Genetic variants in the DRD2 gene moderate the relationship between stressful life events and depressive symptoms in adults: cardiovascular risk in young Finns study

Sex-specific associations between circadian-related genes and depression in UK Biobank participants highlight links to glucose metabolism, inflammation and neuroplasticity pathways

Depressive disorders have increased in global prevalence, making improved management of these disorders a public health priority. Prior research has linked circadian clock genes to depression, either through direct interactions with mood-related pathways in the brain or by modulating the phase of circadian rhythms. Using machine learning and statistical techniques, we explored associations between 157,347 SNP variants from 51 circadian-related genes and depression scores from the patient health questionnaire 9 (PHQ-9) in 99,939 UK Biobank participants. Our results highlight multiple pathways linking the circadian system to mood, including metabolic, monoamine, immune, and stress-related pathways. Notably, genes regulating glucose metabolism and inflammation (GSK3B, LEP, RORA, and NOCT) were prominent factors in females, in addition to DELEC1 and USP46, two genes of unknown function. In contrast, FBXL3 and DRD4 emerged as significant risk factors for male depression. We also found epistatic interactions involving RORA, NFIL3, and ZBTB20 as either risk or protective factors for depression, underscoring the importance of transcription factors (ZBTB20, NFIL3) and hormone receptors (RORA) in depression etiology. Understanding the complex, sex-specific links between circadian genes and mood disorders will facilitate the development of therapeutic interventions and enhance the efficacy of multi-target treatments for depression.

ADHD co-morbidities: A review of implication of gene × environment effects with dopamine-related genes

ADHD is a major burden in adulthood, where co-morbid conditions such as depression, substance use disorder and obesity often dominate the clinical picture. ADHD has substantial shared heritability with other mental disorders, contributing to comorbidity. However, environmental risk factors exist but their interaction with genetic makeup, especially in relation to comorbid disorders, remains elusive. This review for the first time summarizes present knowledge on gene x environment (GxE) interactions regarding the dopamine system. Hitherto, mainly candidate (GxE) studies were performed, focusing on the genes DRD4, DAT1 and MAOA. Some evidence suggest that the variable number tandem repeats in DRD4 and MAOA may mediate GxE interactions in ADHD generally, and comorbid conditions specifically. Nevertheless, even for these genes, common variants are bound to suggest risk only in the context of gender and specific environments. For other polymorphisms, evidence is contradictory and less convincing. Particularly lacking are longitudinal studies testing the interaction of well-defined environmental with polygenic risk scores reflecting the dopamine system in its entirety.

Functional Polymorphisms in Oxytocin and Dopamine Pathway Genes and the Development of Dispositional Compassion Over Time: The Young Finns Study

Background: We define compassion as an enduring disposition that centers upon empathetic concern for another person's suffering and the motivation to act to alleviate it. The contribution of specific candidate genes to the development of dispositional compassion for others is currently unknown. We examine candidate genes in the oxytocin and dopamine signaling pathways.

Methods: In a 32-year follow-up of the Young Finns Study (N = 2,130, 44.0% men), we examined with multiple indicators latent growth curve modeling the molecular genetic underpinnings of dispositional compassion for others across the life span. We selected five single nucleotide polymorphisms (SNPs) whose functions are known in humans: rs2268498 (OXTR), rs3796863 (CD38) (related to lower oxytocin levels), rs1800497 (ANKK1/DRD2), rs4680 (COMT), and rs1611115 (DBH) (related to higher dopamine levels). Compassion was measured with Cloninger's Temperament and Character Inventory on three repeated observations spanning 15 years (1997–2012). Differences between gender were tested.

Results: We did not find an effect of the five SNPs in oxytocin and dopamine pathway genes on the initial levels of dispositional compassion for others. Individuals who carry one or two copies of the T-allele of DBH rs1611115, however, tend to increase faster in compassion over time than those homozygotes for the C-allele, b = 0.063 (SE = 0.027; p = 0.018). This effect was largely driven by male participants, 0.206 (SE = 0.046; p < 0.001), and was not significant in female participants when analyzed separately.

Conclusions: Men who are known to have, on average, lower compassion than women seem to reduce this difference over time if they carry the T-allele of DBH rs1611115. The direction of the association indicates that dopamine signaling activity rather than overall dopamine levels might drive the development of compassion.

Uncovering the complex genetics of human character

Human personality is 30-60% heritable according to twin and adoption studies. Hundreds of genetic variants are expected to influence its complex development, but few have been identified. We used a machine learning method for genome-wide association studies (GWAS) to uncover complex genotypic-phenotypic networks and environmental interactions. The Temperament and Character Inventory (TCI) measured the self-regulatory components of personality critical for health (i.e., the character traits of self-directedness, cooperativeness, and self-transcendence). In a discovery sample of 2149 healthy Finns, we identified sets of single-nucleotide polymorphisms (SNPs) that cluster within particular individuals (i.e., SNP sets) regardless of phenotype. Second, we identified five clusters of people with distinct profiles of character traits regardless of genotype. Third, we found 42 SNP sets that identified 727 gene loci and were significantly associated with one or more of the character profiles. Each character profile was related to different SNP sets with distinct molecular processes and neuronal functions. Environmental influences measured in childhood and adulthood had small but significant effects. We confirmed the replicability of 95% of the 42 SNP sets in healthy Korean and German samples, as well as their associations with character. The identified SNPs explained nearly all the heritability expected for character in each sample (50 to 58%). We conclude that self-regulatory personality traits are strongly influenced by organized interactions among more than 700 genes despite variable cultures and environments. These gene sets modulate specific molecular processes in brain for intentional goal-setting, self-reflection, empathy, and episodic learning and memory.

Prediction and Understanding of Resilience in Albertan Families: Longitudinal Study of Disaster Responses (PURLS) - Protocol

Exposure to a natural disaster in childhood can have serious, long-lasting consequences, impacting physical and mental health, development, and learning. Although many children experience negative effects after a disaster, the majority do not, and what differentiates these groups is not well understood. Some of the factors that influence disaster-related outcomes in the midst of adversity include parents' mental health, the home environment, and socioeconomic status. Furthermore, genetics has also a role to play in how children respond to stressors. We had the opportunity to conduct a natural experiment of disaster recovery following the Alberta 2013 Flood. This paper presents the detailed protocol on prediction of resilience in Albertan families, and validation with cortisol data. In addition, data collection procedures, developing resiliency screening tools, candidate gene identification, genotyping, DNA methylation, and genomic analyses are described to achieve the research objectives. This study produced new knowledge by using pre- and post-disaster information on children's health and development, including children's genetics and responses to stress. This information has been identified as important to governments and other organizations invested in early child development. Our comprehensive research plan generates evidence that can be mobilized population-based approaches to improve child and family resiliency.

The CogBIAS longitudinal study protocol: cognitive and genetic factors influencing psychological functioning in adolescence

BACKGROUND

Optimal psychological development is dependent upon a complex interplay between individual and situational factors. Investigating the development of these factors in adolescence will help to improve understanding of emotional vulnerability and resilience. The CogBIAS longitudinal study (CogBIAS-L-S) aims to combine cognitive and genetic approaches to investigate risk and protective factors associated with the development of mood and impulsivity-related outcomes in an adolescent sample.

METHODS

CogBIAS-L-S is a three-wave longitudinal study of typically developing adolescents conducted over 4 years, with data collection at age 12, 14 and 16. At each wave participants will undergo multiple assessments including a range of selective cognitive processing tasks (e.g. attention bias, interpretation bias, memory bias) and psychological self-report measures (e.g. anxiety, depression, resilience). Saliva samples will also be collected at the baseline assessment for genetic analyses. Multilevel statistical analyses will be performed to investigate the developmental trajectory of cognitive biases on psychological functioning, as well as the influence of genetic moderation on these relationships.

DISCUSSION

CogBIAS-L-S represents the first longitudinal study to assess multiple cognitive biases across adolescent development and the largest study of its kind to collect genetic data. It therefore provides a unique opportunity to understand how genes and the environment influence the development and maintenance of cognitive biases and provide insight into risk and protective factors that may be key targets for intervention.

Childhood quality influences genetic sensitivity to environmental influences across adulthood: A life-course Gene × Environment interaction study

While environmental adversity has been shown to increase risk for psychopathology, individuals differ in their sensitivity to these effects. Both genes and childhood experiences are thought to influence sensitivity to the environment, and these factors may operate synergistically such that the effects of childhood experiences on later sensitivity are greater in individuals who are more genetically sensitive. In line with this hypothesis, several recent studies have reported a significant three-way interaction (Gene × Environment × Environment) between two candidate genes and childhood and adult environment on adult psychopathology. We aimed to replicate and extend these findings in a large, prospective multiwave longitudinal study using a polygenic score of environmental sensitivity and objectively measured childhood and adult material environmental quality. We found evidence for both Environment × Environment and Gene × Environment × Environment effects on psychological distress. Children with a poor-quality material environment were more sensitive to the negative effects of a poor environment as adults, reporting significantly higher psychological distress scores. These effects were further moderated by a polygenic score of environmental sensitivity. Genetically sensitive children were more vulnerable to adversity as adults, if they had experienced a poor childhood environment but were significantly less vulnerable if their childhood environment was positive. These findings are in line with the differential susceptibility hypothesis and suggest that a life course approach is necessary to elucidate the role of Gene × Environment in the development of mental illnesses.

24-hour-restraint stress induces long-term depressive-like phenotypes in mice

There is an increasing risk of mental disorders, such as acute stress disorder (ASD), post-traumatic stress disorder (PTSD) and depression among survivors who were trapped in rubble during earthquake. Such long-term impaction of a single acute restraint stress has not been extensively explored. In this study, we subjected mice to 24-hour-restraint to simulate the trapping episode, and investigated the acute (2 days after the restraint) and long-term (35 days after the restraint) impacts. Surprisingly, we found that the mice displayed depression-like behaviors, decreased glucose uptake in brain and reduced adult hippocampal neurogenesis 35 days after the restraint. Differential expression profiling based on microarrays suggested that genes and pathways related to depression and other mental disorders were differentially expressed in both PFC and hippocampus. Furthermore, the depression-like phenotypes induced by 24-hour-restraint could be reversed by fluoxetine, a type of antidepressant drug. These findings demonstrated that a single severe stressful event could produce long-term depressive-like phenotypes. Moreover, the 24-hour-restraint stress mice could also be used for further studies on mood disorders.

Changes of dopamine transporter availability in depressed patients with and without anhedonia: a 123I-N-ω-fluoropropyl-carbomethoxy-3β- (4-Iodophenyl)tropane SPECT study

BACKGROUND/AIMS

Dopamine is an important neurotransmitter involved in the pathophysiology of depression and anhedonia. Dopamine transporters (DAT) may play a crucial role in the pathophysiology of dopaminergic transmission. We investigated the relationship between striatal DAT availability and depression, pointing out possible correlations with anhedonia and treatment outcomes.

METHODS

Ten depressed patients with anhedonia, 10 depressed patients without anhedonia and 20 healthy controls underwent single photon emission computed tomography using (123)I-FP-CIT [(123)I-N-ω-fluoropropyl-carbomethoxy-3β-(4-iodophenyl)tropane]. Psychometric measures included the Snaith-Hamilton Pleasure Scale and the Hamilton Depression Rating Scale. A further assessment of DAT availability was performed in the 10 patients with marked anhedonia after a 3-month pharmacological treatment.

RESULTS

Depressed patients with and without anhedonia showed significantly lower (123)I-FP-CIT binding ratios in the bilateral striatum, caudate and putamen. No significant changes were detected after treatment in the 10 patients with marked anhedonia. When considering clinical outcomes, subjects with remission of depression showed a significant reduction of (123)I-FP-CIT binding ratios in all regions at baseline, but after treatment no differences were found any longer.

CONCLUSIONS

We suppose that a hypofunction of the striatal dopaminergic system may be a 'state' feature of a depressive condition as a whole rather than anhedonia itself. On the other hand, some anhedonic features mainly represent an enduring trait that persists independently of mood state.

Mesocorticolimbic dopamine functioning in primary psychopathy: A source of within-group heterogeneity

Despite similar emotional deficiencies, primary psychopathic individuals can be situated on a continuum that spans from controlled to disinhibited. The constructs on which primary psychopaths are found to diverge, such as self-control, cognitive flexibility, and executive functioning, are crucially regulated by dopamine (DA). As such, the goal of this review is to examine which specific alterations in the meso-cortico-limbic DA system and corresponding genes (e.g., TH, DAT, COMT, DRD2, DRD4) might bias development towards a more controlled or disinhibited expression of primary psychopathy. Based on empirical data, it is argued that primary psychopathy is generally related to a higher tonic and population activity of striatal DA neurons and lower levels of D2-type DA receptors in meso-cortico-limbic projections, which may boost motivational drive towards incentive-laden goals, dampen punishment sensitivity, and increase future reward-expectancy. However, increasingly higher levels of DA activity in the striatum (moderate versus pathological elevations), lower levels of DA functionality in the prefrontal cortex, and higher D1-to-D2-type receptor ratios in meso-cortico-limbic projections may lead to increasingly disinhibited and impetuous phenotypes of primary psychopathy. Finally, in order to provide a more coherent view on etiological mechanisms, we discuss interactions between DA and serotonin that are relevant for primary psychopathy.

Polygenic risk, stressful life events and depressive symptoms in older adults: a polygenic score analysis

BACKGROUND

Previous studies suggest that the relationship between genetic risk and depression may be moderated by stressful life events (SLEs). The goal of this study was to assess whether SLEs moderate the association between polygenic risk of major depressive disorder (MDD) and depressive symptoms in older adults.

METHOD

We used logistic and negative binomial regressions to assess the associations between polygenic risk, SLEs and depressive symptoms in a sample of 8761 participants from the Health and Retirement Study. Polygenic scores were derived from the Psychiatric Genomics Consortium genome-wide association study of MDD. SLEs were operationalized as a dichotomous variable indicating whether participants had experienced at least one stressful event during the previous 2 years. Depressive symptoms were measured using an eight-item Center for Epidemiologic Studies Depression Scale subscale and operationalized as both a dichotomous and a count variable.

RESULTS

The odds of reporting four or more depressive symptoms were over twice as high among individuals who experienced at least one SLE (odds ratio 2.19, 95% confidence interval 1.86-2.58). Polygenic scores were significantly associated with depressive symptoms (β = 0.21, p ⩽ 0.0001), although the variance explained was modest (pseudo r 2 = 0.0095). None of the interaction terms for polygenic scores and SLEs was statistically significant.

CONCLUSIONS

Polygenic risk and SLEs are robust, independent predictors of depressive symptoms in older adults. Consistent with an additive model, we found no evidence that SLEs moderated the association between common variant polygenic risk and depressive symptoms.

The Dopamine D2 Receptor Polymorphism (DRD2 TaqIA) Interacts with Maternal Parenting in Predicting Early Adolescent Depressive Symptoms: Evidence of Differential Susceptibility and Age Differences

Most gene-environment interaction research on depression has largely focused on negative environment and to a lesser extent on positive environment. Moreover, to date few studies have directly examined G × E at different periods in development, particularly during early adolescence. The present study addressed these issues by examining the concurrent and prospective longitudinal effects of maternal parenting, DRD2 TaqIA polymorphism, and their interaction on adolescent depressive symptoms in a sample of 1026 Chinese adolescents (Mage = 11.33 ± 0.47 years at T1, 50.3% girls) in a three-wave longitudinal study from age 11 to 13. Results indicated that maternal positive and negative parenting significantly concurrently predicted adolescent depressive symptoms at all three waves, whereas TaqIA polymorphism had no main effect on depressive symptoms. TaqIA polymorphism interacted with negative parenting in predicting concurrent depressive symptoms at age 11 and 12. A1 carriers were more susceptible to negative parenting compared to A2A2 homozygotes, such that adolescents carrying A1 alleles experiencing high negative parenting reported more depressive symptoms but fared better when experiencing low negative parenting. However, the interaction became nonsignificant at age 13, indicating the interaction of TaqIA polymorphism and maternal parenting may vary with development. Also, there was no G × E effect on longitudinal change in depression. The findings provided evidence in support of the differential susceptibility hypothesis and shed light on the potential for dynamic change in gene-environment interactions over development.

Antidepressant drug development: Focus on triple monoamine reuptake inhibition

Many patients with major depressive disorder (MDD) only partially respond, and some have no clinically meaningful response, to current widely used antidepressant drugs. Due to the purported role of dopamine in the pathophysiology of depression, triple-reuptake inhibitors (TRIs) that simultaneously inhibit serotonin (5-HT), norepinephrine (NE) and dopamine reuptake could be a useful addition to the armamentarium of treatments for MDD. A TRI should more effectively activate mesolimbic dopamine-related reward-networks, restore positive mood and reduce potent 5-HT reuptake blockade associated "hypodopaminergic" adverse effects of decreased libido, weight gain and "blunting" of emotions. On the other hand, dopaminergic effects raise concern over abuse liability and TRIs may have many of the cardiovascular effects associated with NET inhibition. Several clinical development programs for potential TRI antidepressants have failed to demonstrate significantly greater efficacy than placebo or standard of care. Successful late-stage clinical development of a TRI is more likely if experimental research studies in the target population of depressed patients have demonstrated target engagement that differentially and dose-dependently improves assessments of reward-network dysfunction relative to existing antidepressants. TRI treatment could be individualized on the basis of predictive markers such as the burden of decreased positive mood symptoms and/or neuroimaging evidence of reward network dysfunction. This review focuses on how the next generation of monoamine-based treatments could be efficiently developed to address unmet medical need in MDD.

Biological determinants of depression following bereavement

There is considerable variability among people in their response to bereavement. While most people adapt well to bereavement, some develop exaggerated and/or pathological responses and may meet criteria for a major depressive episode. Many studies have investigated the effect of psychosocial factors on bereavement outcome but biological factors have not received much attention, hence the focus of this paper. The biological factors studied to date in relation to bereavement outcomes include genetic polymorphisms, neuroendocrine factors, and immunologic/inflammatory markers. In addition, animal studies have shown the alterations of brain neurotransmitters as well as changes in the plasma levels of the neurotrophic growth factors under the influence of peer loss. Recent studies have also investigated the biological basis of stress resilience, and have found a few genetic polymorphisms and potential biomarkers as protective factors in the face of adversity. Longitudinal studies that include data collection prior to, and also after, bereavement and which chart both biological and psychological measures are needed to develop profiles for the prediction of response to bereavement and personalised interventions.

Differential susceptibility to effects of maternal sensitivity? A study of candidate plasticity genes

Here we tested whether there was genetic moderation of effects of early maternal sensitivity on social–emotional and cognitive–linguistic development from early childhood onward and whether any detected Gene × Environment interaction effects proved consistent with differential-susceptibility or diathesis–stress models of Person × Environment interaction (N= 695). Two new approaches for evaluating models were employed with 12 candidate genes. Whereas maternal sensitivity proved to be a consistent predictor of child functioning across the primary-school years, candidate genes did not show many main effects, nor did they tend to interact with maternal sensitivity/insensitivity. These findings suggest that the developmental benefits of early sensitive mothering and the costs of insensitive mothering look more similar than different across genetically different children in the current sample. Although acknowledgement of this result is important, it is equally important that the generally null Gene × Environment results reported here not be overgeneralized to other samples, other predictors, other outcomes, and other candidate genes.

Stressful life events and depressive symptoms among symptomatic long QT syndrome patients

We examined whether long QT syndrome status moderates the association between stressful life events and depressive symptoms. Participants were 562 ( n = 246 symptomatic) long QT syndrome mutation carriers. Depressive symptoms were measured with a modified version of the Beck’s Depression Inventory. There was an interaction between long QT syndrome status and stressful life events on depressive symptoms. In the symptomatic long QT syndrome patients, stressful life events were associated with depressive symptoms ( B = 0.24, p < 0.001). In the asymptomatic long QT syndrome mutation carriers, this association was 62.5 percent weaker ( B = 0.09, p = 0.057). Compared to asymptomatic long QT syndrome mutation carriers, symptomatic long QT syndrome patients are more sensitive to the depressive effects of stressful life events.

The DRD2 rs1800497 polymorphism increase the risk of mood disorder: evidence from an update meta-analysis

BACKGROUND

Growing studies have revealed the association between rs1800497 polymorphism in the dopamine receptor D2 (DRD2) and susceptibility to mood disorder (MD). However, the results remained inconsistent.

METHODS

To assess the effect of DRD2 rs1800497 polymorphism on MD. We performed a meta-analysis based on eight case-control studies, including a total of 2097 MD cases and 1681 controls. Summary odds ratios (OR) and corresponding 95% confidence intervals (CIs) for DRD2 rs1800497 polymorphism and MD risk were estimated.

RESULTS

Our meta-analysis indicated that DRD2 rs1800497 was associated with an increased MD risk, especially in Asians. Moreover, in the subgroup analysis by the type of MD, DRD2 rs1800497 polymorphism was observed to increase risk in BP.

LIMITATIONS

The results should be treated with caution for lacking of data to perform gene-gene and gene-environment interaction.

CONCLUSIONS

Our results indicated that polymorphism in DRD2 rs1800497 may play a role in development of MD.

Imaging studies on dopamine transporter and depression: a review of literature and suggestions for future research

We review the conflicting results from imaging studies of dopamine transporter availability in depressed patients and also discuss the heterogeneity of the variables involved. Major depression includes diverse clinical manifestations and in recent years there has been an increasing interest in the identification of homogeneous phenotypes and different clinical subtypes of depression, e.g. anhedonic depression, retarded depression, etc. In addition, the use of different radioligands and imaging techniques, diverse rating scales, together with the lack of control of clinical variables (clinical course, recent or past use of substances of abuse, etc.) make it difficult to clearly identify neuronal regions or networks with consistently abnormal structures or functions in major depressive disorder. It is probably necessary to build a shared approach between clinicians and researchers in order to identify standardized procedures to better understand the role of the dopamine transporter in depression. We outline a list of major issues and also suggest some standardized procedures in collecting clinical and imaging data on major depressed patients. Our aim is to delineate a possible "modus operandi" that would be a proposal for neuroreceptor studies on major depression.

Brief report: Emotional distress and recent stressful life events in long QT syndrome mutation carriers

To study emotional distress in symptomatic and asymptomatic long QT syndrome mutation carriers who had experienced a recent stressful life event. The participants were 209 symptomatic and 279 asymptomatic long QT syndrome mutation carriers. Emotional distress was assessed with the Cope questionnaire and stressful life events with the Social Readjustment Rating Scale. Symptomatic long QT syndrome mutation carriers with burdening recent stressful life events reported a higher emotional distress (β = 0.35, p < 0.001), while the asymptomatic did not show such difference (β = 0.13, p = 0.393). Symptomatic long QT syndrome mutation carriers who have experienced stressful life events recently report an increased emotional distress.

The psychodynamic psychotherapist's guide to the interaction among sex, genes, and environmental adversity in the etiology of depression for women

From menarche to menopause, women are highly vulnerable to major depression. While biological and psychosocial differences between men and women have been established, the reason for the preponderance of depression in women has yet to be fully elucidated. Women may be predisposed to depressive illness because of biological factors related to brain structure, function, and the impact of reproductive life stages. They may also be at increased risk because they are differentially disadvantaged with respect to environmental stressors including interpersonal violence, socioeconomic instability, and caregiving burden, among others. However, not all women develop depression, nor do all individuals who suffer from adverse life events. This narrative review focuses on emerging research related to the interaction between sex, genetics, and environmental factors that may help offer clues about why some individuals suffer from depression, and why others may be resilient to this outcome. While many questions remain unanswered, the psychodynamic psychotherapist can use this information to help patients suffering from depression understand some of the complexities of the determinants of risk and resilience, with the goal of moving forward toward recovery.

Assessment of genetic and nongenetic interactions for the prediction of depressive symptomatology: an analysis of the Wisconsin Longitudinal Study using machine learning algorithms

OBJECTIVES

We examined depression within a multidimensional framework consisting of genetic, environmental, and sociobehavioral factors and, using machine learning algorithms, explored interactions among these factors that might better explain the etiology of depressive symptoms.

METHODS

We measured current depressive symptoms using the Center for Epidemiologic Studies Depression Scale (n = 6378 participants in the Wisconsin Longitudinal Study). Genetic factors were 78 single nucleotide polymorphisms (SNPs); environmental factors-13 stressful life events (SLEs), plus a composite proportion of SLEs index; and sociobehavioral factors-18 personality, intelligence, and other health or behavioral measures. We performed traditional SNP associations via logistic regression likelihood ratio testing and explored interactions with support vector machines and Bayesian networks.

RESULTS

After correction for multiple testing, we found no significant single genotypic associations with depressive symptoms. Machine learning algorithms showed no evidence of interactions. Naïve Bayes produced the best models in both subsets and included only environmental and sociobehavioral factors.

CONCLUSIONS

We found no single or interactive associations with genetic factors and depressive symptoms. Various environmental and sociobehavioral factors were more predictive of depressive symptoms, yet their impacts were independent of one another. A genome-wide analysis of genetic alterations using machine learning methodologies will provide a framework for identifying genetic-environmental-sociobehavioral interactions in depressive symptoms.

Ventral striatum reactivity to reward and recent life stress interact to predict positive affect

BACKGROUND

Stressful life events are among the most reliable precipitants of major depressive disorder; yet, not everyone exposed to stress develops depression. It has been hypothesized that robust neural reactivity to reward and associated stable levels of positive affect (PA) may protect against major depressive disorder in the context of environmental adversity. However, little empirical data exist to confirm this postulation. Here, we test the hypothesis that individuals with relatively low ventral striatum (VS) reactivity to reward will show low PA levels in the context of recent life stress, while those with relatively high VS reactivity will be protected against these potentially depressogenic effects.

METHODS

Differential VS reactivity to positive feedback was assessed using blood oxygen level-dependent functional magnetic resonance imaging in a sample of 200 nonpatient young adults. Recent life stress, current depressive symptoms, and PA were assessed via self-report. Linear regression models were used to investigate the moderating effects of VS reactivity on the relationship between recent stress and state PA across participants.

RESULTS

Recent life stress interacted with VS reactivity to predict self-reported state PA, such that higher levels of life stress were associated with lower PA for participants with relatively low, but not for those with high, VS reactivity. These effects were independent of age, gender, race/ethnicity, trait PA, and early childhood trauma.

CONCLUSIONS

The current results provide empirical evidence for the potentially protective role of robust reward-related neural responsiveness against reductions in PA that may occur in the wake of life stress and possibly vulnerability to depression precipitated by stressful life events.

The influence of five monoamine genes on trajectories of depressive symptoms across adolescence and young adulthood

The influence of five monoamine candidate genes on depressive symptom trajectories in adolescence and young adulthood were examined in the Add Health genetic sample. Results indicated that, for all respondents, carriers of the dopamine receptor D4 5-repeat allele were characterized by distinct depressive symptom trajectories across adolescence and early adulthood. Similarly, for males, individuals with the monoamine oxidase A 3.5-repeat allele exhibited unique depressive symptom trajectories. Specifically, the trajectories of those with the dopamine receptor D4 5-repeat allele were characterized by rising levels in the transition to adulthood, while their peers were experiencing a normative drop in depressive symptom frequency. Conversely, males with the monoamine oxidase A 3.5-repeat allele were shown to experience increased distress in late adolescence. An empirical method for examining a wide array of allelic combinations was employed, and false discovery rate methods were used to control the risk of false positives due to multiple testing. Special attention was given to thoroughly interrogate the robustness of the putative genetic effects. These results demonstrate the value of combining dynamic developmental perspectives with statistical genetic methods to optimize the search for genetic influences on psychopathology across the life course.

Gene-environment interaction and the intergenerational transmission of parenting: testing the differential-susceptibility hypothesis

The current study evaluated the differential-susceptibility hypothesis in explaining the intergenerational transmission of parenting, using data from the National Longitudinal Study of Adolescent Health (Add Health). Exposure to maternal parenting was measured prospectively when respondents were adolescents and parental stress was measured when they were parents themselves, some 14 years later, on average. Cumulative-genetic plasticity was measured by dominantly coding the presence of putative plasticity alleles from four genes: the 10R allele of DAT1, the A1 allele of DRD2, the 7R allele of DRD4, and the short allele of 5HTTLPR. Results showed that the more plasticity alleles individuals carried (range 0-4), the more that parenting experienced in adolescence predicted future parenting experience. Those respondents with the most plasticity alleles not only experienced the highest levels of parental stress when exposed to negative maternal parenting in adolescence but the lowest levels when exposed to positive maternal parenting in adolescence. These results indicate that differential susceptibility is operative in the case of the intergenerational transmission of parenting, which could explain why estimates of such transmission have proven so modest in studies which fail to consider GXE interactions.

The dopamine D2 receptor gene, perceived parental support, and adolescent loneliness: longitudinal evidence for gene-environment interactions

BACKGROUND

Loneliness is a common problem in adolescence. Earlier research focused on genes within the serotonin and oxytocin systems, but no studies have examined the role of dopamine-related genes in loneliness. In the present study, we focused on the dopamine D2 receptor gene (DRD2).

METHODS

Associations among the DRD2, sex, parental support, and loneliness were examined in a longitudinal study spanning five annual waves (N = 307).

RESULTS

Using Latent Growth Curve Modeling, DRD2 genotype was not directly related to loneliness. Interactions were found between parental support and DRD2 genotype, showing that adolescents with the A2A2 genotype who perceived little support from their parents had the highest baseline levels of loneliness. Adolescents with an A1 allele were not susceptible to the rewarding effect of parental support.

CONCLUSIONS

The present study is the first to examine the role of the DRD2 genotype in loneliness. Our results contribute to a further understanding of the environmental and genetic basis of loneliness in adolescence.

Influence and interaction of genetic polymorphisms in catecholamine neurotransmitter systems and early life stress on antidepressant drug response

BACKGROUND

Catecholamine neurotransmission plays an important role in major depression. Variation in genes implicated in the synthesis and signal transduction of catecholamines (norepinephrine and dopamine) may interact with environmental factors to affect the outcome of antidepressant treatment. We aimed to determine how a range of polymorphisms in noradrenergic and dopaminergic genes influence this response to treatment and how they interact with childhood trauma and recent life stress in a Chinese sample.

METHODS

In a sample of 308 Chinese Han patients with major depressive disorder, 13 single nucleotide polymorphisms (SNPs) in coding regions of six genes (MAOA, SLC6A2, TH, COMT, DRD2, DRD3) with minor allele frequencies >5% were successfully genotyped from an initial series of 35 SNPs in 11 candidate genes associated with catecholamine neurotransmission. The responses to 6 weeks' treatment with antidepressant drugs was determined by changes in the 17-item Hamilton Depression Rating Scale (HAMD-17) score, and previous stressful events were evaluated by the Life Events Scale (LES) and Childhood Trauma Questionnaire-Short Form (CTQ-SF). Single SNP and haplotype associations with treatment response were analysed by UNPHASED 3.0.13, gene-gene interactions were analysed by generalized multifactor dimensionality reduction (GMDR) and gene-environment interactions by logistic regression.

RESULTS

A haplotype in MAOA (rs1137070 and rs6323) was significantly associated with antidepressant response in the total group, the nonSSRI subgroup and the female subgroup. Two haplotypes in COMT (involving rs4633, rs4818 and rs769224) were significantly associated with antidepressant response in the nonSSRI subgroup. The SLC6A2 SNPs interacted with childhood trauma to influence antidepressant response.

CONCLUSIONS

A haplotype in MAOA and two haplotypes in COMT are found to be associated with antidepressant treatment response in this sample. Stressors in early life may interact with polymorphisms in SLC6A2 to influence response to antidepressant treatment.

Interaction of early environment, gender and genes of monoamine neurotransmission in the aetiology of depression in a large population-based Finnish birth cohort

Objectives Depression is a worldwide leading cause of morbidity and disability. Genetic studies have recently begun to elucidate its molecular aetiology. The authors investigated candidate genes of monoamine neurotransmission and early environmental risk factors for depressiveness in the genetically isolated population-based Northern Finland Birth Cohort 1966 (12 058 live births). Design The authors ascertained and subdivided the study sample (n=5225) based on measures of early development and of social environment, and examined candidate genes of monoamine neurotransmission, many of which have shown prior evidence of a gene-environment interaction for affective disorders, namely SLC6A4, TPH2, COMT, MAOA and the dopamine receptor genes DRD1-DRD5. Results and conclusion The authors observed no major genetic effects of the analysed variants on depressiveness. However, when measures of early development and of social environment were considered, some evidence of interaction was observed. Allelic variants of COMT interacted with high early developmental risk (p=0.005 for rs2239393 and p=0.02 for rs4680) so that the association with depression was detected only in individuals at high developmental risk group (p=0.0046 and β=0.056 for rs5993883-rs2239393-rs4680 risk haplotype CGG including Val158), particularly in males (p=0.0053 and β=0.083 for the haplotype CGG). Rs4274224 from DRD2 interacted with gender (p=0.017) showing a significant association with depressiveness in males (p=0.0006 and β=0.0023; p=0.00005 and β=0.069 for rs4648318-rs4274224 haplotype GG). The results support the role of genes of monoamine neurotransmission in the aetiology of depression conditional on environmental risk and sex, but not direct major effects of monoaminergic genes in this unselected population.

Dysfunctional attitudes and the serotonin transporter promoter polymorphism (5-HTTLPR)

Dysfunctional attitudes may be one phenotype by which genes increase risk for depression. Building on research demonstrating associations between serotonin abnormalities and dysfunctional attitudes, we examined the covariation between dysfunctional attitudes and the serotonin transporter gene-linked polymorphic region (5-HTTLPR). In a sample of nondepressed young adults (N=131), people with one or two copies of the low-expressing alleles reported stronger endorsement of dysfunctional attitudes regarding performance evaluation than people who were homozygous for the high-expressing alleles; there was no association between the 5-HTTLPR polymorphism and dysfunctional attitudes regarding approval by others. These results add to the literature linking the 5-HTTLPR polymorphism and cognitive vulnerabilities for depression.

Convergent functional genomics of anxiety disorders: translational identification of genes, biomarkers, pathways and mechanisms

Anxiety disorders are prevalent and disabling yet understudied from a genetic standpoint, compared with other major psychiatric disorders such as bipolar disorder and schizophrenia. The fact that they are more common, diverse and perceived as embedded in normal life may explain this relative oversight. In addition, as for other psychiatric disorders, there are technical challenges related to the identification and validation of candidate genes and peripheral biomarkers. Human studies, particularly genetic ones, are susceptible to the issue of being underpowered, because of genetic heterogeneity, the effect of variable environmental exposure on gene expression, and difficulty of accrual of large, well phenotyped cohorts. Animal model gene expression studies, in a genetically homogeneous and experimentally tractable setting, can avoid artifacts and provide sensitivity of detection. Subsequent translational integration of the animal model datasets with human genetic and gene expression datasets can ensure cross-validatory power and specificity for illness. We have used a pharmacogenomic mouse model (involving treatments with an anxiogenic drug--yohimbine, and an anti-anxiety drug--diazepam) as a discovery engine for identification of anxiety candidate genes as well as potential blood biomarkers. Gene expression changes in key brain regions for anxiety (prefrontal cortex, amygdala and hippocampus) and blood were analyzed using a convergent functional genomics (CFG) approach, which integrates our new data with published human and animal model data, as a translational strategy of cross-matching and prioritizing findings. Our work identifies top candidate genes (such as FOS, GABBR1, NR4A2, DRD1, ADORA2A, QKI, RGS2, PTGDS, HSPA1B, DYNLL2, CCKBR and DBP), brain-blood biomarkers (such as FOS, QKI and HSPA1B), pathways (such as cAMP signaling) and mechanisms for anxiety disorders--notably signal transduction and reactivity to environment, with a prominent role for the hippocampus. Overall, this work complements our previous similar work (on bipolar mood disorders and schizophrenia) conducted over the last decade. It concludes our programmatic first pass mapping of the genomic landscape of the triad of major psychiatric disorder domains using CFG, and permitted us to uncover the significant genetic overlap between anxiety and these other major psychiatric disorders, notably the under-appreciated overlap with schizophrenia. PDE10A, TAC1 and other genes uncovered by our work provide a molecular basis for the frequently observed clinical co-morbidity and interdependence between anxiety and other major psychiatric disorders, and suggest schizo-anxiety as a possible new nosological domain.

DRD2/ANKK1 TaqI A polymorphism affects corticostriatal activity in response to negative affective facial stimuli

DRD2/ANKK1 TaqI A polymorphism has been suggested to be involved in a reward-related psychiatric disorders. However, the effect of Dopamine receptor D2 (DRD2) on emotional processing has not been investigated yet. We investigated the possible relationship between DRD2/ANKK1 TaqI A polymorphism and corticostriatal response to negative facial stimuli using functional magnetic resonance imaging. All participants were genotyped with regard to the DRD2/ANKK1 TaqI A polymorphism. Our results suggest an association between the DRD2/ANKK1 TaqI A polymorphism and activations in the putamen, the anterior cingulate cortex, and amygdala in response to negative facial stimuli. Furthermore, molecular heterosis at the TaqI polymorphism of DRD2/ANKK1 may play an important role in affective regulation by corticostriatal pathway.

Droplets of black bile? Development of vulnerability and resilience to depression in young age

Major depressive disorder is predicted by enduring anxiety-related personality traits, in particular by neuroticism, which have genetic foundations. Neuroticism in turn is strongly related with the genetic risk for depression. Search for gene variants associated with neuroticism and depression has led to some good candidates, but the consistency of findings is very far from ideal. Adverse life events are causal to development of mood disorders, and often the vulnerability genes can be detected only when environmental impact has been objectively assessed. Yet the continuity of depression diagnosis from early childhood to adulthood is limited, while childhood depression increases odds of other affect-related disorders such as substance abuse and personality disorders. Whether specific genes have an impact seems to depend on the period of life both because of biological maturation and differences in major environmental factors, but also active engagement--or the failure to do so--of the vulnerable subjects with their environment. It is proposed that subjects with genetically determined neurotic tendencies are likely to attempt to select coping strategies that reduce events perceived as harmful and can by this means develop resilience towards affective disorders.

Association study of 44 candidate genes with depressive and anxiety symptoms in post-partum women

The post-partum period is a time of extreme vulnerability for a whole spectrum of psychiatric disorders. Delivery may be considered an important risk factor in genetically susceptible women. Five hundred and eight SNPs in 44 genes at candidate pathways putatively related to mood changes after delivery were genotyped in a multicenter cohort of 1804 women from Spain. Participants completed two scales at 2-3 days, 8 weeks, and 32 weeks post-partum, the Edinburgh Post-partum Depression Scale (EPDS) and the Spielberger State-Trait Anxiety Inventory (STAI). Those women who scored 9 or more on EPDS were evaluated for major depression using the Diagnostic Interview for Genetics Studies (DIGS) adapted for post-partum depression. Association with major depression was assessed using likelihood ratio tests under a codominant genotype model. Association with scale scores was tested using linear mixed models to take into account repeated measures over time. Two intronic SNPs, one at the serotonin transporter gene (SLC6A4) and another at dopa decarboxylase (DDC), were significantly associated to STAI anxiety scores after multiple testing correction (nominal P=0.0000513 and 0.000097, respectively). In addition, post hoc analysis at the unphased haplotype level using nominal significant SNPs revealed an association with a combination of three SNPs at protein kinase C, beta (PRKCB) with major depression, significant after multiple testing correction (nominal global P=0.0001596). In conclusion, we detected a role of SLC6A4 in mood changes after stressful events, and revealed new putative associations involving DDC and PRKCB. Therefore, these genes deserve further investigation to confirm these results.

Dopamine and serotonin systems modify environmental effects on human behavior: a review

The relative influences of genetic and environmental factors in the development of human behavior have been a long-term topic for an intense debate. Recent behavioral genetic studies suggest focusing on the joint effect of genes and environment, and especially on the life-course developmental interplay between nature and nurture. Vulnerability to environmental adversities and sensitivity to its benefits may be conditional on genetic background, and regarding psychological outcomes, these kinds of gene x environment interactions may be of higher importance than direct gene-trait associations. In our recent series of studies, we have shown that different variants of serotonergic and dopaminergic genes may moderate the influence of environmental conditions on a range of psychological outcomes, i.e. temperament, depression, hostility, and educational attainment. These studies suggest that depending on their genotype, people may be differentially sensitive to the environmental conditions they encounter. In the light of these results it seems highly plausible that the effects of genes may become evident only when studied in the context of environmental factors.

Neurotransmission-related genetic polymorphisms, negative affectivity traits, and gender predict tobacco abstinence symptoms across 44 days with and without nicotine patch

Genetic and personality trait moderators of tobacco abstinence-symptom trajectories were assessed in a highly controlled study. Based on evidence suggesting their importance in stress reactivity and smoking, moderators studied were serotonin transporter gene (5-HTTLPR) and dopamine D2 receptor gene (DRD2) polymorphisms and personality traits related to negative affect (NA). Smokers were randomly assigned to quit smoking with nicotine or placebo patches. Financial incentives resulted in 80% verified abstinence across the 44-day study. Individuals with 1 or 2 short alleles of 5-HTTLPR (S carriers) experienced larger increases in NA symptoms than did those without a short allele. Nicotine replacement therapy (NRT) alleviated anxiety only in S carriers. NRT reduced NA to a greater extent in DRD2 A1 carriers than in A2A2 individuals during the 1st 2 weeks of treatment (when on the 21-mg patch); however, A1 carriers experienced a renewal of NA symptoms when switched to the 7-mg patch and when off the patch, while A2A2 individuals continued to benefit from NRT. The results suggest that the effects of genotype and treatment may vary across different durations of abstinence, treatment doses, and genotypes.

Emergent research in the cause of mental illness in women across the lifespan

PURPOSE OF REVIEW

In recent years, there has been an increased appreciation of gender and sex differences in mental illness. This perspective has included attention to sex differences in neurobiology, neurochemistry, sex steroids, endocrine sex reactivity and psychosocial stressors. However, emerging research investigating gene-environment interactions presents another layer of complexity in understanding sex differences in epidemiology, clinical features and treatment of mental disorders across the lifespan.

RECENT FINDINGS

The main themes in the current literature point to gene-environment interactions underlying sex-specific differences in the psychiatric sequelae of both early childhood and current life stress. Evidence related to the serotonin-linked polymorphic region (5HTTLPR) polymorphism is strongest, but evidence exists for other candidate genes. There is also emerging support for genetic factors that increase susceptibility of some women to hormonal changes of the reproductive life cycle. The interaction of these genetic factors with various environmental stressors, many of which are more common in women, may increase the risk of mental illness, especially mood disorders.

SUMMARY

Further research into sex-specific gene-environment interactions across the lifespan is needed with the goal of improving preventive efforts and optimizing treatment in women's mental health.

DRD2 C32806T modifies the effect of child-rearing environment on adulthood novelty seeking

Preliminary evidence suggests that there may be longitudinal interactions between environmental and genetic factors in predicting Novelty seeking. We have previously found in small and selected subsample from the Cardiovascular Risk in Young Finns study, that an association between the polymorphism of dopamine receptor D4 was moderated by the childhood environment, as indexed by hostile maternal child-rearing. We wanted to replicate this finding in a population based sample of 1,114 men and women using another candidate gene of dopaminergic system, that is, the dopamine receptor D2 (DRD2). The child-rearing environment of the participants was assessed by their mothers when the participants were children or adolescents, and adulthood Novelty seeking was self-rated by the participants 17 and 21 years later at the ages of 24-39. Genotyping of DRD2 C32806T (rs 1800497) was performed using TaqMan 5'nuclease assay. DRD2 was not directly associated with Novelty seeking, but there was a significant DRD2 x strict maternal disciplinary style interaction in predicting Novelty seeking (F = 7.08, P = 0.008). The interaction showed that when the child-rearing environment was punitive, participants carrying any A1 allele of the DRD2 gene had higher scores on Novelty seeking than carriers of the A2/A2 genotype. The genotype had no effect on Novelty seeking when the childhood environment was more favorable. The findings suggest that the DRD2 may have an environmentally moderated impact on Novelty seeking and that the origins of such an association may lie already in childhood.

Depressive symptoms in the congenital long QT syndrome

BACKGROUND

A proportion of patients with congenital long QT syndrome (LQTS) experience potentially life-threatening cardiac arrhythmias.

AIM

To examine whether depressive symptoms are related to arrhythmic events among symptomatic and asymptomatic LQTS patients, and syncope events among their relatives not carrying the family's LQTS-causing mutation.

METHODS

The participants were 569 molecularly defined LQTS mutation carriers and 622 non-carrier relatives from the Finnish LQTS registry. Depressive symptoms were self-rated with a revised version of the Beck Depression Inventory.

RESULTS

LQTS patients with arrhythmic events scored higher on depressive symptoms than those without (P=0.011) or the control group (P=0.005). In addition, in the binary logistic regression analysis including symptomatic and asymptomatic LQTS mutation carriers, depressive symptoms showed an age- and sex-adjusted association of odds ratio (OR) 1.40 (95% confidence interval (CI) 1.12-1.74) with symptomatic status of LQTS. In similar analysis including non-carriers of the LQTS mutation, there was no association between depressive symptoms and history of syncope events OR 1.23 (95% CI 0.99-1.53).

CONCLUSION

Our results from this relatively large genotyped LQTS patient cohort indicate that depressive symptoms are associated with arrhythmic events in LQTS patients. Whether depressive symptoms are causally related to arrhythmias in LQTS remains uncertain.

The interaction of DRD2 and violent victimization on depression: an analysis by gender and race

BACKGROUND

Recent research has shown that a polymorphism in the dopamine D2 receptor gene (DRD2) moderates the association between stressful life events and depression. The present study builds off this literature and examines whether DRD2 moderates the effect of violent victimization on depression. Furthermore, the current analyses investigate whether the effects of DRD2 and violent victimization vary by gender and by race for females.

METHODS

Respondents from waves II and III of the National Longitudinal Study of Adolescent Health (Add Health) completed questionnaires regarding their depressive symptoms and violent victimization experiences (n = 2380).

RESULTS

Multivariate regression results reveal that violent victimization has a strong independent effect on depressive symptoms for Caucasian females. In contrast, violent victimization is only associated with higher levels of depressive symptoms among African American females when they carry at least one A1 allele of DRD2. Results also show that DRD2 has a significant independent effect on depressive symptoms for males and African American females.

CONCLUSIONS

The results suggest that African American females who carry the A1 allele of DRD2 may be more vulnerable to the negative effects of violent victimization than African American females who do not carry at least one copy of the A1 allele.

LIMITATIONS

The current study's findings may not generalize to clinical populations, adults, and individuals residing in other countries. In addition, the effects of DRD2 may reflect other polymorphisms that are in linkage with DRD2.

Hypothesizing that brain reward circuitry genes are genetic antecedents of pain sensitivity and critical diagnostic and pharmacogenomic treatment targets for chronic pain conditions

While it is well established that the principal ascending pathways for pain originate in the dorsal horn of the spinal cord and in the medulla, the control and sensitivity to pain may reside in additional neurological loci, especially in the mesolimbic system of the brain (i.e., a reward center), and a number of genes and associated polymorphisms may indeed impact pain tolerance and or sensitivity. It is hypothesized that these polymorphisms associate with a predisposition to intolerance or tolerance to pain. It is further hypothesized that identification of certain gene polymorphisms provides a unique therapeutic target to assist in the treatment of pain. It is hereby proposed that pharmacogenetic testing of certain candidate genes (i.e., mu receptors, PENK etc.) will result in pharmacogenomic solutions personalized to the individual patient, with potential improvement in clinical outcomes.

Depression, anhedonia, and psychomotor symptoms: the role of dopaminergic neurocircuitry

The heterogeneity of major depression suggests that multiple neurocircuits and neurochemicals are involved in its pathogenesis. Anhedonia and psychomotor symptoms are, however, particularly characteristic features of major depression and may provide insights into its underlying psychobiology. Importantly, these symptoms appear to be mediated by dopaminergic mesolimbic and mesostriatal projections, the function of which is, in turn, influenced by key gene variants and environment stressors. Indeed, there is growing evidence of the way in which the dopaminergic system is associated with cognitive-affective disturbances in depression, and provides a useful target for therapeutic interventions. At the same time, a range of other systems are likely to contribute to the psychobiology of this condition.