have implicated the genes in the dopaminergic pathway in the aetiology of ADHD.

CONCLUSIONS

The current evidence on the genetics of ADHD is insufficient to justify genetic screening tests but it will provide important clues as to the aetiology of ADHD. Genetic information on susceptibility to ADHD has the potential to be abused and to stigmatize individuals. Researchers and clinicians need to be mindful of these issues in interpreting and disseminating the results of genetic studies of ADHD.

Genetic screening for susceptibility to depression: can we and should we?

OBJECTIVE

To summarize current knowledge about genetic susceptibility to mood disorders and examine ethical and policy issues that will need to be addressed if robustly replicated susceptibility alleles lead to proposals to screen and intervene with persons at increased genetic risk of developing mood disorders.

METHOD

Empirical studies and reviews of the genetics of unipolar and bipolar depression were collected via MEDLINE and psycINFO database searches.

RESULTS

A number of candidate genes for depression have been identified, each of which increases the risk of mood disorders two- or threefold. None of the associations between these alleles and mood disorders have been consistently reported to date.

CONCLUSIONS

Screening the population for genetic susceptibility to mood disorders is unlikely to be a practically useful policy (given plausible assumptions). Until there are effective treatments for persons at increased risk, screening is arguably unethical. Screening within affected families to advise on risks of developing depression would entail screening children and adolescents, raising potentially serious ethical issues of consent and stigmatization. Genetic research on depression should continue under appropriate ethical guidelines that protect the interests of research participants.

Ethical aspects of research into the etiology of autism

Advances in understanding autism and other developmental neuropsychiatric disorders will come from an integration of various research strategies including phenomenologic, functional neuroimaging, and pharmacologic methods, as well as epidemiologic approaches aimed at identifying genetic and environmental risk factors. The highly heritable nature of autism makes it scientifically valuable to involve parents and siblings as research participants. However, many studies on autism pose ethical challenges because they do not offer the prospect of direct benefit to subjects. In this article, we present an in-depth ethical analysis of current nontherapeutic research strategies that are common in autism research. The ethical analysis applies a proposed ethical framework for evaluating clinical research focusing on seven ethical requirements: (1) social or scientific value, (2) scientific validity, (3) fair subject selection, (4) favorable risk-benefit ratio, (5) independent review, (6) informed consent, and (7) respect for potential and enrolled research participants.

Signaling networks in the pathophysiology and treatment of mood disorders

Over the past decade, the focus of research into the pathophysiology of mood disorders (bipolar disorder and unipolar depression in particular) has shifted from an interest in the biogenic amines to an emphasis on second messenger systems within cells. Second messenger systems rely on cell membrane receptors to relay information from the extracellular environment to the interior of the cell. Within the cell, this information is processed and altered, eventually to the point where gene and protein expression patterns are changed. There is a preponderance of evidence implicating second messenger systems and their primary contact with the extracellular environment, G proteins, in the pathophysiology of mood disorders. After an introduction to G proteins and second messenger pathways, this review focuses on the evidence implicating G proteins and two second messenger systems-the adenylate cyclase (cyclic adenosine monophosphate, cAMP) and phosphoinositide (protein kinase C, PKC) intracellular signaling cascades-in the pathophysiology and treatment of bipolar disorder and unipolar depression. Emerging evidence implicates changes in cellular resiliency, neuroplasticity and additional cellular pathways in the pathophysiology of mood disorders. The systems discussed within this review have been implicated in neuroplastic processes and in modulation of many other cellular pathways, making them likely candidates for mediators of these findings.

Neurobiology of depression

Current treatments for depression are inadequate for many individuals, and progress in understanding the neurobiology of depression is slow. Several promising hypotheses of depression and antidepressant action have been formulated recently. These hypotheses are based largely on dysregulation of the hypothalamic-pituitary-adrenal axis and hippocampus and implicate corticotropin-releasing factor, glucocorticoids, brain-derived neurotrophic factor, and CREB. Recent work has looked beyond hippocampus to other brain areas that are also likely involved. For example, nucleus accumbens, amygdala, and certain hypothalamic nuclei are critical in regulating motivation, eating, sleeping, energy level, circadian rhythm, and responses to rewarding and aversive stimuli, which are all abnormal in depressed patients. A neurobiologic understanding of depression also requires identification of the genes that make individuals vulnerable or resistant to the syndrome. These advances will fundamentally improve the treatment and prevention of depression.

The DRD4 VNTR polymorphism influences reactivity to smoking cues

Recent research has indicated that craving for tobacco can be reliably elicited by exposure to smoking cues, suggesting that cue-elicited craving for tobacco may be a useful phenotype for research on genetic factors related to nicotine dependence. Given the potential role of dopamine in cue-elicited craving, the authors examined whether the DRD4 VNTR polymorphism is associated with cue-elicited craving for tobacco. Participants who were homozygous or heterozygous for the 7 repeat (or longer) allele were classified as DRD4 L, and all other participants were classified as DRD4 S. Participants were exposed to smoking cues before smoking either high-nicotine cigarettes or control cigarettes. Analyses suggested that participants in the L group demonstrated significantly greater craving, more arousal, less positive affect, and more attention to the smoking cues than did the participants in the S group.

Psychogenomics: opportunities for understanding addiction

The term psychogenomics is used here to describe the process of applying the powerful tools of genomics and proteomics to achieve a better understanding of the biological substrates of normal behavior and of diseases of the brain that manifest themselves as behavioral abnormalities. Applying psychogenomics to the study of drug addiction will lead to the identification of genes and their protein products that control the reward pathways of the brain and their adaptations to drugs of abuse, as well as variations in these genes that confer genetic risk for addiction and related disorders. The ultimate goal is to use this information to develop more effective treatments for these disorders as well as objective diagnostic tools, preventive measures, and eventually cures.

Genetics of affective disorders

Despite substantial evidence for heritability in affective disorders the contributing genes have proven elusive. Here we discuss the genetic epidemiology of depression, as well as methodological issues and results from molecular genetic studies. There has been rapid advances in genetics, genomics and statistical modelling, facilitating the search for molecular mechanisms underlying affective disorders and several strategies reviewed in this paper hold promise to provide progress in the field. Considering the poorly understood biological basis of vulnerability to affective disorders, the identification of genes involved in the pathophysiology will unravel mechanisms and pathways that could permit more personalized therapeutic strategies and result in new targets for pharmacological intervention.

Impact of molecular medicine on neuropsychiatry: the clinician's perspective

Clinical neuropsychiatry has traditionally relied on individual practitioner experience or the apprentice-training model for formulating cases and choosing treatment. Scientifically-based diagnostic criteria and treatment algorithms have been lacking in the overlap area between psychiatry and neurology, owing largely to the complexity of this population population. However, the novel application of new molecular technologies is promising to change the care of neuropsychiatric patients. This review will highlight recent advances in molecular medicine pertaining to neuropsychiatry.Introduction

Culture and psychopharmacology

In this brief review the authors strive to provide a broad overview of various factors that impinge on psychopharmacotherapeutic practices. The literature revealed an impressive progress in research focusing on the delineation of the biologic mechanisms responsible for cross-ethnic variations in psychotropic metabolism and effects. With the field progressing at an accelerating pace, there is little doubt that in the coming decade clinicians will be provided with a detailed map showing the prevalence and distribution of genetic polymorphisms of most, if not all, of the drug-metabolizing enzymes, and clinicians also will have an overall picture on what these polymorphisms mean clinically. At the same time, clinicians should also start to have a good grasp on the meaning of the variations of the genes that encode therapeutic targets of psychotropics (e.g., neurotransmitter transporters and receptors). Such genetic fingerprinting, which will soon become a clinical reality, will provide tremendous help in ensuring that pharmacotherapies are increasingly more individually tailored, taking into consideration each patients genetic makeups that vary substantially across ethnic groups. As exciting as these new developments will be, they are dwarfed by the challenges ahead on the cultural side of the equation. Issues that are still awaiting further clarification include the following: How do we assess patients' beliefs and expectations related to psychotropic treatment? How do we minimize the communication gaps between patients and clinicians who are often from divergent sociocultural backgrounds? To what extent, and in what ways, do cultural (environmental) factors interact with biologic factors, and what might be the most efficient way to systematically assess such interactions? Data that have emerged in the past several decades clearly indicate the importance of culture and ethnicity in influencing patients' psychopharmacological response. It is expected that continuing progress in the near future will bring a better understanding on the way these cultural and biologic processes, separately and in interaction with each other, mediate treatment responses. Such knowledge will be crucial for the optimal pharmacotherapeutic care of for the majority of patients who will increasingly be of diverse ethnic and cultural backgrounds and will represent a significant contribution to the field of psychopharmacology as a whole.

An animal model for the study of the genetic bases of behaviour in men: the multiple marker strains (MMS)

Animal models are often used for preclinical research on the neurobiology of psychiatric disorders. Whereas many are employed to screen new therapeutic agents, few of them are used to study the genetic bases of psychiatric diseases, probably because of the complex genetic determinism underlying quantitative behavioral traits such as mood, personality or intelligence. The present article presents a short review introducing an analysis model using mice: the marker strains model. Using this model it is possible both to display genetic determinism data and to locate some of the chromosomal fragments involved in the regulation of anxiogenic processes. At present it cannot accurately determine the position of one or more genes, but it does provide a valuable means of 'scanning' the genome for an approximation. Through genetic analysis, using the model, an attempt will be made to identify autosomal fragments which may be involved in two behavioural traits: anxiety and chemical-induced seizures. In this paper, after reviewing theoretical aspects of looking for genes involved in behaviour, we will successively introduce studies in genetic topics in psychiatric human studies as well as appropriated behavioural animal studies. Then we will present a genetic model in mice which allows us to locate chromosomal fragments associated with a behavioural trait: multiple marker strains.

The genetics of panic disorder

Of the anxiety disorders, panic disorder (PD) has been the most extensively studied from a genetic standpoint. Results of family studies have consistently demonstrated that PD runs in families, and twin studies indicate that genes contribute to this familiality. However, phenotypic and genetic complexity has made finding the specific genes involved in PD a challenge. There is still uncertainty about how best to define the phenotype for genetic studies and whether it is the clinical phenotype of PD or more latent psychologic and biologic traits that are inherited. To date, molecular genetic studies have suggested some chromosomal regions and genes that may contribute to risk, but none of these have been established. We review the genetic epidemiology of PD as well as recent molecular genetic studies of the disorder, and conclude with a discussion of promising strategies that attempt to uncover specific genetic loci involved in the etiology of PD.

Genetic risk: the new frontier for the duty to warn

Mental health professionals usually think of the "duty to warn" in the context of mental illness. However, two state appellate courts have endorsed a duty to warn when children of a patient may be at risk genetically for acquiring the disease of their parents. In these cases, the courts held that a physician's legal obligations extended beyond his or her patient to the patient's children. This article discusses these cases, as well as issues regarding implementation of such a duty and the implications for the physician-patient relationship in a health care environment that will be dominated increasingly by genetics issues. The article concludes that it is premature to apply a duty to warn to the treatment of mental illness and to concerns regarding future criminal behavior.

Genetic and imaging strategies in obsessive-compulsive disorder: potential implications for treatment development

In recent years, advances in brain research have resulted in a striking strategic shift in studies designed to develop new, effective treatments for neuropsychiatric disorders. This involves a multidisciplinary approach with recursive interactions among respective disciplines with the ultimate goal of contributing to treatment development. In this review we focus on treatment implications of brain imaging and molecular and pharmacogenetic studies in obsessive-compulsive disorder. Translational components of this research are addressed, including the potential for integrating advances in brain imaging and molecular and pharmacogenetic assessments as they may potentially relate to neurodiagnostic assessment and treatment development. Studies of putative susceptibility alleles in obsessive-compulsive disorder involving the serotonergic, glutamatergic, and dopaminergic systems may provide a focus for these divergent approaches. Taken together, neuroimaging and genetic methods may ultimately lead to a mechanistic understanding of the pathogenesis and maintenance of neuropsychiatric disorders such as obsessive-compulsive disorder that may, in turn, result in the development of new neurodiagnostic and treatment approaches.

DNA

The authors predict that in a few years, many areas of psychology will be awash in specific genes responsible for the widespread influence of genetics on behavior. As the focus shifts from finding genes (genomics) to understanding how genes affect behavior (behavioral genomics), it is important for the future of psychology as a science that pathways between genes and behavior be examined not only at the molecular biological level of cells or the neuroscience level of the brain but also at the psychological level of analysis. After a brief overview of quantitative genetic research, the authors describe how genes that influence complex traits like behavioral dimensions and disorders in human and nonhuman animals are being found. Finally, the authors discuss behavioral genomics and predict that DNA will revolutionize psychological research and treatment early in the 21st century.

Genes and addiction

Drug addiction, like all psychiatric disorders, is defined solely in behavioural terms. For example, addiction can be considered a loss of control over drug-taking, or compulsive drug-seeking and -taking despite horrendous consequences. Abnormal behaviours are a consequence of aberrant brain function, which means that it is a tangible goal to identify the biological underpinnings of addiction. The genetic basis of addiction encompasses two broad areas of enquiry. One of these is the identification of genetic variation in humans that partly determines susceptibility to addiction. The other is the use of animal models to investigate the role of specific genes in mediating the development of addiction. Whereas recent advances in this latter effort are heartening, a major challenge remains: to understand how the many genes implicated in rodent models interact to yield as complex a phenotype as addiction.

A regulatory polymorphism of the monoamine oxidase-A gene may be associated with variability in aggression, impulsivity, and central nervous system serotonergic responsivity

This study presents preliminary evidence of an association between polymorphic variation in the gene for monoamine oxidase-A (MAOA) and interindividual variability in aggressiveness, impulsivity and central nervous system (CNS) serotonergic responsivity. An apparently functional 30-bp VNTR in the promoter region of the X-chromosomal MAOA gene (MAOA-uVNTR), as well as a dinucleotide repeat in intron 2 (MAOA-CAn), was genotyped in a community sample of 110 men. All participants had completed standard interview and questionnaire measures of impulsivity, hostility and lifetime aggression history; in a majority of subjects (n=75), central serotonergic activity was also assessed by neuropsychopharmacologic challenge (prolactin response to fenfluramine hydrochloride). The four repeat variants of the MAOA-uVNTR polymorphism were grouped for analysis (alleles '1+ 4' vs. '2+3') based on prior evidence of enhanced transcriptional activity in MAOA promoter constructs with alleles 2 and 3 (repeats of intermediate length). Men in the 1/4 allele group scored significantly lower on a composite measure of dispositional aggressiveness and impulsivity (P<0.015) and showed more pronounced CNS serotonergic responsivity (P<0.02) than men in the 2/3 allele group. These associations were also significant on comparison of the more prevalent one and three alleles alone (encompassing 93% of subjects). Although in linkage disequilibrium with the MAOA-uVNTR polymorphism, MAOA-CAn repeat length variation did not vary significantly with respect to behavior or fenflluramine challenge in this sample. We conclude that the MAOA-uVNTR regulatory polymorphism may contribute, in part, to individual differences in both CNS serotonergic responsivity and personality traits germane to impulse control and antagonistic behavior.

Neurotransmitter dysfunction in patients with borderline personality disorder

Neurotransmitter system dysfunction may contribute to the borderline personality disorder traits of impulsive aggression and affective instability. This article reviews evidence from neurochemical assays, receptor-density studies, neuroendocrine-challenge paradigms, functional neuroimaging studies, and candidate-gene research, which converge to identify particular neurotransmitter systems that seem to be dysregulated in patients with borderline personality disorder.

Genetic studies of autism: from the 1970s into the millennium

Reviewers in the 1960s and early 1970s were skeptical about any substantial role for genetic factors in the etiology of autism. A realization that the 2% rate of autism in siblings (as estimated at that time) was far above the general population base rate, and that this suggested a possible high genetic liability, led to the first small-scale twin study of autism. The replicated evidence from both twin and family studies undertaken in the 1970s and 1980s indicated both strong genetic influences and the likelihood that they applied to a phenotype that was much broader than the traditional diagnostic category of autism. Medical and chromosomal findings also indicated genetic heterogeneity. Advances in molecular genetics led to genome-wide scans of affected relative pair samples with a positive log of the odds to base 10 score for a location on chromosome 7. The major remaining research challenges and the likely clinical benefits that should derive from genetic research are considered in relation to both current knowledge and that anticipated to emerge from research over the next decade.