Smoking moderates association of 5-HTTLPR and in vivo availability of serotonin transporters

Although preclinical studies clearly indicate an effect of 5-HTTLPR genotype on 5-HT transporter (5-HTT) expression, studies in humans provided inconclusive results, hypothetically due to environmental factors and differences in individual behavior. For example, nicotine and other constituents of tobacco smoke elevate serotonin (5-HT) levels in the brain and may thereby cause homeostatic adaptations in 5-HTT availability that moderate effects of 5-HTTLPR genotype. To test whether 5-HTT availability in the midbrain is affected by smoking status and 5-HTTLPR genotype, we pooled data from prior studies on in vivo 5-HTT availability (BP_ND) measured with positron emission tomography (PET) and [¹¹C]DASB. In total, we reanalyzed 5-HTT availability in 116 subjects using ANCOVA statistics. ROI analysis revealed that current smokers and non-smokers do not differ in midbrain BP_ND. Interestingly, smoking status significantly interacted with 5-HTTLPR genotype: active smoking was associated with reduced 5-HTT availability only in LL subjects but not in carriers of the S-allele. From the perspective of genotype effects, non-smokers showed the expected association with 5-HTTLPR, i.e. higher 5-HTT availability in LL subjects compared to carriers of the S-allele, whereas this pattern was actually reversed for active smokers. Our study indicates that smoking status moderates the association of 5-HTTLPR genotype and 5-HTT expression, which may help to explain inconsistent findings in previous studies. Regarding the mechanism, we suggest that smoking may induce epigenetic processes such as methylation of SLC6A4, which can differ depending on its genetic constitution.

Serotonin system genes and obsessive-compulsive trait dimensions in a population-based, pediatric sample: a genetic association study

BACKGROUND

Serotonin system genes are commonly studied in obsessive-compulsive disorder (OCD), but genetic studies to date have produced inconsistent results, possibly because phenotypic heterogeneity has not been adequately accounted for. In this paper, we studied candidate serotonergic genes and homogenous phenotypic subgroups as presented through obsessive-compulsive (OC) trait dimensions in a general population of children and adolescents. We hypothesized that different serotonergic gene variants are associated with different OC trait dimensions and, furthermore, that they vary by sex.

METHODS

Obsessive-compulsive trait dimensions (Cleaning/Contamination, Counting/Checking, Symmetry/Ordering, Superstition, Rumination, and Hoarding) were examined in a total of 5,213 pediatric participants in the community using the Toronto Obsessive-Compulsive Scale (TOCS). We genotyped candidate serotonin genes (directly genotyping the 5-HTTLPR polymorphism in SLC6A4 for 2018 individuals and using single nucleotide polymorphism (SNP) array data for genes SLC6A4, HTR2A, and HTR1B for 4711 individuals). We assessed the association between variants across these genes and each of the OC trait dimensions, within males and females separately. We analyzed OC traits as both (a) dichotomized based on a threshold value and (b) quantitative scores.

RESULTS

The [L_G + S] variant in 5-HTTLPR was significantly associated with hoarding in males (p-value of 0.003 and 0.004 for categorical and continuous analyses, respectively). There were no significant findings for 5-HTTLPR in females. Using SNP array data, there were significant findings for rumination in males for HTR2A SNPs (p-value of 1.04e-6 to 5.20e-6).

CONCLUSIONS

This represents the first genetic association study of OC trait dimensions in a community-based pediatric sample. Our strongest results indicate that hoarding and rumination may be distinct in their association with serotonin gene variants and that serotonin gene variation may be specific to sex. Future genetic association studies in OCD should properly account for heterogeneity, using homogenous subgroups stratified by symptom dimension, sex, and age group.

EEG cross-frequency correlations as a marker of predisposition to affective disorders

EEG cross-frequency amplitude-amplitude correlation (CF-AAC) has been considered as a potential marker of social anxiety and other affective disturbances. Functional significance of this phenomenon remains unclear, partly because the majority of studies used channel-level analysis, which precluded the spatial localization of observed effects. It is not also clear whether CF-AAC may serve as a marker of specific pathological conditions and specific states, or a more general predisposition to affective disturbances. We used source-level analysis of EEG data obtained in resting conditions in a nonclinical sample and patients with major depressive disorder (MDD) and investigated associations of CF-AAC measures with a broad range of known risk factors for affective disorders, including age, gender, genotype, stress exposure, personality, and self-reported ‘neurotic’ symptomatology. A consistent pattern of associations showed that all investigated risk factors were associated with an enhancement of CF-AAC in cortical regions associated with emotional and self-referential processing. It could be concluded that CF-AAC is a promising candidate marker of a general predisposition to affective disorders at preclinical stages.

No evidence for the involvement of serotonin or the 5-HTTLPR genotype in intertemporal choice in a larger community sample

BACKGROUND

Serotonin has been implicated in impulsive behaviours such as temporal discounting. While animal studies and theoretical approaches suggest that reduced tonic serotonin levels increase temporal discounting rates and vice versa, evidence from human studies is scarce and inconclusive. Furthermore, an important modulator of serotonin signalling, a genetic variation in the promoter region of the serotonin transporter gene (5-HTTLPR), has not been investigated for temporal discounting so far.

OBJECTIVE

First, the purpose of this study was to test for a significant association between 5-HTTLPR and temporal discounting. Second, we wished to investigate the effect of high/low tonic serotonin levels on intertemporal choice and blood oxygen-level-dependent response, controlling for 5-HTTLPR.

METHODS

We tested the association of 5-HTTLPR with temporal discounting rates using an intertemporal choice task in 611 individuals. We then manipulated tonic serotonin levels with acute tryptophan interventions (depletion, loading, balanced) in a subsample of 45 short (S)-allele and 45 long (L)/L-allele carriers in a randomised double-blind crossover design using functional magnetic resonance imaging and an intertemporal choice task.

RESULTS

Overall, we did not find any effect of serotonin and 5-HTTLPR on temporal discounting rates or the brain networks associated with valuation and cognitive control.

CONCLUSION

Our findings indicate that serotonin may not be directly involved in choices including delays on longer timescales such as days, weeks or months. We speculate that serotonin plays a stronger role in dynamic intertemporal choice tasks where the delays are on a timescale of seconds and hence are therefore directly experienced during the experiment.

Functional Connectivity Patterns and the Role of 5-HTTLPR Polymorphism on Network Architecture in Female Patients With Anorexia Nervosa

Introduction

Recent neuroimaging studies suggest that anorexia nervosa (AN) symptoms emerge from failures in the relationships between spatially distributed networks that support different cognitive, emotional, and somatosensory functions. The 5-HTTLPR genotype has been shown to modulate all these abilities in AN, as well as the connectivity patterns between brain regions that support their functioning. This study aims at exploring the presence of any difference in functional connectome properties between AN patients and healthy controls (HC) by means of graph theory tools. The effect of 5-HTTLPR genotype on regional and global network characteristics in AN and HC was also explored.

Methods

A sample of 74 subjects (38 HC, 36 AN) underwent a resting state functional magnetic resonance imaging and was genotyped for 5-HTTLPR polymorphism. Comparisons of network properties were made between the AN and HC groups and, within each group, between 5-HTTLPR carriers of low-functioning alleles and carriers of the long–long genotype.

Results

Patients with AN displayed lower network clustering than HC (p = 0.04 at Mann–Whitney U test). Based on both degree and betweenness, a different distribution of network hubs emerged in the two groups. In particular, the anterior part of the anterior cingulate cortex was a hub only in the patient group. A correlation emerged between differences in brain volumes between patients and HC and differences in degree values of basal ganglia, nodes in the insula, and those in the parietal cortex. Carriers of the short allele of the 5-HTTLPR polymorphism were characterized by lower small-world properties (p = 0.027) and modularity (p = 0.031) in the patient group, and a trend toward higher modularity (p = 0.033) and small-world values (p = 0.123) in the HC group.

Discussion

Patients with AN showed differences in hubs distribution, providing evidence of the presence of a different functional architectural backbone in this group. Since some correlation emerged between different degree values of nodes and differences in volumes, further longitudinal studies are warranted to better understand the role of malnutrition on brain network architecture. The opposite effects of 5-HTTLPR polymorphism on global network characteristics in the two groups suggest an interaction of the short allele and malnutrition in modulating brain network properties.

Neurodegenerative Disease Caregivers' 5-HTTLPR Genotype Moderates the Effect of Patients' Empathic Accuracy Deficits on Caregivers' Well-Being

OBJECTIVE

To test the hypothesis that a functional polymorphism of the serotonin transporter gene (serotonin-transporter-linked polymorphic region [5-HTTLPR]), which is thought to be associated with differential environmental sensitivity, moderates the association between low levels of empathic accuracy (i.e., ability to recognize emotions in others) in patients with neurodegenerative disease and caregivers' well-being.

METHODS

Participants were 54 patients with neurodegenerative disease and their caregivers. Patients' empathic accuracy was measured using a dynamic tracking task in which they continuously rated the emotions of a character in a film; accuracy was determined by comparing patient ratings with those made by an expert panel. Caregivers provided a saliva sample for genotyping. Caregivers' well-being was measured as a latent construct indicated by validated measures of depression, anxiety, and negative affect.

RESULTS

Lower levels of patients' empathic accuracy were associated with lower levels of caregivers' well-being. Importantly, caregivers' 5-HTTLPR genotype moderated this association such that lower empathic accuracy in patients predicted lower well-being for caregivers with the short/short genotype (standardized β = 0.66), but not for caregivers with the short/long (standardized β = 0.05) or long/long genotypes (standardized β = -0.21).

CONCLUSION

Consistent with previous findings that the short/short variant of 5-HTTLPR is associated with greater sensitivity to environmental influences, caregivers with the short/short variant manifest lower well-being when caring for a patient with low levels of empathic accuracy than caregivers with the other variants. This finding contributes to the authors' understanding of biological factors associated with individual differences in caregiver vulnerability and resilience.

The involvement of sleep in the relationship between the serotonin transporter gene-linked polymorphic region (5-HTTLPR) and depression: A systematic review

BACKGROUND

Recent meta-analyses stimulate an ongoing debate whether 5-HTTLPR modulates the risk for depression including a more pronounced association between stress and depression in the short (S) allele relative to the long (L) allele. Elucidating the pathways by which 5-HTTLPR contributes to depression could resolve this controversy. Insomnia independently contributes to the onset and course of negative affective symptoms and, hence, represents one of the primary risk factors for depression. To evaluate the relevance of this relationship for the interaction between 5-HTTLPR and stress in depression, the present review investigated the moderating influence of 5-HTTLPR on the relationship between stress and sleep quality as well as on the relationship between sleep and affective symptomatology.

METHODS

A systematic search was performed in the PubMed and PsycINFO databases to include a complete outline of studies investigating the relationships of interest.

RESULTS

Results of the included articles reveal that the 5-HTTLPR S-allele relative to the L-allele increases the risk for stress-related sleep quality reductions and promotes the negative affective consequences of inadequate sleep.

LIMITATIONS

The apparent involvement of sleep in the association between 5-HTTLPR and depression remains to be more directly (empirically) examined and studies exploring the influence of 5-HTTLPR on sleep quality produced inconsistent results.

CONCLUSIONS

The reviewed findings support the involvement of sleep in the interaction between 5-HTTLPR and stress in depression. This could have important implications for the inconsistent findings characterizing this field of research and may provide valuable insight into the pathophysiological mechanisms underlying genetic contributions to depression.

The serotonin transporter gene-linked polymorphic region (5-HTTLPR) and the sleep-promoting effects of tryptophan: A randomized placebo-controlled crossover study

BACKGROUND

The low-expressive short (S) allele of a functional polymorphism (5-HTTLPR) within the serotonin (5-hydroxytriptamine; 5-HT) transporter gene (SLC6A4) has been associated with a reduced functioning of the brain 5-HT system relative to the long (L) allele. As a consequence, the S-allele is found to predispose individuals to a higher risk of sleep quality reduction and clinical insomnia.

AIMS

The present study investigated whether subchronic pre-sleep tryptophan administration could compensate for this predisposition by improving sleep in 5-HTTLPR S-allele carriers.

METHODS

In a double-blind placebo-controlled crossover design a sample of homozygous 5-HTTLPR S-allele (n = 47) and L-allele (n = 51) carriers were assessed for subjective (sleep diary) and objective (actigraphy) sleep during a treatment protocol consisting of 1 week of placebo (1000 mg/day) and 1 week of tryptophan administration (1000 mg/day).

RESULTS

The results support the sleep-promoting effects of tryptophan. Tryptophan improved objective sleep efficiency and objective wake after sleep onset irrespective of allelic variation. There was a marginally significant improvement of subjective sleep quality in the 5-HTTLPR S-allele group but not in the L-allele group following tryptophan relative to placebo intake. In contrast, a significantly poorer sleep quality in the S-allele as opposed to the L-allele group in the placebo condition was not observed in the tryptophan condition.

CONCLUSIONS

Tryptophan augmentation promises to be a valuable treatment strategy for sleep impairments related to genetic deficiencies in 5-HT functioning.

Characterization of Serotonin Signaling Components in Patients with Inflammatory Bowel Disease

BACKGROUND

Tryptophan hydroxylase (TPH)1 catalyzes the biosynthesis of serotonin (5-hydroxytrptamine; 5-HT) in enterochromaffin (EC) cells, the predominant source of gut 5-HT. Secreted 5-HT regulates various gut functions through diverse 5-HT receptor (5-HTR) families, and 5-HT transporter (5-HTT) sequesters its activity via uptake into surrounding cells. In inflammatory bowel disease (IBD) mucosal 5-HT signaling is altered, including upregulated EC cell numbers and 5-HT levels. We examined key mucosal 5-HT signaling components and blood 5-HT levels and, as part of a pilot study, investigated the association between 5-HTT gene-linked polymorphic region (5HTTLPR) and Crohn's disease (CD).

METHODS

In the context of inflammation, colonic expressions of TPH1, 5-HTT and 5-HTRs were studied in CD patients (n=15) and healthy controls (HC; n=10) using quantitative polymerase chain reaction (qPCR). We also investigated 5HTTLPR in 40 CD patients and HC utilizing PCR and measured platelet-poor plasma (PPP) and plasma 5-HT concentrations.

RESULTS

Compared with HC, inflammation in CD patients was associated with elevated TPH1, 5-HTR3, 5-HTR4, 5-HTR7 and downregulated 5-HTT expressions. In our second cohort of participants, significantly higher PPP and plasma 5-HT levels and higher S-genotype (L/S+S/S) than L/L genotype were observed in CD patients compared with HC.

CONCLUSION

Our results suggest that augmented mucosal 5-HT signaling and specific 5-HTTLPR genotype-associated decreased efficiency in 5-HT reuptake, the latter through increased 5-HT availability, may contribute to inflammation in CD patients. These findings revealed important information on various components of 5-HT signaling in intestinal inflammation which may ultimately lead to effective strategies targeting this pathway in IBD.

Association of DRD2, 5-HTTLPR, and 5-HTTVNTR Gene Polymorphisms With Posttraumatic Stress Disorder in Tibetan Adolescents: A Case-Control Study

BACKGROUND

Earthquake exposure is a source of stress, yet only a minority of survivors experience clinically meaningful disturbance in psychological function. Genetic epidemiological research has found that posttraumatic stress disorder (PTSD) symptoms are associated with genetic factors. Further research to reveal which genetic loci relate to the development of PTSD is warranted.

METHOD

We investigated the relationships between PTSD and the dopamine D2 receptor ( DRD2) gene Taq I polymorphism and the serotonin transporter gene ( SCL6A4) polymorphisms 5-hydroxytryptamine transporter gene-linked polymorphic region (5-HTTLPR) and 5-HTTVNTR in 565 adolescent earthquake survivors. PTSD-positive adolescents were identified using the PTSD Checklist-Civilian Version and the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders 4. Genotypes were analyzed using the polymerase chain reaction-restriction fragment length polymorphism analysis. The Pearson χ² test was used to investigate the differences in genotype and allele frequencies between case and control groups. Binary logistic regression analysis was performed to identify possible influencing factors for PTSD.

RESULTS

The DRD2 Taq I and 5-HTTVNTR polymorphisms had statistically significant effects on PTSD, while 5-HTTLPR did not. Specifically, the DRD2 Taq I A1 allele was highly positively correlated with PTSD, whereas the 10 allele of 5-HTTVNTR was negatively correlated.

CONCLUSIONS

These data suggest that the DRD2 Taq I and 5-HTTVNTR genotypes moderate sensitivity to stress and the expression of emotional disturbance involving PTSD symptoms. These findings have important implications for PTSD etiology as well as for both primary prevention and treatment strategies.

Association between polymorphisms in the serotonin transporter gene-linked polymorphic region and risk for irritable bowel syndrome in China: evidence based on a meta-analysis

Objective

The association between mutations in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) and irritable bowel syndrome (IBS) differs between populations. This meta-analysis was designed to assess the relationship between 5-HTTLPR polymorphisms and IBS in a Chinese population.

Methods

Relevant published studies from PubMed, Embase, Web of Science, the Cochrane Library, and China National Knowledge Infrastructure databases were accessed prior to May 2018. Odds ratios (ORs) with 95% confidence intervals (CIs) were pooled using STATA software.

Results

A total of 754 IBS cases and 578 healthy controls in six studies were included in this meta-analysis. Significant results were obtained between 5-HTTLPR polymorphisms and IBS risk among studies with the genotype distribution of controls in Hardy–Weinberg equilibrium (L vs. S, OR =  1.41, 95% CI: 1.11–1.79; LL vs. SS, OR = 2.17, 95% CI: 1.16–4.08; LL vs. LS + SS, OR = 2.29, 95% CI: 1.25–4.20). In subgroup analyses, 5-HTTLPR polymorphisms were significantly associated with increased IBS-C risk in China; however, no risk was observed for IBS-D and IBS-M.

Conclusion

This meta-analysis clearly indicates that 5-HTTLPR polymorphisms are associated with an increased risk of IBS in the Chinese population, especially IBS-C.

No Interaction Between Childhood Maltreatment and Serotonin Transporter Gene in Recurrent Major Depressive Disorder: A Clinical Sample

Introduction

There is inconsistent evidence of interaction between childhood adversities and a serotonin transporter promoter polymorphism (5-HTTLPR) in depression. It is hypothesized that genetic sensitivity to stress could be more specific to recurrent major depressive disorder (MDD). The aim of the study is to replicate a recent study which provided preliminary evidence of interaction between severity of childhood maltreatment and the 5-HTTLPR polymorphism in recurrent MDD.

Methods

Participants included a well-characterized clinical sample of 70 recurrent MDD cases and 67 never psychiatrically ill controls, aged 18 years or over. Socio-demographic and clinical information form, Composite International Diagnostic Interview (CIDI), Childhood Trauma Questionnaire (CTQ), Beck Depression Inventory (BDI) were applied to both groups, along with genotyping.

Results

There was no interaction between childhood maltreatment and the 5-HTTLPR in relation to recurrent MDD. All forms of childhood maltreatment were reported as more severe by cases than controls, and there was an independent association between maltreatment and recurrent MDD.

Conclusion

The path forward to detect genetic risk loci for depression remains challenging. Taking childhood maltreatment history into account could lead to a richer understanding of differences in biological correlates, genetic underpinnings, and outcomes.

Adaptive developmental plasticity in rhesus macaques: the serotonin transporter gene interacts with maternal care to affect juvenile social behaviour

Research has increasingly highlighted the role that developmental plasticity-the ability of a particular genotype to produce variable phenotypes in response to different early environments-plays as an adaptive mechanism. One of the most widely studied genetic contributors to developmental plasticity in humans and rhesus macaques is a serotonin transporter gene-linked polymorphic region (5-HTTLPR), which determines transcriptional efficiency of the serotonin transporter gene in vitro and modifies the availability of synaptic serotonin in these species. A majority of studies to date have shown that carriers of a loss-of-function variant of the 5-HTTLPR, the short (s) allele, develop a stress-reactive phenotype in response to adverse early environments compared with long (l) allele homozygotes, leading to the prevalent conceptualization of the s-allele as a vulnerability allele. However, this framework fails to address the independent evolution of these loss-of-function mutations in both humans and macaques as well as the high population prevalence of s-alleles in both species. Here we show in free-ranging rhesus macaques that s-allele carriers benefit more from supportive early social environments than l-allele homozygotes, such that s-allele carriers which receive higher levels of maternal protection during infancy demonstrate greater social competence later in life. These findings provide, to our knowledge, the first empirical support for the assertion that the s-allele grants high undirected biological sensitivity to context in primates and suggest a mechanism through which the 5-HTTLPR s-allele is maintained in primate populations.

Interactive effects of genetic polymorphisms and childhood adversity on brain morphologic changes in depression

The etiology of depression is characterized by the interplay of genetic and environmental factors and brain structural alteration. Childhood adversity is a major contributing factor in the development of depression. Interactions between childhood adversity and candidate genes for depression could affect brain morphology via the modulation of neurotrophic factors, serotonergic neurotransmission, or the hypothalamus-pituitary-adrenal (HPA) axis, and this pathway may explain the subsequent onset of depression. Childhood adversity is associated with structural changes in the hippocampus, amygdala, anterior cingulate cortex (ACC), and prefrontal cortex (PFC), as well as white matter tracts such as the corpus callosum, cingulum, and uncinate fasciculus. Childhood adversity showed an interaction with the brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism, serotonin transporter-linked promoter region (5-HTTLPR), and FK506 binding protein 51 (FKBP5) gene rs1360780 in brain morphologic changes in patients with depression and in a non-clinical population. Individuals with the Met allele of BDNF Val66Met and a history of childhood adversity had reduced volume in the hippocampus and its subfields, amygdala, and PFC and thinner rostral ACC in a study of depressed patients and healthy controls. The S allele of 5-HTTLPR combined with exposure to childhood adversity or a poorer parenting environment was associated with a smaller hippocampal volume and subsequent onset of depression. The FKBP5 gene rs160780 had a significant interaction with childhood adversity in the white matter integrity of brain regions involved in emotion processing. This review identified that imaging genetic studies on childhood adversity may deepen our understanding on the neurobiological background of depression by scrutinizing complicated pathways of genetic factors, early psychosocial environments, and the accompanying morphologic changes in emotion-processing neural circuitry.

Interactive effect of 5-HTTLPR and BDNF polymorphisms on amygdala intrinsic functional connectivity and anxiety

The serotonin transporter (5-HTTLPR) and brain-derived neurotrophic factor (BDNF) gene polymorphisms have been associated with risk for affective disorders and functional variability of the amygdala. We examined whether the two genotypes interactively influence intrinsic functional connectivity (FC) of the amygdala and whether FC mediates the genetic association with anxiety. Eighty genotyped healthy adults underwent resting state fMRI and completed the self-reported State-Trait Anxiety Inventory. Interactive genetic association with anxiety was observed such that effects of 5-HTTLPR depended on the BDNF Val66Met polymorphism (rs6265 variant), with higher anxiety scores in short and Met carriers compared to the other allelic groups. Voxel-wise FC with left and right amygdala seeds identified regions that were sensitive to variability in anxiety scores. A significant moderated mediation model demonstrated that the effect of 5-HTTLPR genotype on anxiety, moderated by BDNF Val66Met genotype, was fully mediated by FC between the left amygdala and the right dorsolateral prefrontal cortex, a cognitive control-related region, during a task-free state. FC was highest in carriers of the 5-HTTLPR short allele and BDNF Met allele. These findings establish intrinsic amygdala-prefrontal functional connectivity as a potential intermediate phenotype for anxiety, an important step toward identification of causal pathways for vulnerability to affective disorders.

Associations of the serotonin transporter promoter polymorphism (5-HTTLPR) with bipolar disorder and treatment response: A systematic review and meta-analysis

BACKGROUND

Associations of the serotonin transporter promoter polymorphism (5-HTTLPR) with bipolar disorder (BPD) and treatment response in bipolar patients were not conclusive. This study not only assessed the association between the 5-HTTLPR and BPD with accumulating relevant studies, but also in the first time evaluated the effect of the 5-HTTLPR on both anti-depressive and anti-manic treatment responses in bipolar patients.

METHODS

PubMed, Embase, PsycINFO, Cochrane Library and Cochrane Control Trials databases were systematically searched before February 2017. This meta-analysis followed the PRISMA guidelines.

RESULTS

A total of 32 population-based studies (5567 cases and 6993 controls) and 9 family-based studies (837 trios) were finally screened out and statistically joined into a single meta-analysis that revealed an association between S allele and an increased risk of BPD (OR = 1.06, p = .038). Pooled analysis of the 32 population-based studies indicated an association of S-carrier genotypes with an increased risk of BPD (OR = 1.10, p = .029). Meanwhile, the association remained significant in Caucasians (OR = 1.15, p = .004), which could provide an enough power (88%) to detect a significant association. Regarding the treatment response studies, 6 studies reporting the relationship of the 5-HTTLPR in anti-depressive remission rate (1034 patients) and 7 studies reporting in response rate (1098 patients) were included for pooled analyses. We observed a significant association of S-carrier genotypes with a reduced anti-depressive remission rate (OR = 0.64, p = .006) but not with anti-depressive response rate. The association between the 5-HTTLPR with anti-manic response rate was not observed in the included 6 studies (676 patients).

CONCLUSIONS

The present study supported the presence of a marginal but detectable effect of the 5-HTTLPR on susceptibility to BPD. Moreover, the detected association in Caucasian was statistically reliable. Besides, the 5-HTTLPR was identified as a useful predictor for anti-depressive remission but not for anti-depressive or anti-manic response.

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.

Hydroxytryptamine transporter gene-linked polymorphic region (5HTTLPR) is associated with delusions in Alzheimer's disease

Background

Serotoninergic pathways underlying delusion symptoms in Alzheimer's disease (AD) have not been fully clarified. 5-Hydroxytryptamine transporter gene-linked polymorphic region (5-HTTLPR) is a variable number tandem repeats in the promoter region of serotonin transporter encoding-gene affecting transcription.

Methods

We investigated the association of 5-HTTLPR with delusions in a total of 257 consecutive patients clinically diagnosed as AD according to the National Institute on Aging-Alzheimer's Association criteria. All participants underwent a comprehensive evaluation with a standardized comprehensive geriatric assessment and Neuropsychiatric Inventory.

Results

Delusion symptoms were observed in 171 patients (66.54%). In respect to AD patients without delusions, AD patients with delusions showed a low prevalence of S-plus carriers (5-HTTLPR-L/S + 5-HTTLPR-S/S genotypes) [p < 0.001; odds ratio (OR) = 0.240, 95% confidence interval (CI) = 0.121-0.471]. Logistic regression analysis adjusted for the apolipoprotein E polymorphism showed that in AD patients with delusions the presence of an 5-HTTLPR-S allele may reduce disease duration (p = 0.005; OR = 0.680, 95% CI = 0.522-0.886) and increase aberrant motor activity (p = 0.013; OR = 2.257, 95% CI = 1.195-4.260). The present findings suggested that 5-HTTLPR might be associated with delusions in AD. S-plus carriers might be associated with protective effect against delusions in AD.

Conclusions

More studies on wider samples of high selected demented patients are needed to confirm our results. However, the present findings suggested that a genetic factor related to serotonin metabolism might exert a protective role on the clinical expression of neuropsychiatric clusters in AD with important implications regarding mechanisms underlying delusions and their possible treatment across the AD and dementia spectrum.

COMTVal158Met Genotype Affects Complex Emotion Recognition in Healthy Men and Women

The catechol-o-methyltransferase (COMT) gene has repeatedly been shown to change amygdala activity and amygdala-prefrontal connectivity during face processing. Although the COMT gene appears to induce a negativity bias during the neural processing of faces, it is currently unclear whether a similar negativity bias emerges during the behavioral processing of faces. To address this issue, we investigated differences in complex emotion recognition between participants (n = 181) that had been a priori genotyped for functional polymorphisms of the COMT (Val158Met) and serotonin transporter (5-HTTLPR) gene. We were, thus, able to analyze differences in face processing on basis of participants’ COMT genotype while controlling for participants’ 5-HTTLPR genotype. Variations of participants’ COMT but not 5-HTTLPR genotype accounted for differences in participants’ emotion recognition performance: Met/Met carriers and Met/Val carriers were more accurate in the recognition of negative, but not neutral or positive, expressions than Val/Val carriers. We, therefore, revealed a similar negativity bias during the behavioral processing of faces that has already been demonstrated during the neural processing of faces, indicating that genotype-dependent changes in catecholamine metabolism may affect face processing on the behavioral and neural level.

The influence of the serotonin transporter gene 5-HTTLPR polymorphism on suicidal behaviors: a meta-analysis

Suicidal Behavior (SB) is the second leading cause of death among youths worldwide and the tenth among all age groups. Inherited genetic differences have a role in suicidality with heritability ranging from 30 to 55%. The SLC6A4 5-HTTLPR gene variant has been largely investigated for association with SB, with controversial results. In this work, we sought to determine whether the results of previous meta-analyses were confirmed or modified subsequent to the inclusion of more recent literature data. An electronic literature search was performed to identify relevant studies published until July 2018. Data were analysed through RevMan v5.3. Subgroup and sensitivity meta-analyses were performed considering different SB sub-phenotypes, ethnicity, gender and psychiatric diagnostic categories. Our literature search yielded 1186 articles; among these, we identified 45 pertinent case-control studies (15,341 subjects). No association was found between low-expressing alleles or genotypes (S + L_G alleles or S' carrier genotypes) and SB in the primary analyses. However, low-expressing alleles (S + L_G) were associated with an increased risk of Violent Suicide Attempt (OR = 1.44, C.I. 1.17-1.78, p = .0007). An effect of the same alleles on SB was found in a subpopulation of substance abusers, but this result was not confirmed after the exclusion of healthy subjects from the control group. The other sensitivity meta-analyses did not show any significant effect. Our findings contribute to clarify the conflicting previous evidence by suggesting an association between the 5-HTTLPR and Violent SB. Nonetheless, many other modulators, including environmental factors and epigenetic mechanisms may act to further increase the level of complexity.

Association Between 5-HTTLPR Polymorphism and the Risk of Autism: A Meta-Analysis Based on Case-Control Studies

Background: Recently, many case-control studies have reported the association between 5-HTTLPR polymorphism and autism risk. However, the results are inconclusive and conflicting. To investigate the genetic association of 5-HTTLPR polymorphism and autism risk, we conducted a comprehensive meta-analysis based on previous case-control studies. Methods: Literature search was performed through PubMed, Embase, Web of Knowledge and CNKI databases until June 27, 2018. The strength of the association was assessed by relative risk (RR) and its corresponding 95% confidence interval (CI). Fixed or random effect model was selected based on the results of heterogeneity test. Further, subgroup analyses were conducted to explore the association of 5-HTTLPR polymorphism and autism risk in different population. Results: Eleven studies with 930 cases and 1234 controls were identified. Although there was a significant association between 5-HTTLPR polymorphism and autism risk under the dominant model after removing the studies causing heterogeneity, the significance did not exist after Bonferroni's correction. Subgroup analyses also showed similar results after Bonferroni's correction. In addition, there was no obvious publication bias in our meta-analysis. Conclusions: Our present meta-analysis does not support a direct effect of 5-HTTLPR polymorphism on autism risk according to present results. Further analyses of the effect of genetic networks and more well designed studies with larger sample size are required.

Impact of serotonin transporter gene on rTMS augmentation of SSRIs for obsessive compulsive disorder

OBJECTIVE

Repetitive transcranial magnetic stimulation (rTMS) is beneficial for treatment-resistant patients with obsessive-compulsive disorder (OCD). The serotonin transporter gene (SLC6A4) may be associated with OCD. We aimed to determine whether SLC6A4 impacts the beneficial effects of rTMS in patients with OCD treated with selective serotonin reuptake inhibitors (SSRIs).

METHODS

Fifty-seven untreated patients with OCD were randomly assigned to receive active or sham rTMS in a 4-week double-blind study. The participants received 1-Hz rTMS over the supplementary motor area once per day, for 5 days a week, for 4 weeks. One of the widely employed SSRIs was utilized at the initiation of active or sham rTMS. Yale-Brown obsessive-compulsive scale (Y-BOCS) scores were used for assessing the symptoms. The most-researched polymorphism of SLC6A4, 5-HTTLPR (L/S), was also examined.

RESULTS

Y-BOCS scores in the active group at the completion of the treatment were significantly lower than those in the sham group. Interestingly, the improvement in Y-BOCS scores in patients with the LL genotype treated with active rTMS was significantly (p<0.05) greater than in those treated with sham rTMS. Conversely, rTMS did not produce significant improvements in S allele carriers.

CONCLUSIONS

The findings of this study suggest that rTMS can augment the beneficial effects of SSRIs in OCD patients with the LL genotype of 5-HTTLPR. Therefore, the presence of 5-HTTLPR (L/S) in SLC6A4 may be a predictable biomarker for the beneficial effects of rTMS, although more studies using larger sample sizes are warranted for confirming the results.

Association of serotonin and GABA pathway gene polymorphisms with alcohol dependence: A preliminary study

BACKGROUND

Alcohol dependence (AD), characterized by profound disruptions in specific circuits of the brain is influenced by both environmental, which play a significant role in developing addiction and genetic factors, which make some individuals more susceptible to disruptions. Various polymorphisms in the neurotransmitter genes are reported to increase the risk of developing dependence. The present study aimed to identify association of serotonin and GABA polymorphisms with AD in Indian subjects.

METHOD

The study group comprised of 141 AD cases recruited as per DSM IV TR criteria from the outpatient Department of Psychiatry and 110 volunteers from the general population. Clinical and family history was noted and 5 ml blood drawn for genetic studies. Polymorphisms 5-HTTLPR and STin2 of serotonin and rs2279020 and rs3219151 of the GABA pathway were analyzed and results correlated with age at first use quantity consumed, duration of use, dependence and age at onset of dependence.

RESULTS

The marker frequencies were similar between cases and controls except for rs3219151. 5-HTTLPR was significantly associated with high AUDIT scores and alcohol intake (p < 0.0001), GABA_A rs2279020 and rs3219151 with age at first use (p < 0.0001); rs2279020 with higher AUDIT score (p = 0.002) and rs3219151 with quantity (p = 0.0001). High frequency of GABRA6 rs3219151 TT genotype in AD and its association with lower age at first use, higher intake/day, and higher duration of dependence appears to confer risk.

CONCLUSIONS

This preliminary study, though on a smaller sample size, suggests an association of 5-HTTLPR and GABA_A receptor polymorphisms with AD in our population.

The serotonin transporter polymorphism (5-HTTLPR) and cortisol stress responsiveness: preliminary evidence for a modulating role for sleep quality

The short (S) allele of a functional polymorphism (5-HTTLPR) within the promoter region of the serotonin transporter gene (SLC6A4) is found to predispose the risk for stress-related affective disorders relative to the long (L) allele. Evidence suggests that elevated stress reactivity of the hypothalamic-pituitary-adrenal (HPA) axis might underlie this association although there is little understanding about the origin of inconsistent findings. Since inadequate sleep is commonly known to promote HPA stress reactivity, it might well play an important modulating role. The present study tested this hypothesis by investigating whether sleep quality moderates the relationship between 5-HTTLPR and cortisol stress responsiveness. From a large 5-HTTLPR database (n = 771), a sample of healthy male and female participants homozygous for either the 5-HTTLPR S-allele (n = 25) or L-allele (n = 25) were assessed for sleep quality and salivary cortisol secretion during acute laboratory stress. Diminished sleep quality was found to exclusively potentiate cortisol stress reactivity in the homozygous L-allele genotype. Accounting for this 5-HTTLPR-dependent influence enhanced the predictive value of 5-HTTLPR on cortisol stress responsiveness, revealing greater HPA reactivity in S-allele relative to L-allele carriers. Current findings suggest that variations in sleep quality may serve as a confounding factor in the search for genetic differences in stress sensitivity and related affective disorders.