Early-emerging cognitive vulnerability to depression and the serotonin transporter promoter region polymorphism

Role of Serotonylation and SERT Posttranslational Modifications in Alzheimer's Disease Pathogenesis

The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) is implicated mainly in Alzheimer's disease (AD) and reported to be responsible for several processes and roles in the human body, such as regulating sleep, food intake, sexual behavior, anxiety, and drug abuse. It is synthesized from the amino acid tryptophan. Serotonin also functions as a signal between neurons to mature, survive, and differentiate. It plays a crucial role in neuronal plasticity, including cell migration and cell contact formation. Various psychiatric disorders, such as depression, schizophrenia, autism, and Alzheimer's disease, have been linked to an increase in serotonin-dependent signaling during the development of the nervous system. Recent studies have found 5-HT and other monoamines embedded in the nuclei of various cells, including immune cells, the peritoneal mast, and the adrenal medulla. Evidence suggests these monoamines to be involved in widespread intracellular regulation by posttranslational modifications (PTMs) of proteins. Serotonylation is the calcium-dependent process in which 5-HT forms a long-lasting covalent bond to small cytoplasmic G-proteins by endogenous transglutaminase 2 (TGM2). Serotonylation plays a role in various biological processes. The purpose of our article is to summarize historical developments and recent advances in serotonin research and serotonylation in depression, aging, AD, and other age-related neurological diseases. We also discussed several of the latest developments with Serotonin, including biological functions, pathophysiological implications and therapeutic strategies to treat patients with depression, dementia, and other age-related conditions.

Genetic architecture of well-being: cumulative effect of serotonergic polymorphisms

Serotonin influences mental health and well-being. To understand the influences of genetic variations in serotonin pathway on well-being, we examined the effects of seven serotonergic polymorphisms on subjective well-being (i.e. affective balance and global life satisfaction) and psychological well-being (i.e. optimal psychological functions in the face of existential challenges) in a larger sample. Results indicated that the cumulative genetic score, but single genetic effects of serotonergic polymorphisms, was related to individual differences in well-being. Specifically, individuals with a greater cumulative genetic score, which is related to a low risk of depression, tended to exhibit high levels of subjective well-being and psychological well-being. These findings suggest that the overall serotoninergic genetic profile, rather than a specific genetic polymorphism, could greatly influence the individual differences in well-being.

Effects of serotonin transporter and receptor polymorphisms on depression

INTRODUCTION

Serotonin is highly implicated in the regulation of emotional state and the execution of cognitive tasks, so much so that the serotonin transporter genes (5-HTT, SLC6A4) and the serotonin receptor genes (HTR1A, HTR1B, HTR2A) have become the perfect candidates when studying the effects that these genes and their polymorphic variations have on depression characteristics.

OBJECTIVE

A review of research reports that have studied the effects of variations in the serotonin transporter and receptor genes on different clinical features of depression.

METHODS

A search of the Scopus, Web of Science and PubMed databases was conducted using the keywords ("depression" AND "polymorphism").

CONCLUSIONS

According to the review of 54 articles, the short allele of the 5-HTTLPR polymorphism was found to be the most reported risk factor related to the development of depression and its severity. Variations in the genes studied (SLC6A4, HTR1A, HTR2A) can generate morphological alterations of brain structures.

Emotional valence of self-defining memories in older adults: A longitudinal study

The present study aimed to evaluate the pleasantness bias and fading affect bias in self-defining memories (SDMs) and to examine the relationship between their emotional valence of SDMs and cognitive function and serotonin transporter polymorphisms (5-HTTLPR) with a prospective longitudinal method. Ninety-two older adults recalled SDMs twice at an interval of one year (T1 and T2). The results showed a pleasantness bias and a fading affect bias in SDMs. The higher the working memory was, the higher the vividness of SDMs and the higher the concordance rate of SDMs between T1 and T2. Meanwhile, cognitive performance had no effect on the emotional valence of SDMs. Additionally, the repeatedly recalled SDMs in the S/S allele carriers of the 5-HTTLPR polymorphism changed with a lower negative valence at T2 than at T1. The 5-HTTLPR polymorphism may be a plasticity factor that predicts positive outcomes in positive situations.

Effects of Serotonin Transporter and Receptor Polymorphisms on Depression

INTRODUCTION

Serotonin is highly implicated in the regulation of emotional state and the execution of cognitive tasks, so much so that the serotonin transporter genes (5-HTT, SLC6A4) and the serotonin receptor genes (HTR1A, HTR1B, HTR2A) have become the perfect candidates when studying the effects that these genes and their polymorphic variations have on depression characteristics.

OBJECTIVE

A review of research reports that have studied the effects of variations in the serotonin transporter and receptor genes on different clinical features of depression.

METHODS

A search of the Scopus, Web of Science and PubMed databases was conducted using the keywords ("depression" AND "polymorphism").

CONCLUSIONS

According to the review of 54 articles, the short allele of the 5-HTTLPR polymorphism was found to be the most reported risk factor related to the development of depression and its severity. Variations in the genes studied (SLC6A4, HTR1A, HTR2A) can generate morphological alterations of brain structures.

Baseline knowledge and receptiveness to genetic testing for hereditary breast and ovarian cancer syndromes in Chinese high-risk females

Limited studies have examined the pre-counselling knowledge and attitudes of high-risk women on hereditary breast and ovarian cancer (HBOC) syndromes genetic screening in Asia Pacific regions, particularly among Chinese. After controlling cost, an intrinsic barrier to undertake such screening, comprehensive understanding of the baseline characteristics of this cohort towards HBOC genetic counselling and testing service (GT) could be sought. This study aimed at exploring the baseline knowledge, possible motivators, barriers, and decisional factors of undertaking such service. One hundred and forty-two Southern Hong Kong Chinese high-risk females (89.4% with cancer history; 10.6% were cancer-free at-risk family members) completed a questionnaire right before their pre-testing GT. Results showed that perceived benefits to self and family members with reference to cancer prevention are important decisional motivators. A sponsored cancer genetic testing service in this cohort was crucial as 71.3% would not have opted for self-financed screening. Pre-testing and post-testing counselling were essential, particularly for older and less educated high-risk individuals. More importantly, after thorough pre-counselling with Q&A session, the entire cohort in this study gave written consent to undertake GT. Moreover, those proven to be germline pathogenic variant carriers were willing to share the information with family members and successfully persuaded them to pursue GT.

Depression and prostate cancer: implications for urologists and oncologists

Many patients with prostate cancer experience severe levels of depression, which can negatively affect their treatment and disease course. Some prostate cancer treatments can increase the severity of a patient's depression, for example, by increasing anhedonia and erectile dysfunction. Depression is often thought of as a unitary phenomenon, but multiple subtypes can be distinguished. This variety of manifestations challenges the successful application of universal antidepressant treatment options and argues for a multi-symptom assessment process that considers a patient's disease burden and their particular form of depression. Inclusion of screening and detailed diagnosis of depression can be argued to be part of good practice, and clinicians are urged to consider when and how this might be accomplished within their urological practice.

Cognitive and attentional vulnerability to depression in youth: A review

Although depressive disorders are among the most common disorders in youth, highly efficacious treatments for childhood affective disorders are lacking. There is significant need to better understand the factors that contribute to the development and maintenance of depression in youth so that treatments can be targeted at optimal mechanisms. The aim of the current paper was to synthesize research on cognitive and neurobiological factors associated with youth depression, guided by De Raedt and Koster's model (2010) for vulnerability to depression in adults. Consistent with model predictions, there is evidence that attentional impairments are greatest in the context of negative information, relative to positive or neutral information, and some evidence that attentional deficits are associated with rumination in depressed youth. However, we found little evidence for the model's assumption that attentional bias is an etiological and maintenance factor for depression. There are several other model predictions that require additional study as current data are lacking. Overall, De Raedt and Koster's (2010) integrative cognitive and biological framework has tremendous potential to move the field forward in understanding the development of depression in youth. Additional longitudinal studies incorporating measures across biological and cognitive levels of analysis are needed.

Negative self-referential processing is associated with genetic variation in the serotonin transporter-linked polymorphic region (5-HTTLPR): Evidence from two independent studies

The current research examined whether carriers of the short 5-HTTLPR allele (in SLC6A4), who have been shown to selectively attend to negative information, exhibit a bias towards negative self-referent processing. The self-referent encoding task (SRET) was used to measure self-referential processing of positive and negative adjectives. Ratcliff's diffusion model isolated and extracted decision-making components from SRET responses and reaction times. Across the initial (N = 183) and replication (N = 137) studies, results indicated that short 5-HTTLPR allele carriers more easily categorized negative adjectives as self-referential (i.e., higher drift rate). Further, drift rate was associated with recall of negative self-referential stimuli. Findings across both studies provide further evidence that genetic variation may contribute to the etiology of negatively biased processing of self-referent information. Large scale studies examining the genetic contributions to negative self-referent processing may be warranted.

Semantic Distances in Depression: Relations Between ME and PAST, FUTURE, JOY, SADNESS, HAPPINESS

Using the Semantic Distance Task, we investigated the semantic distances between ME and five metaphorically conceptualized notions: PAST, FUTURE, JOY, SADNESS, and HAPPINESS. Three Polish-speaking groups participated in the study: depressive subjects ([Formula: see text]), patients in remission ([Formula: see text]), and non-depressed individuals ([Formula: see text]). T-test and the Kruskal-Wallis nonparametric equivalent of ANOVA analyses showed that subjects in remission placed ME significantly farther away from PAST than non-depressed individuals and depressed patients. Data mining algorithms indicated the distances ME-SADNESS, ME-PAST, and ME-FUTURE as the three strongest predictors of group membership. We interpret the findings in the light of a contrast effect and defense mechanisms. We propose that intergroup differences are especially prominent in tasks requiring creation of semantic associative relations, that is, in the first stage of conceptual processing. We suggest treating the results as confirmation that Beck's theory of depression applies at the level of notion comprehension, proving that processing of key concepts in depression symptoms (particularly PAST) runs differently in all three groups under consideration.

The Serotonin Transporter Promoter Variant, Stress, and Attentional Biases in Middle Childhood

Although evidence suggests that 5-HTTLPR variants may shape risk for depression, the influence is likely complex, and involves effects on endophenotypes. We examined associations between 5-HTTLPR and biases in attention to affective stimuli in a sample of girls and a sample of both boys and girls. Children with at least one short (S) variant of the 5-HTTLPR polymorphism had lower positive attentional bias scores in both samples. This association was qualified by an interaction with stress in one sample, such that links between the S allele and decreased positive attentional bias was significant only when life stress was elevated. This difference in findings between the two samples was explained by sex differences in samples; the GXE interaction was significant only in boys. Findings are discussed in the context of sex differences in GXE.

Cognition-related brain networks underpin the symptoms of unipolar depression: Evidence from a systematic review

This systematic review sources the latest neuroimaging evidence for the role of cognition-related brain networks in depression, and relates their abnormal functioning to symptoms of the disorder. Using theoretically informed and rigorous inclusion criteria, we integrate findings from 59 functional neuroimaging studies of adults with unipolar depression using a narrative approach. Results demonstrate that two distinct neurocognitive networks, the autobiographic memory network (AMN) and the cognitive control network (CCN), are central to the symptomatology of depression. Specifically, hyperactivity of the introspective AMN is linked to pathological brooding, self-blame, rumination. Anticorrelated under-engagement of the CCN is associated with indecisiveness, negative automatic thoughts, poor concentration, distorted cognitive processing. Downstream effects of this imbalance include reduced regulation of networks linked to the vegetative and affective symptoms of depression. The configurations of these networks can change between individuals and over time, plausibly accounting for both the variable presentation of depressive disorders and their fluctuating course. Framing depression as a disorder of neurocognitive networks directly links neurobiology to psychiatric practice, aiding researchers and clinicians alike.

Interaction of the 5-HTTLPR and childhood trauma influences memory bias in healthy individuals

The tendency to recall more negative and less positive information has been frequently related to the genetic susceptibility to depression. This memory bias may be associated with depression candidate genes especially in individuals who experienced stressful childhood events. The serotonin transporter gene, SLC6A4/5-HTT, regulates the reuptake of serotonin. The 5-HTTLPR polymorphism in the gene's promoter region has a short (S) and a long (L) allele, of which L contains a further SNP (rs25531), resulting in a triallelic polymorphism: La, Lg, and S. Both S and Lg result in increased serotonin signaling (to simplify, we refer to both alleles as 'S'), which in turn appears associated with depression vulnerability, specifically in individuals with stressful events. In non-depressed individuals (N=1083), we examined the interaction between the 5-HTTLPR genotype (LaLa, SLa, and SS) and stressful childhood events in association with explicit verbal memory bias (positive, negative). Two types of stressful childhood events were studied, namely childhood adverse events (e.g. parental loss) and interpersonal traumatic childhood events (e.g. abuse). Less positive memory bias was found for individuals with the SS genotype who had experienced interpersonal childhood traumatic events. No general association of genotype with memory bias was found, nor was there a significant interaction between genotype and childhood adverse events. Our results suggest that the depression-susceptibility genotype of the 5-HTTLPR is associated with depressive information processing styles when occurring in combination with traumatic childhood events. Tailoring treatment to specific risk profiles based on genetic susceptibility and childhood stress could be promising.

Shame and Guilt-Proneness in Adolescents: Gene-Environment Interactions

Rooted in people’s preoccupation with how they are perceived and evaluated, shame and guilt are self-conscious emotions that play adaptive roles in social behavior, but can also contribute to psychopathology when dysregulated. Shame and guilt-proneness develop during childhood and adolescence, and are influenced by genetic and environmental factors that are little known to date. This study investigated the effects of early traumatic events and functional polymorphisms in the brain-derived neurotrophic factor (BDNF) gene and the serotonin transporter gene promoter (5-HTTLPR) on shame and guilt in adolescents. A sample of N = 271 healthy adolescents between 14 and 17 years of age filled in measures of early traumatic events and proneness to shame and guilt, and were genotyped for the BDNF Val66Met and 5-HTTLPR polymorphisms. Results of moderator analyses indicated that trauma intensity was positively associated with guilt-proneness only in carriers of the low-expressing Met allele of BDNF Val66Met. This is the first study that identifies a gene-environment interaction that significantly contributes to guilt proneness in adolescents, with potential implications for developmental psychopathology.

Cognitive representations (Metaphorical Conceptualizations) of past, future, joy, sadness and happiness in depressive and non-depressive subjects: cognitive distortions in depression at the level of notion

The aim of this study was to see if and how the intensity of depression correlates with the cognitive representation of notions, and if any influence is reversed during remission. The cognitive representation indices used were the valence and number of metaphors produced for a notion. Three adult groups took part: persons with depression ([Formula: see text]), persons in remission ([Formula: see text]), and a control group ([Formula: see text]). Five notions were considered: PAST, FUTURE, JOY, SADNESS, and HAPPINESS. The Questionnaire of the Metaphorical Conceptualization of a Notion was used. The results showed that (a) depressive subjects did not have problems with metaphorical processing, (b) depressive subjects demonstrated strong interpretational negativism, (c) subjects during remission did not present distorted conceptual processing. The results are discussed in the context of theories of automatic metaphor processing, and conceptions of cognitive depressive distortions, in tasks requiring effort and substantial involvement of cognitive resources.

Children at risk for depression: memory biases, self-schemas, and genotypic variation

BACKGROUND

Daughters of depressed mothers are at increased risk for developing a depressive disorder. We know relatively little, however, about the specific factors that contribute to this elevated risk. The present study investigated the effects of familial risk for depression and the 5-HTTLPR and COMT Val158Met polymorphisms, which have been associated with risk for depression, on biases in endorsement of and memory for positive and negative adjectives.

METHODS

Following a negative mood induction, 60 girls between the ages of 10 and 14 who had recurrent depressed mothers (high risk for depression) and 91 age-matched daughters of never-disordered mothers (low risk for depression) completed a Self-Referent Encoding Task in which they decided whether negative and positive adjectives described them. Following the task they were asked to recall as many of the adjectives as they could.

RESULTS

Despite the absence of significant group differences in endorsement of positive or negative adjectives, high-risk girls with the COMT Val158Met Val/Val polymorphism recalled more positive (but not negative) words that they had endorsed than did high-risk girls who were homozygous for the Met allele. COMT was not associated with recall of valenced adjectives in low-risk girls. Across risk groups, 5-HTTLPR polymorphism was not associated with recall of valenced adjectives.

LIMITATIONS

Even with over 150 participants, there were relatively small numbers in some of the cells of this study, limiting its statistical power.

CONCLUSIONS

These results suggest that assessing the interaction of familial risk status and COMT polymorphism is important in understanding the development of depressive disorders.

The serotonin transporter linked polymorphic region and brain-derived neurotrophic factor valine to methionine at position 66 polymorphisms and maternal history of depression: associations with cognitive vulnerability to depression in childhood

Preliminary work indicates that cognitive vulnerability to depression may be associated with variants of the serotonin transporter promoter polymorphism (5-HTTLPR) and the valine to methionine at position 66 (val66met) polymorphism of the brain-derived neurotrophic factor (BDNF) gene; however, existing reports come from small samples. The present study sought to replicate and extend this research in a sample of 375 community-dwelling children and their parents. Following a negative mood induction, children completed a self-referent encoding task tapping memory for positive and negative self-descriptive traits. Consistent with previous work, we found that children with at least one short variant of the 5-HTTLPR had enhanced memory for negative self-descriptive traits. The BDNF val66met polymorphism had no main effect but was moderated by maternal depression, such that children with a BDNF methionine allele had a heightened memory for negative self-descriptive traits when mothers had experienced depression during children's lifetimes; in contrast, children with a methionine allele had low recall of negative traits when mothers had no depression history. The findings provide further support for the notion that the 5-HTTLPR is associated with cognitive markers of depression vulnerability and that the BDNF methionine allele moderates children's sensitivity to contextual factors.

Post-stroke depression and the aging brain

Ageing is associated with changes in the function of various organ systems. Changes in the cardiovascular system affect both directly and indirectly the function in a variety of organs, including the brain, with consequent neurological (motor and sensory performance) and cognitive impairments, as well as leading to the development of various psychiatric diseases. Post-stroke depression (PSD) is among the most frequent neuropsychiatric consequences of cerebral ischemia. This review discusses several animal models used for the study of PSD and summarizes recent findings in the genomic profile of the ageing brain, which are associated with age-related disorders in the elderly. Since stroke and depression are diseases with increased incidence in the elderly, great clinical benefit may especially accrue from deciphering and targeting basic mechanisms underlying PSD. Finally, we discuss the relationship between ageing, circadian rhythmicity and PSD.

Never-depressed females with a family history of depression demonstrate affective bias

According to cognitive theories of depression, individuals susceptible to depression attend selectively to negative information. The purpose of the study was to examine if such an affective processing bias is present in never-depressed individuals with a family history of major depressive disorder (MDD). Formerly depressed female patients having at least one first-degree relative with a history of MDD (n=23), their never-depressed female siblings (n=21) and never-depressed female controls (n=21) performed a conventional and an emotional Stroop task using negative, positive and neutral words. A significant effect was found of group on negative processing bias; post hoc comparisons indicated that never-depressed siblings showed a larger negative processing bias than never-depressed controls. No significant differences were observed in positive bias or conventional interference between the three groups. Our findings suggest that never-depressed females with a family history of depression, like depressed patients, have more difficulties to inhibit negative material and to direct their attention towards task-specific material. This adds to the existing evidence that affective processing bias is a trait characteristic that contributes to the onset of depression and that could be a useful endophenotype for MDD.

Gene-environment studies and borderline personality disorder: a review

We review recent gene-environment studies relevant to borderline personality disorder, including those focusing on impulsivity, emotion sensitivity, suicidal behavior, aggression and anger, and the borderline personality phenotype itself. Almost all the studies reviewed suffered from a number of methodological and statistical problems, limiting the conclusions that currently can be drawn. The best evidence to date supports a gene-environment correlation (rGE) model for borderline personality traits and a range of adverse life events, indicating that those at risk for BPD are also at increased risk for exposure to environments that may trigger BPD. We provide suggestions regarding future research on GxE interaction and rGE effects in borderline personality.

Platelets and depression in cardiovascular disease: A brief review of the current literature

Major depression is an independent risk factor for cardiovascular mortality and morbidity. The exact mechanisms linking depression and increased cardiovascular risk remain poorly understood. Several mechanisms have been proposed including increased platelet reactivity. This review focuses on the current literature that examines the platelet hypothesis of depression. To date studies show increased serotonin response, increased platelet serotonin receptor density, decreased serotonin transporter binding, and decreased platelet serotonin levels in individuals with depression. However other studies have shown no change in serotonin uptake. In addition to platelet serotonin specific pathways, other platelet pathways that have shown significant changes in depressed individuals include blunting of the platelet adenosine response, increased platelet thrombin response, increased glycoprotein Ib expression, increased P-selectin, β thromboglobulin, and platelet factor four, as well as decreased platelet brain derived neurotrophic factor. However there are other studies that show conflicting evidence of increased platelet activation as measured by integrin receptor α_2bβ₃. Other conflicting data include α adrenergic density and platelet response to augmented serotonin. The direction of future research in platelet functional changes in depression and coronary artery disease should continue to focus on serotonin specific pathways with emphasis on potential mechanisms of specific pathway changes.

Toward an integration of cognitive and genetic models of risk for depression

There is growing interest in integrating cognitive and genetic models of depression risk. We review two ways in which these models can be meaningfully integrated. First, information-processing biases may represent intermediate phenotypes for specific genetic influences. These genetic influences may represent main effects on specific cognitive processes or may moderate the impact of environmental influences on information-processing biases. Second, cognitive and genetic influences may combine to increase reactivity to environmental stressors, increasing risk for depression in a gene×cognition×environment model of risk. There is now growing support for both of these ways of integrating cognitive and genetic models of depression risk. Specifically, there is support for genetic influences on information-processing biases, particularly the link between 5-HTTLPR and attentional biases, from both genetic association and gene×environment (G×E) studies. There is also initial support for gene×cognition×environment models of risk in which specific genetic influences contribute to increased reactivity to environmental influences. We review this research and discuss important areas of future research, particularly the need for larger samples that allow for a broader examination of genetic and epigenetic influences as well as the combined influence of variability across a number of genes.

The effect of the serotonin transporter polymorphism (5-HTTLPR) on empathic and self-conscious emotional reactivity

We examined the relationship between a functional polymorphism of the serotonin transporter gene (5-HTTLPR) and individual differences in emotional reactivity in two laboratory studies. In Study 1, empathic responding and physiological reactivity to viewing films of others in distress were assessed in healthy adults in three age groups. In Study 2, emotional responding to watching oneself in an embarrassing situation was assessed in healthy adults and in patients with neurodegenerative diseases. In Study 1, participants with two short alleles of 5-HTTLPR reported more personal distress and showed higher levels of physiological responses in response to the films than participants with long alleles. In Study 2, participants with two short alleles reported more anger and amusement and displayed more emotional expressive behaviors in response to the embarrassing situation than participants with long alleles. These two findings from diverse samples of participants converge to indicate that individuals who are homozygous for the short allele variant of 5-HTTLPR have greater levels of emotional reactivity in two quite different socially embedded contexts.

The serotonin transporter gene linked polymorphic region is associated with the behavioral response to repeated stress exposure in infant rhesus macaques

The short allele of the serotonin transporter linked polymorphic region (5-HTTLPR) moderates the effects of stress on vulnerability to mood and anxiety disorders. The mechanism by which this occurs may relate to differential sensitivity to stressful life events. Here we explored whether 5-HTTLPR and sex affected behavioral responses to repeated maternal separation in infant rhesus macaques. Behaviors were collected during the acute (Day 1) and the chronic (Days 2-4) phases of the separation, and the effects of duration of separation (acute vs. chronic), genotype (long/long vs. short allele), and sex (male vs. female) on behavioral responses were analyzed across four successive separations. Males increased their levels of locomotion with repeated maternal separation, whereas females exhibited an increase in frequency of self-directed behavior, a measure of "depression-like" behavior. The short-allele predicted increased environmental exploration, particularly during the chronic phase of social separation, indicative of higher arousal. In addition, the short-allele carriers were more likely to increase their levels of self-directed behavior during the chronic phase of separation, as a function of repeated exposures. These findings suggest that the short allele may increase reactivity to repeated, chronic stressors, leaving them more vulnerable to affective psychopathology, with females particularly vulnerable.

Brooding rumination and risk for depressive disorders in children of depressed mothers

The goal of the current study was to examine the role of brooding rumination in children at risk for depression. We found that children of mothers with a history of major depression exhibited higher levels of brooding rumination than did children of mothers with no depression history. Examining potential mechanisms of this risk, we found no evidence for shared genetic influences (BDNF or 5-HTTLPR) or modeling of mothers' rumination. However, we did find that children with a history of prior depressive disorders exhibited higher current levels of brooding rumination than children with no depression history. Importantly, children's brooding predicted prospective onsets of new depressive episodes over a 20-month follow-up even when we statistically controlled for depressive symptom levels at the initial assessment, suggesting that the predictive effect of brooding rumination in children was not due simply to co-occurring depressive symptoms.

Amygdala to hippocampal volume ratio is associated with negative memory bias in healthy subjects

BACKGROUND

Negative memory bias is thought to be one of the main cognitive risk and maintenance factors for depression, but its neural substrates are largely unknown. Here, we studied whether memory bias is related to amygdala and hippocampal volume, two structures that are critical for emotional memory processes and that show consistent volume alterations in depression.

METHOD

Structural magnetic resonance imaging (MRI) was carried out in 272 healthy participants (62% female, 18-50 years old). All images were acquired on 1.5 T Siemens MRI scanners. Automatic segmentation of amygdala and hippocampus was performed using the FIRST module of FSL. Negative memory bias was assessed by the self-referent encoding/evaluation test.

RESULTS

Negative memory bias was associated with larger amygdala (p=0.042) and smaller hippocampal (p=0.029) volumes. In additional analyses, we found that, compared with the associations found with hippocampus and amygdala volume separately, a stronger association was found between negative memory bias and the ratio of amygdala:hippocampus volume (p=0.021).

CONCLUSIONS

In non-depressed subjects we found that larger amygdala and smaller hippocampal volumes are associated with negative memory bias. This suggests that an increased amygdala:hippocampus volume ratio plays a role in cognitive vulnerability often seen in individuals with high risk for depression and that these structural brain differences may pre-date the onset of depression.

Cognitive mechanisms of treatment in depression

Cognitive abnormalities are a core feature of depression, and biases toward negatively toned emotional information are common, but are they a cause or a consequence of depressive symptoms? Here, we propose a 'cognitive neuropsychological' model of depression, suggesting that negative information processing biases have a central causal role in the development of symptoms of depression, and that treatments exert their beneficial effects by abolishing these biases. We review the evidence pertaining to this model: briefly with respect to currently depressed patients, and in more detail with respect to individuals at risk for depression and the effects of antidepressant treatments. As well as being present in currently depressed individuals, negative biases are detectable in those vulnerable for depression due to neuroticism, genetic risk, or previous depressive illness. Recent evidence provides strong support for the notion that both antidepressant drugs and psychological therapies modify negative biases, providing a common mechanism for understanding treatments for depression. Intriguingly, it may even be possible to predict which patients will benefit most from which treatments on the basis of neural responses to negative stimuli. However, further research is required to ascertain whether negative processing biases will be useful in predicting, detecting, and treating depression, and hence in preventing a chronic, relapsing course of illness.

Response to psychosocial treatment in poststroke depression is associated with serotonin transporter polymorphisms

BACKGROUND AND PURPOSE

The Living Well With Stroke study has demonstrated effectiveness of a brief psychosocial treatment in reducing depressive symptoms after stroke. The purpose of this analysis was to determine whether key variables associated with prevalence of poststroke depression also predicted treatment response.

METHODS

Response to a brief psychosocial/behavioral intervention for poststroke depression was measured with the Hamilton Rating Scale for Depression. Analysis of covariance models tested for interaction of potential predictor variables with treatment group on percent change in Hamilton Rating Scale for Depression from pre- to post-treatment as an outcome.

RESULTS

Initial depression severity, hemispheric location, level of social support, age, gender, and antidepressant adherence did not interact with the treatment with respect to percent change in Hamilton Rating Scale for Depression when considered 1 at a time. Participants who carried 1 or 2 s-alleles at the 5-HTTLPR serotonin transporterpolymorphism or 1 or 2 9- or 12-repeats of the STin2 VNTR polymorphism had significantly better response to psychosocial treatment than those with no s-alleles or no 9- or 12-repeats.

CONCLUSIONS

Opposite to the effects of antidepressant drug treatment with selective serotonin reuptake inhibitors, the Living Well With Stroke psychotherapy intervention was most effective in 5-HTTLPR s-allele carriers and STin2VNTR 9- or 12-repeat carriers.

CLINICAL TRIAL REGISTRATION

URL: www.clinicaltrials.gov/ct/show/NCT00194454?order_1. Unique identifier: NCT00194454.

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.

The serotonin transporter promoter polymorphism and childhood positive and negative emotionality

Association studies of the serotonin transporter promoter polymorphism (5-HTTLPR) and negative emotionality (NE) are inconclusive. However, emerging evidence suggests that the association between this polymorphism and NE may be influenced by levels of another temperament trait, positive emotionality (PE). Therefore, this study examined whether the association between the 5-HTTLPR and NE was moderated by PE. A community sample of 413 three-year-old children completed a standardized battery of laboratory tasks designed to tap temperamental emotionality. Children were also genotyped for the 5-HTTLPR. No direct association between 5-HTTLPR genotype and NE was found. However, the interaction of child PE and NE predicted 5-HTTLPR genotype. Furthermore, children with a short allele who were also low in PE had significantly greater NE than children without a short allele or children with high PE. Our findings suggest that the short allele of the 5-HTTLPR is associated with NE only in the context of low PE. Inconsistent links between NE and this gene in previous research may stem from the failure to consider other temperament traits that moderate associations.

Serotonin transporter and BDNF genetic variants interact to predict cognitive reactivity in healthy adults

BACKGROUND

Cognitive theory and empirical evidence both suggest that cognitive reactivity (the tendency to think more negatively when in a sad mood) is an important marker of depression vulnerability. Research has not yet determined whether genetic factors contribute to the expression of cognitive reactivity.

METHODS

The present study examined associations between the 5-HTTLPR polymorphism of the SLC6A4 gene, the Val66Met polymorphism of the brain-derived neurotrophic factor (BDNF) gene, and cognitive reactivity in a never depressed, unmedicated, young adult sample (N=151).

RESULTS

The interaction between 5-HTTLPR and Val66Met polymorphisms significantly predicted change in dysfunctional thinking from before to after a standardized sad mood provocation. Cognitive reactivity increased among S/L(G) 5-HTTLPR homozygotes if they were also homozygous for the Val Val66Met allele. In contrast, presence of a Met Val66Met allele was associated with attenuated cognitive reactivity among S/L(G) 5-HTTLPR homozygotes.

LIMITATIONS

The sample size of the current study is relatively small for modern genetic association studies. However, results are consistent with previous research demonstrating biological epistasis between SLC6A4 and BDNF for predicting connectivity among neural structures involved in emotion regulation.

CONCLUSIONS

The BDNF Met allele may protect S/L(G) 5-HTTLPR homozygotes from increased dysfunctional thinking following a sad mood provocation. Study results are the first to demonstrate an epistatic genetic relationship predicting cognitive reactivity and suggest the need for more complex and integrative models of depression vulnerability.

Cognition and depression: current status and future directions

Cognitive theories of depression posit that people's thoughts, inferences, attitudes, and interpretations, and the way in which they attend to and recall information, can increase their risk for depression. Three mechanisms have been implicated in the relation between biased cognitive processing and the dysregulation of emotion in depression: inhibitory processes and deficits in working memory, ruminative responses to negative mood states and negative life events, and the inability to use positive and rewarding stimuli to regulate negative mood. In this review, we present a contemporary characterization of depressive cognition and discuss how different cognitive processes are related not only to each other, but also to emotion dysregulation, the hallmark feature of depression. We conclude that depression is characterized by increased elaboration of negative information, by difficulties disengaging from negative material, and by deficits in cognitive control when processing negative information. We discuss treatment implications of these conclusions and argue that the study of cognitive aspects of depression must be broadened by investigating neural and genetic factors that are related to cognitive dysfunction in this disorder. Such integrative investigations should help us gain a more comprehensive understanding of how cognitive and biological factors interact to affect the onset, maintenance, and course of depression.

Tianeptine: an antidepressant with memory-protective properties

The development of effective pharmacotherapy for major depression is important because it is such a widespread and debilitating mental disorder. Here, we have reviewed preclinical and clinical studies on tianeptine, an atypical antidepressant which ameliorates the adverse effects of stress on brain and memory. In animal studies, tianeptine has been shown to prevent stress-induced morphological sequelae in the hippocampus and amygdala, as well as to prevent stress from impairing synaptic plasticity in the prefrontal cortex and hippocampus. Tianeptine also has memory-protective characteristics, as it blocks the adverse effects of stress on hippocampus-dependent learning and memory. We have further extended the findings on stress, memory and tianeptine here with two novel observations: 1) stress impairs spatial memory in adrenalectomized (ADX), thereby corticosterone-depleted, rats; and 2) the stress-induced impairment of memory in ADX rats is blocked by tianeptine. These findings are consistent with previous research which indicates that tianeptine produces anti-stress and memory-protective properties without altering the response of the hypothalamic-pituitary-adrenal axis to stress. We conclude with a discussion of findings which indicate that tianeptine accomplishes its anti-stress effects by normalizing stress-induced increases in glutamate in the hippocampus and amygdala. This finding is potentially relevant to recent research which indicates that abnormalities in glutamatergic neurotransmission are involved in the pathogenesis of depression. Ultimately, tianeptine’s prevention of depression-induced sequelae in the brain is likely to be a primary factor in its effectiveness as a pharmacological treatment for depression.

Genetic sensitivity to the environment: the case of the serotonin transporter gene and its implications for studying complex diseases and traits

Evidence of marked variability in response among people exposed to the same environmental risk implies that individual differences in genetic susceptibility might be at work. The study of such Gene-by-Environment (GxE) interactions has gained momentum. In this article, the authors review research about one of the most extensive areas of inquiry: variation in the promoter region of the serotonin transporter gene (SLC6A4; also known as 5-HTT) and its contribution to stress sensitivity. Research in this area has both advanced basic science and generated broader lessons for studying complex diseases and traits. The authors evaluate four lines of evidence about the 5-HTT stress-sensitivity hypothesis: 1) observational studies about the serotonin transporter linked polymorphic region (5-HTTLPR), stress sensitivity, and depression in humans; 2) experimental neuroscience studies about the 5-HTTLPR and biological phenotypes relevant to the human stress response; 3) studies of 5-HTT variation and stress sensitivity in nonhuman primates; and 4) studies of stress sensitivity and genetically engineered 5-HTT mutations in rodents. The authors then dispel some misconceptions and offer recommendations for GxE research. The authors discuss how GxE interaction hypotheses can be tested with large and small samples, how GxE research can be carried out before as well as after replicated gene discovery, the uses of GxE research as a tool for gene discovery, the importance of construct validation in evaluating GxE research, and the contribution of GxE research to the public understanding of genetic science.

Association between a serotonin transporter length polymorphism and primary insomnia

STUDY OBJECTIVE

To test the hypothesis that a 44-base-pair insertion/deletion polymorphism in the 5' regulatory region of the serotonin transporter gene (5-HTTLPR) is associated with primary insomnia.

DESIGN

Association study.

SETTING

Sleep laboratory at the Central Institute of Mental Health, Mannheim, Germany.

PATIENTS

157 patients with primary insomnia and 827 healthy controls.

INTERVENTIONS

N/A.

MEASUREMENT AND RESULTS

We found the short (s-) allele of the 5-HTTLPR to be significantly more frequent in patients suffering from insomnia than in control individuals (47.1% vs. 39.9%: OR = 1.34).

CONCLUSIONS

This finding contributes to the understanding of the pathophysiology of primary insomnia and suggests a biological basis between the prevalent comorbidity of primary insomnia and other psychiatric disorders.

Mood state moderates the role of serotonin in cognitive biases

Reduction of the monoamine serotonin (5-HT) via the dietary manipulation of tryptophan (acute tryptophan depletion; ATD) has been shown to induce negative cognitive biases similar to those found in depression in healthy individuals. However, evidence also indicates that there can be positive effects of ATD on both mood and reinforcement processing. Here, we present two separate studies, with remarkably similar findings, which may help explain these discrepancies. In both experiments, we assessed cognitive biases following experimentally induced mood states under both a balanced amino acid drink (BAL) and ATD. A significant interaction between treatment, mood state and cognitive bias was observed in both experiments. In the first experiment, subjects undergoing positive mood induction demonstrated a positive cognitive bias on BAL, which was abolished by ATD. The same effect was observed in subjects undergoing neutral mood induction in the second experiment. These effects replicate findings in healthy individuals undergoing ATD. Subjects undergoing negative mood induction, by contrast, demonstrated the opposite pattern of results; in both experiments, they showed no bias under BAL but induction of a positive cognitive bias by ATD. These results mimic previous findings in currently depressed patients undergoing ATD. We therefore suggest that mood state moderates the effect of ATD on cognitive biases. This, in turn, has important implications for the understanding of the role of 5-HT in psychiatric disorders.

The serotonin transporter gene and risk for alcohol dependence: a meta-analytic review

Previous studies have implicated a relationship between particular allelic variations of the serotonin transporter gene (5HTTLPR) and alcohol dependence. To provide a current estimate of the strength of this association, particularly in light of inconsistent results for 5HTTLPR, we conducted a meta-analytic review of the association between 5HTTLPR and a clinical diagnosis of alcohol dependence. Of 145 studies initially identified, 22 (including 8050 participants) met inclusion criteria. Results indicated that there was a significant albeit modest association between alcohol dependence diagnosis and the presence of at least 1 short allele (OR=1.15, 95% CI=1.01, 1.30, p<.05). Slightly more robust results were observed for participants who were homogeneous for the short allele (OR=1.21, 95% CI=1.02, 1.44, p<.05). These results were unrelated to sex and race/ethnicity of participants; however, the effect size was moderated by study sample size and publication year. Additionally, the fail-safe N analysis indicated potential publication bias. Therefore, although our review indicates that there is a significant association between 5HTTLPR and alcohol dependence diagnosis, this result should be interpreted with caution.

Transition from stress sensitivity to a depressive state: longitudinal twin study

BACKGROUND

Daily-life stress sensitivity is associated with depression, but prospective data are lacking.

AIMS

To examine associations between baseline ecological daily-life stress sensitivity and later depression, and to identify genetic and non-genetic factors moderating the transition from stress sensitivity to depression.

METHOD

Daily-life stress sensitivity was assessed at baseline in twins (n = 502). One baseline and four follow-up measurements of depressive symptoms and negative life events were collected, as well as interview-based diagnoses at baseline and last follow-up. Hypothesised genetic markers were determined.

RESULTS

Baseline stress sensitivity was associated with increased depressive symptoms at follow-up and risk of major depressive disorder. Both genetic liability and major life events moderated the probability of transition from stress sensitivity to depression.

CONCLUSIONS

Onset of depression is attributable to pre-onset ecological measurements of stress sensitivity, particularly where genetic liability is high and individuals have reached a stage where the influence of competing environmental causes is low.

Developmental origins of cognitive vulnerabilities to depression: review of processes contributing to stability and change across time

Cognitive theories of depression have been shown to be potent predictors of future increases in depressive symptoms and disorder in children, adolescents, and adults. This article focuses on potential developmental origins of the main cognitive vulnerabilities, including dysfunctional attitudes, negative cognitive style, and rumination. We selectively review processes and factors that have been hypothesized to contribute to the emergence and stabilization of these cognitive risk factors. This review focuses on genetic factors, temperament, parents and peers as salient interpersonal influences, and stressful life events. We end with suggestions for future theory development and research. In particular, we emphasize the need for additional conceptual and empirical work integrating these disparate processes together into a coherent, developmental psychopathological model, and we highlight the coexistence of both stability and change in the development of cognitive vulnerabilities to depression across the lifespan.

Association of the serotonin transporter gene promoter region (5-HTTLPR) polymorphism with biased attention for emotional stimuli

A deletion polymorphism in the serotonin transporter-linked polymorphic region (5-HTTLPR) has been associated with vulnerability to affective disorders, yet the mechanism by which this gene confers vulnerability remains unclear. Two studies examined associations between the 5-HTTLPR polymorphism and attentional bias for emotional stimuli among nondepressed adults. Biased attention, attention engagement, and difficulty with attention disengagement were assessed with a spatial cuing task using emotional stimuli. Results from Study 1 (N = 38) indicated that short 5-HTTLPR allele carriers experienced greater difficulty disengaging their attention from sad and happy stimuli compared with long allele homozygotes. Study 2 participants (N = 144) were genotyped for the 5-HTTLPR polymorphism, including single nucleotide polymorphism rs25531 in the long allele of the 5-HTTLPR. Consistent with Study 1, individuals homozygous for the low-expressing 5-HTTLPR alleles (i.e., S and LG) experienced greater difficulty disengaging attention from sad, happy, and fear stimuli than high-expressing 5-HTTLPR homozygotes. Because this association exists in healthy adults, it may represent a susceptibility factor for affective disorders that becomes problematic during stressful life experiences.

Imaging serotonergic transmission with [11C]DASB-PET in depressed and non-depressed patients infected with HIV

INTRODUCTION

Site-selective imaging can provide significant insight into the mechanism of HIV-associated neurological disease. The goal of this study was to evaluate the involvement of serotonergic transmission in HIV-associated depression using [(11)C]DASB, a serotonin transporter (5-HTT)-specific radiopharmaceutical for positron emission tomography (PET).

METHODS

Nine depressed HIV+ subjects (HIV-D), 9 non-depressed HIV+ subjects (HIV-ND) and 7 healthy controls (HC) underwent an MRI scan and a [(11)C]DASB-PET scan. The outcome measure was 5-HTT binding potential normalized to non-displaceable tissue radioligand (BP(ND)).

RESULTS

HIV-ND subjects had lower mean regional 5-HTT BP(ND) estimates across regions compared to HC, while HIV-D subjects demonstrated higher mean regional binding values than HIV-ND subjects in most regions. Prior to correction for the false discovery rate, HIV-ND had significantly lower BP(ND) values compared to HC subjects in two regions (insula and anterior cingulate) and all HIV+ patients had significantly lower binding than HC in all regions except for the midbrain, thalamus and pons. After correction for the false discovery rate, only the insula showed significantly lower binding in HIV+ subjects compared to HC (P<0.0045). Despite a significant difference in the duration of illness between the HIV-D and HIV-ND groups, there was no definite correlation between the duration of illness and BP(ND).

CONCLUSION

Lower [(11)C]DASB binding in HIV+ patients compared to HC may reflect serotonergic neuronal loss as a component of generalized HIV-associated neurodegeneration. Higher mean regional BP(ND) values in HIV-D compared to HIV-ND subjects could reflect increased density of 5-HTT, leading to increased clearance of serotonin from the synapse, which could account, in part, for symptoms of depression. The lack of correlation between duration of illness and binding argues against these findings being the result of differential neurodegeneration only. Our findings suggest a possible role for dysregulated serotonergic transmission in HIV-associated depression.

Children's attentional biases and 5-HTTLPR genotype: potential mechanisms linking mother and child depression

In this study, we examined the roles of specific cognitive (attentional bias) and genetic (5-HTTLPR) risk factors in the intergenerational transmission of depression. Focusing first on the link between maternal history of major depressive disorder (MDD) and children's attentional biases, we found that children of mothers with a history of MDD during their children's lives, compared to children of mothers with no depression history, exhibited greater attentional avoidance of sad faces. This attention bias was specific to sad, rather than happy or angry, faces. There was also preliminary evidence that this relation is stronger among children carrying the 5-HTTLPR S or L(G) allele than among those homozygous for the L(A) allele. Next, conceptualizing mothers' levels of depressive symptoms during the multi-wave prospective follow-up within a vulnerability-stress framework, we found evidence for a three-way child 5-HTTLPR x attentional bias x mother depressive symptom interaction predicting children's depressive symptoms. Specifically, the relation between mother and child depressive symptom levels over time was strongest among children carrying the 5-HTTLR S or L(G) allele who also exhibited attentional avoidance of sad faces. These findings provide initial support for role of children's 5-HTTLPR genotype and attentional biases for sad faces in the intergenerational transmission of depression.

The BDNF Val66Met polymorphism is associated with rumination in healthy adults

This study examined associations between the tendency to ruminate and 2 polymorphisms: the Val66Met polymorphism in the brain-derived neurotrophic factor (BDNF) gene and 5-HTTLPR polymorphism in the serotonin transporter gene (SLC6A4). Participants were a homogeneous group of healthy, unmedicated, never depressed individuals with few current symptoms of depression (N = 71). Results indicated that met heterozygotes of the BDNF allele were significantly more likely to ruminate than individuals homozygous for the val BDNF allele. There was no association between rumination and the 5-HTTLPR polymorphism. Furthermore, the interaction between the 5-HTTLPR and BDNF polymorphisms did not predict rumination. Results suggest that variation in the BDNF gene may contribute to the tendency to ruminate. Because this association exists in healthy adults, it may represent a susceptibility factor for affective disorders.