Etiology Of Major Depression Research Articles

Association of 11 variants of the dopaminergic and cognitive pathways genes with major depression, schizophrenia and bipolar disorder in the Pakistani population

Background: The dopaminergic pathways control neural signals that modulate mood and behaviour along and have a vital role in the aetiology of major depression (MDD), schizophrenia (SHZ) and bipolar disorder (BD). Genome-wide association studies (GWAS) have reported several dopaminergic and cognitive pathway genes association with these disorders however, no such comprehensive data was available regarding the Pakistani population.Objective: The present study was conducted to analyse the 11 genetic variants of dopaminergic and cognitive system genes in MDD, SHZ, and BD in the Pakistani population.Methods: A total of 1237 subjects [MDD n = 479; BD n = 222; SHZ n = 146; and controls n = 390], were screened for 11 genetic variants through polymerase chain reaction (PCR) techniques. Univariant followed by multivariant logistic regression analysis was applied to determine the genetic association.Results: Significant risk associations were observed for rs4532 and rs1799732 with MDD; and rs1006737 and rs2238056 with BD. However, after applying multiple test corrections rs4532 and rs1799732 association did not remain significant for MDD. Moreover, a protective association was found for three variants; DRD4-120bp, rs10033951 and rs2388334 in the current cohort.Conclusions: The present study revealed the risk association of single nucleotide polymorphisms (SNPs) rs1006737 and rs2238056 with BD and the protective effect of the DRD4-120bp variant in MDD and BD, of rs2388334 in BD and of rs10033951 in MDD, BD, and SHZ in the current Pakistani cohort. Thus, the study is valuable in understanding the genetic basis of MDD, BD and SHZ in the Pakistani population, which may pave the way for future functional studies.

Chronic Stress Impairs the Structure and Function of Astrocyte Networks in an Animal Model of Depression.

Now astrocytes appear to be the key contributors to the pathophysiology of major depression. Evidence in rodents shows that chronic stress is associated with a decreased expression of astrocyticGFAP-immunoreactivitywithin the cortex in addition to changes in the complexity and length of astrocyte processes. Furthermore, postmortem brains of individuals with depression have revealed a decrease in astrocyte density. Notably, astrocytes are extensively coupled to one another through gap junctions to form a network, or syncytium, and we have previously demonstrated that syncytial isopotentiality is a mechanism by which astrocytes function as an efficient system with respect to brain homeostasis. Interestingly, the question of how astrocyte network function changes following chronic stress is yet to be elucidated. Here, we sought to examine the effects of chronic stress on network-level astrocyte (dys)function. Using a transgenic aldh1l1-eGFPastrocyte reporter mouse, a six-week unpredictable chronic mild stress (UCMS) paradigm as a rodent model of major depression, and immunohistochemical approaches, we show that the morphology of individual astrocytes is altered by chronic stress exposure. Additionally, in astrocyte syncytial isopotentiality measurement, we found that UCMS impairs the syncytial coupling strength of astrocytes within the hippocampus and prefrontal cortex-two brain regions that have been implicated in the regulation of mood. Together, these findings reveal that chronic stress leads toastrocyte atrophyand impairedgap junction coupling, raising the prospect that both individual and network-level astrocyte functionality are important in the etiology of major depression and other neuropsychiatric disorders.

The Importance of Ki67, Glial Fibrillar Acidic Protein and Vitamin D Receptor in the Central Nervous System of Postmortem Suicide Cases

Death by suicide is a tragic public health problem. Major depressive patients constitute some of these deaths. Although the etiology of major depression has not been clarified, there are studies suggesting that the hippocampus and caudate nucleus may be effective. In this study, it was aimed to compare vitamin D receptor (VDR), Ki67 and glial fibrial acidic protein (GFAP) antibodies in the brain tissues (hippocampus and caudate nucleus) of untreated major depression patients who died because of suicide with the control group. Left hippocampus and caudate nuclei of seven patients with untreated major depression who died of suicide in a one-year period and six psychiatrically normal patients were taken during autopsy. The hippocampus was stained with VDR, GFAP and Ki67 antibodies, and the caudate nucleus was stained with VDR and GFAP antibodies. There was no significant difference in the number of Ki67-positive cells in the anterior and posterior dentate gyrus between the major depression and control groups (P > 0.05). In the major depression group, a negative correlation was reported between the number of Ki67-positive cells in the anterior dentate gyrus and age (r: 0.867, P < 0.05). In the anterior dentate gyrus, posterior dentate gyrus and caudate nucleus, there was no significant difference between the suicide and control groups in the fraction of the immunoreactive area with GFAP antibodies (P > 0.05). While the percentage of immunoreactive granular cells for vitamin D receptor in the anterior dentate gyrus was significantly higher than the control group (P <0.05), no significant difference was reported in the posterior dentate gyrus. Vitamin D receptor immunoreactive neuron positivity in the caudate nucleus was not significantly different between the major depression and control groups (P > 0.05). In untreated major depression, additional immunohistochemical changes are observed in the anterior hippocampus, and the vitamin D receptor increases in the granular cells as a protective factor.

Specific and cumulative lifetime stressors in the aetiology of major depression: A longitudinal community-based population study.

Early-life stressful circumstances (i.e. childhood maltreatment) coupled with stressful events later in life increase the likelihood of subsequent depression. However, very few studies have been conducted to examine the specific and cumulative effects of these stressors in the development of depression. There is also a paucity of research that simultaneously considers the role of biological factors combined with psychosocial stressors in the aetiology of depression. Guided by the biopsychosocial model proposed by Engel, the present study aims to examine to what extent the experience of stressors across the lifespan is associated with depression while taking into account the role of genetic predispositions. Data analysed were from the Social and Psychiatric Epidemiology Catchment Area of the Southwest of Montreal (ZEPSOM), a large-scale, longitudinal community-based cohort study. A total of 1351 participants with complete information on the lifetime diagnoses of depression over a 10-year follow-up period were included in the study. Stressful events across the lifespan were operationalised as specific, cumulative and latent profiles of stressful experiences. Latent profile analysis (LPA) was used to explore the clustering of studied stressors including childhood maltreatment, poor parent-child relationship, and stressful life events. A polygenetic risk score was calculated for each participant to provide information on genetic liability. Multivariate logistic regression was used to examine the association between specific, cumulative and latent profiles of stressors and subsequent depression. We found that different subtypes of childhood maltreatment, child-parent bonding and stressful life events predicted subsequent depression. Furthermore, a significant association between combined effects of cumulative stressful experiences and depression was found [odds ratio (OR) = 1.20, 95% confidence interval (CI): 1.12-1.28]. Three latent profiles of lifetime stressors were identified in the present study and named as 'low-level of stress' (75.1%), 'moderate-level of stress' (6.8%) and 'high-level of stress' (18.1%). Individuals with a 'high-level of stress' had a substantially higher risk of depression (OR = 1.80, 95% CI: 1.08-3.00) than the other two profiles after adjusting for genetic predispositions, socio-demographic characteristics, and health-related factors. While controlling for genetic predispositions, the present study provides robust evidence to support the independent and cumulative as well as compositional effects of early- and later-on lifetime psychosocial stressors in the subsequent development of depression. Consequently, mental illness prevention and mental health promotion should target the occurrence of stressful events as well as build resilience in people so they can better cope with stress when it inevitably occurs.

Comet Parameters and Plasma 8-Iso-Prostaglandins F2α

Background: Major depression can be characterized by isolated episodes of disturbance in psychosomatic functions for a duration of at least two weeks along with intermediate non-symptomatic periods. The factors playing important role in the etiology of major depression were family history, genetic factors, decreased levels of serotonin and norepinephrine; increased levels of interleukins or any other medical illness having an increased cytokine production. The pathogenesis of major depression involves oxidative stress, which consists of synthesis of free radicals causing damage to nucleic acids, lipids, carbohydrates, and proteins present in the cells. Oxidative stress – induced DNA damage consists of numerous types of lesions which can be assessed by the comet assay method. Prostaglandin F2-alpha is produced because of oxidative stress-induced peroxidation of cell membrane lipids and has elevated plasma levels in patients with major depression. Fluoxetine is the drug of choice for major depression and found to have antioxidant properties. The present study was done to assess the correlation between plasma 8-iso-PGF2α levels and the comet parameters, namely comet length (CL), head diameter (HD), % of DNA in head (%DNA Head), tail length (TL) and % of DNA in tail (%DNA Tail), before starting and after finishing the eight-week fluoxetine therapy. Methodology: The prospective clinical study was conducted in the Department of Anatomy in collaboration at, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry. The study group consisted of drug naïve, newly diagnosed major depression patients belonging to age-group of ≥ 18 to 50 years and followed up after eight weeks of fluoxetine therapy. Results: The correlation was found to be positive between the levels of 8-iso-PGF2α in the plasma and all the comet parameters except %DNA Tail, which showed a negative (inverse) relationship with the levels of 8-iso-PGF2α in the plasma. Conclusion: The current study suggested the role of oxidative stress in causing DNA damage and lipid peroxidation in major depression patients and the antioxidant role of fluoxetine in causing decrease in the levels of parameters of oxidative stress and subsequent DNA repair.

Increased neutrophil-lymphocyte ratios in depressive adolescents is correlated with the severity of depression

We aimed to investigate the neutrophil-lymphocyte ratio and platelet-lymphocyte ratio in adolescents with major depression. Sixty-seven adolescents and 121 healthy controls were enrolled in the study. The diagnosis was made by using both the Kiddie and Young Adult Schedule for Affective Disorders and Schizophrenia Present and Lifetime Version and the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition. The severity of depressive symptoms was evaluated using the Beck depression inventory (BDI). The neutrophil-lymphocyte ratios of the adolescents with depression were significantly higher than those of the control group, even after adjusting for age, sex, BMI, and BDI scores, whereas there was no significant difference in platelet-lymphocyte ratios. A positive correlation between the severity of depression and neutrophil-lymphocyte ratios and platelet-lymphocyte ratios were determined in the case group. The results of this study may promote the hypothesis that inflammation plays an important role in the etiology of major depression in adolescents.

Epigenetic mechanisms of major depression: Targeting neuronal plasticity

Major depressive disorder is one of the most common mental illnesses as it affects more than 350 million people globally. Major depressive disorder is etiologically complex and disabling. Genetic factors play a role in the etiology of major depression. However, identical twin studies have shown high rates of discordance, indicating non-genetic mechanisms as well. For instance, stressful life events increase the risk of depression. Environmental stressors also induce stable changes in gene expression within the brain that may lead to maladaptive neuronal plasticity in regions implicated in disease pathogenesis. Epigenetic events alter the chromatin structure and thus modulate expression of genes that play a role in neuronal plasticity, behavioral response to stress, depressive behaviors, and response to antidepressants. Here, we review new information regarding current understanding of epigenetic events that may impact depression. In particular, we discuss the roles of histone acetylation, DNA methylation, and non-coding RNA. These novel mechanisms of action may lead to new therapeutic strategies for treating major depression.

Depressive vulnerability, stressful life events and episode onset of major depression: a longitudinal model.

The nature of the relationship between depressive vulnerability (DV) and acute adversity in the etiology of major depression (MD) remains poorly understood. Stressful life events (SLEs) and MD onsets in the last year were assessed at four waves in cohort 1 (females) and at two waves in cohort 2 (males and females) from the Virginia Adult Twin Study. Structural equation modeling was conducted in Mplus. In cohort 1, DV was strongly indexed by depressive episodes over the four waves (paths from +0.72 to 0.79) and predicted by SLEs in the month of their occurrence (+0.31 to 0.36). Wave-specific DV was associated both with stable DV (+0.29 to 0.33) and by forward transmission of DV from the preceding wave (+0.33 to 0.36). SLEs were predicted by stable DV (+0.29) and from SLEs in the preceding month (+0.06). As the cohort aged, MD onsets were better indexed by DV and more poorly predicted by SLEs. Parameter estimates were similar in males and females from cohort 2. In individuals with prior depressive episodes, the association between MD onset and SLEs was weakened while the prediction of SLEs from DV was substantially strengthened. We found no evidence for 'reverse causation' from MD episodes to SLEs. The interrelationship between DV and acute adversity in the etiology of MD is complex and temporally dynamic. DV impacts on MD risk both directly and indirectly through selection into high stress environments. Over time, depressive episodes become more autonomous. Both DV and SLEs transmit forward over time and therefore form clear targets for intervention.

Inadequate Homocysteine Metabolism: A Theory of Depression

Over the past 100 years, theories regarding the etiology of major depression have appeared as the proverbial blind man’s interpretation of the elephant. It is now possible to discuss depression in terms of neuroendocrine dysregulation, differences in neuroanatomy, inflammatory response, a gene-environment interaction, or in purely psychological terms—and without any contradiction in the evidence. Indeed, a disorder as complex and variable as depression is expected to have multiple risk factors and etiologic influences. Yet, all roads eventually lead to a functional shortage of monoamines, and the monoamine hypothesis remains the basis of treatment for millions of patients. Elevated homocysteine (HCY) has long been recognized as a risk factor for major depressive disorder (MDD), and many neurologic and psychiatric conditions; however, a full understanding of HCY metabolism and monoamine synthesis indicates that perhaps HCY elevation in the central nervous system is the driving force behind MDD. The HCY theory argues that a genetically based inability to optimally metabolize HCY leads to inadequate supplies of monoamines, particularly in the presence of psychosocial stress, and results in the clinical syndrome of MDD. [ Psychiatr Ann . 2015;45(9):469–472.]

The Cortisol Awakening Response in Patients with Poststroke Depression Is Blunted and Negatively Correlated with Depressive Mood.

It is important to reduce poststroke depression (PSD) to improve the stroke outcomes and quality of life in stroke patients, but the underlying mechanisms of PSD are not completely understood. As many studies implicate dysregulation of hypothalamic-pituitary-adrenal axis in the etiology of major depression and stroke, we compared the cortisol awakening response (CAR) of 28 admitted PSD patients with that of 23 age-matched caregiver controls. Saliva samples for cortisol measurement were collected immediately, 15, 30, and 45 min after awakening for two consecutive days. Depressive mood status in PSD patients was determined with Beck Depression Inventory and Hamilton Depression Rating Scale. Salivary cortisol levels of PSD patients did not rise significantly at any sampling time, showing a somewhat flat curve. Caregiver controls showed significantly higher CAR at 15 and 30 min after awakening compared to PSD patients even though the two groups did not differ at awakening or 45 min after awakening. Area-under-the-curve analysis revealed a significant negative correlation between the CAR and the degree of depression in PSD patients. Thus, our findings suggest that poststroke depression is closely related with dysfunctional HPA axis indicated by blunted CAR.

Early life stress and serotonin transporter gene variation interact to affect the transcription of the glucocorticoid and mineralocorticoid receptors, and the co-chaperone FKBP5, in the adult rat brain.

The short allelic variant of the serotonin transporter (5-HTT) promoter-linked polymorphic region (5-HTTLPR) has been associated with the etiology of major depression by interaction with early life stress (ELS). A frequently observed endophenotype in depression is the abnormal regulation of levels of stress hormones such as glucocorticoids. It is hypothesized that altered central glucocorticoid influence on stress-related behavior and memory processes could underlie the depressogenic interaction of 5-HTTLPR and ELS. One possible mechanism could be the altered expression of the genes encoding the glucocorticoid and mineralocorticoid receptors (GR, MR) and their inhibitory regulator FK506-binding protein 51 (FKBP5) in stress-related forebrain areas. To test this notion, we exposed heterozygous (5-HTT+/−) and homozygous (5-HTT−/−) serotonin transporter knockout rats and their wildtype littermates (5-HTT+/+) to daily 3 h maternal separations from postnatal day 2 to 14. In the medial prefrontal cortex (mPFC) and hippocampus of the adult male offspring, we found that GR, MR, and FKBP5 mRNA levels were affected by ELS × 5-HTT genotype interaction. Specifically, 5-HTT+/+ rats exposed to ELS showed decreased GR and FKBP5 mRNA in the dorsal and ventral mPFC, respectively. In contrast, 5-HTT+/− rats showed increased MR mRNA levels in the hippocampus and 5-HTT−/− rats showed increased FKBP5 mRNA in the ventral mPFC after ELS exposure. These findings indicate that 5-HTT genotype determines the specific adaptation of GR, MR, and FKBP5 expression in response to early life adversity. Therefore, altered extra-hypothalamic glucocorticoid signaling should be considered to play a role in the depressogenic interaction of ELS and 5-HTTLPR.

Early life adversity and serotonin transporter gene variation interact at the level of the adrenal gland to affect the adult hypothalamo-pituitary-adrenal axis

The short allelic variant of the serotonin transporter (5-HTT) promoter-linked polymorphic region (5-HTTLPR) has been associated with the etiology of major depression by interaction with early life stress (ELS). Furthermore, 5-HTTLPR has been associated with abnormal functioning of the stress-responsive hypothalamo-pituitary-adrenal (HPA) axis. Here, we examined if, and at what level, the HPA-axis is affected in an animal model for ELS × 5-HTTLPR interactions. Heterozygous and homozygous 5-HTT knockout rats and their wild-type littermates were exposed daily at postnatal days 2–14 to 3 h of maternal separation. When grown to adulthood, plasma levels of adrenocorticotropic hormone (ACTH), and the major rat glucocorticoid, corticosterone (CORT), were measured. Furthermore, the gene expression of key HPA-axis players at the level of the hypothalamus, pituitary and adrenal glands was assessed. No 5-HTT genotype × ELS interaction effects on gene expression were observed at the level of the hypothalamus or pituitary. However, we found significant 5-HTT genotype × ELS interaction effects for plasma CORT levels and adrenal mRNA levels of the ACTH receptor, such that 5-HTT deficiency was associated under control conditions with increased, but after ELS with decreased basal HPA-axis activity. With the use of an in vitro adrenal assay, naïve 5-HTT knockout rats were furthermore shown to display increased adrenal ACTH sensitivity. Therefore, we conclude that basal HPA-axis activity is affected by the interaction of 5-HTT genotype and ELS, and is programmed, within the axis itself, predominantly at the level of the adrenal gland. This study therefore emphasizes the importance of the adrenal gland for HPA-related psychiatric disorders.

Distribution of the glucocorticoid receptor in the human amygdala; changes in mood disorder patients

Exposure to stress activates the hypothalamic-pituitary-adrenal (HPA) axis that stimulates glucocorticoid (GC) release from the adrenal. These hormones exert numerous effects in the body and brain and bind to a.o. glucocorticoid receptors (GR) expressed in the limbic system, including the hippocampus and amygdala. Hyperactivity of the HPA axis and disturbed stress feedback are common features in major depression. GR protein is present in the human hypothalamus and hippocampus, but little is known-neither in healthy subjects nor in depressed patients-about GR expression in the amygdala, a brain structure involved in fear and anxiety. Since chronic stress in rodents affects GR expression in the amygdala, altered GR protein level in depressed versus healthy controls can be expected. To test this, we investigated GR-α protein expression in the post-mortem human amygdala and assessed changes in ten major or bipolar depressed patients and eight non-depressed controls. Abundant GR immunoreactivity was observed in the human amygdala, both in neurons and astrocytes, with a similar pattern in its different anatomical subnuclei. In major depression, GR protein level as well as the percentage of GR-containing astrocytes was significantly higher than in bipolar depressed patients or in control subjects. Taken together, the prominent expression of GR protein in the human amygdala indicates that this region can form an important target for corticosteroids and stress, while the increased GR expression in major, but not bipolar, depression suggests possible involvement in the etiology of major depression.

Screening genetic variability at the CNR1 gene in both major depression etiology and clinical response to citalopram treatment

The endocannabinoid system has been implicated in the pathogenesis of major depression (MD) as well as in the mediation of antidepressant drug effects. To analyze CNR1 gene variants in MD and clinical response to citalopram (selective serotonin re-uptake inhibitors [SSRI]). The role of CNR1 gene (rs806368, rs1049353, rs806371, rs806377 and rs1535255) was investigated in 319 outpatients with MD and 150 healthy individuals. A subsample of 155 depressive patients were treated with citalopram and evaluated for response (fourth week) and remission (12th week) by the 21-item Hamilton Depression Rating Scale (HDRS). We observed a higher frequency of rs806371 G carriers in MD patients with both presence of melancholia (p = 0.018) and psychotic symptoms (p = 0.007) than in controls. Haplotype frequency distributions between MD sample and controls showed a significant difference for Block 1 (rs806368-rs1049353-rs806371) (p = 0.008). This haplotype finding was consistent when we compared controls with MD subsample stratified by melancholia (p = 0.0009) and psychotic symptoms (p = 0.014). The TT homozygous of the rs806368 and rs806371 presented more risk of no Remission than the C carriers (p = 0.008 and 0.012, respectively). Haplotype frequency distributions according to Remission status showed a significant difference for Block 1 (p = 0.032). Also, we observed significant effect of time-sex-genotype interaction for the rs806368, showing that the C carrier men presented a better response to antidepressant treatment throughout the follow-up than TT homozygous men and women group (p = 0.026). These results suggest an effect of CNR1 gene in the etiology of MD and clinical response to citalopram.

No support for a role for BDNF gene polymorphisms rs11030101 and rs61888800 in major depressive disorder or antidepressant response in patients of Finnish origin

Brain-derived neurotrophic factor (BDNF) is suggested to play a role in the aetiology of major depression and in the antidepressant response in patients with major depression. Several BDNF gene polymorphisms have been investigated in the above-mentioned context. The aim of the present study was to examine the role of two BDNF gene polymorphisms (rs11030101 and rs61888800) in relation to the response to selective serotonin reuptake inhibitor medication in 106 patients of Finnish origin suffering from major depression. The secondary objective was to evaluate the association of these two BDNF polymorphisms in major depression, as we also had a control population of 386 healthy individuals. We did not find any significant differences in the distribution of these two BDNF gene polymorphisms in our patient population in relation to remission or response to treatment with selective serotonin reuptake inhibitor. Also, there were no significant differences between the patients and the controls.

Polymorphic variation at the serotonin 1-A receptor gene is associated with comorbid depression and generalized anxiety

Serotonin 1-A receptors are key regulators of serotonin activity and their dysregulation might be implicated in the emergence of both major depression (MD) and generalized anxiety disorder (GAD). Previous studies have yielded inconclusive results as to whether the 5-HT1A receptor gene (HTR1A) has a role in the aetiology of MD and no study up to date has analysed this polymorphism on either pure MD or MD comorbid with GAD. In this study, 1059 patients taking part in the PREDICT-Gene study were ascertained for Diagnostic and Statistical Manual of Mental Disorders-IV MD and GAD diagnoses using the Composite International Diagnostic Interview and the Primary Care Evaluation of Mental Disorders questionnaire, respectively. They were also genotyped for the C(-1019)G functional polymorphism at the promoter region of HTR1A gene. Genetic variability at HTR1A was significantly associated with MD [odds ratio (OR) = 1.67; 95% confidence interval (CI) = 1.14-2.44; P = 0.008], although this effect disappeared after adjusting for GAD (OR = 1.43; 95% CI = 0.96-2.14; P = 0.080). Similarly, a crude association between C(-1019)G polymorphism and GAD was found (OR = 2.54; 95% CI = 1.28-4.86; P = 0.003), but these results became no longer significant after adjusting for MD (OR = 1.97; 95% CI = 0.99-3.91; P = 0.050). However, a main effect of HTR1A G(-1019) allele on comorbid MD-GAD was found (OR = 3.41; 95% CI = 1.44-8.05; P = 0.005) and it remained robust and statistically significant after adjusting by sex, age and family history of psychological problems (OR = 2.82; 95% CI = 1.18-6.77; P = 0.020). In our study, the HTR1A C(-1019)G polymorphism was found to be associated to the frequent clinical presentation of comorbid MD and GAD, suggesting a common genetic background for mixed depression and anxiety states. These findings should be considered as preliminary. Future replications in independent samples would be needed to confirm or discard such association.

PCLO rs2522833 impacts HPA system activity in healthy young adults

Recent genetic studies showed evidence for a role of the single-nucleotide polymorphism rs2522833 within the PCLO gene in the etiology of major depression, and rs2522833 has been shown to modulate hypothalamic pituitary adrenal (HPA) axis activity during antidepressant treatment. Monoaminergic modulation of the HPA system may be one possible pathomechanism by which PCLO exerts its effect on depression. In the present study, we investigated the effect of rs2522833 on the cortisol awakening response (CAR) in healthy young adults. A total of 66 healthy volunteers from the community (36 men and 30 women) aged 18–25 years without individual or family history of affective disorders and schizophrenia collected saliva cortisol samples at 0, 30, 45 and 60 min after awakening on two consecutive working days. We identified a blunted CAR (AUCinc) in rs2522833 risk-allele (C) carriers, possibly indicating exhausted regulatory mechanisms underlying the HPA system. We also identified higher neuroticism scores in rs2522833 risk-allele carriers but no phenotypic correlation between the CAR (AUCinc) and neuroticism. These findings suggest that the rs2522833 risk variant might increase vulnerability to depression both by physiological and behavioral pathways, which appear, however, not to be substantially overlapped. Replication with larger samples is warranted.

Genome-Wide Association-, Replication-, and Neuroimaging Study Implicates HOMER1 in the Etiology of Major Depression

Genome-wide association studies are a powerful tool for unravelling the genetic background of complex disorders such as major depression. We conducted a genome-wide association study of 604 patients with major depression and 1364 population based control subjects. The top hundred findings were followed up in a replication sample of 409 patients and 541 control subjects. Two SNPs showed nominally significant association in both the genome-wide association study and the replication samples: 1) rs9943849 (p(combined) = 3.24E-6) located upstream of the carboxypeptidase M (CPM) gene and 2) rs7713917 (p(combined) = 1.48E-6), located in a putative regulatory region of HOMER1. Further evidence for HOMER1 was obtained through gene-wide analysis while conditioning on the genotypes of rs7713917 (p(combined) = 4.12E-3). Homer1 knockout mice display behavioral traits that are paradigmatic of depression, and transcriptional variants of Homer1 result in the dysregulation of cortical-limbic circuitry. This is consistent with the findings of our subsequent human imaging genetics study, which revealed that variation in single nucleotide polymorphism rs7713917 had a significant influence on prefrontal activity during executive cognition and anticipation of reward. Our findings, combined with evidence from preclinical and animal studies, suggest that HOMER1 plays a role in the etiology of major depression and that the genetic variation affects depression via the dysregulation of cognitive and motivational processes.

Stressful Life Events, Genetic Liability, and Onset of an Episode of Major Depression in Women

Objective:This study was undertaken to clarify how genetic liability and stressful life events interact in the etiology of major depression. Method:Information about stressful life events and onset of major depressive episodes in the past year was collected in a population-based sample of female-female twin pairs including 2,164 individuals, 53,215 person-months of observation, and 492 onsets of depression. Results:Nine “personal” and three aggregate “network” stressful events significantly predicted onset of major depression in the month of occurrence, four of which predicted onset with an odds ratio of >10 and were termed “severe”: death of a close relative, assault, serious marital problems, and divorce/breakup. Genetic liability also had a significant impact on risk of onset of depression. Four severe stressful events, as well as for 10 of the 12 individuals stressful events, the best-fitting model for the joint effect of stressful events and genetic liability on onset of major depression suggested ge...

Altered expression of genes involved in inflammation and apoptosis in frontal cortex in major depression

The etiology of major depression (MDD), a common and complex disorder, remains obscure. Gene expression profiling was conducted on post-mortem brain tissue samples from Brodmann Area 10 (BA10) in the prefrontal cortex from psychotropic drug-free persons with a history of MDD and age, gender, and post-mortem interval matched normal controls (n=14 pairs of subjects). Microarray analysis was conducted using the Affymetrix Exon 1.0 ST arrays. A list of differential expression changes were determined by dual fold change-probability criteria (|ALR|>0.585 [equivalent to a 1.5-fold difference in either direction], p<0.01), while molecular pathways of interest were evaluated using Gene Set Enrichment Analysis (GSEA) software. The results strongly implicate increased apoptotic stress in the samples from the MDD group. Three anti-apoptotic factors, Y-box binding protein 1 (YBX1), Caspase-1 dominant-negative inhibitor pseudo-ICE (COP1), and the putative apoptosis inhibitor FKGS2 were over-expressed. Gene set analysis suggested up-regulation of a variety of pro- and anti-inflammatory cytokines, including interleukin 1α (IL1α), IL2, IL3, IL5, IL8, IL9, IL10, IL12A, IL13, IL15, IL18, interferon gamma (IFNγ), and lymphotoxin alpha (LTA; TNF super family member 1). The genes showing reduced expression included metallothionein 1M (MT1M), a zinc binding protein with a significant role in the modulation of oxidative stress. The results of this study suggest that post-mortem brain tissue samples from BA10, a region which is involved in reward-related behavior, show evidence of local inflammatory, apoptotic, and oxidative stress in MDD.