Affective neural responses modulated by serotonin transporter genotype in clinical anxiety and depression

Impact of Intolerance of Uncertainty on Brain Structural Changes in Panic Disorder

OBJECTIVE

This study investigated the impact of intolerance of uncertainty (IU) on structural changes in the brain and symptom severity in patients with panic disorder.

METHODS

This study included 90 participants diagnosed with panic disorder. The IU Scale, Panic Disorder Severity Scale (PDSS), Beck Depression Inventory-II (BDI-II), Penn State Worry Questionnaire (PSWQ), Self-Forgiveness Scale (SFS), and Short Form 36 Health Survey (SF) were used. A voxel-wise correlation analysis was conducted to investigate the structural differences in the gray matter.

RESULTS

As IU increased, the cortical thickness of the right lingual gyrus decreased significantly, while the gray matter volume of the right pars triangularis increased. The cortical thickness of the right lingual gyrus showed a significant negative correlation with the BDI-II score and a positive correlation with the SFS. Additionally, the gray matter volume of the right pars triangularis was positively correlated with the PDSS, PSWQ, and BDI-II scores and negatively correlated with the mental health domain of the SF.

CONCLUSION

According to our findings, elevated IU in participants with panic disorder was associated with cortical thinning in the lingual gyrus and increased gray matter volume in the pars triangularis. These structural alterations may also have an impact on perceived quality of life, as well as high levels of depression and anxiety.

Intolerance of uncertainty and functional connectivity of the anterior insula during anticipation of unpredictable reward

Individuals with high intolerance of uncertainty (IU) tend to display maladaptive cognitive, behavioral, physiological, and/or neural responses during anticipation of uncertain or ambiguous outcomes, both positive and negative in valence. Importantly, high IU has been proposed as a key transdiagnostic phenotypic risk factor for the onset and maintenance of several psychiatric disorders. Within the context of reward processing, high IU has been related to dysfunctional reward anticipation, which may be mediated by hyperactive anterior insula (AIC) response to uncertainty. The present study further investigated the relationship between the AIC and IU by examining the association between individual differences in IU and task-based functional connectivity of the right AIC using functional magnetic resonance imaging (fMRI). Participants (N = 171) completed a self-report measure of IU and a reward anticipation task during fMRI. Generalized psychophysiological interaction (gPPI) analyses were performed with a seed in the right AIC. In the U-threat model, we found that greater self-reported levels of IU were correlated with increased functional connectivity between the right AIC and the dorsal anterior cingulate cortex (dACC) and the right dorsolateral prefrontal cortex (dlPFC). In the P-threat model, we did not find these associations, perhaps indicating that they may be more robust during uncertainty. These preliminary findings suggest that parts of salience and central executive control networks may be impacted by and underlie the expression of IU. Future studies should examine the generalizability of these findings to clinical populations and investigate how disruption of these functional networks may contribute to psychopathology.

Predictive utility of symptom measures in classifying anxiety and depression: A machine-learning approach

Major depressive disorder (MDD) and generalized anxiety disorder (GAD) are highly prevalent, co-occurring disorders with significant symptom overlap, posing challenges in accurately distinguishing and diagnosing these disorders. The tripartite model proposes that anxious arousal is specific to anxiety and anhedonia is specific to depression, though anxious apprehension may play a greater role in GAD than anxious arousal. The present study tested the efficacy of the Mood and Anxiety Symptom Questionnaire anhedonic depression (MASQ-AD) and anxious arousal (MASQ-AA) scales and the Penn State Worry Questionnaire (PSWQ) in identifying lifetime or current MDD, current major depressive episode (MDE), and GAD using binary support vector machine learning algorithms in an adult sample (n = 150). The PSWQ and MASQ-AD demonstrated predictive utility in screening for and identification of GAD and current MDE respectively, with the MASQ-AD eight-item subscale outperforming the MASQ-AD 14-item subscale. The MASQ-AA did not predict MDD, current MDE, or GAD, and the MASQ-AD did not predict current or lifetime MDD. The PSWQ and MASQ-AD are efficient and accurate screening tools for GAD and current MDE. Results support the tripartite model in that anhedonia is unique to depression, but inclusion of anxious apprehension as a separate dimension of anxiety is warranted.

Genetics of social anxiety disorder: a systematic review

Social anxiety disorder (SAD) is a common psychiatric disorder, often associated with avoidant temperament. Research studies have implicated a strong genetic architecture of SAD. We have conducted a systematic review on the genetics of SAD and yielded 66 articles. In general, prior research studies have focused on the serotonin transporter, oxytocin receptor, brain-derived neurotrophic factor and catechol-O-methyltransferase genes. Mixed and inconsistent results have been reported. Additional approaches and phenotypes have also been investigated, including pharmacogenetics of treatment response, imaging genetics and gene-environment interactions. Future directions warrant further international collaborative efforts, deep-phenotyping of clinical characteristics including consistent and reliable measurement-based symptom severity, and larger sample sizes to ensure sufficient power for stratification due to the heterogeneity of this chronic and often debilitating condition.

Correlation of Expression Changes between Genes Controlling 5-HT Synthesis and Genes Crh and Trh in the Midbrain Raphe Nuclei of Chronically Aggressive and Defeated Male Mice

Midbrain raphe nuclei (MRNs) contain a large number of serotonergic neurons associated with the regulation of numerous types of psychoemotional states and physiological processes. The aim of this work was to study alterations of the MRN transcriptome in mice with prolonged positive or negative fighting experience and to identify key gene networks associated with the regulation of serotonergic system functioning. Numerous genes underwent alterations of transcription in the MRNs of male mice that either manifested aggression or experienced social defeat in daily agonistic interactions. The expression of the Tph2 gene encoding the rate-limiting enzyme of the serotonin synthesis pathway correlated with the expression of many genes, 31 of which were common between aggressive and defeated mice and were downregulated in the MRNs of mice of both experimental groups. Among these common differentially expressed genes (DEGs), there were genes associated with behavior, learning, memory, and synaptic signaling. These results suggested that, in the MRNs of the mice, the transcriptome changes associated with serotonergic regulation of various processes are similar between the two groups (aggressive and defeated). In the MRNs, more DEGs correlating with Tph2 expression were found in defeated mice than in the winners, which is probably a consequence of deeper Tph2 downregulation in the losers. It was shown for the first time that, in both groups of experimental mice, the changes in the transcription of genes controlling the synthesis and transport of serotonin directly correlate with the expression of genes Crh and Trh, which control the synthesis of corticotrophin- and thyrotropin-releasing hormones. Our findings indicate that CRH and TRH locally produced in MRNs are related to serotonergic regulation of brain processes during a chronic social conflict.

Whole blood serotonin levels in healthy elderly are negatively associated with the functional activity of emotion-related brain regions

Understanding the role of neuromodulators of socio-affective processing is important to ensure psychological wellbeing during older years. Here, we investigated the link between blood serotonin levels and brain and behavioral responses to emotional information in healthy elderly. A priori regions of interest (ROI) were selected due to their role in emotion processing and their dense serotonergic innervation. Correlation analyses were performed between ROI-specific responses to emotional stimuli and whole blood serotonin levels. We found significant negative associations between serotonin and functional activity for the bilateral insula, dorsal anterior cingulate cortex and subgenual gyrus. No association with behavioral measures survived correction for multiple testing. Our results mirror prior pharmacological and genetic work on the link between serotonin and emotional brain reactivity in younger adults. Given the involvement of serotonin in several age-related changes, our study encourages future research to characterize the role of this neuromodulator in emotion processing across the lifespan.

Influence of psychosocial stress on activation in human brain regions: moderation by the 5-HTTLPR genetic locus

Variants of the serotonin transporter linked polymorphic region (5-HTTLPR) of the serotonin transporter gene SLC6A4 have been related with the onset of depression, anxiety, and other mental disorders. Homozygotes for the short 5-HTTLPR variant, referred to as the SS genotype, have greater cortisol responses to experimentally induced psychosocial stress. In the current study, we used functional magnetic resonance imaging (fMRI) to compare regional brain activations across 5-HTTLPR genotypes in subjects performing the Montreal Imaging Stress Task (MIST). Subjects with an SS genotype had significant greater increases in cortisol concentrations after the task than subjects with at least one long 5-HTTLPR allele. Additionally, relative to L carriers, the SS group had greater activation in the dorsomedial prefrontal cortex(dmPFC), dorsal anterior cingulate cortex, anterior insula.

Towards precision medicine in generalized anxiety disorder: Review of genetics and pharmaco(epi)genetics

Generalized anxiety disorder (GAD) is a prevalent and chronic mental disorder that elicits widespread functional impairment. Given the high degree of non-response/partial response among patients with GAD to available pharmacological treatments, there is a strong need for novel approaches that can optimize outcomes, and lead to medications that are safer and more effective. Although investigations have identified interesting targets predicting treatment response through pharmacogenetics (PGx), pharmaco-epigenetics, and neuroimaging methods, these studies are often solitary, not replicated, and carry several limitations. This review provides an overview of the current status of GAD genetics and PGx and presents potential strategies to improve treatment response by combining better phenotyping with PGx and improved analytical methods. These strategies carry the dual benefit of delivering data on biomarkers of treatment response as well as pointing to disease mechanisms through the biology of the markers associated with response. Overall, these efforts can serve to identify clinical, genetic, and epigenetic factors that can be incorporated into a pharmaco(epi)genetic test that may ultimately improve treatment response and reduce the socioeconomic burden of GAD.

Activity alterations in the bed nucleus of the stria terminalis and amygdala during threat anticipation in generalized anxiety disorder

Sustained anticipatory anxiety is central to Generalized Anxiety Disorder (GAD). During anticipatory anxiety, phasic threat responding appears to be mediated by the amygdala, while sustained threat responding seems related to the bed nucleus of the stria terminalis (BNST). Although sustained anticipatory anxiety in GAD patients was proposed to be associated with BNST activity alterations, firm evidence is lacking. We aimed to explore temporal characteristics of BNST and amygdala activity during threat anticipation in GAD patients. Nineteen GAD patients and nineteen healthy controls (HC) underwent functional magnetic resonance imaging (fMRI) during a temporally unpredictable threat anticipation paradigm. We defined phasic and a systematic variation of sustained response models for blood oxygen level-dependent responses during threat anticipation, to disentangle temporally dissociable involvement of the BNST and the amygdala. GAD patients relative to HC responded with increased phasic amygdala activity to onset of threat anticipation and with elevated sustained BNST activity that was delayed relative to the onset of threat anticipation. Both the amygdala and the BNST displayed altered responses during threat anticipation in GAD patients, albeit with different time courses. The results for the BNST activation hint towards its role in sustained threat responding, and contribute to a deeper understanding of pathological sustained anticipatory anxiety in GAD.

Genetics of generalized anxiety disorder and related traits

This review serves as a systematic guide to the genetics of generalized anxiety disorder (GAD) and further focuses on anxiety-relevant endophenotypes, such as pathological worry fear of uncertainty, and neuroticism. We inspect clinical genetic evidence for the familialityl heritability of GAD and cross-disorder phenotypes based on family and twin studies. Recent advances of linkage studies, genome-wide association studies, and candidate gene studies (eg, 5-HTT, 5-HT1A, MAOA, BDNF) are outlined. Functional and structural neuroimaging and neurophysiological readouts relating to peripheral stress markers and psychophysiology are further integrated, building a multilevel disease framework. We explore etiologic factors in gene-environment interaction approaches investigating childhood trauma, environmental adversity, and stressful life events in relation to selected candidate genes (5-HTT, NPSR1, COMT, MAOA, CRHR1, RGS2), Additionally, the pharmacogenetics of selective serotonin reuptake inhibitor/serotonin-norepinephrine reuptake inhibitor treatment are summarized (5-HTT, 5-HT2A, COMT, CRHR1). Finally, GAD and trait anxiety research challenges and perspectives in the field of genetics, including epigenetics, are discussed.

Revisiting the tryptophan-serotonin deficiency and the inflammatory hypotheses of major depression in a biopsychosocial approach

Background

The aim of this cross-sectional study was to identify important biopsychosocial correlates of major depression. Biological mechanisms, including the inflammatory and the tryptophan-serotonin deficiency hypotheses of major depression, were investigated alongside health-related quality of life, life satisfaction, and social support.

Methods

The concentrations of plasma tryptophan, plasma kynurenine, plasma kynurenic acid, serum quinolinic acid, and the tryptophan breakdown to kynurenine were determined alongside health-related quality of life (Medical Outcome Study Form, SF-36), life satisfaction (Life Satisfaction Questionnaire, FLZ), and social support (Social Support Survey, SSS) in 71 depressive patients at the time of their in-patient admittance and 48 healthy controls.

Results

Corresponding with the inflammatory hypothesis of major depression, our study results suggest a tryptophan breakdown to kynurenine in patients with major depression, and depressive patients had a lower concentration of neuroprotective kynurenic acid in comparison to the healthy controls (Mann-Whitney-U: 1315.0; p = 0.046). Contradicting the inflammatory theory, the concentrations of kynurenine (t: -0.945; df = 116; p = 0.347) and quinolinic acid (Mann-Whitney-U: 1376.5; p = 0.076) in depressive patients were not significantly different between depressed and healthy controls. Our findings tend to support the tryptophan-serotonin deficiency hypothesis of major depression, as the deficiency of the serotonin precursor tryptophan in depressive patients (t: -3.931; df = 116; p < 0.001) suggests dysfunction of serotonin neurotransmission. A two-step hierarchical linear regression model showed that low tryptophan concentrations, low social support (SSS), occupational requirements (FLZ), personality traits (FLZ), impaired physical role (SF-36), and impaired vitality (SF-36) predict higher Beck Depression Inventory (BDI-II) scores.

Discussion

Our study results argue for the validity of a biopsychosocial model of major depression with multiple pathophysiological mechanisms involved.

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.