Increased serotonin-2 binding sites in frontal cortex of suicide victims

The role of serotonin in depression-A historical roundup and future directions

Depression is one of the most common psychiatric disorders worldwide, affecting approximately 280 million people, with probably much higher unrecorded cases. Depression is associated with symptoms such as anhedonia, feelings of hopelessness, sleep disturbances, and even suicidal thoughts. Tragically, more than 700 000 people commit suicide each year. Although depression has been studied for many decades, the exact mechanisms that lead to depression are still unknown, and available treatments only help a fraction of patients. In the late 1960s, the serotonin hypothesis was published, suggesting that serotonin is the key player in depressive disorders. However, this hypothesis is being increasingly doubted as there is evidence for the influence of other neurotransmitters, such as noradrenaline, glutamate, and dopamine, as well as larger systemic causes such as altered activity in the limbic network or inflammatory processes. In this narrative review, we aim to contribute to the ongoing debate on the involvement of serotonin in depression. We will review the evolution of antidepressant treatments, systemic research on depression over the years, and future research applications that will help to bridge the gap between systemic research and neurotransmitter dynamics using biosensors. These new tools in combination with systemic applications, will in the future provide a deeper understanding of the serotonergic dynamics in depression.

Psychedelic-Induced Serotonin 2A Receptor Downregulation Does Not Predict Swim Stress Coping in Mice

Serotoninergic psychedelics such as psilocybin have been reported to elicit a long-lasting reduction in depressive symptoms. Although the main target for serotoninergic psychedelics, serotonin type 2A receptor (5-HT_2A), has been established, the possible mechanism of the antidepressant action of psychedelics remains unknown. Using the mouse forced swim test model, we examined whether the administration of the synthetic serotoninergic psychedelic 2,5-dimethoxy-4-iodoamphetamine (DOI) would modulate 5-HT_2A receptor levels in the medial prefrontal cortex (mPFC) and revert stress-induced changes in behavior. Mice subjected to swim stress developed a passive stress-coping strategy when tested in the forced swim test 6 days later. This change in behavior was not associated with the hypothesized increase in 5-HT_2A receptor-dependent head twitch behaviors or consistent changes in 5-HT_2A receptor levels in the mPFC. When DOI was administered 1 day before the forced swim test, a low dose (0.2 mg/kg i.p.) unexpectedly increased immobility while a high dose (2 mg/kg i.p.) had no significant effect on immobility. Nevertheless, DOI evoked a dose-dependent decrease in 5-HT_2A levels in the mPFC of mice previously exposed to swim stress. Our findings do not support the hypothesis that the downregulation of 5-HT_2A receptors in the mPFC contributes to the antidepressant-like properties of serotoninergic psychedelics.

Relationship Between Affective Temperaments and Suicide Risk in Patients With First-Onset Major Depressive Disorder

Background

People may endorse suicidal behavior during a major depressive episode. Affective temperaments may play a role in this risk. We explored the relationship between affective temperaments and suicide and identified some traits that can predict suicide risk in depression.

Materials and Methods

We analyzed the results of the Temperament Evaluation of the Memphis, Pisa, Paris, and San Diego Auto-questionnaire (TEMPS-A) in 284 participants recruited from a psychiatric clinic and the community in Beijing and compared the subscale scores (temperaments of cyclothymic, dysthymic, anxious, irritable, and hyperthymic) among major depressive disorders (MDDs) vs. the general population as well as depressive patients with vs. without suicide risk, using Student's test, chi-square test, rank-sum test, and multivariable regression modeling.

Results

The incidence of suicidal risk in depressive subjects was 47.62% (80/168). Being unmarried (p < 0.001), unemployed (p = 0.007), and temperaments of dysthymic, cyclothymic, anxious, and irritable scores (all p < 0.001) were significantly more prevalent in patients with depression than in the general population. Young age (p < 0.001), female sex (p = 0.037), unmarried (p = 0.001), more severe depression (p < 0.001), and dysthymic, anxious, and cyclothymic temperament (all p < 0.05) were significantly more prevalent in patients with depressive disorder than those without suicide risk. The logistic regression analysis showed that younger age (odds ratio [OR] = 0.937, 95% CI 0.905∼0.970), female sex (OR = 2.606, 95% CI 1.142∼5.948), more severe depression (OR = 1.145, 95% CI 1.063∼1.234), cyclothymic temperament (OR = 1.275, 95% CI 1.102∼1.475), and dysthymic temperament (OR = 1.265, 95% CI 1.037∼1.542) were all independently associated with high suicidal risk in patients with first-onset major depression (p < 0.05).

Conclusion

Temperament traits differ between the general population and people suffering from MDD. Subjects with MDD who have much more severe depressive symptoms and a cyclothymic or dysthymic temperament were at a high risk of suicide.

Microglia as a Hub for Suicide Neuropathology: Future Investigation and Prevention Targets

Suicide is a complex public health challenge associated worldwide with one death every 40 s. Research advances in the neuropathology of suicidal behaviors (SB) have defined discrete brain changes which may hold the key to suicide prevention. Physiological differences in microglia, the resident immune cells of the brain, are present in post-mortem tissue samples of individuals who died by suicide. Furthermore, microglia are mechanistically implicated in the outcomes of important risk factors for SB, including early-life adversity, stressful life events, and psychiatric disorders. SB risk factors result in inflammatory and oxidative stress activities which could converge to microglial synaptic remodeling affecting susceptibility or resistance to SB. To push further this perspective, in this Review we summarize current areas of opportunity that could untangle the functional participation of microglia in the context of suicide. Our discussion centers around microglial state diversity in respect to morphology, gene and protein expression, as well as function, depending on various factors, namely brain region, age, and sex.

Effects of stress on endophenotypes of suicide across species: A role for ketamine in risk mitigation

Suicide is a leading cause of death and morbidity worldwide, yet few interventions are available to mitigate its risk. Barriers to effective treatments involve a limited understanding of factors that predict the onset of suicidal thoughts and behaviors. In the context of suicide risk, stress is a precipitating factor that is largely overlooked in the literature. Indeed, the pathophysiology of stress and suicide are heavily interconnected, underscoring the need to target the stress system in suicide prevention. In this review, we integrate findings from the preclinical and clinical literature that links stress and suicide. We focus specifically on the effects of stress on underlying biological functions and processes associated with suicide, allowing for the review of research using animal models. Owing to the rapid anti-suicidal effects of (R,S)-ketamine, we discuss its ability to modulate various stress-related endophenotypes of suicide, as well as its potential role in preventing suicide in those with a history of chronic life stress (e.g., early life adversity). We highlight future research directions that could advance our understanding of stress-related effects on suicide risk, advocating a dimensional, endophenotype approach to suicide research.

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Suicide and chronic stress pathophysiology are interconnected.

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Chronic stress has profound impacts on several endophenotypes of suicide.

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Animal and human research points to stress as a precipitating factor in suicide.

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Ketamine modulates specific biological processes associated with stress and suicide.

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Suicide research into endophenotypes can help inform risk-mitigation strategies.

Integrating the monoamine and cytokine hypotheses of depression: Is histamine the missing link?

Psychiatric diseases, like depression, largely affect the central nervous system (CNS). While the underlying neuropathology of depressive illness remains to be elucidated, several hypotheses have been proposed as molecular underpinnings for major depressive disorder, including the monoamine hypothesis and the cytokine hypothesis. The monoamine hypothesis has been largely supported by the pharmaceuticals that target monoamine neurotransmitters as a treatment for depression. However, these antidepressants have come under scrutiny due to their limited clinical efficacy, side effects, and delayed onset of action. The more recent, cytokine hypothesis of depression is supported by the ability of immune-active agents to induce "sickness behaviour" akin to that seen with depression. However, treatments that more selectively target inflammation have yielded inconsistent antidepressive results. As such, neither of these hypotheses can fully explain depressive illness pathology, implying that the underlying neuropathological mechanisms may encompass aspects of both theories. The goal of the current review is to integrate these two well-studied hypotheses and to propose a role for histamine as a potential unifying factor that links monoamines to cytokines. Additionally, we will focus on stress-induced depression, to provide an updated perspective of depressive illness research and thereby identify new potential targets for the treatment of major depressive disorder.

Pivotal mental states

This paper introduces a new construct, the 'pivotal mental state', which is defined as a hyper-plastic state aiding rapid and deep learning that can mediate psychological transformation. We believe this new construct bears relevance to a broad range of psychological and psychiatric phenomena. We argue that pivotal mental states serve an important evolutionary function, that is, to aid psychological transformation when actual or perceived environmental pressures demand this. We cite evidence that chronic stress and neurotic traits are primers for a pivotal mental state, whereas acute stress can be a trigger. Inspired by research with serotonin 2A receptor agonist psychedelics, we highlight how activity at this particular receptor can robustly and reliably induce pivotal mental states, but we argue that the capacity for pivotal mental states is an inherent property of the human brain itself. Moreover, we hypothesize that serotonergic psychedelics hijack a system that has evolved to mediate rapid and deep learning when its need is sensed. We cite a breadth of evidences linking stress via a variety of inducers, with an upregulated serotonin 2A receptor system (e.g. upregulated availability of and/or binding to the receptor) and acute stress with 5-HT release, which we argue can activate this primed system to induce a pivotal mental state. The pivotal mental state model is multi-level, linking a specific molecular gateway (increased serotonin 2A receptor signaling) with the inception of a hyper-plastic brain and mind state, enhanced rate of associative learning and the potential mediation of a psychological transformation.

Dysregulation of Protein Kinase C in Adult Depression and Suicide: Evidence From Postmortem Brain Studies

BACKGROUND

Several lines of evidence suggest the abnormalities of protein kinase C (PKC) signaling system in mood disorders and suicide based primarily on the studies of PKC and its isozymes in the platelets and postmortem brain of depressed and suicidal subjects. In this study, we examined the role of PKC isozymes in depression and suicide.

METHODS

We determined the protein and mRNA expression of various PKC isozymes in the prefrontal cortical region (Brodmann area 9) in 24 normal control subjects, 24 depressed suicide (DS) subjects, and 12 depressed nonsuicide (DNS) subjects. The levels of mRNA in the prefrontal cortex were determined by quantitative real-time reverse transcription PCR, and the protein expression was determined by western blotting.

RESULTS

We observed a significant decrease in mRNA expression of PKCα, PKCβI, PKCδ, and PKCε and decreased protein expression in either the membrane or the cytosol fraction of PKC isozymes PKCα, PKCβI, PKCβII, and PKCδ in DS and DNS subjects compared with normal control subjects.

CONCLUSIONS

The current study provides detailed evidence of specific dysregulation of certain PKC isozymes in the postmortem brain of DS and DNS subjects and further supports earlier evidence for the role of PKC in the platelets and brain of the adult and teenage depressed and suicidal population. This comprehensive study may lead to further knowledge of the involvement of PKC in the pathophysiology of depression and suicide.

Hierarchical structure of molybdenum disulfide-reduced graphene oxide nanocomposite for the development of a highly efficient serotonin biosensing platform

Molybdenum disulfide-reduced graphene oxide nanocomposite based immunosensor for the serotonin detection.

Is depression a disorder of a receptor superfamily? A critical review of the receptor theory of depression and the appraisal of a new heuristic model

The monoamine hypothesis of depression and its direct derivation, the receptor theory, have constituted for several years a frame of reference for researchers working in the field of biological psychiatry. Although most of the data are derived from animal findings and must be considered inconclusive in view of various controversies, some guidelines may be identified: these would suggest that changes in postsynaptic beta-adrenoreceptors, presynaptic alpha 2-adrenoreceptors, as well as in type 2 serotonin receptors and dopaminergic autoreceptors may be involved in the mode of action of antidepressant drugs and, consequently, in the pathophysiology of depression. Nowadays, any attempt to correlate depression with the dysfunction of a single neurotransmitter or receptor is no longer tenable, since it is clear that depression is a heterogeneous disorder which involves abnormalities in the interactive relationships between neurotransmitters and receptors. If, on the one hand, this new model has opened up new fields of research and has led to the investigation of new systems,egthe GABAergic and GABA B receptors, on the other hand, it has been strongly limited by the lack of research tools and reliable peripheral CNS models forin vivostudies. A possible approach to this unresolved dilemma may be provided by molecular biology techniques, which have permitted the identification of the genes and sequencing of the primary structure of several membrane receptors. It is now established that receptors may be grouped into four superfamilies; in depression, there exists compelling evidence of alterations mainly in receptors belonging to the G-protein-coupled family: it is plausible that depression may be related to a disorder of the G-protein-coupled receptor superfamily. Such an hypothesis would represent an attempt to unify the different receptor abnormalities found in depression or following antidepressant treatments, and to shift from the monoamine paradigm to a new heuristic model. In addition, it would accommodate the various dysfunctions likely to be encountered and would open up new theoretical perspectives in the treatment of depression.

Microglial Dysregulation and Suicidality: A Stress-Diathesis Perspective

According to the stress-diathesis model of suicidal behavior, completed suicide depends on the interaction between psychosocial stressors and a trait-like susceptibility. While there are likely multiple biological processes at play in suicidal behavior, recent findings point to over-activation of microglia, the resident macrophages of the central nervous system, as implicated in stress-induced suicidal behavior. However, it remains unclear how microglial dysregulation can be integrated into a clinical model of suicidal behavior. Therefore, this narrative review aims to (1) examine the findings from human post-mortem and neuroimaging studies that report a relationship between microglial activation and suicidal behavior, and (2) update the clinical model of suicidal behavior to integrate the role of microglia. A systematic search of SCOPUS, PubMed, PsycINFO, and Embase databases revealed evidence of morphological alterations in microglia and increased translocator protein density in the brains of individuals with suicidality, pointing to a positive relationship between microglial dysregulation and suicidal behavior. The studies also suggested several pathological mechanisms leading to suicidal behavior that may involve microglial dysregulation, namely (1) enhanced metabolism of tryptophan to quinolinic acid through the kynurenine pathway and associated serotonin depletion; (2) increased quinolinic acid leading to excessive N-methyl-D-aspartate-signaling, resulting in potential disruption of the blood brain barrier; (3) increased quinolinic acid resulting in higher neurotoxicity, and; (4) elevated interleukin 6 contributing to loss of inhibition of glutamatergic neurons, causing heightened glutamate release and excitotoxicity. Based on these pathways, we reconceptualized the stress-diathesis theory of suicidal behavior to incorporate the role of microglial activity.

5-HT1A receptor, 5-HT2A receptor and serotonin transporter binding in the human auditory cortex in depression

BACKGROUND

Serotonergic system abnormalities are implicated in many psychiatric disorders, including major depression. The temporal lobe receives a high density of serotonergic afferent projections, and responses in the primary auditory cortex to sound are modulated by serotonergic tone. However, the associations between changes in serotonergic tone, disease state and changes in auditory cortical function remain to be clarified.

METHODS

We quantified serotonin 1A (5-HT1A) receptor binding, serotonin 2A (5-HT2A) receptor binding, and serotonin transporter (SERT) binding in Brodmann areas (BA) 41/42, 22, 9 and 4 from postmortem brain sections of 40 psychiatrically healthy controls and 39 individuals who had a history of a major depressive episode (MDE).

RESULTS

There was 33% lower 5-HT2A receptor binding in BA 41/42 in individuals who had an MDE than in controls (p = 0.0069). Neither 5-HT1A nor SERT binding in BA 41/42 differed between individuals who had an MDE and controls. We also found 14% higher 5-HT1A receptor binding (p = 0.045) and 21% lower SERT binding in BA 9 of individuals who had an MDE (p = 0.045).

LIMITATIONS

The study was limited by the small number of postmortem brain samples including BA 41/42 available for binding assays and the large overlap between suicide and depression in the MDE sample.

CONCLUSION

Depression may be associated with altered serotonergic function in the auditory cortex involving the 5-HT2A receptor and is part of a wider view of the pathophysiology of mood disorders extending beyond psychopathology.

Quantification of 5-HT1A and 5-HT2A receptor Binding in Depressed Suicide Attempters and Non-Attempters

OBJECTIVE

To determine serotonin system abnormalities related to major depression or previous suicidal behavior.

METHODS

[¹¹C]WAY100635, [¹⁸F]altanserin and positron emission tomography were used to compare 5-HT_1A and 5-HT_2A binding in MDD patients divided into eight past suicide attempters (>4yrs prior to scanning) and eight lifetime non-attempters, and both groups were compared to eight healthy volunteers.

RESULTS

The two receptor types differed in binding pattern across brain regions from each other, but there were no differences in binding between healthy volunteers and the two depressed groups or between depressed suicide attempters and non-attempters. No effects of depression severity or lifetime aggression were observed for either receptor.

CONCLUSION

Limitations of this study include small sample size and absence of high lethality suicide attempts in the depressed attempter group. No trait-like binding correlations with past suicide attempt or current depression were observed. Given the heterogeneity of nonfatal suicidal behavior, a larger sample study emphasizing higher lethality suicide attempts may find the serotonin biological phenotype seen in suicide decedents.

Fish consumption and risk of depression: Epidemiological evidence from prospective studies

INTRODUCTION

The evidence on the association of fish or omega-3 fatty acid intake with depression is inconsistent. We conducted a systematic review and meta-analysis of prospective cohort studies to examine this association.

METHODS

Database searches in PubMed and Web of Science were conducted to identify relevant articles published up to April 2018, which were supplemented by hand-searches of reference lists of the retrieved articles. Using a random-effects model, we calculated pooled relative risks (RR) of depression in relation to consumption of fish or omega-3 fatty acids after adjusting for potential confounders.

RESULTS

A total of 10 prospective cohort studies with 6672 cases of depression among 109 764 participants were included in the meta-analysis. The pooled adjusted RR of depression for the highest vs lowest category of fish consumption was 0.89 (95% CI: 0.80-0.99). The pooled adjusted RR of depression for the highest vs lowest category of omega-3 intake was 0.87 (95% CI: 0.74-1.04). In the dose-response analysis, the pooled adjusted RRs for an increment of 1 serving/week of fish consumption and 500 mg/day of omega-3 fatty acid intake were 0.89 (95% CI: 0.75-1.04) and 0.99 (95% CI: 0.94-1.04), respectively. There was no evidence of heterogeneity.

DISCUSSION

Our findings provide quantitative evidence for a modest inverse association between fish or omega-3 fatty acid intake and risk of depression, especially in women. These findings from the observational studies need to be confirmed through large randomized clinical trials of fish consumption or omega-3 fatty acid intake and risk of depression.

Alterations in anterior cingulate cortex myoinositol and aggression in veterans with suicidal behavior: A proton magnetic resonance spectroscopy study

Studies investigating the neurochemical changes that correspond with suicidal behavior (SB) have not yielded conclusive results. Suicide correlates such as aggression have been used to explore risk factors for SB. Yet the neurobiological basis for the association between aggression and SB is unclear. Aggression and SB are both prevalent in veterans relative to civilian populations. The current study evaluated the relationship between brain chemistry in the anterior (ACC) and the posterior cingulate cortex (POC), as well as the relationship between aggression and SB in a veteran population using proton magnetic resonance spectroscopy (¹H-MRS). Single-voxel MRS data at 3 Tesla (T) were acquired from the ACC and POC voxels using a 2-dimensional J-resolved point spectroscopy sequence and quantified using the ProFit algorithm. Participants also completed a structured diagnostic interview and a clinical battery. Our results showed that the myoinositol (mI)/H2O ratio in the ACC and POC was significantly higher in veterans who reported SB when compared to veterans who did not. The two groups did not differ significantly with regard to other metabolites. Second, verbal aggression and SB measures positively correlated with mI/H2O in the ACC. Finally, verbal aggression mediated the relationship between mI/H2O in the ACC and SB.

Fish consumption and depression in Korean adults: the Korea National Health and Nutrition Examination Survey, 2013-2015

BACKGROUND/OBJECTIVES

There is a growing body of evidence that supports the potential role of fish consumption in relation to depression, but the data in Korean population is scarce. Thus, we examined the association between fish consumption and depression in Korean adults.

SUBJECTS/METHODS

We conducted a cross-sectional study in 9183 Korean adults aged 19-64 years who participated in the 6TH Korea National Health and Nutrition Examination Survey (2013-2015), which is a large nationally representative study of Korean population. Fish consumption and depression status were assessed using questionnaires. Multivariable logistic regression models were used to compute odds ratios (ORs) and 95% confidence intervals (CIs) for physician-diagnosed clinical depression.

RESULTS

Out of the 9183 subjects, 389 (4.2%) were diagnosed with depression. After adjusting for potential confounders, the multivariable-adjusted ORs for clinical depression across fish consumption were 1.00 (reference) for <1 time/week, 0.76 (95% CI: 0.56-1.04) for 1-3 times/week and 0.52 (95% CI: 0.37-0.74) for ≥4 times/week (P for trend = 0.0005). The inverse association for ≥4 times/week of fish consumption was stronger in women (OR = 0.44, 95% CI: 0.29-0.67, P for trend < .0001), but there was no significant association in men.

CONCLUSIONS

Our findings suggest that high consumption of fish is associated with lower odds of depression in Korean adults, particularly in women. These results warrant further prospective studies to verify the association between fish consumption and risk of depression in Korean adults.

Serotonin and brain function: a tale of two receptors

Previous attempts to identify a unified theory of brain serotonin function have largely failed to achieve consensus. In this present synthesis, we integrate previous perspectives with new and older data to create a novel bipartite model centred on the view that serotonin neurotransmission enhances two distinct adaptive responses to adversity, mediated in large part by its two most prevalent and researched brain receptors: the 5-HT1A and 5-HT2A receptors. We propose that passive coping (i.e. tolerating a source of stress) is mediated by postsynaptic 5-HT1AR signalling and characterised by stress moderation. Conversely, we argue that active coping (i.e. actively addressing a source of stress) is mediated by 5-HT2AR signalling and characterised by enhanced plasticity (defined as capacity for change). We propose that 5-HT1AR-mediated stress moderation may be the brain's default response to adversity but that an improved ability to change one's situation and/or relationship to it via 5-HT2AR-mediated plasticity may also be important - and increasingly so as the level of adversity reaches a critical point. We propose that the 5-HT1AR pathway is enhanced by conventional 5-HT reuptake blocking antidepressants such as the selective serotonin reuptake inhibitors (SSRIs), whereas the 5-HT2AR pathway is enhanced by 5-HT2AR-agonist psychedelics. This bipartite model purports to explain how different drugs (SSRIs and psychedelics) that modulate the serotonergic system in different ways, can achieve complementary adaptive and potentially therapeutic outcomes.

Stress inhibits tryptophan hydroxylase expression in a rat model of depression

Serotonin (5-hydroxytryptamine, 5-HT) dysfunction is associated with the pathophysiology of depression. Tryptophan hydroxylase (TPH), the rate-limiting enzyme in 5-HT biosynthesis, is believed to have essential role in many mental disorders, including depression. In the present study, we generated a rat model of depression by exposing the animals to stress, and the rats were then treated with paroxetine. The results indicated that the concentration of 5-HT in the brain and liver tissues were significantly lower in the rat model of depression than in healthy or treated rats. Immunohistochemical analyses of TPH1/2 showed less TPH1 and TPH2 expression, specifically TPH2, in the brain, liver and kidney of the depressive rats than in the healthy rats; In addition, the two TPH isoforms, TPH1 and TPH2, had different spatial distributions,the mRNAs of the TPH1/2 genes were significantly decreased and TPH1/2 were highly methylated in the depressive model rat, but treatment with paroxetine ameliorated the expression and methylation of TPH1/2. All together, stress was able to inhibit expression of TPH1/2 in brain tissue and decrease concentration of 5-HT, the mechanism maybe involve in increasing the methylation of TPH2 genes promoter; Paroxetine has a role in confronting the effect of stress in depressive rat model.

Personality traits as an endophenotype in genetic studies on suicidality in bipolar disorder

Introduction The influence of personality traits on suicidal behaviour risk has been well documented. Personality traits and suicidal behaviour are partially genetically determined and personality has been described as an endophenotype of suicidal behaviour. The aim of this study was to investigate a possible association between personality traits with suicidal behaviour and selected serotonergic gene polymorphisms.

METHODS

In the study we included 156 patients meeting DSM-IV criteria for bipolar disorder (BP) and 93 healthy controls. The personality dimensions were assessed using the Temperament and Character Inventory (TCI). We genotyped two selected polymorphisms of the tryptophan hydroxylase 1 (TPH1) gene (rs1800532 218A>C and rs1799913 779A>C) and polymorphism in the promoter region of serotonin transporter gene (5-HTTLPR, rs25531) related to serotoninergic neurotransmission. Multiple poisson regression, logistic regression and Kruskal-Wallis tests were applied.

RESULTS

We found numerous differences between the BP patients and the control group in terms of their TCI dimensions/subdimensions. Significant differences were found between patients with, and without, suicidal attempts in fatigability and asthenia (Ha4), as well as in harm avoidance (Ha). We also found that the interactions between TCI subdimensions (the interaction of disordiness (Ns4) and spiritual acceptance (St3), disordiness (Ns4) and integrated conscience (C5), extravagance (Ns3) and resourcefulness (Sd3)) were significantly contributing for suicidal behaviour risk. We found association between all studied genetic polymorphisms and several TCI dimensions and subdimensions.

CONCLUSION

Our results confirm that personality traits are partially determined by genes. Both personality traits and the interactions between temperament and character traits, may be helpful in predicting suicidal behaviour.

The Life Span Model of Suicide and Its Neurobiological Foundation

The very incomprehensibility of the suicidal act has been occupying the minds of researchers and health professionals for a long time. Several theories of suicide have been proposed since the beginning of the past century, and a myriad of neurobiological studies have been conducted over the past two decades in order to elucidate its pathophysiology. Both neurobiology and psychological theories tend to work in parallel lines that need behavioral and empirical data respectively, to confirm their hypotheses. In this review, we are proposing a "Life Span Model of Suicide" with an attempt to integrate the "Stress-Diathesis Model" and the "Interpersonal Model of Suicide" into a neurobiological narrative and support it by providing a thorough compilation of related genetic, epigenetic, and gene expression findings. This proposed model comprises three layers, forming the capability of suicide: genetic factors as the predisposing Diathesis on one side and Stress, characterized by epigenetic marks on the other side, and in between gene expression and gene function which are thought to be influenced by Diathesis and Stress components. The empirical evidence of this model is yet to be confirmed and further research, specifically epigenetic studies in particular, are needed to support the presence of a life-long, evolving capability of suicide and identify its neurobiological correlates.

Suicide behavior as a quantitative trait and its genetic background

INTRODUCTION

Studies have not given yet a clear answer what is the genetic background of suicidal predisposition. The associations between polymorphisms of the TPH1 and 5-HTTLPR genes and violent suicidal behavior was revealed with the least inconsistencies.

METHOD

We selected 10 "strong candidate genes" and 35 SNPs, SLC6A4 and ACP1 for replication study. We searched associations between precisely described suicidal phenotype in 825 affective patients and polymorphisms of selected neurobiological pathways genes as well as their interactions that constitute suicidal risk.

RESULTS

The results confirm the role of TPH1, TPH2, 5HT2A, CRHR1 and ACP1 variants in the risk of suicidal behavior.

LIMITATIONS

In our study we analyzed limited number of candidate genes and only one of them is linked to lithium mechanism of action. We had no data on pharmacological treatment of investigated patients and its relation to the time of suicide attempt.

CONCLUSION

Our results indicate that polymorphisms of various signaling pathways are involved in the pathogenesis of suicidal behavior. Non-genetic factors are also involved in the risk of suicidal attempts.

Early Childhood Environment and Genetic Interactions: the Diathesis for Suicidal Behavior

Adverse childhood experiences are associated with higher risk for suicide and suicidal behavior later in life. There are known associations between childhood trauma, particularly sexual abuse, and higher rates of suicide, non-lethal suicide attempts, and non-suicidal self-injurious behaviors in adolescence and adulthood. Emotional abuse/neglect, disrupted parental attachment, and cumulative effect of multiple forms of maltreatment, also increase risk. Yet, the causal relationship remains unclear. The diathesis-stress model provides a framework for understanding how early life adverse experiences contribute to suicide vulnerability. Current findings from the fields of biology, neurology, and genetics shed new light on mediating variables and possible causal links between early childhood trauma and suicide. In this paper, we review recent advances, particularly regarding the interaction of early life environmental adverse events with genetics factors, that increase the diathesis for psychological traits are associated with subsequent deliberate self-harm behaviors.

Smoking, Suicidality and Psychosis: A Systematic Meta-Analysis

The aim of this study is to systematically review the literature that explored the association between smoking and suicidal risk among those with serious mental illness and to estimate the risk of suicidal behaviors attributable to smoking among this patient group. Multiple databases (CINAHL, PsycINFO, EMBASE, Informit Health Collection and the Cochrane Library databases) were searched from 1 January 1975 through 15 January 2014, along with references from relevant articles for observational studies that ascertained the association between smoking and suicidal behaviors among patients with psychotic disorders conducted in adult patients. Thirteen studies involving 6813 patients with severe mental illness were included. We found that smoking was significantly associated with suicidality in psychosis with an Odds Ratio of 2.12 (95% CI 1.67–2.7). Smoking is associated with suicidal risk amongst individuals with a severe mental illness; however, it is still unclear whether this represents a true risk factor or a confounder or a mediator via mechanisms, hitherto unknown, needs to be studied further.

A Model of Post-Infection Fatigue Is Associated with Increased TNF and 5-HT2A Receptor Expression in Mice

It is well documented that serotonin (5-HT) plays an important role in psychiatric illness. For example, myalgic encephalomyelitis (ME/CFS), which is often provoked by infection, is a disabling illness with an unknown aetiology and diagnosis is based on symptom-specific criteria. However, 5-HT2A receptor expression and peripheral cytokines are known to be upregulated in ME. We sought to examine the relationship between the 5-HT system and cytokine expression following systemic bacterial endotoxin challenge (LPS, 0.5 mg/kg i.p.), at a time when the acute sickness behaviours have largely resolved. At 24 hours post-injection mice exhibit no overt changes in locomotor behaviour, but do show increased immobility in a forced swim test, as well as decreased sucrose preference and reduced marble burying activity, indicating a depressive-like state. While peripheral IDO activity was increased after LPS challenge, central activity levels remained stable and there was no change in total brain 5-HT levels or 5-HIAA/5-HT. However, within the brain, levels of TNF and 5-HT2A receptor mRNA within various regions increased significantly. This increase in receptor expression is reflected by an increase in the functional response of the 5-HT2A receptor to agonist, DOI. These data suggest that regulation of fatigue and depressive-like moods after episodes of systemic inflammation may be regulated by changes in 5-HT receptor expression, rather than by levels of enzyme activity or cytokine expression in the CNS.

Serotonin and mental disorders: a concise review on molecular neuroimaging evidence

Serotonin is one of the most important neurotransmitters influencing mental health and, thus, is a potential target for pharmaco-logical treatments. Functional neuroimaging techniques, such as positron-emission tomography (PET) and single photon emission computed tomography (SPECT), could provide persuasive evidence for the association between mental disorders and serotonin. In this concise review, we focus on evidence of the links between serotonin and major depressive disorders, as well as other mood disorders, anxiety disorders, schizophrenia, addiction, attention deficit hyperactivity disorder (ADHD), and autism.

Toward a biosignature for suicide

OBJECTIVE

Suicide, a major cause of death worldwide, has distinct biological underpinnings. The authors review and synthesize the research literature on biomarkers of suicide, with the aim of using the findings of these studies to develop a coherent model for the biological diathesis for suicide.

METHOD

The authors examined studies covering a large range of neurobiological systems implicated in suicide. They provide succinct descriptions of each system to provide a context for interpreting the meaning of findings in suicide.

RESULTS

Several lines of evidence implicate dysregulation in stress response systems, especially the hypothalamic-pituitary-adrenal axis, as a diathesis for suicide. Additional findings related to neuroinflammatory indices, glutamatergic function, and neuronal plasticity at the cellular and circuitry level may reflect downstream effects of such dysregulation. Whether serotonergic abnormalities observed in individuals who have died by suicide are independent of stress response abnormalities is an unresolved question.

CONCLUSIONS

The most compelling biomarkers for suicide are linked to altered stress responses and their downstream effects, and to abnormalities in the serotonergic system. Studying these systems in parallel and in the same populations may elucidate the role of each and their interplay, possibly leading to identification of new treatment targets and biological predictors.

The molecular bases of the suicidal brain

Suicide ranks among the leading causes of death around the world and takes a heavy emotional and public health toll on most societies. Both distal and proximal factors contribute to suicidal behaviour. Distal factors - such as familial and genetic predisposition, as well as early-life adversity - increase the lifetime risk of suicide. They alter responses to stress and other processes through epigenetic modification of genes and associated changes in gene expression, and through the regulation of emotional and behavioural traits. Proximal factors are associated with the precipitation of a suicidal event and include alterations in key neurotransmitter systems, inflammatory changes and glial dysfunction in the brain. This Review explores the key molecular changes that are associated with suicidality and discusses some promising avenues for future research.

Genes in the serotonin pathway are associated with bipolar affective disorder in a Han Chinese population

Serotonin plays an important role in mood regulation, but the involvement of serotonin pathway genes in the development of bipolar I disorder (BP-I), a mood disorder, is not clear. We selected 21 single-nucleotide polymorphisms (SNPs) within the HTR2A gene, 8 within the SLC6A4 gene and 23 within the TPH2 gene for genotyping using the GoldenGate genotyping assay. A total of 375 patients with BP-I and 475 normal controls were recruited. Two out of 21 SNPs (rs1475196 and rs9567747) in the HTR2A gene and 1/23 SNPs (rs17110566) in the TPH2 gene were significantly associated with BP-I, both genotype-wise and allele-wise. Furthermore, a specific haplotype in the HTR2A gene showed a significant association with BP-I. Our results indicate that the HTR2A and TPH2 genes in the serotonin pathway play important roles in susceptibility to BP-I.

The fall and rise of pharmacology--(re-)defining the discipline?

Pharmacology is an integrative discipline that originated from activities, now nearly 7000 years old, to identify therapeutics from natural product sources. Research in the 19th Century that focused on the Law of Mass Action (LMA) demonstrated that compound effects were dose-/concentration-dependent eventually leading to the receptor concept, now a century old, that remains the key to understanding disease causality and drug action. As pharmacology evolved in the 20th Century through successive biochemical, molecular and genomic eras, the precision in understanding receptor function at the molecular level increased and while providing important insights, led to an overtly reductionistic emphasis. This resulted in the generation of data lacking physiological context that ignored the LMA and was not integrated at the tissue/whole organism level. As reductionism became a primary focus in biomedical research, it led to the fall of pharmacology. However, concerns regarding the disconnect between basic research efforts and the approval of new drugs to treat 21st Century disease tsunamis, e.g., neurodegeneration, metabolic syndrome, etc. has led to the reemergence of pharmacology, its rise, often in the semantic guise of systems biology. Against a background of limited training in pharmacology, this has resulted in issues in experimental replication with a bioinformatics emphasis that often has a limited relationship to reality. The integration of newer technologies within a pharmacological context where research is driven by testable hypotheses rather than technology, together with renewed efforts in teaching pharmacology, is anticipated to improve the focus and relevance of biomedical research and lead to novel therapeutics that will contain health care costs.

Cerebral 5-HT2A receptor binding, but not mGluR2, is increased in tryptophan hydroxylase 2 decrease-of-function mice

Transgenic mice with a knock-in (KI) of a tryptophan hydroxylase 2 (Tph2) R439H mutation, analogous to the Tph2 R441H single-nucleotide polymorphism originally identified in a late life depression cohort, have markedly reduced levels of 5-hydroxytryptamine (5-HT). These Tph2KI mice are therefore interesting as a putative translational model of low endogenous 5-HT function that allows for assessment of adaptive changes in different anatomical regions. Here, we determined 5-HT2A receptor binding in several brain regions using in vitro receptor autoradiography and two different radioligands. When using the 5-HT2A receptor selective antagonist radioligand (3)H-MDL100907, we found higher binding in the prefrontal cortex (10%, P=0.009), the striatum (26%, P=0.005), and the substantia nigra (21%, P=0.027). The increase was confirmed in the same regions with the 5-HT2A/C receptor agonist, (3)H-CIMBI-36 (2-(4-Bromo-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethanamine). 5-HT2A receptors establish heteromeric receptor complexes with metabotropic glutamate 2 receptors (mGluR2), but binding levels of the mGluR2/3 ligand (3)H-LY341495 were unaltered in brain areas with increased 5-HT2A receptor levels. These data show that in distinct anatomical regions, 5-HT2A receptor binding sites are up-regulated in 5-HT deficient mice, and this increase is not associated with changes in mGluR2 binding.

Biological basis of suicide and suicidal behavior

OBJECTIVE

Suicide is a major public health concern as each year 30000 people die by suicide in the USA alone. In the teenage population, it is the second leading cause of death. There have been extensive studies of psychosocial factors associated with suicide and suicidal behavior. However, very little is known about the neurobiology of suicide. Recent research has provided some understanding of the neurobiology of suicide, which is the topic of this review.

METHODS

Neurobiology of suicide has been studied using peripheral tissues such as platelets, lymphocytes, and cerebrospinal fluid obtained from suicidal patients or from the postmortem brains of suicide victims.

RESULTS

These studies have provided encouraging information with regard to the neurobiology of suicide. They show an abnormality of the serotonergic mechanism, such as increased serotonin receptor subtypes and decreased serotonin metabolites (e.g. 5-hydroxyindoleacetic acid). These studies also suggest abnormalities of receptor-linked signaling mechanisms such as phosphoinositide and adenylyl cyclase. Other biological systems that appear to be dysregulated in suicide involve the hypothalamic-pituitary-adrenal axis, and neurotrophins and neurotrophin receptors. More recently, several studies have also indicated abnormalities of neuroimmune functions in suicide.

CONCLUSIONS

Some encouraging information emerged from the present review, primarily related to some of the neurobiological mechanisms mentioned above. It is hoped that neurobiological studies may eventually result in the identification of appropriate biomarkers for suicidal behavior as well as appropriate therapeutic targets for its treatment.

Glucocorticoid treatment increases density of serotonin 5-HT2A receptors in humans

BACKGROUND

Interactions between the serotonergic system and the hypothalamic-pituitary-adrenal axis have been suggested, albeit the details for such interactions have yet to be established. Animal studies have shown that the density of serotonin 5-HT2A receptors is increased after administration of exogenous glucocorticoids.

OBJECTIVE

The objective of this study was to explore possible changes in the pattern of density and affinity of 5-HT2A receptors in humans after treatment with glucocorticoids.

METHODS

Using a radioactive binding assay, the density and affinity (measured as Bmax and Kd) of 5-HT2A serotonin receptors were measured in blood samples drawn from 27 individuals diagnosed with polymyalgia rheumatica and/or giant cell arteritis before and after start of an oral treatment with prednisolone. For each patient Bmax and Kd at baseline before prednisolone treatment were compared with Bmax and Kd in samples drawn at a first and second follow-up clinic visit at an average of 8.8 (±2.5) days and 33.6 (±6.8) days, respectively.

RESULTS

The density of 5-HT2A receptors increased after treatment in 23 individuals. The mean Bmax value at baseline for all patients was 45.2 fmol/mg protein compared with 64.9 fmol/mg protein in the corresponding samples drawn at the second follow-up visit (p=0.001). There also was an association between individuals accumulated prednisolone dose and the magnitude of change in Bmax between baseline and the first follow-up visit. Erythrocyte sedimentation rate, platelet count or gender had no influence on the results. There were no significant differences in Kd during the treatment period. However, a low Kd value at baseline was a predictor for an increase in Bmax following treatment.

CONCLUSIONS

The results of this study showed that the density of 5-HT2A serotonin receptors in man is increased after a subchronic treatment with glucocorticoids. The magnitude of the increase appears to be associated with the affinity of 5-HT2A receptors before treatment and the accumulated dose of glucocorticoid early in the treatment period.

Family-based study of HTR2A in suicide attempts: observed gene, gene × environment and parent-of-origin associations

While suicidal behavior is frequently accompanied by serotonergic system alterations, specific associations with genetic variation in the serotonin 2A receptor (HTR2A) gene have been inconsistent. Using a family-based study design of 660 offspring who have made a suicide attempt (SA) and both parents, we conducted an association and linkage analysis using single-nucleotide polymorphisms (SNPs) with extensive gene coverage, and included the study of parent-of-origin (POE) and gene-environment interaction (G × E), also using previously unstudied exposures. The main finding was a G × E between the exon 1 SNP rs6313 and exposure to cumulative types of lifetime stressful life events (SLEs), driven by overtransmission of CT and undertransmission of TT, both in relation to other genotypes. Further exploratory analysis revealed a significant POE in this G × E in female subjects, which followed a polar overdominant inheritance pattern. In addition, rs6310 and rs6305 were found to significantly associate with SA in the total sample. A G × E in female subjects (rs7322347 × physical assault in childhood/adolescence) confirmed features of a previously observed association with SA. Other potentially interesting nominally significant findings were observed, but like the G × E of rs7322347 did not pass a false-discovery rate cutoff. Taken together, this study found multiple associations of HTR2A SNPs on SA, with strongest statistical evidence for a G × E involving rs6313, and further suggested the importance of taking into account different inheritance patterns and G × Es with regard to HTR2A.

Biomarker investigations related to pathophysiological pathways in schizophrenia and psychosis

Post-mortem brain investigations of schizophrenia have generated swathes of data in the last few decades implicating candidate genes and protein. However, the relation of these findings to peripheral biomarker indicators and symptomatology remain to be elucidated. While biomarkers for disease do not have to be involved with underlying pathophysiology and may be largely indicative of diagnosis or prognosis, the ideal may be a biomarker that is involved in underlying disease processes and which is therefore more likely to change with progression of the illness as well as potentially being more responsive to treatment. One of the main difficulties in conducting biomarker investigations for major psychiatric disorders is the relative inconsistency in clinical diagnoses between disorders such as bipolar and schizophrenia. This has led some researchers to investigate biomarkers associated with core symptoms of these disorders, such as psychosis. The aim of this review is to evaluate the contribution of post-mortem brain investigations to elucidating the pathophysiology pathways involved in schizophrenia and psychosis, with an emphasis on major neurotransmitter systems that have been implicated. This data will then be compared to functional neuroimaging findings as well as findings from blood based gene expression investigations in schizophrenia in order to highlight the relative overlap in pathological processes between these different modalities used to elucidate pathogenesis of schizophrenia. In addition we will cover some recent and exciting findings demonstrating microRNA (miRNA) dysregulation in both the blood and the brain in patients with schizophrenia. These changes are pertinent to the topic due to their known role in post-transcriptional modification of gene expression with the potential to contribute or underlie gene expression changes observed in schizophrenia. Finally, we will discuss how post-mortem studies may aid future biomarker investigations.

Cholinergic connectivity: it's implications for psychiatric disorders

Acetylcholine has been implicated in both the pathophysiology and treatment of a number of psychiatric disorders, with most of the data related to its role and therapeutic potential focusing on schizophrenia. However, there is little thought given to the consequences of the documented changes in the cholinergic system and how they may affect the functioning of the brain. This review looks at the cholinergic system and its interactions with the intrinsic neurotransmitters glutamate and gamma-amino butyric acid as well as those with the projection neurotransmitters most implicated in the pathophysiologies of psychiatric disorders; dopamine and serotonin. In addition, with the recent focus on the role of factors normally associated with inflammation in the pathophysiologies of psychiatric disorders, links between the cholinergic system and these factors will also be examined. These interfaces are put into context, primarily for schizophrenia, by looking at the changes in each of these systems in the disorder and exploring, theoretically, whether the changes are interconnected with those seen in the cholinergic system. Thus, this review will provide a comprehensive overview of the connectivity between the cholinergic system and some of the major areas of research into the pathophysiologies of psychiatric disorders, resulting in a critical appraisal of the potential outcomes of a dysregulated central cholinergic system.

The neurobiology of suicide - A Review of post-mortem studies

The neurobiology of suicidal behaviour, which constitutes one of the most serious problems both in psychiatry and general medical practice, still remains to a large degree unclear. As a result, scientists constantly look for new opportunities of explaining the causes underlying suicidality. In order to elucidate the biological changes occurring in the brains of the suicide victims, studies based on post-mortem brain tissue samples are increasingly being used. These studies employ different research methods to provide an insight into abnormalities in brain functioning on various levels, including gene and protein expression, neuroplasticity and neurotransmission, as well as many other areas. The aim of this paper to summarize the available data on the post-mortem studies, to provide an overview of main research directions and the most up-to-date findings, and to indicate the possibilities of further research in this field.

Microglial activation, increased TNF and SERT expression in the prefrontal cortex define stress-altered behaviour in mice susceptible to anhedonia

A chronic stress paradigm comprising exposure to predation, tail suspension and restraint induces a depressive syndrome in C57BL/6J mice that occurs in some, but not all, animals. Here, we sought to extend our behavioural studies to investigate how susceptibility (sucrose preference<65%) or resilience (sucrose preference>65%) to stress-induced anhedonia affects the 5HT system and the expression of inflammation-related genes. All chronically stressed animals, displayed increased level of anxiety, but susceptible mice exhibited an increased propensity to float in the forced swim test and demonstrate hyperactivity under stressful lighting conditions. These changes were not present in resilient or acutely stressed animals. Compared to resilient animals, susceptible mice showed elevated expression of tumour necrosis factor alpha (TNF) and the 5-HT transporter (SERT) in the pre-frontal area. Enhanced expression of 5HT(2A) and COX-1 in the pre-frontal area was observed in all stressed animals. In turn, indoleamine-2,3-dioxygenase (IDO) was significantly unregulated in the raphe of susceptible animals. At the cellular level, increased numbers of Iba-1-positive microglial cells were also present in the prefrontal area of susceptible animals compared to resilient animals. Consequently, the susceptible animals display a unique molecular profile when compared to resilient, but anxious, animals. Unexpectedly, this altered profile provides a rationale for exploring anti-inflammatory, and possibly, TNF-targeted therapy for major depression.

NEUROBIOLOGICAL ASPECTS OF SUICIDE AND SUICIDE ATTEMPTS IN BIPOLAR DISORDER

Suicide and bipolar disorder (BD) are challenging, complex, and intertwined areas of study in contemporary psychiatry. Indeed, BD is associated with the highest lifetime risk for suicide attempt and completion of all the psychiatric conditions. Given that several clinical risk factors for both suicide and BD have been well noted in the literature, exploring the neurobiological aspects of suicide in BD may provide insights into both preventive measures and future novel treatments. This review synthesizes findings regarding the neurobiological aspects of suicide and, when applicable, their link to BD. Neurochemical findings, genes/epigenetics, and potential molecular targets for current or future treatments are discussed. The role of endophenotypes and related proximal and distal risk factors underlying suicidal behavior are also explored. Lastly, we discuss the manner in which preclinical work on aggression and impulsivity may provide additional insights for the future development of novel treatments.

The role of the serotonergic system in suicidal behavior

Serotonin is a widely investigated neurotransmitter in several psychopathologies, including suicidal behavior (SB); however, its role extends to several physiological functions involving the nervous system, as well as the gastrointestinal and cardiovascular systems. This review summarizes recent research into ten serotonergic genes related to SB. These genes - TPH1, TPH2, SLC6A4, SLC18A2, HTR1A, HTR1B, HTR2A, DDC, MAOA, and MAOB - encode proteins that are vital to serotonergic function: tryptophan hydroxylase; the serotonin transporter 5-HTT; the vesicular transporter VMAT2; the HTR1A, HTR1B, and HTR2A receptors; the L-amino acid decarboxylase; and the monoamine oxidases. This review employed a systematic search strategy and a narrative research methodology to disseminate the current literature investigating the link between SB and serotonin.

Neurochemical imaging and depressive behaviours

Neurochemical imaging is frequently applied to measure markers of pathological change so as to understand mechanisms that create symptoms of major depressive disorder. For example, indices of greater monoamine oxidase A(MAO-A) level, particularly in the prefrontal and anterior cingulate cortex, are associated with depressed mood states, and high-risk states for onset of major depressive episodes. MAO-A metabolises monoamines, and greater metabolism of monoamines occurs when MAO-A is elevated in brain. Lower extracellular serotonin is associated with greater pessimism in humans and chronic serotonin deficiency is associated with upregulation of 5-HT2A (serotonin2A) receptors in cortex. During major depressive episodes when pessimism is more severe, greater 5-HT2A BPND, an index of density occurs in prefrontal and anterior cingulate cortex. These results argue for a mechanism of lowering extracellular serotonin in the prefrontal and anterior cingulate cortex, consequent to elevated MAO-A level. The relationship between elevated 5-HTT BPND and greater pessimism during major depressive episodes suggests that greater 5-HTT density in the context of elevated MAO-A level further contributes to serotonin deficiency in these brain regions. A similar mechanism may explain the association between neuroimaging indices of greater dorsal striatal D2 density, DAT density and symptoms of motor retardation: Greater MAO-A level and relatively greater DAT density lower extracellular dopamine in the dorsal striatum, leading to motor retardation. Indices of greater 5-HT1A density, particularly in the cingulate cortex, have been associated with major depressive disorder, and well as anxiety disorders, suggesting that this abnormality is mechanistically related to presence of anxiety symptoms. To date, abnormalities of Glx a measure reflecting glutamate and glutamine levels have been most strongly associated with presence of major depressive episodes, with greater levels in occipital cortex, and reduced levels in prefrontal cortex. Ultimately, the future for neurochemical imaging is to better understand the mechanisms that predispose toward onset of MDE so as to create biologically informed, novel, methods of prevention, and superior, more symptom-targeted treatments.