CRP, IL-6 and depression: a systematic review and meta-analysis of longitudinal studies

Biomarkers of psychiatric diseases: current status and future prospects

Abnormal behavior and disturbed cognition, often assumed to represent psychiatric illness, may actually result from some form of occult organic brain disease that can be detected by means of one or more biomarkers. This truth was discovered more than a century ago by Aloysius Alzheimer, a German psychiatrist and neuropathologist. As a psychiatrist, he described the behavioral manifestations of "senile dementia" in a 51-year-old female; as a neuropathologist, he was the first to recognize the significance of the senile plaques and neurofibrillary tangles found in her brain after her death at age 55 years. It was Alzheimer who made the connection between these "biomarkers" and the symptoms of the increasingly prevalent disease that now bears his name. In recent years, the search for psychiatry-relevant biomarkers of major depression, schizophrenia, bipolar disease, and other important psychiatric/neuropsychiatric disorders has intensified. Biomarkers in psychiatry and neuropsychiatry have the potential of clarifying the etiology of an ambiguous clinical presentation-making it possible, for example, to detect underlying differences between psychological maladies that have confusingly similar symptoms. In addition, attempts are now being made to classify mental disorders on the basis of biomarkers. Biomarkers may also disclose the presence of a previously unsuspected physical explanation for behavior(s) originally presumed to be "psychiatric" in origin. Although clinically usable biomarkers in the diagnosis and treatment of mental illness await validation, candidate genomic biomarkers and protein profiling of candidate biomarkers in psychiatry are rapidly gaining ground as areas of interest, with considerable future potential. This review considers biomarker-related issues germane to psychiatry and neuropsychiatry in the context of new data that can be used to tailor therapies to the individual psychiatric patient.

Association between C reactive protein level and depressive symptoms in an elderly Korean population: Korean Social Life, Health and Aging Project

OBJECTIVE

The relationship between inflammatory markers and depressive symptoms has been reported inconsistently. Moreover, there were only a few studies conducted in an Asian population. The purpose of this study was to examine the association between C reactive protein (CRP) and depressive symptoms in an elderly Korean population.

DESIGN, SETTING AND PARTICIPANTS

This study used data from the Korean Social Life, Health and Aging Project Health Examination Cohort, which started in 2011. Among participants aged 60 or over recruited from a rural community, 569 (224 men and 345 women) without a history of stroke, angina pectoris, myocardial infarction or CRP≥20 mg/L were employed for cross-sectional analyses. As a marker of systemic inflammation, CRP was measured. Depressive symptoms were measured with the Center for Epidemiologic Studies Depression (CES-D) scale. Multiple linear regression analysis was used to investigate the relationship between CRP and depressive symptoms.

RESULTS

In men, CRP levels had significant associations with depressive symptoms before (β=0.420, p=0.010) and after (β=0.336, p=0.025) adjusting for age, body mass index, systolic blood pressure, number of comorbidities, smoking status, alcohol intake, marital status, education and sleep duration. However, in women, the association between CRP and depressive symptoms was not significant before (p=0.250) and after (p=0.256) adjustment.

CONCLUSIONS

Our findings suggest that elevated CRP levels are independently associated with the presence of depressive symptoms in elderly Korean men.

Advances in biomarkers of major depressive disorder

Major depressive disorder (MDD) is characterized by mood, vegetative, cognitive, and even psychotic symptoms and signs that can cause substantial impairments in quality of life and functioning. Biomarkers are measurable indicators that could help diagnosing MDD or predicting treatment response. In this chapter, lipid profiles, immune/inflammation, and neurotrophic factor pathways that have long been implicated in the pathogenesis of MDD are discussed. Then, pharmacogenetics and epigenetics of serotonin transport and its metabolism pathway, brain-derived neurotrophic factor, and abnormality of hypothalamo-pituitary-adrenocortical axis also revealed new biomarkers. Lastly, new techniques, such as proteomics and metabolomics, which allow researchers to approach the studying of MDD with new directions and make new discoveries are addressed. In the future, more data are needed regarding pathophysiology of MDD, including protein levels, single nucleotide polymorphism, epigenetic regulation, and clinical data in order to better identify reliable and consistent biomarkers for diagnosis, treatment choice, and outcome prediction.

Psychosocial stress as a risk factor for sepsis: a population-based cohort study

OBJECTIVE

To characterize the relationship between stress and future risk of sepsis. We also evaluated the role of depression in this relationship.

METHODS

We used population-based data on 30,183 participants in the Reasons for Geographic and Racial Differences in Stroke cohort, characterizing stress using the Perceived Stress Scale (PSS) and depressive symptoms using the Center for Epidemiologic Studies Depression Scale (CES-D). We identified incident sepsis events as hospitalizations for a serious infection with the presence of at least two systemic inflammatory response syndrome criteria. We assessed associations between PSS and incidence of sepsis for 1 and 10 years of follow-up, adjusting for demographics and chronic medical conditions and assessing the role of health behaviors and CES-D in these relationships.

RESULTS

In 2003 to 2012, 1500 participants experienced an episode of sepsis. Mean PSS and CES-D scores were 3.2 (2.9) and 1.2 (2.1). PSS was associated with increased 1-year adjusted incidence of sepsis (hazard ratio [HR] = 1.21 per PSS standard deviation, 95% confidence interval = 1.06-1.38); multivariable adjustment for health behaviors and CES-D did not change this association (1.20, 1.03-1.39). PSS was also associated with increased 10-year adjusted incidence of sepsis (HR = 1.07 per PSS standard deviation; 95% confidence interval = 1.02-1.13). Multivariable adjustment showed that health behaviors did not affect this long-term association, whereas the addition of CES-D reduced the association between PSS and sepsis during 10-year follow-up (HR = 1.04, 0.98-1.11).

CONCLUSIONS

Increased stress was associated with higher 1-year adjusted incidence of sepsis, even after accounting for depressive symptoms. The association between stress and 10-year adjusted incidence of sepsis was also significant, but this association was reduced when adjusting for depressive symptoms. Reduction of stress may limit short-term sepsis risk.

C-reactive protein gene variants: independent association with late-life depression and circulating protein levels

C-reactive protein (CRP) is a heritable biomarker of systemic inflammation that is commonly elevated in depressed patients. Variants in the CRP gene that influence protein levels could thus be associated with depression but this has seldom been examined, especially in the elderly. Depression was assessed in 990 people aged at least 65 years as part of the ESPRIT study. A clinical level of depression (DEP) was defined as having a score of ⩾16 on The Center for Epidemiologic Studies Depression scale or a diagnosis of current major depression based on the Mini-International Neuropsychiatric Interview and according to Diagnostic and Statistical Manual of Mental Disorders-IV criteria. Five single-nucleotide polymorphisms spanning the CRP gene were genotyped, and circulating levels of high-sensitivity CRP were determined. Multivariable analyses adjusted for socio-demographic characteristics, smoking, ischemic pathologies, cognitive impairment and inflammation-related chronic pathologies. The minor alleles of rs1130864 and rs1417938 were associated with a decreased risk of depression in women at Bonferroni-corrected significance levels (P=0.002). CRP gene variants were associated with serum levels in a gender-specific manner, but only rs1205 was found to be nominally associated with both an increased risk of DEP and lower circulating CRP levels in women. Variants of the CRP gene thus influence circulating CRP levels and appear as independent susceptibility factors for late-life depression.

A role for inflammatory metabolites as modulators of the glutamate N-methyl-D-aspartate receptor in depression and suicidality

BACKGROUND

Patients with depression and suicidality suffer from low-grade neuroinflammation. Pro-inflammatory cytokines activate indoleamine 2,3-dioxygenase, an initial enzyme of the kynurenine pathway. This pathway produces neuroactive metabolites, including quinolinic- and kynurenic acid, binding to the glutamate N-methyl-d-aspartate-receptor, which is hypothesized to be part of the neural mechanisms underlying symptoms of depression. We therefore hypothesized that symptoms of depression and suicidality would fluctuate over time in patients prone to suicidal behavior, depending on the degree of inflammation and kynurenine metabolite levels in the cerebrospinal fluid (CSF).

METHODS

We measured cytokines and kynurenine metabolites in CSF, collected from suicide attempters at repeated occasions over 2 years (total patient samples n=143, individuals n=30) and healthy controls (n=36). The association between the markers and psychiatric symptoms was assessed using the Montgomery Asberg Depression Rating Scale and the Suicide Assessment Scale.

RESULTS

Quinolinic acid was increased and kynurenic acid decreased over time in suicidal patients versus healthy controls. Furthermore, we found a significant association between low kynurenic acid and severe depressive symptoms, as well as between high interleukin-6 levels and more severe suicidal symptoms.

CONCLUSIONS

We demonstrate a long-term dysregulation of the kynurenine pathway in the central nervous system of suicide attempters. An increased load of inflammatory cytokines was coupled to more severe symptoms. We therefore suggest that patients with a dysregulated kynurenine pathway are vulnerable to develop depressive symptoms upon inflammatory conditions, as a result the excess production of the NMDA-receptor agonist quinolinic acid. This study provides a neurobiological framework supporting the use of NMDA-receptor antagonists in the treatment of suicidality and depression.

Five-factor model personality traits and inflammatory markers: new data and a meta-analysis

The purpose of this research is to examine the association between five major dimensions of personality and systemic inflammation through (a) new data on C-reactive protein (CRP) from three large national samples of adults that together cover most of the adult lifespan and (b) a meta-analysis of published studies on CRP and interleukin-6 (IL-6). New data (total N=26,305) were drawn from the National Longitudinal Study of Adolescent Health, the Midlife in the United States study, and the Health and Retirement Study. PRISMA guidelines were used for the meta-analysis to combine results of up to seven studies on CRP (N=34,067) and six on IL-6 (N=7538). Across the three new samples, higher conscientiousness was associated with lower CRP. The conscientiousness-CRP relation was virtually identical controlling for smoking; controlling for body mass index attenuated this association but did not eliminate it. Compared to participants in the highest quartile of conscientiousness, participants in the lowest quartile had an up to 50% increased risk of CRP levels that exceeded the clinical threshold (≥3 mg/l). The meta-analysis supported the association between conscientiousness and both CRP and IL-6 and also suggested a negative association between openness and CRP; no associations were found for neuroticism, extraversion and agreeableness. The present work indicates a modest, but consistent, association between conscientiousness and a more favorable inflammatory profile, which may contribute to the role of conscientiousness in better health across the lifespan.

Herpesviruses, inflammatory markers and incident depression in a longitudinal study of Detroit residents

BACKGROUND

Depression is predicted to become the leading cause of disability worldwide by 2030 and moreover, socioeconomic inequalities in depression persist. Herpesviruses, which are more prevalent among socioeconomically disadvantaged populations, subject to stress-induced reactivation and are associated with increased levels of pro-inflammatory cytokines implicated in the etiology of depression, may serve as novel risk factors for depression onset.

METHODS

Data are from individuals in the Detroit Neighborhood Health Study tested for herpes simplex virus-1 (HSV-1) and cytomegalovirus (CMV) seropositivity/immunoglobulin G (IgG) antibody levels (N=263) as well as interleukin-6 (IL-6) (N=245) and C-reactive protein (CRP) (N=236) levels and assessed for incident depression via the Patient Health Questionnaire-9. Linear and logistic regression models were used to examine associations between pathogen seropositivity/IgG antibody levels, pro-inflammatory markers and incident depression over approximately one-year of follow-up.

RESULTS

For every one unit increase in CMV IgG antibody level, the odds of incident depression increased by 26% and individuals with IgG antibody levels in the highest quartile had over three times greater odds of incident depression (odds ratio 3.87, 95% confidence interval 1.47, 10.19), compared to those in the lower three quartiles. Neither CMV or HSV-1 seropositivity nor HSV-1 IgG antibody level were associated with IL-6 or CRP levels at Wave 1, nor were IL-6 or CRP levels associated with incident depression at Wave 2.

CONCLUSIONS

Further examination of the biological pathways linking CMV and depression are warranted.

The longitudinal association between inflammation and incident depressive symptoms in men: the effects of hs-CRP are independent of abdominal obesity and metabolic disturbances

BACKGROUND

This cohort study evaluates whether the association between low-grade inflammation and incident depressive symptoms is independent of abdominal obesity and metabolic disturbances.

METHODS

A cohort of 1167 non-depressed men aged 35 to 80 years were followed up over 5 years to assess incident depressive symptoms measured by the Centre for Epidemiology Scale-Depression or Beck Depression Inventory-I. Venous tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and high sensitivity C-reactive protein (hsCRP) were quantified at baseline and 5years. Logistic regression determined whether hsCRP, IL-6 and TNF-α were associated with incident depressive symptoms independent of abdominal obesity and metabolic factors. Ancillary analysis utilizing depression z scores stratified participants by waist circumference ≥ 102 cm and ≥2 metabolic disturbances.

RESULTS

Incident depressive symptoms occurred in 95 men at 5 years (8.14% of total). Clinically relevant depressive symptoms were associated with baseline hsCRP (adjusted OR=1.04; 95% CI 1.00-1.07, p=.03) and annualized ΔhsCRP (adjusted OR=1.04; 95% CI 1.01-1.08, p=.02). Ancillary analysis showed that the association between annualized ΔhsCRP and depression z score was only significant in men with waist circumference<102 cm (β=.19, p<.001) and ≤1 metabolic disturbance (β=.18, p<.001). None of the measured cytokines were significantly associated with depression.

CONCLUSIONS

hsCRP and annualized ΔhsCRP were positively associated with depressive symptoms in a cohort of men. Further investigation into the role of abdominal obesity and metabolic disturbances in the inflammation-depression hypothesis is warranted.

C-reactive protein and depression in persons with Human Immunodeficiency Virus infection: the Positive Living with HIV (POLH) Study

BACKGROUND

Human Immunodeficiency Virus (HIV) infection has been frequently associated with chronic inflammation as well as depression. C-reactive protein (CRP) is positively associated with depression in people without HIV infection. We tested the hypothesis of an independent relationship between CRP and depression in a cohort of HIV-positive people.

METHODS

A cross-sectional survey was conducted among 316 HIV-positive people (181 men and 135 women) aged 18-60years residing in the Kathmandu Valley, Nepal. The latex agglutination turbidimetric method was used to measure serum CRP concentrations and the Beck Depression Inventory (BDI)-I method was used to measure depression, with a cut off of ⩾20 indicating likely depression. The relationship between CRP concentrations and depression symptoms was assessed using both multiple linear regression analysis and multiple logistic regression analysis, with adjustment for potential socio-demographic, cardiovascular, life-style, and HIV-related clinical and treatment confounding factors.

RESULTS

Twenty-six percent participants (men: 23%; women: 29%) met criteria for depression. In multiple regression analysis, the authors observed a linear relation between serum CRP concentrations and BDI score (beta for 1 unit change in ln(CRP)=1.13, p=0.001) in HIV-positive participants. In a logistic regression analysis, participants with serum CRP levels>3mg/L had a 2.3-fold higher odds of depression symptoms compared to those with serum CRP level⩽3mg/L (p=0.005). In analyses stratified by sex, associations were stronger in men than in women. For example, CRP>3mg/L was associated with a 3.6-fold higher odds of depression in men (p=0.002), while in women the odds ratio was 1.7 (p=0.33).

CONCLUSION

We found a linear relationship between serum CRP concentrations and depression symptoms score in HIV-positive people, and evidence that risk of depression is elevated among HIV-positive men with a high level of inflammation (CRP>3mg/L). Further prospective study to confirm the role of inflammation in depression among HIV-positive people is warranted.

Saffron (Crocus sativus) for depression: a systematic review of clinical studies and examination of underlying antidepressant mechanisms of action

BACKGROUND

Saffron, a spice derived from the flower of Crocus sativus, has now undergone several trials examining its antidepressant effects and, in a recent meta-analysis, was confirmed to be effective for the treatment of major depression.

OBJECTIVE

To provide an expanded systematic analysis of the completed clinical studies on saffron and depression, detailing dosages, extract sources, standardisations, safety profile and treatment duration; and, through a narrative review, to examine its potential antidepressant mechanisms of action.

DESIGN

In the systematic review of clinical trials, electronic databases were searched for high-quality, randomised, double-blind studies, with placebo or antidepressant controls. A narrative review of in vivo and in vitro studies was conducted to examine its potential antidepressant mechanisms of action.

RESULTS

In the systematic review, six studies were identified. In the placebo-comparison trials, saffron had large treatment effects and, when compared with antidepressant medications, had similar antidepressant efficacy. Saffron's antidepressant effects potentially are due to its serotonergic, antioxidant, anti-inflammatory, neuro-endocrine and neuroprotective effects.

CONCLUSIONS

Research conducted so far provides initial support for the use of saffron for the treatment of mild-to-moderate depression. Further research is required to expand our understanding of the role and actions of saffron in major depression.

Common mental disorder symptoms among patients with malaria attending primary care in Ethiopia: a cross-sectional survey

Background

Common Mental Disorders (CMDs) are frequent among patients attending primary care. In Africa, CMDs are often misdiagnosed as physical illnesses because many of the patients complain of somatic symptoms of mental distress. We explored whether there was difference in the levels of CMD symptoms between patients with thick film confirmed and clinical cases of malaria with negative thick film in primary care.

Methods

A cross-sectional comparative study was conducted on 300 adults with a clinical diagnosis of malaria in primary care centres in Jimma, Ethiopia. Patients were recruited consecutively until 100 cases of ‘malaria’ with a negative thick film and 200 cases of malaria with a positive thick film consented to participate. The 20-item Self-Reporting Questionnaire (SRQ-20) was used to measure CMD. The non-parametric Wilcoxon rank-sum test was used to explore the association between thick film result and CMD.

Results

Participants had a mean age of 28.2 (S.D = 10.9) years and the majority (57.3%) were women. The prevalence of high CMD symptoms (six or more symptoms on the SRQ-20) was 24.5%. Suicidal ideation was reported by 13.8% of the participants. CMD symptoms were significantly higher in patients who had taken medication prior to visiting the primary care (p = 0.012) and in those whose symptoms had been present for seven days or more (p = 0.041). There was no statistically significant association between level of CMD symptoms and having a negative thick film result (OR 0.98; 95%CI 0.92, 1.04) or objective presence of fever (OR 1.04; 95%CI 0.93, 1.15).

Conclusions

CMD symptoms among cases of malaria did not appear to be associated with a negative thick film result. The high levels of CMD symptoms, including suicidal ideation, calls for further studies to investigate the persistence and progression of these symptoms following resolution of the acute malarial episode.

C-reactive protein, depressive symptoms, and risk of diabetes: results from the English Longitudinal Study of Ageing (ELSA)

OBJECTIVES

Raised levels of C-reactive protein (CRP), an inflammatory biomarker, and depressive symptoms are both independently linked to risk of diabetes. The purpose of this study was to assess the joint association of CRP and depressive symptomatology with diabetes incidence in a representative sample of English people ≥50 years old.

METHOD

Data were from the English Longitudinal Study of Ageing, a prospective study of community-dwelling older adults. The sample was comprised of 4955 participants without self-reported doctor-diagnosed diabetes at baseline. High CRP level was dichotomized as >3 mg/L. Elevated depressive symptomatology was defined as ≥4 using the 8-item Center for Epidemiologic Studies Depression Scale. Incident diabetes was determined based on newly self-reported doctor-diagnosed diabetes. Cox proportional hazard regressions were used to examine the association between CRP and depressive symptoms with incidence of type 2 diabetes.

RESULTS

During approximately 63.2 months of follow-up, 194 participants reported diabetes diagnosis. After adjustment for socio-demographics, lifestyle behaviors, clinical factors, and BMI, the hazard ratio for diabetes was 1.63 (95% CI 0.88-3.01) for people with elevated depressive symptoms only, 1.43 (95% CI 0.99-2.07) for people with high CRP only, and 2.03 (95% CI 1.14-3.61) for people with both high CRP and elevated depressive symptoms.

CONCLUSION

The presence of both high CRP levels and elevated depressive symptoms was associated with risk of diabetes. Further investigation into this relationship could aid in understanding the mechanisms underlying inflammation, depression, and diabetes.

Microbial 'old friends', immunoregulation and socioeconomic status

The immune system evolved to require input from at least three sources that we collectively term the ‘old friends’: (i) the commensal microbiotas transmitted by mothers and other family members; (ii) organisms from the natural environment that modulate and diversify the commensal microbiotas; and (iii) the ‘old’ infections that could persist in small isolated hunter-gatherer groups as relatively harmless subclinical infections or carrier states. These categories of organism had to be tolerated and co-evolved roles in the development and regulation of the immune system. By contrast, the ‘crowd infections’ (such as childhood virus infections) evolved later, when urbanization led to large communities. They did not evolve immunoregulatory roles because they either killed the host or induced solid immunity, and could not persist in hunter-gatherer groups. Because the western lifestyle and medical practice deplete the ‘old’ infections (for example helminths), immunoregulatory disorders have increased, and the immune system has become more dependent upon microbiotas and the natural environment. However, urbanization maintains exposure to the crowd infections that lack immunoregulatory roles, while accelerating loss of exposure to the natural environment. This effect is most pronounced in individuals of low socioeconomic status (SES) who lack rural second homes and rural holidays. Interestingly, large epidemiological studies indicate that the health benefits of living close to green spaces are most pronounced for individuals of low SES. Here we discuss the immunoregulatory role of the natural environment, and how this may interact with, and modulate, the proinflammatory effects of psychosocial stressors in low SES individuals.

Broken or maladaptive? Altered trajectories in neuroinflammation and behavior after early life adversity

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This paper reviews how early life adversity alters neuroimmune mechanisms.

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Neuroimmune sensitization from early life adversity impacts circuitry at discrete life stages.

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Neuroimmune and neurodevelopmental influences can impact behavior and vulnerability.

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Sexual dimorphism in immune and brain development yield distinct effects of early life adversity.

Exposure to adversity and stress early in development yields vulnerability to mental illnesses throughout the lifespan. Growing evidence suggests that this vulnerability has mechanistic origins involving aberrant development of both neurocircuitry and neuro-immune activity. Here we review the current understanding of when and how stress exposure initiates neuroinflammatory events that interact with brain development. We first review how early life adversity has been associated with various psychopathologies, and how neuroinflammation plays a role in these pathologies. We then summarize data and resultant hypotheses describing how early life adversity may particularly alter neuro-immune development with psychiatric consequences. Finally, we review how sex differences contribute to individualistic vulnerabilities across the lifespan. We submit the importance of understanding how stress during early development might cause outright neural or glial damage, as well as experience-dependent plasticity that may insufficiently prepare an individual for sex-specific or life-stage specific challenges.

Inflammatory biomarker profiles of mental disorders and their relation to clinical, social and lifestyle factors

In the last few decades, mental health research has increasingly provided evidence supporting the role of inflammation in pathogenesis, course and treatment of mental disorders. With such a steep incline of research, resulting in a wealth of emerged findings, it has become difficult to follow developments within the field. The present review sets out to present the recent developments and to give an overview of the inflammatory profiles of depression, psychosis and bipolar disorder, as well as variations within these disorders. Moreover, mediating factors such as social environment and childhood experience are discussed, both in terms of their potential in elucidating the complex interface between the inflammation and other closely related biological systems, as well as the possibly confounding impact of various lifestyle factors. Whilst many issues in this fascinating area of research remain to be fully understood and elaborated, all current evidence suggests that inflammation plays a key role in mental disorders and may open up novel avenues for clinical treatment.

The Alterations of IL-1Beta, IL-6, and TGF-Beta Levels in Hippocampal CA3 Region of Chronic Restraint Stress Rats after Electroacupuncture (EA) Pretreatment

Immunological reactions induced by proinflammatory cytokines have been involved in the pathogenesis of depressive disorders. Recent studies showed that Electroacupuncture (EA) was able to reduce depressive symptoms; however, the underlying mechanism and its potential targets remain unknown. In the present study, we used a 21-day chronic restraint stress rats as a model to investigate how EA could alleviate depression. Open field test was carried out to evaluate the depressive symptoms at selected time points. At the end of study, immunohistochemistry (IHC) was performed to detect the expressions of IL-1beta, IL-6, and TGF-beta in hippocampal CA3 region. We found that chronic restraint stress significantly decreased behavioral activities, whereas EA stimulation at points Baihui (GV 20) and Yintang (GV 29) showed protective effect during the test period. In addition, the IL-1beta, IL-6, and TGF-beta increased in rats exposed to chronic restraint stress, while EA downregulated the levels of IL-1beta and IL-6. These findings implied that EA pretreatment could alleviate depression through modulating IL-1beta and IL-6 expression levels in hippocampal CA3 region.

Targeting classical IL-6 signalling or IL-6 trans-signalling in depression?

INTRODUCTION

Increased IL-6 and soluble IL-6 receptor (sIL-6R) levels in depressed patients was first shown over 20 years ago. The pro-inflammatory effects of IL-6 are predominantly mediated by IL-6 trans-signalling via the sIL-6R, whereas IL-6R membrane signalling has anti-inflammatory effects.

AREAS COVERED

We review data on IL-6 and sIL-6R in inflammation, depression, animal models of depression and the effects of different classes of antidepressants. The biological context for IL-6 trans-signalling as a pathogenic factor in depression involves its role in the acute phase response, disorders in zinc and the erythron, hypothalamic-pituitary-adrenal axis activation, induction of the tryptophan catabolite pathway, oxidative stress, bacterial translocation, transition towards sensitisation, autoimmune processes and neuroprogression and the multicausal aetiology of depression, considering that psychosocial stressors and comorbid immune-inflammatory diseases are associated with the onset of depression.

EXPERT OPINION

The homeostatic functions of IL-6 imply that ubiquitous IL-6 inhibitors, for example, tocilizumab, may not be the optimal treatment target in depression. A more promising target may be to increase soluble glycoprotein 130 (sgp130) inhibition of IL-6 trans-signalling, while allowing the maintenance of IL-6R membrane signalling. Future research should delineate the effects of treatments with sgp130Fc in combination with antidepressants in various animal models of chronic depression.

Adherence to the Mediterranean diet is inversely related to binge eating disorder in patients seeking a weight loss program

BACKGROUND & AIM

The key factors influencing the development of Binge Eating Disorder (BED) are not well known. Adherence to the Mediterranean diet (MD) has been suspected to reduce the risk of several mental illnesses such as depression and anxiety. There are no existing studies that have examined the relationships between BED and MD.

METHODS

Cross-sectional study of 1472 participants (71.3% women; mean age: 44.8 ± 12.7) at high risk of BED. A MD score (MED-score) was derived from a validated food frequency questionnaire and BED by Binge Eating Scale questionnaire (BES). Body mass index, waist circumference and total body fat (%) were assessed by anthropometric measurements.

RESULTS

376 (25.5%) cases of self reported BED were identified. 11.1% of participants had a good adherence to MD (MED-score ≥ 9). After adjustments for age, gender, nutritional status, education, and physical activity level, high MED-score was associated with lower odds for BED (odds ratios and 95% confidence intervals of a BED disorder for successive levels of MED-score were 1 (reference), 0.77 (0.44, 1.36), 0.66 (0.37, 1.15), 0.50 (0.26, 0.96), and 0.45 (0.22, 0.55) (P for trend: <0.01). Olive oil and nut consumption were associated with low risk of BED development whereas butter, cream, sweets and commercial bakery/sweets/cakes consumption increased the risk. We did not find a cumulative effect of depression and anxiety on MED-score in binge eaters.

CONCLUSIONS

These results demonstrate an inverse association between MD and the development of BED in a clinical setting among subjects at risk of BED. Therefore, we should be cautious about generalizing the results to the whole population, although reverse causality and confounding cannot be excluded as explanation. Further prospective studies are warranted.

A review of peripheral biomarkers in major depression: the potential of inflammatory and oxidative stress biomarkers

Biomarkers are regularly used in medicine to provide objective indicators of normal biological processes, pathogenic processes or pharmacological responses to therapeutic interventions, and have proved invaluable in expanding our understanding and treatment of medical diseases. In the field of psychiatry, assessment and treatment has, however, primarily relied on patient interviews and questionnaires for diagnostic and treatment purposes. Biomarkers in psychiatry present a promising addition to advance the diagnosis, treatment and prevention of psychiatric diseases. This review provides a summary on the potential of peripheral biomarkers in major depression with a specific emphasis on those related to inflammatory/immune and oxidative stress/antioxidant defences. The complexities associated with biomarker assessment are reviewed specifically around their collection, analysis and interpretation. Focus is placed on the potential of peripheral biomarkers to aid diagnosis, predict treatment response, enhance treatment-matching, and prevent the onset or relapse of major depression.

C-reactive protein and cortisol in drug-naïve patients with short-illness-duration first episode major depressive disorder: possible role of cortisol immunomodulatory action at early stage of the disease

BACKGROUND

Hypercortisolemia and low grade systemic inflammation are observed in major depressive disorder (MDD). Studies on markers of systematic inflammation and Hypothalamic-Pituitary-Adrenal (HPA) axis dysregulation in MDD produce confounded results due to heterogeneity of MDD patients related to illness stages and severity with a large proportion suffering from remitted-recurrent and treatment-resistant/chronic depression with first-episode major depression being underrepresented. This study was designed to examine whether and to what extent CRP is related to baseline cortisol concentrations in a well defined cohort of short-illness-duration first-episode, treatment-naïve MDD patients.

METHODS

The levels of salivary C-reactive protein (CRP) and baseline plasma cortisol concentrations were studied in this cross-sectional case-control study on 20 non-late-life adult, treatment- naïve MDD patients with short-illness-duration first affective episode and in 20 age- and sex-matched healthy controls. Depressed patients showed a basal score in the Hamilton Rating Scale for Depression (HAMD-17) higher than 20.

RESULTS

No significant difference in CRP concentration between MDD and control groups was found. Significantly higher baseline cortisol (p=0.01) concentration was observed in MDD as compared to controls. Significant positive correlation was found between cortisol and CRP levels both in MDD subjects (r=0.57; p=0.008) and controls (r=0.61; p=0.004).

LIMITATIONS

The current study is limited by its cross-sectional design and small sample size.

CONCLUSION

The study supports data on elevated cortisol concentration in MDD providing no evidence for elevated CRP levels at the early stage of the disease.

Neuropathology of stress

Environmental challenges are part of daily life for any individual. In fact, stress appears to be increasingly present in our modern, and demanding, industrialized society. Virtually every aspect of our body and brain can be influenced by stress and although its effects are partly mediated by powerful corticosteroid hormones that target the nervous system, relatively little is known about when, and how, the effects of stress shift from being beneficial and protective to becoming deleterious. Decades of stress research have provided valuable insights into whether stress can directly induce dysfunction and/or pathological alterations, which elements of stress exposure are responsible, and which structural substrates are involved. Using a broad definition of pathology, we here review the "neuropathology of stress" and focus on structural consequences of stress exposure for different regions of the rodent, primate and human brain. We discuss cytoarchitectural, neuropathological and structural plasticity measures as well as more recent neuroimaging techniques that allow direct monitoring of the spatiotemporal effects of stress and the role of different CNS structures in the regulation of the hypothalamic-pituitary-adrenal axis in human brain. We focus on the hypothalamus, hippocampus, amygdala, nucleus accumbens, prefrontal and orbitofrontal cortex, key brain regions that not only modulate emotions and cognition but also the response to stress itself, and discuss disorders like depression, post-traumatic stress disorder, Cushing syndrome and dementia.

Social isolation after stroke leads to depressive-like behavior and decreased BDNF levels in mice

Social isolation prior to stroke leads to poorer outcomes after an ischemic injury in both animal and human studies. However, the impact of social isolation following stroke, which may be more clinically relevant as a target for therapeutic intervention, has yet to be examined. In this study, we investigated both the sub-acute (2 weeks) and chronic (7 weeks) effects of social isolation on post-stroke functional and histological outcome. Worsened histological damage from ischemic injury and an increase in depressive-like behavior was observed in isolated mice as compared to pair-housed mice. Mice isolated immediately after stroke showed a decrease in the levels of brain-derived neurotrophic factor (BDNF). These changes, both histological and behavioral, suggest an overall negative effect of social isolation on stroke outcome, potentially contributing to post-stroke depression and anxiety. Therefore, it is important to identify patients who have perceived isolation post-stroke to hopefully prevent this exacerbation of histological damage and subsequent depression.