5-HTTLPR, anxiety and gender interaction moderates right amygdala volume in healthy subjects

The effects of acute versus repeated cannabidiol administration on trauma-relevant emotional reactivity: A double-blind, randomized, placebo-controlled trial

Despite the widespread use and perceived efficacy of cannabidiol (CBD) as an anxiolytic, few controlled studies have evaluated the effects of CBD on anxiety-relevant indications, and only one has done so in the context of trauma-related symptoms. The current study was designed to address this gap in the literature. Participants were 42 trauma-exposed individuals (Mage = 23.12 years, SDage = 6.61) who endorsed elevated stress. They were randomly assigned to take 300 mg of oral CBD or placebo daily for 1 week. Acute (i.e., following an initial 300 mg dose) and repeated (i.e., following 1 week of daily 300 mg dosing) effects of CBD were evaluated in relation to indicators of anxious arousal (i.e., anxiety, distress, heart rate) in response to idiographic trauma script presentation. The results of the current study suggest that relative to placebo, 300 mg CBD did not significantly reduce anxiety, B = 13.37, t(37) = 1.71, p = .096, d = 0.09, Bayes factor (BF10) = 0.54; distress, B = 15.20, t(37) = 1.31, p = .197, d = 0.07, BF10 = 0.51; or heart rate, B = -1.09, t(36) = -0.32, p = .755, d = 0.02, BF10 = 0.29, evoked by idiographic trauma script presentation in the context of acute or repeated administration. These data suggest that CBD may not effectively reduce trauma-relevant emotional arousal; however, more work is needed to confidently assert such claims due to the small sample size. The current study extends the groundwork for additional studies in this important area.

Factors associated with gender and sex differences in anxiety prevalence and comorbidity: A systematic review

Background: The prevalence and comorbidity of anxiety disorders are significantly different between women and men, with research showing a greater impact on women. The aim of this review was to identify the psychosocial and biological factors that have been considered to explain this gender and sex difference in prevalence and determine whether these factors are related to any anxiety comorbidity differences between men and women. Methods: Following the PRISMA guidelines, we carried out a systematic review of studies published between 2008 and 2021 in PsycINFO and PubMed databases. Empirical and review studies evaluating psychosocial and biological factors that could influence the difference in prevalence and comorbidity between men and women were included. A qualitative narrative synthesis was performed to describe the results. Results: From 1012 studies, 44 studies were included. Retrieved articles were categorized depending on their object of study: psychosocial factors (n = 21), biological factors (n = 16), or comorbidity (n = 7). Results showed that differences in anxiety between women and men have been analyzed by psychosocial and biological factors but rarely together. Among the psychosocial factors analyzed, masculinity may be a protective factor for anxiety development, while femininity can be a risk factor. In the studies that took biological factors into account, the potential influence of brain structures, genetic factors, and fluctuations in sexual hormones are pointed out as causes of greater anxiety in women. Concerning comorbidity, the results noted that women tend to develop other internalizing disorders (e.g. depression), while men tend to develop externalizing disorders (e.g. substance abuse). Conclusions: For an accurate understanding of differences between women and men in anxiety, both biological and psychosocial factors should be considered. This review highlights the need to apply the biopsychosocial model of health and the gender perspective to address differences in anxiety between sexes.

Subclinical Cognitive and Neuropsychiatric Correlates and Hippocampal Volume Features of Brain White Matter Hyperintensity in Healthy People

White matter hyperintensities (WMH) are associated with brain aging and behavioral symptoms as a possible consequence of disrupted white matter pathways. In this study, we investigated, in a cohort of asymptomatic subjects aged 50 to 80, the relationship between WMH, hippocampal atrophy, and subtle, preclinical cognitive and neuropsychiatric phenomenology. Thirty healthy subjects with WMH (WMH+) and thirty individuals without (WMH−) underwent comprehensive neuropsychological and neuropsychiatric evaluations and 3 Tesla Magnetic Resonance Imaging scan. The presence, degree of severity, and distribution of WMH were evaluated with a semi-automated algorithm. Volumetric analysis of hippocampal structure was performed through voxel-based morphometry. A multivariable logistic regression analysis indicated that phenomenology of subclinical apathy and anxiety was associated with the presence of WMH. ROI-based analyses showed a volume reduction in the right hippocampus of WMH+. In healthy individuals, WMH are associated with significant preclinical neuropsychiatric phenomenology, as well as hippocampal atrophy, which are considered as risk factors to develop cognitive impairment and dementia.

Structural brain changes with lifetime trauma and re-experiencing symptoms is 5-HTTLPR genotype-dependent

Background: Findings on structural brain alterations following trauma are inconsistent due probably to heterogeneity in imaging studies and population, clinical presentations, genetic vulnerability, and selection of controls. This study examines whether trauma and re-experiencing symptoms are associated with specific alterations in grey matter volumes and if this varies according to 5-HTTLPR genotype. Methods: Structural MRI was used to acquire anatomical scans from 377 community-dwelling older adults. Quantitative regional estimates of 22 subregional volumes were derived using FreeSurfer software. Lifetime trauma was assessed using the validated Watson's PTSD inventory, which evaluates the most severe trauma experienced according to DSM criteria. Analyses adjusted for age, sex, total brain volume, head injury, and comorbidities. Results: Of the 212 participants reporting lifetime trauma, 35.4% reported re-experiencing symptoms and for 1.9%, this was severe enough to meet criteria for full threshold PTSD. In participants with the SS 5-HTTLPR genotype only, re-experiencing symptoms were associated with smaller volumes in middle and superior temporal, frontal (lateral orbital, rostral and caudal middle) and parietal (precuneus, inferior and superior) regions. The trauma-exposed participants without re-experiencing symptoms were not significantly different from the non-trauma-exposed participants except for smaller precuneus and superior parietal region in traumatized participants and a larger amygdala in traumatized women specifically. Conclusions: In the non-clinical sample, lifetime trauma and re-experiencing symptoms were associated with smaller volume in prefrontal, temporal and parietal cortex subregions, and this varied according to serotonergic genetic vulnerability, 5-HTTLPR SS individuals being most susceptible.

Altered temporal variance and functional connectivity of BOLD signal is associated with state anxiety during acute systemic inflammation

Systemic inflammation is accompanied by complex behavioral changes and disturbed emotion regulation that have been related to the pathophysiology of mood disorders including depression and anxiety. However, the causal role of systemic inflammation on mood disorders is still unclear. We herein investigated neural resting state patterns of temporal variance of the amygdala and functional connectivity within the salience network underlying changes in state anxiety during experimentally-induced systemic inflammation. In this randomized, double-blind study, N = 43 healthy men received an intravenous injection of either low-dose lipopolysaccharide (LPS, 0.4 ng/kg body weight) or saline. Resting state functional magnetic resonance imaging was assessed before and 3.5 h after injection. State anxiety, assessed with a standardized questionnaire, and plasma cytokine concentrations were repeatedly measured. LPS administration induced a transient systemic inflammatory response reflected in increases in plasma Interleukin (IL)-6 and Tumor Necrosis Factor (TNF)-α concentration. Compared to placebo, state anxiety and temporal variance in the amygdala significantly increased while functional connectivity in the salience network decreased during LPS-induced systemic inflammation. Together, these data indicate that acute systemic inflammation alters temporal variance of the BOLD signal as well as functional connectivity in brain regions and networks implicated in emotion processing and regulation. These results are of translational importance to encourage further research on the role of inflammatory pathways in the pathophysiology of neuropsychiatric conditions including anxiety disorders.

Risky driving and the persistent effect of a randomized intervention focusing on impulsivity: The role of the serotonin transporter promoter polymorphism

Road traffic accidents are a serious public health issue, and real-life traffic offences are an excellent indicator of the behavioural tendencies of impulsivity and risk-taking. We have previously reported on short-term efficacy of a brief intervention in driving schools to reduce traffic risks (Paaver et al., Accid. Anal. Prev., 2013; 50, 430-437), and have now addressed the question of whether does the impact of the intervention last for a few years, and whether traffic behaviour and the intervention effect are associated with the serotonin transporter polymorphism (5-HTTLPR) genotype as the central serotonin system is strongly associated with impulse control. Participants of the study were 1866 novice car-drivers (mean age 23.0, SD = 7.2 years). Data on traffic violations were obtained four years after intervention from the police database and on traffic collisions from the national traffic insurance database. DNA samples were available for 767 participants and 5-HTTLPR genotypes were classified using the triallelic model. For the observation period after the intervention, speeding, drunk driving and involvement in traffic accidents were significantly lower in the intervention group. 5-HTTLPR genotype was associated with traffic behaviour: The S'-allele carriers had significantly lower odds for speeding offences and traffic accidents. The lower prevalence of S'-allele carriers among those who had committed speeding offences was statistically significant in females, while the lower prevalence of having been involved in a traffic accident was rather observed in males. Statistically significant intervention effects were observed only in the L'/L' homozygotes who had higher prevalence of traffic incidents. Conclusively, the brief intervention in traffic schools had a significant impact on traffic safety within subsequent four years, and traffic behaviour was associated with the serotonin transporter genotype. These findings suggest that subjects who are less likely to self-regulate their driving habits while gaining experience would benefit from training of impulsivity recognition.

IL-18 Serum Levels and Variants of the Serotonin Transporter Gene Are Related to Awareness of Emotions in Healthy Subjects: A Preliminary Study

OBJECTIVE

Interaction between the nervous and immune systems may influence emotions, ultimately affecting human health. Cytokines may play a role in developing emotional dysregulation as in alexithymia, a personality construct characterized by the subclinical inability to identify and describe emotions, often associated with several psychiatric and psychosomatic disorders. The proinflammatory cytokine IL-18, with a recognized role in brain functions, may influence serotonin metabolism and appears to be associated with alexithymia. Healthy individuals carrying the long allele (L) of the serotonin transporter gene polymorphic region (5-HTTLPR), and thus having lower concentrations of serotonin in the synaptic cleft, show a greater tendency toward alexithymia, with some gender differences. To explore a potential physiological interaction between IL-18, serotonin neurotransmission, and alexithymia, we investigated whether IL-18 serum levels and 5-HTTLPR are linked to alexithymic traits in healthy subjects.

METHODS

We measured IL-18 serum levels in 115 Italian-Caucasian healthy subjects genotyped for 5-HTTLPR allele variants, divided by gender and assessed for alexithymia scores using the 20-item Toronto Alexithymia Scale.

RESULTS

IL-18 levels are significantly more elevated in individuals with the LL genotype (n = 25) than in carriers of the short allele (n = 90, p = 0.0073). Specifically, in LL males (n = 11), i.e., the group with the most relevant increase in IL-18, cytokine values positively correlated with difficulty identifying feelings, which is a component of alexithymia (r = 0.634, p = 0.036).

CONCLUSIONS

These results indicate a possible novel interaction between IL-18 and the serotoninergic system to mediate emotional unawareness, suggesting putative biological predictors of emotional dysregulation, which in turn can act as a risk factor for a variety of medical conditions in susceptible subjects.

The association of measures of the serotonin system, personality, alcohol use, and smoking with risk-taking traffic behavior in adolescents in a longitudinal study

Studies on the neurobiological basis of risk-taking behavior have most often focused on the serotonin system. The promoter region of the gene encoding the serotonin transporter contains a polymorphic site (5-HTTLPR) that is important for the transcriptional activity, and studies have demonstrated its association with brain activity and behavior. Another molecular mechanism that reflects the capacity of the central serotonin system is the activity of the enzyme monoamine oxidase (MAO) as measured in platelets. The purpose of the present study was to examine how measures of the serotonin system (platelet MAO activity and the 5-HTTLPR polymorphism), personality variables, alcohol use and smoking are associated with risk-taking traffic behavior in schoolchildren through late adolescence. The younger cohort of the longitudinal Estonian Children Personality Behaviour and Health Study (originally n = 583) filled in questionnaires about personality traits, smoking status, alcohol use and traffic behavior at age 15 and 18 years. From venous blood samples, platelet MAO activity was measured radioenzymatically and 5-HTTLPR was genotyped. During late adolescence, subjects with lower platelet MAO activity were more likely to belong to the high-risk traffic behavior group. Male 5-HTTLPRs'-allele carriers were more likely to belong to the high-risk traffic behavior group compared to the l'/l' homozygotes. Other variables predicting risk group were alcohol use, smoking and Maladaptive impulsivity.The results suggest that lower capacity of the serotoninergic system is associated with more risky traffic behavior during late adolescence, but possibly by different mechanisms in boys and girls.

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.

A positron emission tomography study of the serotonergic system in relation to anxiety in depression

Symptoms of anxiety are highly comorbid with major depressive disorder (MDD) and are known to alter the course of the disease. To help elucidate the biological underpinnings of these prevalent disorders, we previously examined the relationship between components of anxiety (somatic, psychic and motoric) and serotonin 1A receptor (5-HT_1A) binding in MDD and found that higher psychic and lower somatic anxiety was associated with greater 5-HT_1A binding. In this work, we sought to examine the correlation between these anxiety symptom dimensions and 5-HTT binding. Positron emission tomography with [¹¹C]-3-amino-4-(3-dimethylamino-methylphenylsulfanyl)-benzonitrile ([¹¹C]DASB) and a metabolite-corrected arterial input function were used to estimate regional 5-HTT binding in 55 subjects with MDD and anxiety symptoms. Somatic anxiety was negatively correlated with 5-HTT binding in the thalamus (β=-.33, p=.025), amygdala (β=-.31, p=.007) and midbrain (β=-.72, p<.001). Psychic anxiety was positively correlated with 5-HTT binding in midbrain only (β=.46, p=.0025). To relate to our previous study, correlation between 5-HT_1A and 5-HTT binding was examined, and none was found. We also examined how much of the variance in anxiety symptom dimensions could be explained by both 5-HTT and 5-HT_1A binding. The developed model was able to explain 68% (p<.001), 38% (p=.012) and 32% (p=.038) of the total variance in somatic, psychic, and motoric anxiety, respectively. Results indicate the tight coupling between the serotonergic system and anxiety components, which may be confounded when using aggregate anxiety measures. Uncovering serotonin's role in anxiety and depression in this way may give way to a new generation of therapeutics and treatment strategies.

5-HTTLPR moderates the association between interdependence and brain responses to mortality threats

While behavioral research suggests an association between cultural worldview and decreased anxiety of death, the underlying neurobiological mechanisms remain unclear. Using functional MRI, we investigated whether and how the serotonin transporter promoter polymorphism (5-HTTLPR), which has been associated with mental disorders such as anxiety and depression, moderates the associations between a cultural trait (i.e., interdependence) and self-report of death anxiety/depression and between interdependence and brain responses to mortality threats. Long/long and short/short allele carriers of the 5-HTTLPR were scanned using fMRI while they performed a one-back task on death-related, death-unrelated negative, and neutral words. Participants' interdependence and death anxiety/depression were assessed using questionnaires after scanning. We found that participants who assessed themselves with greater interdependence reported lower death anxiety/depression and showed decreased neural response to death-related words in emotion-related brain regions including the anterior cingulate, putamen, and thalamus. However, these results were evident in long/long allele carriers of the 5-HTTLPR but not in short/short allele carriers who even showed positive associations between interdependence and neural activities in the anterior cingulate, putamen and thalamus in response to death-related words. Our findings suggest candidate mechanisms for explaining the complex relationship between genotype, cultural traits, and mental/neural responses to mortality threats. Hum Brain Mapp 38:6157-6171, 2017. © 2017 Wiley Periodicals, Inc.

Imaging genetics in neurodevelopmental psychopathology

Neurodevelopmental disorders are defined by highly heritable problems during development and brain growth. Attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorders (ASDs), and intellectual disability (ID) are frequent neurodevelopmental disorders, with common comorbidity among them. Imaging genetics studies on the role of disease-linked genetic variants on brain structure and function have been performed to unravel the etiology of these disorders. Here, we reviewed imaging genetics literature on these disorders attempting to understand the mechanisms of individual disorders and their clinical overlap. For ADHD and ASD, we selected replicated candidate genes implicated through common genetic variants. For ID, which is mainly caused by rare variants, we included genes for relatively frequent forms of ID occurring comorbid with ADHD or ASD. We reviewed case-control studies and studies of risk variants in healthy individuals. Imaging genetics studies for ADHD were retrieved for SLC6A3/DAT1, DRD2, DRD4, NOS1, and SLC6A4/5HTT. For ASD, studies on CNTNAP2, MET, OXTR, and SLC6A4/5HTT were found. For ID, we reviewed the genes FMR1, TSC1 and TSC2, NF1, and MECP2. Alterations in brain volume, activity, and connectivity were observed. Several findings were consistent across studies, implicating, for example, SLC6A4/5HTT in brain activation and functional connectivity related to emotion regulation. However, many studies had small sample sizes, and hypothesis-based, brain region-specific studies were common. Results from available studies confirm that imaging genetics can provide insight into the link between genes, disease-related behavior, and the brain. However, the field is still in its early stages, and conclusions about shared mechanisms cannot yet be drawn.

A Potential Role of the 5-HTTLPR Polymorphism in Self-Reported Executive Functioning

Intense effort is directed toward searching for associations between genes and neuropsychological measures of executive functions. In contrast, the impact of genetic polymorphisms on self-rating of everyday executive functioning has not been investigated so far. This study was designed to test associations of self-reported executive functioning, measured with the Behavior Rating Inventory of Executive Function (BRIEF-A), with dopaminergic and serotoninergic genes in non-clinical population and to assess impact of neuropsychological and personality characteristics on these associations. One hundred healthy adults completed the BRIEF-A, personality inventories SPQ-74, STAI, MMPI, and neuropsychological tests for executive functions. Polymorphisms in the DRD4, COMT, DRD2, HTR2A, and SLC6A4 genes were genotyped. We revealed a significant main effect of the SLC6A4's 5-HTTLPR polymorphism on BRIEF-A scores (F = 2.21, P = .018, η2 = .24). Among the BRIEF-A measures, the genotype effect was significant for the Plan/Organize (F = 7.34, P = .008, η2 = .07) and Task Monitor scales (F = 4.33, P = .04, η2 = .04), and the Metacognition index (F = 4.21, P = .043, η2 = .04). Carriers of the short allele reported fewer problems than homozygotes for the long allele. Correlations of the BRIEF-A measures with neuropsychological variables were weak, while those with personality characteristics were strong, with trait anxiety being the most powerful predictor of the BRIEF-A scores. However, the relationship between the 5-HTTLPR and BRIEF-A scores remained significant when trait anxiety was controlled for. The results suggest a potential role of the 5-HTTLPR in self-reported everyday task planning and monitoring.

Increased cerebellar gray matter volume in head chefs

OBJECTIVE

Chefs exert expert motor and cognitive performances on a daily basis. Neuroimaging has clearly shown that that long-term skill learning (i.e., athletes, musicians, chess player or sommeliers) induces plastic changes in the brain thus enabling tasks to be performed faster and more accurately. How a chef's expertise is embodied in a specific neural network has never been investigated.

METHODS

Eleven Italian head chefs with long-term brigade management expertise and 11 demographically-/ psychologically- matched non-experts underwent morphological evaluations.

RESULTS

Voxel-based analysis performed with SUIT, as well as, automated volumetric measurement assessed with Freesurfer, revealed increased gray matter volume in the cerebellum in chefs compared to non-experts. The most significant changes were detected in the anterior vermis and the posterior cerebellar lobule. The magnitude of the brigade staff and the higher performance in the Tower of London test correlated with these specific gray matter increases, respectively.

CONCLUSIONS

We found that chefs are characterized by an anatomical variability involving the cerebellum. This confirms the role of this region in the development of similar expert brains characterized by learning dexterous skills, such as pianists, rock climbers and basketball players. However, the nature of the cellular events underlying the detected morphological differences remains an open question.

The influence of 5-HTTLPR and Val66Met polymorphisms on cortical thickness and volume in limbic and paralimbic regions in depression: a preliminary study

BACKGROUND

Structural brain abnormalities have been investigated in multi-genetic and complex disorders such as major depressive disorder (MDD). Among the various candidate genes implicated in MDD, the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and 5-HT transporter gene linked polymorphism (5-HTTLPR) have garnered the most attention due to their putative roles in neural plasticity and antidepressant response. However, relatively few studies have assessed the influence of these polymorphysims on cortical thickness or brain volume in para-limbic and limbic regions in MDD, which was the aim of this study.

METHODS

Forty-three adults with MDD and 15 healthy controls (HC) underwent structural magnetic resonance imaging (MRI). Cortical thickness was assessed in frontal, cingulate and temporal regions. Volumetric measures were carried out in the thalamus, caudate, putamen, pallidum, hippocampus and amygdala. Participants were genotyped to determine their 5-HTTLPR (tri-allelic) and Val66Met polymorphisms.

RESULTS

In the combined sample (MDD + HC), smaller right pallidum volumes were found in LA/S (LA/S & LA/LG) heterozygotes compared to S/S (S/S, LG/S & LG/LG) homozygotes, though the effect was modest. In the MDD group, larger left thalamus and putamen volumes were observed in LA/LA homozygotes. No Val66Met or 5-HTTLPR genotype effects existed on cortical thickness and no main effects of the Val66Met polymorphism were observed.

CONCLUSION

Our preliminary results suggest that the 5-HTTLPR polymorphism is associated with morphometric changes in regions known to play an important role in emotional and reward processing in depression. A larger sample size is required to replicate these findings and to potentially reveal subtle morphometric changes.

Imaging genetics studies on monoaminergic genes in major depressive disorder

Although depression is the leading cause of disability worldwide, current understanding of the neurobiology of depression has failed to be translated into clinical practice. Major depressive disorder (MDD) pathogenesis is considered to be significantly influenced by multiple risk genes, however genetic effects are not simply expressed at a behavioral level. Therefore the concept of endophenotype has been applied in psychiatric genetics. Imaging genetics applies anatomical or functional imaging technologies as phenotypic assays to evaluate genetic variation and their impact on behavior. This paper attempts to provide a comprehensive review of available imaging genetics studies, including reports on genetic variants that have most frequently been linked to MDD, such as the monoaminergic genes (serotonin transporter gene, monoamine oxidase A gene, tryptophan hydroxylase-2 gene, serotonin receptor 1A gene and catechol-O-methyl transferase gene), with regard to key structures involved in emotion processing, such as the hippocampus, amygdala, anterior cingulate cortex and orbitofrontal cortex.

Novel developments in genetic and epigenetic mechanisms of anxiety

PURPOSE OF REVIEW

The present review aims to deliver a systematic overview of current developments and trends in (epi)genetics of anxiety and to identify upcoming challenges and opportunities.

RECENT FINDINGS

Genes related to peptide and hormone signaling have been suggested for anxiety-related phenotypes, e.g., the NPSR1 gene, which has been associated predominantly with panic disorder in women, and shown to interact with environmental factors and to influence psychometric, neurophysiological, and neuroimaging correlates of anxiety. Similar multi-level results have been reported for genetic and epigenetic variation in the OXTR gene, especially in social anxiety disorder (SAD), and for CRHR1 gene variation in women with panic disorder. Variants in RGS2 and ASIC1 genes were linked to panic disorder, with the latter also being implicated in SAD treatment response. Finally, monoaminergic 'risk' genes (SLC6A4, MAOA, HTR1A) were related to SAD, generalized anxiety disorder and women with panic disorder, anxiety traits and response to psychopharmacological and psychotherapeutic interventions.

SUMMARY

Converging evidence for potential genetic and epigenetic risk markers has been gathered and future studies call for independent replications and multi-level integration of dimensional approaches, environmental factors, and biological readouts, while considering sex-specific substratification. Particularly, epigenetic variation appears promising for disease course and treatment response predictions.

5-HTTLPR Expression Outside the Skin: An Experimental Test of the Emotional Reactivity Hypothesis in Children

Background

There is increasing evidence that variation in the promoter region of the serotonin transporter gene SLC6A4 (i.e., the 5-HTTLPR polymorphism) moderates the impact of environmental stressors on child psychopathology. Emotional reactivity −the intensity of an individual’s response to other’s emotions− has been put forward as a possible mechanism underlying these gene-by-environment interactions (i.e., G×E). Compared to children homozygous for the L-allele (LL-genotypes), children carrying an S-allele (SS/SL-genotypes), specifically when they have been frequently exposed to negative emotions in the family environment, might be more emotionally reactive and therefore more susceptible to affective environmental stressors. However, the association between 5-HTTLPR and emotional reactivity in children has not yet been empirically tested. Therefore, the goal of this study was to test this association in a large-scale experiment.

Methods

Children (N = 521, 52.5% boys, Mage = 9.72 years) were genotyped and randomly assigned to happy, angry or neutral dynamic facial expressions and vocalizations. Motor and affective emotional reactivity were assessed through children’s self-reported negative and positive affect (n = 460) and facial electromyography activity (i.e., fEMG: the zygomaticus or “smile” muscle and the corrugator or “frown” muscle, n = 403). Parents reported on their negative and positive parenting behaviors.

Results

Children mimicked and experienced the emotion they were exposed to. However, neither motor reactivity nor affective reactivity to these emotions depended on children’s 5-HTTLPR genotype: SS/SL-genotypes did not manifest any stronger response to emotional stimuli than LL-genotypes. This finding remained the same when taking the broader family environment into account, controlling for kinship, age, gender and genetic ancestry, and when including a tri-allelic factor.

Conclusions

We found no evidence for an association between the 5-HTTLPR polymorphism and children’s emotional reactivity. This finding is important, in discounting one potential underlying endophenotype of G×E between the 5-HTTLPR and affective environmental stressors.

Serotonin transporter gene polymorphism (5-HTTLPR) influences trait anxiety by modulating the functional connectivity between the amygdala and insula in Han Chinese males

A functional polymorphism (5-hydroxytryptamine transporter linked polymorphic region [5-HTTLPR]) in the promoter region of human serotonin transporter gene has been found to be associated with several dimensions of neuroticism and psychopathology, especially anxiety. However, the neural basis underlying the association between 5-HTTLPR and anxiety is less clear. Here, we explored how 5-HTTLPR influenced anxiety by modulating the spontaneous brain activities in Han Chinese. First, we found an association between 5-HTTLPR and anxiety only in the male and not in the female population, where male S/S homozygotes had a significantly higher level of anxiety than male L allele carriers. Then, we examined how 5-HTTLPR influenced anxiety at both regional and network levels in the brain at rest. At the regional level, we found a significantly higher fractional amplitude of low-frequency fluctuations in the amygdala in male S/S homozygotes relative to male L allele carriers. At the network level, male S/S homozygotes showed a weaker resting-state functional connectivity (RSFC) between the amygdala and various regions, including the insula, Heschl's gyrus, lateral occipital cortex, superior temporal gyrus, and hippocampus, and a stronger RSFC between the amygdala and various regions, including the supramariginal gyrus and middle frontal gyrus. However, at both levels, only was the amygdala-insula RSFC correlated with anxiety. Mediation analyses further revealed that the amygdala-insula RSFC mediated the association between 5-HTTLPR and anxiety. In short, our study provided the first empirical evidence that the amygdala-insula RSFC served as the neural basis underlying the association between 5-HTTLPR and anxiety, suggesting a potential neurogenetic susceptibility mechanism for anxiety.

Allelic variation at 5-HTTLPR is associated with brain morphology in a Chinese population

Previous studies have reported significant associations of 5-HTTLPR with brain structures mainly in Europeans, but the situations in other ethnic groups remain largely unknown. Here we examined the association of 5-HTTLPR with regional gray matter volume in Han Chinese, and observed significant association in the postcentral gyrus and precuneus cortex.

Pleiotropic locus for emotion recognition and amygdala volume identified using univariate and bivariate linkage

OBJECTIVE

The role of the amygdala in emotion recognition is well established, and amygdala volume and emotion recognition performance have each been shown separately to be highly heritable traits, but the potential role of common genetic influences on both traits has not been explored. The authors investigated the pleiotropic influences of amygdala volume and emotion recognition performance.

METHOD

In a sample of randomly selected extended pedigrees (N=858), the authors used a combination of univariate and bivariate linkage to investigate pleiotropy between amygdala volume and emotion recognition performance and followed up with association analysis.

RESULTS

The authors found a pleiotropic region for amygdala volume and emotion recognition performance on chromosome 4q26 (LOD score=4.40). Association analysis conducted in the region underlying the bivariate linkage peak revealed a variant meeting the corrected significance level (Bonferroni-corrected p=5.01×10(-5)) within an intron of PDE5A (rs2622497, p=4.4×10(-5)) as being jointly influential on both traits. PDE5A has been implicated previously in recognition-memory deficits and is expressed in subcortical structures that are thought to underlie memory ability, including the amygdala.

CONCLUSIONS

This study extends our understanding of the shared etiology between the amygdala and emotion recognition by showing that the overlap between amygdala volume and emotion recognition performance is due at least in part to common genetic influences. Moreover, this study identifies a pleiotropic locus for the two traits and an associated variant, which localizes the genetic signal even more precisely. These results, when taken in the context of previous research, highlight the potential utility of PDE5 inhibitors for ameliorating emotion recognition deficits in individuals suffering from mental or neurodegenerative illness.