Differential effects of 5-HTTLPR genotypes on inhibition of negative emotional information following acute stress exposure and tryptophan challenge

The serotonin gene 5-HTTLPR and brain food-reward responses during sadness: a mood-induction neuroimaging study

BACKGROUND

High-calorie foods become particularly rewarding and difficult to resist under affective stressful circumstances. Individuals carrying the short allele variant of the serotonin transporter gene (s-allele 5-HTTLPR) often exhibit enhanced emotional and neuroendocrine stress responsiveness, which increases their risk to gain weight or to develop obesity.

OBJECTIVE

To explore whether homozygous S-allele 5-HTTLPR carriers are more sensitive to the rewarding effects of high- compared to low-calorie foods during sad mood.

METHODS

From a large (n = 827) DNA 5-HTTLPR database, a selected subgroup of homozygous S-allele and L-allele carriers were monitored for affective-motivational (mood, wanting-liking) and neural (fMRI) food-reward responsiveness during a food exposure task, before and after sad mood induction. Brain responsiveness was measured for high versus low calorie food pictures in a set of appetitive- and cognitive control ROIs, respectively.

RESULTS

Mood induction significantly increased sad mood in the majority of participants. Analyses revealed a genotype x mood induction interaction in cognitive control but not in affective ROIs. LL- compared to SS-carriers exhibited greater contrast value in the inferior frontal sulcus, dorsolateral PFC and superior parietal lob when viewing high- compared to low-calorie food pictures, which only in LL-genotypes significantly declined after sad mood induction.

CONCLUSION

LL- compared to SS-genotypes may have stronger high-calorie food responses in cognitive control brain areas in the absence of stress indicating better capacity to resist the rewarding effects of palatable foods.

Genetic Variants Associated With Resilience in Human and Animal Studies

Resilience is broadly defined as the ability to maintain or regain functioning in the face of adversity and is influenced by both environmental and genetic factors. The identification of specific genetic factors and their biological pathways underpinning resilient functioning can help in the identification of common key factors, but heterogeneities in the operationalisation of resilience have hampered advances. We conducted a systematic review of genetic variants associated with resilience to enable the identification of general resilience mechanisms. We adopted broad inclusion criteria for the definition of resilience to capture both human and animal model studies, which use a wide range of resilience definitions and measure very different outcomes. Analyzing 158 studies, we found 71 candidate genes associated with resilience. OPRM1 (Opioid receptor mu 1), NPY (neuropeptide Y), CACNA1C (calcium voltage-gated channel subunit alpha1 C), DCC (deleted in colorectal carcinoma), and FKBP5 (FKBP prolyl isomerase 5) had both animal and human variants associated with resilience, supporting the idea of shared biological pathways. Further, for OPRM1, OXTR (oxytocin receptor), CRHR1 (corticotropin-releasing hormone receptor 1), COMT (catechol-O-methyltransferase), BDNF (brain-derived neurotrophic factor), APOE (apolipoprotein E), and SLC6A4 (solute carrier family 6 member 4), the same allele was associated with resilience across divergent resilience definitions, which suggests these genes may therefore provide a starting point for further research examining commonality in resilience pathways.

The association between childhood maltreatment and empathic perspective taking is moderated by the 5-HTT linked polymorphic region: Another example of "differential susceptibility"

Previous research has suggested that the short (S)-allele of the 5-HT transporter gene-linked polymorphic region (5-HTTLPR) may confer "differential susceptibility" to environmental impact with regard to the expression of personality traits, depressivity and impulsivity. However, little is known about the role of 5-HTTLPR concerning the association between childhood adversity and empathy. Here, we analyzed samples of 137 healthy participants and 142 individuals diagnosed with borderline personality disorder (BPD) focusing on the 5-HTTLPR genotype (S/L-carrier) and A/G SNP (rs25531), in relation to childhood maltreatment and empathy traits. Whereas no between-group difference in 5-HTTLPR genotype distribution emerged, the S-allele selectively moderated the impact of childhood maltreatment on empathic perspective taking, whereby low scores in childhood trauma were associated with superior perspective taking. In contrast, L-homozygotes seemed to be largely unresponsive to variation in environmental conditions in relation to empathy, suggesting that the S-allele confers "differential susceptibility". Moreover, a moderation analysis and tests for differential susceptibility yielded similar results when transcriptional activity of the serotonin transporter gene was taken into account. In conclusion, our findings suggest that the S-allele of the 5-HTTLPR is responsive to early developmental contingencies for "better and worse", i.e. conferring genetic plasticity, especially with regard to processes involving emotional resonance.

Effects of 5-HTTLPR genotype and cognitive rumination on long-term cortisol reactivity measured in human hair

Ample experimental and associative studies have shown that carrying two short (S) alleles of the serotonin transporter gene (5-HTTLPR) contributes to an increased vulnerability for stress and related affective disorders. Recent findings indicate that this relationship might become even more profound when also possessing a negative ruminative (stress-related) thinking style. However, previous studies on the relationship among 5-HTTLPR, stress, and stress-responsiveness almost exclusively measured salivary cortisol concentrations during exposure to a single acute (laboratory) stressor. Measuring cortisol concentrations over longer periods of time might better reflect (chronic) Gene by biological (HPA) stress responsiveness associations. In recent years, the strategy to assess hair cortisol concentration (HCC) has been established as a more reliable marker for chronic HPA activations. The current study explored associations between 3-months accumulated HCC and the tendency to ruminate about negative events in 27 S/S and 27 L/L 5-HTTLPR-carriers (screened from a large n = 827 DNA database). Hierarchical regression (including moderation) analyses revealed clear significant interactions between Genotype and Rumination (p < 0.01, f²=0.26); indicating greatest accumulation of HCC in high ruminating S/S-allele carriers. These findings implicate that the combined possession of a genetic (S-allele 5-HTTLPR) and cognitive (Rumination) stress-vulnerability might meaningfully increases long-term stress responsiveness; most likely due to increased daily (chronic) stress experiences. Lay summary   The current study investigated whether the combined possession of a biological (genetic) and cognitive (negative thinking pattern) stress vulnerability may lead to a greater vulnerability to experience daily stress. This hypothesis was confirmed as a higher accumulation of the cortisol stress hormone was found over the past 3 months in scalp hair of participants that carried both vulnerability factors in combination.

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.

Neurobiological Mechanisms of Stress Resilience and Implications for the Aged Population

BACKGROUND

Stress is a common reaction to an environmental adversity, but a dysregulation of the stress response can lead to psychiatric illnesses such as major depressive disorder (MDD), post-traumatic stress disorder (PTSD), and anxiety disorders. Yet, not all individuals exposed to stress will develop psychiatric disorders; those with enhanced stress resilience mechanisms have the ability to adapt successfully to stress without developing persistent psychopathology. Notably, the potential to enhance stress resilience in at-risk populations may prevent the onset of stress-induced psychiatric disorders. This novel idea has prompted a number of studies probing the mechanisms of stress resilience and how it can be manipulated.

METHODS

Here, we review the neurobiological factors underlying stress resilience, with particular focus on the serotoninergic (5-HT), glutamatergic, and γ-Aminobutyric acid (GABA) systems, as well as the hypothalamic-pituitary axis (HPA) in rodents and in humans. Finally, we discuss stress resiliency in the context of aging, as the likelihood of mood disorders increases in older adults.

RESULTS

Interestingly, increased resiliency has been shown to slow aging and improved overall health and quality of life. Research in the neurobiology of stress resilience, particularly throughout the aging process, is a nascent, yet, burgeoning field.

CONCLUSION

Overall, we consider the possible methods that may be used to induce resilient phenotypes, prophylactically in at-risk populations, such as in military personnel or in older MDD patients. Research in the mechanisms of stress resilience may not only elucidate novel targets for antidepressant treatments, but also provide novel insight about how to prevent these debilitating disorders from developing.

Tryptophan supplementation and serotonin function: genetic variations in behavioural effects

The neurotransmitter serotonin has a role in affective disorders such as depression and anxiety, as well as sleep, cognitive function and appetite. This review examines the evidence that serotonin-related genotypes may moderate the behavioural effects of supplementation with the serotonin precursor amino acidl-tryptophan (TRP), on which synthesis of serotonin (or 5-hydroxytryptamine; 5-HT) depends. However, 95 % of serotonin is synthesised and used in the periphery, and TRP is also metabolised via non-5-HT routes such as the kynurenine pathway. Moreover, understanding of genotypes involved in regulation of serotonin raises questions over the generalisability of TRP effects on behaviour across individuals with varied serotonergic genotypes. To date, only differences between variants of the 5-HT transporter-linked promoter region (5-HTTLPR) have been investigated in relation to behavioural effects of TRP supplementation. Effects of 5-HTTLPR genotypes are usually compared between the alleles that are either high (L/L′) or low (S/S′) expressing of mRNA for the 5-HT transporter receptor. Yet, another key genetic variable is sex: in women, the S/S′ genotype predicts sensitivity to improved mood and reduced cortisol by TRP supplementation, during stressful challenges, whereas the L/L′ genotype protects against stress-induced mood deterioration. In men, the L/L′ genotype may confer risk of stress-induced increases in negative affect; there are insufficient data to assess effects on male S/S′ genotypes. However, better-powered studies to detect sex by genotype by stress by TRP interactions, as well as consideration of more genotypes, are needed before strong conclusions and recommendations for behavioural effects of TRP treatment can be reached.

Does stress influence sleep patterns, food intake, weight gain, abdominal obesity and weight loss interventions and vice versa?

Decades of research have reported only weak associations between the intakes of specific foods or drinks and weight gain and obesity. Randomized controlled dietary intervention trials have only shown very modest effects of changes in nutrient intake and diet composition on body weight in obese subjects. This review summarizes the scientific evidence on the role mental stress (either in or not in association with impaired sleep) may play in poor sleep, enhanced appetite, cravings and decreased motivation for physical activity. All these factors contribute to weight gain and obesity, possibly via decreasing the efficacy of weight loss interventions. We also review evidence for the role that lifestyle and stress management may play in achieving weight loss in stress-vulnerable individuals with overweight.

Sex differences modulating serotonergic polymorphisms implicated in the mechanistic pathways of risk for depression and related disorders

Despite consistent observations of sex differences in depression and related emotional disorders, we do not yet know how these sex differences modulate the effects of genetic polymorphisms implicated in risk for these disorders. This Mini-Review focuses on genetic polymorphisms of the serotonergic system to illustrate how sex differences might modulate the neurobiological pathways involved in the development of depression. We consider the interacting role of environmental factors such as early-life stress. Given limited current knowledge about this topic, we highlight methodological considerations, challenges, and guidelines for future research. © 2016 Wiley Periodicals, Inc.

The interaction between 5-HTTLPR genotype and ruminative thinking on BMI

Negative affect or stress is often found to increase energy intake for high palatable energy-rich foods and hence weight gain. Reduced brain serotonin (5-HT) function is known to increase stress vulnerability and the risk for eating-related disturbances. A short (S) allele polymorphism in the serotonin transporter gene (5-HTTLPR) is associated with a less efficient functioning brain serotonin system and therefore higher stress vulnerability. It has been suggested that this genotype may be directly linked to an increased risk for weight gain and/or obesity. However, a high amount of variability has been apparent in replicating such a direct gene on weight gain relationship. A most recent suggestion is that this gene by weight relationship might be moderated by an additional (cognitive) vulnerability factor involving repetitive negative thinking (rumination). Our objective was to investigate whether the S-allele of 5-HTTLPR contributes to weight gain particularly in high cognitive ruminating individuals. A total of 827 healthy young male and female college students (aged 21·3 (sd 3·0) years; BMI 16–41·7 kg/m2) were genotyped for the 5-HTTLPR polymorphism and assessed for rumination (Event Related Ruminative Index) and body weight. In line with the hypothesis, a hierarchical regression model showed that higher BMI scores were observed in specifically high ruminating S'-carriers (P=0·031, f²=0·022). These results suggest that cognitive rumination may be a critical moderator of the association between 5-HTTLPR and body mass.

The importance of nutrition in aiding recovery from substance use disorders: A review

BACKGROUND

Nutrition is a prerequisite for health; yet, there is no special nutritional assessment or guidance for drug and alcohol dependent individuals, despite the fact that their food consumption is often very limited, risking malnutrition. Further, the premise is examined that malnutrition may promote drug seeking and impede recovery from substance use disorders (SUD).

METHOD

A narrative review addressed the relationship between substance use disorders and nutrition, including evidence for malnutrition, as well as their impact on metabolism and appetite regulation. The implications of the biopsychology of addiction and appetite for understanding the role of nutrition in SUD were also considered.

RESULTS

The literature overwhelmingly finds that subjects with alcohol use disorder (AUD) and drug use disorder (DUD) typically suffer from nutrient deficiencies. These nutrient deficiencies may be complicit in the alcoholic myopathy, osteopenia and osteoporosis, and mood disorders including anxiety and depression, observed in AUD and DUD. These same individuals have also been found to have altered body composition and altered hormonal metabolic regulators. Additionally, brain processes fundamental for survival are stimulated both by food, particularly sweet foods, and by substances of abuse, with evidence supporting confusion (addiction transfer) when recovering from SUD between cravings for a substance and craving for food.

CONCLUSION

Poor nutritional status in AUD and DUD severely impacts their physical and psychological health, which may impede their ability to resist substances of abuse and recover their health. This review contributes to a better understanding of interventions that could best support individuals with substance use disorders.

Gene by cognition interaction on stress-induced attention bias for food: Effects of 5-HTTLPR and ruminative thinking

INTRODUCTION

Stress is often found to increase the preference and intake of high caloric foods. This effect is known as emotional eating and is influenced by cognitive as well as biological stress vulnerabilities. An S-allele of the 5-HTTLPR gene has been linked to decreased (brain) serotonin efficiency, leading to decreased stress resilience and increased risks for negative affect and eating related disturbances. Recently it has been proposed that a cognitive ruminative thinking style can further exacerbate the effect of this gene by prolonging the already increased stress response, thereby potentially increasing the risk of compensating by overeating high palatable foods.

OBJECTIVE

This study was aimed at investigating whether there is an increased risk for emotional eating in high ruminative S/S-allele carriers reflected by an increased attention bias for high caloric foods during stress.

METHODS

From a large (N=827) DNA database, participants (N=100) were selected based on genotype (S/S or L/L) and ruminative thinking style and performed an eye-tracking visual food-picture probe task before and after acute stress exposure. A significant Genotype x Rumination x Stress-interaction was found on attention bias for savory food; indicating that a stress-induced attention bias for specifically high-caloric foods is moderated by a gene x cognitive risk factor.

CONCLUSION

Both a genetic (5-HTTLPR) and cognitive (ruminative thinking) stress vulnerability may mutually increase the risk for stress-related abnormal eating patterns.

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.

Stressful life events moderate the relationship between genes and biased attention to emotional faces in youth

Attention bias to emotion may be an intermediate trait for stress-reactive psychopathology associated with biologically plausible candidate genes, yet the precise direction of effects within the youth literature remains unclear. The present study investigated whether stressful life events (SLEs) moderate the link between genetic risk (5-HTTLPR and COMT) and attention bias to emotion among youth (n= 467). Analyses revealed a differential effect of gene. Among youth who had experienced more recent SLEs, those homozygous for the low expressing allele of 5-HTTLPR (S/S) demonstrated preferential attention toward negative emotional expressions, whereas youth homozygous for the high expressing COMT genotype (Val/Val) showed attentional avoidance of positive facial expressions. No interaction between 5-HTTLPR and COMT was found. These findings highlight the importance of investigating stress as a moderator within the intermediate trait literature and suggest that biologically plausible candidate genes may have a differential effect in the pathway to psychological disorders.

Gene × cognition interaction on stress-induced eating: effect of rumination

People often crave for high-caloric sweet foods when facing stress and this 'emotional eating' is a most important cause for weight gain and obesity. Eating under stress contrasts with the normally expected response of a loss of appetite, yet in spite of intensive research from neurobiological and cognitive disciplines we still do not know why stress or negative affect triggers overeating in so many of us. Since the prevalence of overweight and obesity still rises, the discovery of crucial risk factors is a most desirable goal of today's research on sub-optimal eating habits. This paper summarizes the most relevant current knowledge from the (human) literature regarding cognitive and biological vulnerabilities for stress-induced emotional eating. A (non-systematic) review of the most relevant studies reveals that most studies contemplate a rather one-directional way of focusing on either cognitive or biological factors, showing inconsistent results. The current paper elaborates and/or integrates these findings into a biological-cognitive interaction model in which a specific combination of genetic and cognitive vulnerabilities are thought to increase our bio-behavioral response to stress, critically increasing the rewarding value of pleasant foods and, hence, emotional eating.

The Impact of Genetics on Physical Resilience and Successful Aging

Objective: To better understand the impact of genetics on resilience and successful aging, we tested a model of successful aging. Method: This was a descriptive study with a single interview and blood draw done with residents in a continuing care retirement community. Five genes associated with resilience were included in the model. The hypothesis was tested using structural equation modeling. Results: A total of 116 participants completed the survey. Two SNPs from SLC6A4 (rs25533 and rs1042173) and age were the only variables associated with physical resilience and explained 9% of the variance. Cognitive status, age, and depression were directly associated with successful aging; variance in rs25532 or rs1042173, resilience, and pain were indirectly associated with successful aging through depression. Discussion: Continued research to replicate these findings is needed so as to be able to recognize older adults at risk of low physical resilience and implement appropriate interventions.

Interaction between 5-HTTLPR genotype and cognitive stress vulnerability on sleep quality: effects of sub-chronic tryptophan administration

BACKGROUND

Abundant evidence suggests that allelic variation in the serotonin transporter-linked polymorphic region (5-HTTLPR) influences susceptibility to stress and its affective consequences due to brain serotonergic vulnerability. Based on recent assumptions, the present study examined whether the 5-HTTLPR genotype may also interact with a vulnerability to chronic stress experience (conceptualized by trait neuroticism) in order to influence sleep quality and, additionally, whether this is influenced by brain serotonergic manipulations.

METHODS

In a well-balanced experimental design, homozygous S-allele (n = 57) and L-allele (n = 54) genotypes with high and low chronic stress vulnerability (neuroticism) were first assessed for general past sleep quality during a month before onset of the experiment. Then subjects were assessed for sleep quality following 7 days of tryptophan (3.0g/day) or placebo intake.

RESULTS

Although high neuroticism was significantly related to a higher frequency of stressful life events and daily hassles, it did not interact with the 5-HTTLPR genotype on general past sleep quality. However, as expected, a 7 day period of tryptophan administration was exclusively associated with better sleep quality scores in the S'/S' genotype with high trait neuroticism.

CONCLUSIONS

Current findings suggest that 5-HTTLPR does not directly interact with stress vulnerability in order to influence sleep quality. Instead, based on current and previous findings, it is suggested that the S'/S' 5-HTTLPR genotype promotes the risk for stress-related sleep disturbances because of an increased susceptibility to the depressogenic consequences of stress. Accordingly, by way of reducing depressive symptomatology, tryptophan augmentation may particularly improve sleep quality in stress-vulnerable individuals carrying the 5-HTTLPR S-allele.

Sucrose preload reduces snacking after mild mental stress in healthy participants as a function of 5-hydroxytryptamine transporter gene promoter polymorphism

Brain serotonin (5-hydroxytryptamine, 5-HT) dysfunction is considered to promote food intake and eating-related disturbances, especially under stress or negative mood. Vulnerability for 5-HT disturbances is considered to be genetically determined, including a short (S) allele polymorphism in the serotonin transporter gene (5-HTTLPR) that is associated with lower serotonin function. Since 5-HT function may be slightly increased by carbohydrate consumption, S-allele 5-HTTLPR carriers in particular may benefit from a sugar-preload due to their enhanced 5-HT vulnerability. The aim of the current study was to investigate whether a sugar-containing preload may reduce appetite and energy intake after exposure to stress to induce negative mood, depending on genetic 5-HT vulnerability. From a population of 771 healthy young male and female genotyped college students 31 S/S carriers (8 males, 23 females) and 26 long allele (L/L) carriers (9 males, 17 females) (mean ± S.D. 22 ± 1.6 years; body mass index, BMI, 18-33 kg/m(2)) were monitored for changes in appetite and snacking behavior after stress exposure. Results revealed an increased energy intake after mild mental stress (negative mood) mainly for high-fat sweet foods, which was significantly greater in S/S carriers, and only in these genotypes this intake was significantly reduced by a sucrose-containing preload. Although alternative explanations are possible, it is suggested that S/S participants may have enhanced brain (hypothalamic) 5-HT responsiveness to food that makes them more susceptible to the beneficial satiation effects of a sucrose-preload as well as to the negative effects of mild mental stress on weight gain.

Effects of stress and dietary tryptophan enhancement on craving for alcohol in binge and non-binge heavy drinkers

Stress is known to play an important role in alcohol abuse, whereas binge drinking may increase individuals' susceptibility to the development of alcohol dependence. We set out to investigate whether binge drinkers (BDs) or non-BDs (NBDs) are at a greater risk of an increase in their desire for alcohol following experimental stress induction (modified Trier Social Stress Test; Experiment 1) and to explore the biological mechanisms underlying such an effect (Experiment 2). Preclinical evidence suggests that serotonin may mediate stress-induced reinstatement of alcohol intake. We therefore tested whether dietary tryptophan (TRP) enhancement would modulate stress-induced desire for alcohol and whether it would affect the two populations (BD/NBD) differently. In Experiment 1 (14 NBDs, 10 BDs; mean weekly alcohol intake 50.64 U), stress induction selectively increased strong desire for alcohol compared with the nonstressful condition in BDs. Throughout the experiment, BDs reported greater negative reinforcement type of craving than NBDs, but also a higher expectancy of alcohol-induced negative effects. In Experiment 2, 41 participants (22 NBDs, 19 BDs; mean alcohol intake 38.81 U) were given either the TRP-rich (TRP+; 9 BDs, 11 NBD) or the control (CTR; 10 BD, 11 NBD) diet before undergoing stress induction. In BDs, the TRP+ diet prevented the stress-induced increase in strong desire that was observed in individuals receiving the CTR diet. In NBDs, the TRP+ diet appeared to facilitate an increase in strong desire. These findings suggest that BDs may indeed be at a greater risk than NBDs of an increase in their craving for alcohol when stressed. Furthermore, whereas enhancement of 5-hydroxytryptamine function may moderate the impact of stress on craving in BDs, it seems to facilitate stress-induced craving in NBDs, suggesting that the serotonergic system may be differentially involved depending on individual binge drinking status.

Effect of sub chronic tryptophan supplementation on stress-induced cortisol and appetite in subjects differing in 5-HTTLPR genotype and trait neuroticism

Stress or negative effect often increases preference for, and intake of, palatable snack foods and this may be influenced by cognitive and genetic factors related to stress and 5-HT vulnerability. The short (S) compared to the long (L) allele of the 5-HT transporter linked polymorphic region (5-HTTLPR) has been associated (i) with decreased 5-HT transporter function and availability and hence, with 5-HT vulnerability, and (ii) with greater stress-responsiveness. Stress-proneness is furthermore promoted by cognitive stress-vulnerability, a key feature of trait neuroticism. Brain 5-HT function can be manipulated by dietary administration of its amino acid precursor tryptophan (Trp), and the beneficial effects of dietary Trp on stress experience and emotional eating may be greatest following repeated administration in both stress- and 5-HT-vulnerable subjects. The aim was to examine the influence of repeated Trp administration on stress responsiveness and emotional eating in homozygous 5-HTTLPR S-allele (N=60) and L-allele (N=58) carriers with high and low neuroticism. Following seven days of Trp or PLC intake, mood, cortisol and appetite were assessed before and after exposure to acute stress and snack intake and preference were measured post-stress. It was hypothesized that Trp would reduce stress experience and emotional eating particularly in S-allele carriers with high neuroticism. Results revealed Trp treatment caused a clear reduction in stress-induced cortisol levels in S/S-allele carriers exclusively, and prevented a stress-induced increase in appetite only in S/S-allele carriers with high trait neuroticism. The findings reveal an advantageous effect of sub chronic Trp treatment on stress experience and appetite depending on stress and (genetic) serotonergic vulnerability.

Differential influence of the 5-HTTLPR genotype, neuroticism and real-life acute stress exposure on appetite and energy intake

Stress or negative mood often promotes energy intake and overeating. Since the serotonin transporter-linked polymorphic region (5-HTTLPR) is found to mediate stress vulnerability as well as to influence energy intake, this gene may also influence the negative effects of stress exposure on overeating. Moreover, since stress proneness also reflects cognitive stress vulnerability - as often defined by trait neuroticism - this may additionally predispose for stress-induced overeating. In the present study it was investigated whether the 5-HTTLPR genotype interacted with neuroticism on changes in mood, appetite and energy intake following exposure to a real-life academic examination stressor. In a balanced-experimental design, homozygous S-allele and L-allele carriers (N = 94) with the lowest and highest neuroticism scores were selected from a large database of 5-HTTLPR genotyped students. Mood, appetite and energy intake were measured before and after a 2-hour academic examination and compared with a control day. Examination influenced appetite for particular sweet snacks differently depending on 5-HTTLPR genotype and neuroticism. S/S compared with L/L subjects reported greater examination stress, and this was accompanied by a more profound post-stress increase in appetite for sweet snacks. Data also revealed a 5-HTTLPR genotype by trait neuroticism interaction on energy intake, regardless of examination. These results consolidate previous assumptions of 5-HTTLPR involvement in stress vulnerability and suggest 5-HTTLPR and neuroticism may influence stress-induced overeating depending on the type of food available. These findings furthermore link previous findings of increased risk for weight gain in S/S-allele carriers, particularly with high scores on trait neuroticism, to increased energy intake.

Synergistic effect of 5-HT2A receptor gene and MAOA gene on the negative emotion of patients with depression

OBJECTIVE

To analyse the synergistic effect of polymorphism of the tandem repeat sequence u-VNTR of 5-hydroxytryptamine 2A (5-HT2A) receptor gene and monoamine oxidase A (MAOA) gene on the negative emotion in frontal lobe of patients with depression through functional magnetic resonance imaging (fMRI) technique.

METHODS

Functional magnetic resonance imaging scanning was performed for 72 patients with depression and 70 gender, age-matched healthy people with physical examination under negative emotion recognition task. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was adopted to analyse genotype. The superior, middle and inferior gyrus of bilateral frontal lobe was regarded as the brain region of interest, and then the difference of activation intensity in frontal lobe subregion between control groups and patient groups with different genotypes, and the interaction between the two kinds of polymorphism were compared.

RESULTS

The activation intensity in right frontal middle gyrus of patients with CC genotype increased obviously compared with TT and TC genotype patient groups and TT genotype control group (P<0·01); the activation intensity in right frontal inferior gyrus of patients with CC genotype increased obviously compared with TT and TC genotype patient groups and control groups (P<0·01); the activation intensity in right frontal middle gyrus and left frontal inferior gyrus of patients with MAOA high-activity genotype increased obviously compared with patient and control groups with MAOA low-activity genotype (P<0·01). In sum, there existed synergistic effect of the two genotypes on the activation abnormality of negative emotion recognition in right frontal middle gyrus (F = 6·18, P = 0·029). The negative activation in right frontal middle gyrus of patients with CC+H genotypes increased most obviously (P<0·05).

CONCLUSION

The frontal abnormality of patients with depression had certain 5-HT genetic basis, and 5-HT2A receptor CC allele and MAOA-H genotype had synergistic effect on the activity abnormality when recognizing negative emotion in right frontal middle gyrus of patients with depression.

Interaction between the 5-HTTLPR genotype, impact of stressful life events, and trait neuroticism on depressive symptoms in healthy volunteers

INTRODUCTION

Recent biopsychological research on stress-related psychopathology shows promising evidence for the 5-hydroxytryptamine (5-HT) transporter linked polymorphic region (5-HTTLPR) genotype by life event interaction on depression. Yet, there appears to be variability in replicating such findings. From leading cognitive models of depression, it can be deduced that mainly high-impact events, particularly in stress-vulnerable, high trait neuroticism individuals who possess low coping abilities, can cause depression.

OBJECTIVE

The current study therefore examines the interaction between the 5-HTTLPR genotype, impact of life events, and trait neuroticism on depression symptoms.

PARTICIPANTS AND METHODS

A group of 771 healthy individuals, 595 women and 176 men aged 21.0±2.1 years, were genotyped for the 5-HTTLPR polymorphism and were rated for depressive symptoms, impact of life events, and neuroticism.

RESULTS

Only the low-allele expressing (S) 5-HTTLPR carriers showed vulnerability to depression exclusively when they also reported exposure to high-impact events and showed high neuroticism.

CONCLUSION

This suggests that cognitive vulnerabilities may mediate the 5-HTTLPR genotype by life event interaction on depression.

Acute responsivity of the serotonergic system to S-citalopram and positive emotionality-the moderating role of the 5-HTTLPR

According to the idea that the central serotonergic system has a modulatory function on behavior and personality in general, we aimed to highlight its association to habitual positive emotionality. In a placebo-controlled double-blind and randomized cross-over neuroendocrine challenge design (n = 72 healthy males) we investigated the association of the central serotonergic responsivity, 5-HTTLPR-genotype as well as their combined effects on positive emotionality. Regression analyses revealed an involvement of the serotonergic system in positive emotionality. There was, however, no direct association between positive emotionality and cortisol responses to S-citalopram; rather 5-HTTLPR-genotype showed an association (p < 0.05). That is, positive emotionality scores increased with the number of s-alleles carried by the individuals. Most notable was the moderating role of 5-HTTLPR-genotype (p < 0.05) on the association between acute serotonergic responsivity and positive emotionality. Indeed, this association was only found in ss-homozygotes, in which the acute responsivity of the serotonergic system additionally seems to contribute to the level of positive emotionality (r = 0.70, p < 0.05). The findings correspond to previous research demonstrating that the 5-HTTLPR is not only involved in the negative-emotional aspects of behavior and temperament, but is associated, moreover, with positive affectivity-supporting the assumption of its valence-neutrality. In addition, our data are in line with the idea of possible influences of the 5-HTTLPR-genotype on early neuronal development. They also indicate the need for further studies in order to clearly elucidate the role of the serotonergic system and its subcomponents in the regulation of positive emotionality.

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

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

Psilocybin biases facial recognition, goal-directed behavior, and mood state toward positive relative to negative emotions through different serotonergic subreceptors

BACKGROUND

Serotonin (5-HT) 1A and 2A receptors have been associated with dysfunctional emotional processing biases in mood disorders. These receptors further predominantly mediate the subjective and behavioral effects of psilocybin and might be important for its recently suggested antidepressive effects. However, the effect of psilocybin on emotional processing biases and the specific contribution of 5-HT2A receptors across different emotional domains is unknown.

METHODS

In a randomized, double-blind study, 17 healthy human subjects received on 4 separate days placebo, psilocybin (215 μg/kg), the preferential 5-HT2A antagonist ketanserin (50 mg), or psilocybin plus ketanserin. Mood states were assessed by self-report ratings, and behavioral and event-related potential measurements were used to quantify facial emotional recognition and goal-directed behavior toward emotional cues.

RESULTS

Psilocybin enhanced positive mood and attenuated recognition of negative facial expression. Furthermore, psilocybin increased goal-directed behavior toward positive compared with negative cues, facilitated positive but inhibited negative sequential emotional effects, and valence-dependently attenuated the P300 component. Ketanserin alone had no effects but blocked the psilocybin-induced mood enhancement and decreased recognition of negative facial expression.

CONCLUSIONS

This study shows that psilocybin shifts the emotional bias across various psychological domains and that activation of 5-HT2A receptors is central in mood regulation and emotional face recognition in healthy subjects. These findings may not only have implications for the pathophysiology of dysfunctional emotional biases but may also provide a framework to delineate the mechanisms underlying psylocybin's putative antidepressant effects.

Epistasis between 5-HTTLPR and ADRA2B polymorphisms influences attentional bias for emotional information in healthy volunteers

Individual differences in emotional processing are likely to contribute to vulnerability and resilience to emotional disorders such as depression and anxiety. Genetic variation is known to contribute to these differences but they remain incompletely understood. The serotonin transporter (5-HTTLPR) and α2B-adrenergic autoreceptor (ADRA2B) insertion/deletion polymorphisms impact on two separate but interacting monaminergic signalling mechanisms that have been implicated in both emotional processing and emotional disorders. Recent studies suggest that the 5-HTTLPR s allele is associated with a negative attentional bias and an increased risk of emotional disorders. However, such complex behavioural traits are likely to exhibit polygenicity, including epistasis. This study examined the contribution of the 5-HTTLPR and ADRA2B insertion/deletion polymorphisms to attentional biases for aversive information in 94 healthy male volunteers and found evidence of a significant epistatic effect (p<0.001). Specifically, in the presence of the 5-HTTLPR s allele, the attentional bias for aversive information was attenuated by possession of the ADRA2B deletion variant whereas in the absence of the s allele, the bias was enhanced. These data identify a cognitive mechanism linking genotype-dependent serotonergic and noradrenergic signalling that is likely to have implications for the development of cognitive markers for depression/anxiety as well as therapeutic drug effects and personalized approaches to treatment.

Physiological and affective reactivity to a 35% CO₂ inhalation challenge in individuals differing in the 5-HTTLPR genotype and trait neuroticism

The inhalation of 35% carbon dioxide (CO₂) results in an acute stress response in healthy individuals and may accordingly provide a good paradigm to examine potential vulnerability factors for stress reactivity and stress-related psychopathology. It has been proposed that CO₂ reactivity is moderated by genetic (5-HTTLPR) and personality (neuroticism) factors, yet no experimental study has investigated their effects on CO₂ reactivity simultaneously. The current study examined the singular and interactive effects of the 5-HTTLPR genotype and neuroticism in predicting the affective and physiological response to a 35% CO₂ challenge in a healthy sample of male and female students. From a large group of 771 students, 48 carriers of the low/low expressing allele (S/S, S/Lg, Lg/Lg) and 48 carriers of the high/high expressing allele (La/La) with the lowest and the highest neuroticism scores (77 females, 19 males; mean age ± SD: 20.6 ± 2 years) were selected and underwent a 35% CO₂ inhalation. Visual analogue scales for anxiety and discomfort and the Panic Symptom List were used to assess affective symptomatology, while salivary samples and heart rate were assessed to establish the physiological response. A typical pattern of responses to CO₂ was observed, characterised by increases in anxiogenic symptoms and physical panic symptomatology and a reduction in heart rate; however, no effect on salivary cortisol concentration was observed. Additionally, the CO₂ reactivity did not differ between groups divided by the 5-HTTLPR genotype or neuroticism. Findings of the current study do not support a role for singular or interactive effects of the 5-HTTLPR genotype and trait neuroticism on affective and physiological reactivity to a 35% CO₂ inhalation procedure.

Serotonin transporter genotype modulates cognitive reappraisal of negative emotions: a functional magnetic resonance imaging study

A functional polymorphism within the serotonin transporter gene (5-HTTLPR) has been reported to modulate emotionality and risk for affective disorders. The short (S) allele has less functional efficacy than the long (L) allele and has been associated with enhanced emotional reactivity. One possible contributing factor to the high emotionality in S carriers may be inefficient use of cognitive strategies such as reappraisal to regulate emotional responses. The aim of the present study was to test whether the 5-HTTLPR genotype modulates the neural correlates of emotion regulation. To determine neural differences between S and L allele carriers during reappraisal of negative emotions, 15 homozygous S (S'/S') and 15 homozygous L (L'/L') carriers underwent functional magnetic resonance imaging (fMRI), while performing an instructed emotion regulation task including downregulation, upregulation and passive viewing of negative emotional pictures. Compared to L'/L' allele carriers, subjects who carry the S'/S' allele responded with lower posterior insula and prefrontal brain activation during passive perception of negative emotional information but showed greater prefrontal activation and anterior insula activation during down- and upregulation of negative emotional responses. The current results support and extend previous findings of enhanced emotionality in S carriers by providing additional evidence of 5-HTTLPR modulation of volitional emotion regulation.

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.

5-HTTLPR and BDNF Val66Met polymorphisms moderate effects of stress on rumination

This study examined whether polymorphisms in the serotonin transporter (SLC6A4, 5-HTTLPR) and brain-derived neurotropic factor (BDNF Val66Met, rs6265) genes moderate the relationship between life stress and rumination. Participants were a large homogenous group of healthy, unmedicated, never depressed individuals with few current symptoms of depression (N = 273). Results indicate that individuals with two short (S) alleles of the 5-HTTLPR polymorphism or two Met alleles of the BDNF Val66Met polymorphism ruminate more under conditions of life stress, compared to the other genotypes. Moreover, the accumulation of risk alleles (i.e. S and Met alleles) across genes is associated with significantly greater rumination in the context of life stress. These results suggest that both 5-HTTLPR and BDNF Val66Met moderate the relationship between life stress and rumination. These findings support the notion that variation in these genes is associated with biological sensitivity to the negative effects of stress.