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

Genome-wide microarray analysis of gene expression profiling in major depression and antidepressant therapy

Major depressive disorder (MDD) is a serious health concern worldwide. Currently there are no predictive tests for the effectiveness of any particular antidepressant in an individual patient. Thus, doctors must prescribe antidepressants based on educated guesses. With the recent advent of scientific research, genome-wide gene expression microarray studies are widely utilized to analyze hundreds of thousands of biomarkers by high-throughput technologies. In addition to the candidate-gene approach, the genome-wide approach has recently been employed to investigate the determinants of MDD as well as antidepressant response to therapy. In this review, we mainly focused on gene expression studies with genome-wide approaches using RNA derived from peripheral blood cells. Furthermore, we reviewed their limitations and future directions with respect to the genome-wide gene expression profiling in MDD pathogenesis as well as in antidepressant therapy.

Low-grade inflammation predicts persistence of depressive symptoms

RATIONALE

Evidence suggests that depression is cross-sectionally and longitudinally associated with activation of inflammatory response system. A few studies, however, have investigated the longitudinal relationship between raised inflammatory biomarkers and persistence of depressive symptoms. We examined the temporal relationship between serum levels of inflammatory biomarkers and persistence of depressive symptoms among older participants.

METHODS

Center for Epidemiologic Studies Depression Scale (CES-D) was used to assess depressive symptoms at baseline and at 5-year follow-up in 656 participants (233 men, 423 women) aged >60 years of the Rotterdam Study. Markers of inflammation interleukin (IL)-6, alpha-1-antichymotrypsin (ACT) and C-reactive protein (CRP) were assessed at baseline, and all participants taking antidepressant medications were excluded from the analysis.

RESULTS

No cross-sectional association was found between IL-6, ACT and CRP with depressive symptoms at baseline. However, higher levels of IL-6 and CRP predicted depressive symptoms at 5-year follow-up. Adjustment for confounding variables had no impact on the observed associations. Similarly, a positive association was found between baseline levels of IL-6 (OR = 2.44, p = 0.030) and CRP (OR = 1.81, p = 0.052) and persistence of depressive symptoms over 5 years.

CONCLUSION

Our data suggest that dysregulation of the inflammatory response system is associated with a more severe form of depression more likely to re-occur.

Is there Progress? An Overview of Selecting Biomarker Candidates for Major Depressive Disorder

Major depressive disorder (MDD) contributes to a significant worldwide disease burden, expected to be second only to heart disease by 2050. However, accurate diagnosis has been a historical weakness in clinical psychiatry. As a result, there is a demand for diagnostic modalities with greater objectivity that could improve on current psychiatric practice that relies mainly on self-reporting of symptoms and clinical interviews. Over the past two decades, literature on a growing number of putative biomarkers for MDD increasingly suggests that MDD patients have significantly different biological profiles compared to healthy controls. However, difficulty in elucidating their exact relationships within depression pathology renders individual markers inconsistent diagnostic tools. Consequently, further biomarker research could potentially improve our understanding of MDD pathophysiology as well as aid in interpreting response to treatment, narrow differential diagnoses, and help refine current MDD criteria. Representative of this, multiplex assays using multiple sources of biomarkers are reported to be more accurate options in comparison to individual markers that exhibit lower specificity and sensitivity, and are more prone to confounding factors. In the future, more sophisticated multiplex assays may hold promise for use in screening and diagnosing depression and determining clinical severity as an advance over relying solely on current subjective diagnostic criteria. A pervasive limitation in existing research is heterogeneity inherent in MDD studies, which impacts the validity of biomarker data. Additionally, small sample sizes of most studies limit statistical power. Yet, as the RDoC project evolves to decrease these limitations, and stronger studies with more generalizable data are developed, significant advances in the next decade are expected to yield important information in the development of MDD biomarkers for use in clinical settings.

Association of Type D personality with increased vulnerability to depression: Is there a role for inflammation or endothelial dysfunction? - The Maastricht Study

BACKGROUND

Type D personality - the combination of negative affectivity (NA) and social inhibition (SI) - has been associated with depression but little is known about underlying mechanisms. We examined whether (1) Type D is a vulnerability factor for depression in general, (2) Type D is associated with inflammation or endothelial dysfunction, and (3) these biomarkers alter the possible association between Type D and depression.

METHODS

In the Maastricht Study, 712 subjects underwent assessment of NA, SI and Type D personality (DS14), depressive disorder (Mini-International Neuropsychiatric Interview) and depressive symptoms (Patient Health Questionnaire-9). Plasma biomarkers of inflammation (hsCRP, SAA, sICAM-1, IL-6, IL-8, TNF-α) and endothelial dysfunction (sVCAM-1, sICAM-1, E-selectin, vWF) were measured with sandwich immunoassays or ELISA and combined into standardized sumscores.

RESULTS

Regarding personality, 49% of the study population was low in NA and SI, 22% had SI only, 12% NA only and 17% had Type D. Depressive disorder and depressive symptoms were significantly more prevalent in Type D versus the other three personality subgroups. Multivariable regression analyses showed that Type D was associated with inflammation (β=0.228, p=0.014) and endothelial dysfunction (β=0.216, p=0.022). After adjustment for these biomarkers, Type D remained independently associated with increased vulnerability to depressive disorder (OR=13.20, p<0.001) and depressive symptoms (β=3.87, p<0.001).

LIMITATIONS

The cross-sectional design restrained us to draw any conclusions on causality. The relatively low prevalence of depressive disorder restrained us to adjust for more potential confounders.

CONCLUSIONS

Type D personality may be a vulnerability factor for depression, irrespective of levels of inflammation or endothelial dysfunction. Future research should examine possible underlying mechanisms.

Circulating tumour necrosis factor is highly correlated with brainstem serotonin transporter availability in humans

Preclinical studies demonstrate that pro-inflammatory cytokines increase serotonin transporter availability and function, leading to depressive symptoms in rodent models. Herein we investigate associations between circulating inflammatory markers and brainstem serotonin transporter (5-HTT) availability in humans. We hypothesised that higher circulating inflammatory cytokine concentrations, particularly of tumour necrosis factor (TNF-α), would be associated with greater 5-HTT availability, and that TNF-α inhibition with etanercept (sTNFR:Fc) would in turn reduce 5-HTT availability. In 13 neurologically healthy adult women, plasma TNF-α correlated significantly with 5-HTT availability (rho=0.6; p=0.03) determined by [(123)I]-beta-CIT SPECT scanning. This association was replicated in an independent sample of 12 patients with psoriasis/psoriatic arthritis (rho=0.76; p=0.003). Indirect effects analysis, showed that there was a significant overlap in the variance explained by 5-HTT availability and TNF-α concentrations on BDI scores. Treatment with etanercept for 6-8weeks was associated with a significant reduction in 5-HTT availability (Z=2.09; p=0.03; r=0.6) consistent with a functional link. Our findings confirm an association between TNF-α and 5-HTT in both the basal physiological and pathological condition. Modulation of both TNF-α and 5-HTT by etanercept indicate the presence of a mechanistic pathway whereby circulating inflammatory cytokines are related to central nervous system substrates underlying major depression.

Elevated C-reactive protein levels in schizophrenia inpatients is associated with aggressive behavior

BACKGROUND

An association between inflammation and behavioral domains of mental disorders is of growing interest. Recent studies reported an association between aggression and inflammation. In this study, we investigated the association between aggressive behavior and inflammatory markers in schizophrenia inpatients.

METHODS

Adult schizophrenia inpatients without affective symptoms (n=213) were retrospectively identified and categorized according to their C-reactive protein measurement at admission as either elevated (CRP>1 mg/dL; n=57) or normal (CRP<1 mg/dL; n=156). The following indicators of aggression were compared: PANSS excitement component (PANSS-EC), restraints and suicidal behavior during hospitalization. Univariate comparisons between elevated and normal CRP levels were performed and multivariate analysis was conducted to control for relevant covariates.

RESULTS

CRP levels significantly correlated with other laboratory markers indicating increased inflammation including leukocyte count and neutrophil to lymphocyte ratio (r=0.387, P<0.0001 and r=0.356, P<0.0001) respectively. Inpatients with elevated C-reactive protein displayed increased aggressive behavior compared to patients with normal CRP levels (<1 mg/dL). This was manifested by higher rates of restraint during hospitalization (χ(2)=5.22, P=0.031) and increased PANSS-EC score (U=5410.5, P=0.012). Elevated CRP levels were not associated with suicidal behavior. Multivariate analysis revealed that higher PANSS-EC score was associated with elevated CRP after controlling for the covariates age, sex, BMI and smoking.

CONCLUSION

This study identified a potential biological correlate (inflammation) of a specific behavioral endophenotype (aggression) in schizophrenia inpatients.

Neurobiological effects of exercise on major depressive disorder: A systematic review

Exercise displays promise as an efficacious treatment for people with depression. However, no systematic review has evaluated the neurobiological effects of exercise among people with major depressive disorder (MDD). The aim of this article was to systematically review the acute and chronic biological responses to exercise in people with MDD. Two authors conducted searches using Medline (PubMed), EMBASE and PsycINFO. From the searches, twenty studies were included within the review, representing 1353 people with MDD. The results demonstrate that a single bout of exercise increases atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), copepetin and growth hormone among people with MDD. Exercise also potentially promotes long-term adaptations of copeptin, thiobarbituric acid reactive species (TBARS) and total mean frequency (TMF). However, there is limited evidence that exercise promotes adaptations on neurogenesis, inflammation biomarkers and brain structure. Associations between depressive symptoms improvement and hippocampus volume and IL-1β were found. Nevertheless, the paucity of studies and limitations presented within, precludes a more definitive conclusion of the underlying neurobiological explanation for the antidepressant effect of exercise in people with MDD. Further trials should utilize appropriate assessments of neurobiological markers in order to build upon the results of our review and further clarify the potential mechanisms associated with the antidepressant effects of exercise.

The health-enhancing efficacy of Zumba® fitness: An 8-week randomised controlled study

The purpose of this study was to gain a holistic understanding of the efficacy of Zumba® fitness in a community-recruited cohort of overweight and physically inactive women by evaluating (i) its physiological effects on cardiovascular risk factors and inflammatory biomarkers and (ii) its mental health-enhancing effects on factors of health-related quality of life (HRQoL). Participants were randomly assigned to either engagement in one to two 1 h classes of Zumba® fitness weekly (intervention group; n = 10) or maintenance of habitual activity (control group; n = 10). Laboratory assessments were conducted pre- (week 0) and post-intervention (week 8) with anthropometric, physiological, inflammatory and HRQoL data collected. In the intervention group, maximal oxygen uptake significantly increased (P < 0.05; partial η(2) = 0.56) by 3.1 mL · kg(-1) · min(-1), per cent body fat significantly decreased (P < 0.05; partial η(2) = 0.42) by -1.2%, and interleukin-6 and white blood cell (WBC) count both significantly decreased (P < 0.01) by -0.4 pg · mL(-1) (partial η(2) = 0.96) and -2.1 × 10(9) cells · L(-1) (partial η(2) = 0.87), respectively. Large magnitude enhancements were observed in the HRQoL factors of physical functioning, general health, energy/fatigue and emotional well-being. When interpreted in a community-based physical activity and psychosocial health promotion context, our data suggest that Zumba® fitness is indeed an efficacious health-enhancing activity for adults.

Depression-like Behavior Induced by Nesfatin-1 in Rats: Involvement of Increased Immune Activation and Imbalance of Synaptic Vesicle Proteins

Depression is a multicausal disorder and has been associated with metabolism regulation and immuno-inflammatory reaction. The anorectic molecule nesfatin-1 has recently been characterized as a potential mood regulator, but its precise effect on depression and the possible mechanisms remain unknown, especially when given peripherally. In the present study, nesfatin-1 was intraperitoneally injected to the rats and the depression-like behavior and activity of the hypothalamic-pituitary-adrenal (HPA) axis were evaluated. The plasma concentrations of nesfatin-1, interleukin 6 (IL-6), and C-reactive protein (CRP); and the hypothalamic expression levels of nesfatin-1, synapsin I, and synaptotagmin I mRNA were evaluated in nesfatin-1 chronically treated rats. The results showed that both acute and chronic administration of nesfatin-1 increased immobility in the forced swimming test (FST), and resulted in the hyperactivity of HPA axis, as indicated by the increase of plasma corticosterone concentration and hypothalamic expression of corticotropin-releasing hormone (CRH) mRNA. Moreover, after chronic nesfatin-1 administration, the rats exhibited decreased activity and exploratory behavior in the open field test (OFT) and increased mRNA expression of synapsin I and synaptotagmin I in the hypothalamus. Furthermore, chronic administration of nesfatin-1 elevated plasma concentrations of IL-6 and CRP, which were positively correlated with despair behavior, plasma corticosterone level, and the hypothalamic mRNA expression of synapsin I and synaptotagmin I. These results indicated that exogenous nesfatin-1 could induce the immune-inflammatory activation, which might be a central hug linking the depression-like behavior and the imbalanced mRNA expression of synaptic vesicle proteins in the hypothalamus.

Association Between Prenatal Exposure to Maternal Infection and Offspring Mood Disorders: A Review of the Literature

The purpose of this article is to provide a systematic review of studies that have examined the association between prenatal exposure to maternal infection and development of mood disorders across the life course. Drawing from both human- and animal-based studies, we give an overview of hypothesized biological mechanisms by which exposure to maternal infection during critical periods of gestation may contribute to fetal programming of mood disorders in offspring. We discuss studies examining the association between prenatal exposure to maternal infection with pathogens including influenza as well as other respiratory viruses, herpesviruses, hepatitis viruses, and Toxoplasma gondii and mood disorders in human populations. Moreover, we outline strengths and limitations of the current body of evidence and make recommendations for future research. We also discuss findings in the context of well-documented gender and socioeconomic disparities in the prevalence and severity of mood disorders, particularly major depression, and the role that early exposure to infection may play in explaining the perpetuation of such disparities across generations. Overall, this review of the current knowledge on this topic has important implications for determining future research directions, designing interventions as well as prenatal care guidelines targeted at prevention or treatment of infection during pregnancy, and clinical practice for the identification of individuals that may be at increased risk for mood disorders beginning early in life. Importantly, such efforts may not only lower the overall burden of mood disorders but also serve to address social disparities in these adverse mental health conditions in the U.S.

Inflammation: depression fans the flames and feasts on the heat

Depression and inflammation fuel one another. Inflammation plays a key role in depression's pathogenesis for a subset of depressed individuals; depression also primes larger cytokine responses to stressors and pathogens that do not appear to habituate. Accordingly, treatment decisions may be informed by attention to questions of how (pathways) and for whom (predispositions) these links exist, which are the focus of this article. When combined with predisposing factors (moderators such as childhood adversity and obesity), stressors and pathogens can lead to exaggerated or prolonged inflammatory responses. The resulting sickness behaviors (e.g., pain, disturbed sleep), depressive symptoms, and negative health behaviors (e.g., poor diet, a sedentary lifestyle) may act as mediating pathways that lead to further, unrestrained inflammation and depression. Depression, childhood adversity, stressors, and diet can all influence the gut microbiome and promote intestinal permeability, another pathway to enhanced inflammatory responses. Larger, more frequent, or more prolonged inflammatory responses could have negative mental and physical health consequences. In clinical practice, inflammation provides a guide to potential targets for symptom management by signaling responsiveness to certain therapeutic strategies. For example, a theme across research with cytokine antagonists, omega-3 fatty acids, celecoxib, and exercise is that anti-inflammatory interventions have a substantially greater impact on mood in individuals with heightened inflammation. Thus, when inflammation and depression co-occur, treating them in tandem may enhance recovery and reduce the risk of recurrence. The bidirectional links between depression, inflammation, and disease suggest that effective depression treatments could have a far-reaching impact on mood, inflammation, and health.

Genes, environments and depressions in young people

Among the common mental illnesses in childhood and adolescence, the unipolar depressions are the most concerning. These mental illnesses are aetiologically and clinically heterogeneous and little is known about their pathophysiology. This selected review considers the contribution of genetic and environmental factors in the emergence of these illnesses in the second decade of life.

Frequency of and Risk Factors for Depression among Participants in the Swiss HIV Cohort Study (SHCS)

Objectives

We studied the incidence and prevalence of, and co-factors for depression in the Swiss HIV Cohort Study.

Methods

Depression-specific items were introduced in 2010 and prospectively collected at semiannual cohort visits. Clinical, laboratory and behavioral co-factors of incident depression among participants free of depression at the first two visits in 2010 or thereafter were analyzed with Poisson regression. Cumulative prevalence of depression at the last visit was analyzed with logistic regression.

Results

Among 4,422 participants without a history of psychiatric disorders or depression at baseline, 360 developed depression during 9,348 person-years (PY) of follow-up, resulting in an incidence rate of 3.9 per 100 PY (95% confidence interval (CI) 3.5–4.3). Cumulative prevalence of depression during follow-up was recorded for 1,937/6,756 (28.7%) participants. Incidence and cumulative prevalence were higher in injection drug users (IDU) and women. Older age, preserved work ability and higher physical activity were associated with less depression episodes. Mortality (0.96 per 100 PY, 95% CI 0.83–1.11) based upon 193 deaths over 20,102 PY was higher among male IDU (2.34, 1.78–3.09), female IDU (2.33, 1.59–3.39) and white heterosexual men (1.32, 0.94–1.84) compared to white heterosexual women and homosexual men (0.53, 0.29–0.95; and 0.71, 0.55–0.92). Compared to participants free of depression, mortality was slightly elevated among participants with a history of depression (1.17, 0.94–1.45 vs. 0.86, 0.71–1.03, P = 0.033). Suicides (n = 18) did not differ between HIV transmission groups (P = 0.50), but were more frequent among participants with a prior diagnosis of depression (0.18 per 100 PY, 95%CI 0.10–0.31; vs. 0.04, 0.02–0.10; P = 0.003).

Conclusions

Depression is a frequent co-morbidity among HIV-infected persons, and thus an important focus of care.

Lower Urinary Tract Symptoms, Depression, Anxiety and Systemic Inflammatory Factors in Men: A Population-Based Cohort Study

Background

The relationship between lower urinary tract symptoms (LUTS) and common mental health disorders such as depression and anxiety in men remains unclear. Inflammation has recently been identified as an independent risk factor for LUTS and depression. This study aimed to assess the association between depression, anxiety and LUTS, and the moderating influence of systemic inflammation, in the presence of other biopsychosocial confounders.

Methods

Participants were randomly-selected from urban, community-dwelling males aged 35–80 years at recruitment (n = 1195; sample response rate:67.8%). Of these, 730 men who attended baseline (2002–5) and follow-up clinic visits (2007–10), with complete outcome measures, and without prostate or bladder cancer and/or surgery, neurodegenerative conditions, or antipsychotic medications use, were selected for the present study. Unadjusted and multi-adjusted regression models of incident storage and voiding LUTS and incident depression and anxiety were combined with serum inflammatory markers (high-sensitive C-reactive protein (hsCRP), tumor necrosis factor-alpha (TNF-α), interleukin–6 (IL–6), myeloperoxidase (MPO), soluble e-selectin (e-Sel)) and socio-demographic, lifestyle, and health-related factors. Hierarchical multiple regression was used to assessed the moderating effect of inflammatory markers.

Results

The incidence of storage, voiding LUTS, depression and anxiety was 16.3% (n = 108), 12.1% (n = 88), 14.5% (n = 108), and 12.2% (n = 107). Regression models demonstrated that men with depression and anxiety at baseline were more likely to have incident storage, but not voiding LUTS (OR: 1.26, 99%CI: 1.01–4.02; and OR:1.74; 99%CI:1.05–2.21, respectively). Men with anxiety and storage LUTS at baseline were more likely to have incident depression (OR: 2.77, 99%CI: 1.65–7.89; and OR:1.45; 99%CI:1.05–2.36, respectively), while men with depression and voiding LUTS were more likely to have anxiety at follow-up (OR: 5.06, 99%CI: 2.81–9.11; and OR:2.40; 99%CI:1.16–4.98, respectively). CRP, TNF-α, and e-Sel were found to have significant moderating effects on the development of storage LUTS (1.06, 0.91–1.96, R² change: 12.7%), depression (1.17, 1.01–1.54, R² change: 9.8%), and anxiety (1.35, 1.03–1.76, R² change: 10.6%), respectively.

Conclusions

There is a bidirectional relationship between storage, but not voiding, LUTS and both depression and anxiety. We observed variable moderation effects for selected inflammatory markers on the development of depression, anxiety and storage LUTS.

Cumulative meta-analysis of interleukins 6 and 1β, tumour necrosis factor α and C-reactive protein in patients with major depressive disorder

Cumulative meta-analyses are used to evaluate the extent to which further studies are needed to confirm or refute a hypothesis. We used this approach to assess observational evidence on systemic inflammation in individuals with major depressive disorder. We identified 58 studies of four common inflammatory markers in a literature search of PubMed, Embase and PsychInfo databases in May 2014. Pooled data from the earliest eight studies already showed an association between interleukin-6 concentrations and major depression; 23 more recent studies confirmed this finding (d=0.54, p<0.0001). A significant association between C-reactive protein levels and major depression was noted after 14 studies and this did not change after addition of six more studies (d=0.47, p<0.0001). For these two inflammatory markers, there was moderate heterogeneity in study-specific estimates, subgroup differences were small, and publication bias appeared to be an unlikely explanation for the findings. Sensitivity analyses including only high-quality studies and subjects free of antidepressant medication further verified the associations. While there was a link between tumour necrosis factor-α levels and major depression (d=0.40, p=0.002), the cumulative effect remained uncertain due to the extensive heterogeneity in study-specific estimates and inconsistencies between subgroups. No evidence was found for the association between interleukin-1β levels and major depression (d=-0.05, p=0.86). In conclusion, this cumulative meta-analysis confirmed higher mean levels of interleukin-6 and C-reactive protein in patients with major depression compared to non-depressed controls. No consistent association between tumour necrosis factor-α, interleukin-1β and major depression was observed. Future studies should clarify the specific immune mechanisms involved as well as continue testing anti-inflammatory therapies in patients suffering from major depression.

Plasma levels of soluble TNF receptors 1 and 2 after tDCS and sertraline treatment in major depression: Results from the SELECT-TDCS trial

BACKGROUND

The cytokine hypothesis of depression postulates that the pathophysiology of this illness incorporates an increased production of pro-inflammatory cytokines, which leads to an over-activation of the hypothalamic-pituitary-adrenal axis as well as monoaminergic disturbances. Nevertheless, it remains unclear whether the amelioration of depressive symptoms could decrease cytokine levels. Notwithstanding antidepressant drug therapy might exert anti-inflammatory effects, the effects of non-invasive neuromodulatory approaches like transcranial direct current stimulation (tDCS) on pro-inflammatory cytokine networks are largely unknown.

METHODS

We evaluated, in the Sertraline vs. Electric Current Therapy for Treating Depression Clinical Study (SELECT-TDCS) trial, whether the plasma levels of the soluble TNF receptors 1 and 2 (sTNFRs) changed after antidepressant treatment in a sample of 73 antidepressant-free patients with unipolar depressive disorder in an episode of at least moderate intensity.

RESULTS

Although both tDCS and sertraline exerted antidepressant effects, the plasma levels of sTNFRs did not change over time regardless of the intervention and clinical response. Also, baseline sTNFRs levels did not predict antidepressant response.

LIMITATIONS

Our negative findings could be a type II error, as this trial did not use an equivalence design.

CONCLUSIONS

To conclude, in this novel placebo-controlled trial prospectively evaluating the changes of sTNFRs in depressed patients, we found that these molecules are not surrogate biomarkers of treatment response of tDCS, whose antidepressant effects occurred regardless of normalization of immunological activity.

Sex Differences in Depression: Does Inflammation Play a Role?

Women become depressed more frequently than men, a consistent pattern across cultures. Inflammation plays a key role in initiating depression among a subset of individuals, and depression also has inflammatory consequences. Notably, women experience higher levels of inflammation and greater autoimmune disease risk compared to men. In the current review, we explore the bidirectional relationship between inflammation and depression and describe how this link may be particularly relevant for women. Compared to men, women may be more vulnerable to inflammation-induced mood and behavior changes. For example, transient elevations in inflammation prompt greater feelings of loneliness and social disconnection for women than for men, which can contribute to the onset of depression. Women also appear to be disproportionately affected by several factors that elevate inflammation, including prior depression, somatic symptomatology, interpersonal stressors, childhood adversity, obesity, and physical inactivity. Relationship distress and obesity, both of which elevate depression risk, are also more strongly tied to inflammation for women than for men. Taken together, these findings suggest that women's susceptibility to inflammation and its mood effects may contribute to sex differences in depression. Depression continues to be a leading cause of disability worldwide, with women experiencing greater risk than men. Due to the depression-inflammation connection, these patterns may promote additional health risks for women. Considering the impact of inflammation on women's mental health may foster a better understanding of sex differences in depression, as well as the selection of effective depression treatments.

Effect of Pet Insects on the Psychological Health of Community-Dwelling Elderly People: A Single-Blinded, Randomized, Controlled Trial

Background: There is evidence that animal-assisted therapy has positive effects on mental health, especially in elderly people. Caring for insects is easy, relatively inexpensive, and does not require much space. Objective: The aim of this 8-week randomized, controlled, single-blinded study was to investigate the effect of pet insects on the psychological health of community-dwelling elderly people. Methods: Elderly subjects (≥65 years old) attending a community center in Daegu, Korea, were enrolled in the study between April and May 2014 and randomized at a 1:1 ratio to receive insect therapy and health advice or only health advice. The insect group received 5 crickets in a cage with sufficient fodder and a detailed instruction manual. At baseline and at 8 weeks, all subjects underwent psychometric tests via a direct interview [Beck Anxiety Inventory, Geriatric Depression Scale (GDS-15), Mini-Mental State Examination (MMSE), 36-Item Short Form Health Survey, Insomnia Severity Index, Fatigue Severity Scale, and Brief Encounter Psychosocial Instrument] and laboratory analyses of inflammatory and oxidative stress markers (erythrocyte sedimentation rate, high-sensitivity C-reactive protein, biological antioxidant potential, and derivatives of reactive oxygen metabolites). Results: The insect-caring (n = 46) and control (n = 48) groups did not differ in baseline characteristics. The insect-caring group had significantly lower GDS-15 scores at week 8 (3.20 vs. 4.90, p = 0.004) and, after adjustment for baseline values, a significantly greater change in GDS-15 scores relative to baseline (-1.12 vs. 0.20, p = 0.011). They also had a significantly greater change in MMSE scores relative to baseline (1.13 vs. 0.31, p = 0.045). The two groups did not differ in terms of other psychometric and laboratory tests. No serious risks or adverse events were reported. Conclusion: Caring for insects, which is cost-effective and safe, was associated with a small to medium positive effect on depression and cognitive function in community-dwelling elderly people.

The longitudinal associations between C-reactive protein and depressive symptoms: evidence from the English Longitudinal Study of Ageing (ELSA)

OBJECTIVES

The inflammatory marker C-reactive protein (CRP) is associated with depression. We examined the directional relations between CRP and symptoms of depression among older adults.

METHOD

The sample consisted of 3397 participants from the English Longitudinal Study of Ageing, a prospective study of community-dwelling older adults. CRP and depressive symptoms were measured at baseline and follow-up. A 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. Logistic regressions computed the association between high CRP levels at baseline with elevated depressive symptoms at follow-up, and vice versa.

RESULTS

After adjusting for baseline depressive symptoms, baseline high CRP levels were associated with subsequent elevated symptoms of depression (OR = 1.49; 95% CI, 1.19-1.88). This relationship was no longer significant after simultaneous adjustments for metabolic and health variables. In the other direction, after adjusting for baseline CRP levels, baseline elevated depressive symptoms was not associated with subsequent high CRP levels (OR = 1.12; 95% CI, 0.88-1.42).

CONCLUSION

High CRP levels at baseline are related to elevated depressive symptomatology at follow-up due to clinical factors. No association was found in the opposite direction.

Pathophysiology of major depressive disorder: mechanisms involved in etiology are not associated with clinical progression

Meta-analyses support the involvement of different pathophysiological mechanisms (inflammation, hypothalamic-pituitary (HPA)-axis, neurotrophic growth and vitamin D) in major depressive disorder (MDD). However, it remains unknown whether dysregulations in these mechanisms are more pronounced when MDD progresses toward multiple episodes and/or chronicity. We hypothesized that four central pathophysiological mechanisms of MDD are not only involved in etiology, but also associated with clinical disease progression. Therefore, we expected to find increasingly more dysregulation across consecutive stages of MDD progression. The sample from the Netherlands Study of Depression and Anxiety (18-65 years) consisted of 230 controls and 2333 participants assigned to a clinical staging model categorizing MDD in eight stages (0, 1A, 1B, 2, 3A, 3B, 3C and 4), from familial risk at MDD (stage 0) to chronic MDD (stage 4). Analyses of covariance examined whether pathophysiological mechanism markers (interleukin (IL)-6, C-reactive protein (CRP), cortisol, brain-derived neurotrophic factor and vitamin D) showed a linear trend across controls, those at risk for MDD (stages 0, 1A and 1B), and those with full-threshold MDD (stages 2, 3A, 3B, 3C and 4). Subsequently, pathophysiological differences across separate stages within those at risk and with full-threshold MDD were examined. A linear increase of inflammatory markers (CRP P=0.026; IL-6 P=0.090), cortisol (P=0.025) and decrease of vitamin D (P<0.001) was found across the entire sample (for example, from controls to those at risk and those with full-threshold MDD). Significant trends of dysregulations across stages were present in analyses focusing on at-risk individuals (IL-6 P=0.050; cortisol P=0.008; vitamin D P<0.001); however, no linear trends were found in dysregulations for any of the mechanisms across more progressive stages of full-threshold MDD. Our results support that the examined pathophysiological mechanisms are involved in MDD's etiology. These same mechanisms, however, are less important in clinical progression from first to later MDD episodes and toward chronicity.

Tumour necrosis factor-α inhibitor therapy in chronic physical illness: A systematic review and meta-analysis of the effect on depression and anxiety

OBJECTIVE

Depression is more common among individuals with chronic physical illness than in the general population. New treatments for severe and chronic inflammatory conditions which inhibit tumour necrosis factor alpha (TNF-α), a pro-inflammatory cytokine, may be able to shed some light on the role of inflammatory mediators in depression. This systematic review and meta-analysis of randomised controlled trials determined the effects of TNF-α inhibitor therapy on depression and anxiety in people with chronic physical illness.

METHODS

Seven databases were searched from inception to January 2014: AMED, Central, Cochrane Database of Systematic Reviews, CINAHL, Embase, MEDLINE, and PsycINFO. Articles were screened for inclusion independently by two reviewers. Data extraction and appraisal were conducted by one reviewer and checked by a second. Random-effects meta-analyses were performed.

RESULTS

Six randomised controlled trials (reported in seven articles) met eligibility criteria and were included in the final review. In total 2540 participants were enrolled across the trials, with participants presenting with rheumatoid arthritis (n=3 trials), psoriasis (n=2) or ankylosing spondylitis (n=1). Meta-analyses, using standardised mean differences, showed evidence of small reductions in depression (-0.24; 95% CI -0.33 to -0.14; p<0.001), and anxiety (-0.17; 95% CI -0.31 to -0.02; p=0.02).

CONCLUSION

TNF-α inhibitor therapy reduces depression in people with chronic disease though the effects are small. Whilst this is consistent with inflammation contributing to the development of depression, further studies investigating a more detailed timeline of changes in depression, inflammatory biomarkers and disease activity status are required.

Sickness: From the focus on cytokines, prostaglandins, and complement factors to the perspectives of neurons

Systemic inflammation leads to a variety of physiological (e.g. fever) and behavioral (e.g. anorexia, immobility, social withdrawal, depressed mood, disturbed sleep) responses that are collectively known as sickness. While these phenomena have been studied for the past few decades, the neurobiological mechanisms by which sickness occurs remain unclear. In this review, we first revisit how the body senses and responds to infections and injuries by eliciting systemic inflammation. Next, we focus on how peripheral inflammatory molecules such as cytokines, prostaglandins, and activated complement factors communicate with the brain to trigger neuroinflammation and sickness. Since depression also involves inflammation, we further elaborate on the interrelationship between sickness and depression. Finally, we discuss how immune activation can modulate neurons in the brain, and suggest future perspectives to help unravel how changes in neuronal functions relate to sickness responses.

Adrenal gland volume, intra-abdominal and pericardial adipose tissue in major depressive disorder

Major depressive disorder (MDD) is associated with an increased risk for the development of cardio-metabolic diseases. Increased intra-abdominal (IAT) and pericardial adipose tissue (PAT) have been found in depression, and are discussed as potential mediating factors. IAT and PAT are thought to be the result of a dysregulation of the hypothalamus-pituitary-adrenal axis (HPAA) with subsequent hypercortisolism. Therefore we examined adrenal gland volume as proxy marker for HPAA activation, and IAT and PAT in depressed patients. Twenty-seven depressed patients and 19 comparison subjects were included in this case-control study. Adrenal gland volume, pericardial, intraabdominal and subcutaneous adipose tissue were measured by magnetic resonance imaging. Further parameters included factors of the metabolic syndrome, fasting cortisol, fasting insulin, and proinflammatory cytokines. Adrenal gland and pericardial adipose tissue volumes, serum concentrations of cortisol and insulin, and serum concentrations tumor-necrosis factor-α were increased in depressed patients. Adrenal gland volume was positively correlated with intra-abdominal and pericardial adipose tissue, but not with subcutaneous adipose tissue. Our findings point to the role of HPAA dysregulation and hypercortisolism as potential mediators of IAT and PAT enlargement. Further studies are warranted to examine whether certain subtypes of depression are more prone to cardio-metabolic diseases.

Association between suicidal behaviour and impaired glucose metabolism in depressive disorders

BACKGROUND

Disturbances in lipid metabolism have been linked to suicidal behaviour, but little is known about the association between suicide risk and abnormal glucose metabolism in depression. Hyperglycaemia and hyperinsulinaemia may increase the risk of depression and also the risk for suicide, we therefore studied associations between suicidal behaviour and disturbances in glucose metabolism in depressive patients who had been referred to depression nurse case managers.

METHODS

Patients aged 35 years and older (N = 448, mean age 51 years) who were experiencing a new depressive episode, who were referred to depression nurse case managers in 2008-2009 and who scored ≥10 on the Beck Depression Inventory were enrolled in this study. The study was conducted in municipalities within the Central Finland Hospital District (catchment area of 274 000 inhabitants) as part of the Finnish Depression and Metabolic Syndrome in Adults study. The patients' psychiatric diagnoses and suicidal behaviour were confirmed by the Mini-International Neuropsychiatric Interview. Blood samples, for glucose and lipid determinations, were drawn from participants after 12 h of fasting, which was followed by a 2-hour oral glucose tolerance test (OGTT) when blood was drawn at 0 and 2 h. Insulin resistance was measured by the Quantitative Insulin Sensitivity Check Index (QUICKI) method.

RESULTS

Suicidal ideation (49 %) and previous suicide attempts (16 %) were common in patients with major depressive disorder or dysthymia. Patients with depression and suicidal behaviour had higher blood glucose concentrations at baseline and at 2 hours in the OGTT. Glucose levels associated positively with the prevalence of suicidal behaviour, and the linearity was significant at baseline (p for linearity: 0.012, adjusted for age and sex) and for 2-hour OGTT glucose (p for linearity: 0.004, adjusted for age and sex). QUICKI levels associated with suicidal behavior (p for linearity across tertiles of QUICKI: 0.026). Total and LDL cholesterol and triglyceride levels were also higher in those patients with suicidal behaviour. Multivariate analysis revealed that blood glucose levels, BDI scores and antidepressive medications associated with suicidal behaviour.

CONCLUSION

Insulin resistance and disturbances in glucose and lipid metabolism may be more common in middle-aged depressive patients with suicidal behaviour.

Glia in the cytokine-mediated onset of depression: fine tuning the immune response

Major depressive disorder (MDD) is a mood disorder of multifactorial origin affecting millions of people worldwide. The alarming estimated rates of prevalence and relapse make it a global public health concern. Moreover, the current setback of available antidepressants in the clinical setting is discouraging. Therefore, efforts to eradicate depression should be directed towards understanding the pathomechanisms involved in the hope of finding cost-effective treatment alternatives. The pathophysiology of MDD comprises the breakdown of different pathways, including the hypothalamus-pituitary-adrenal (HPA) axis, the glutamatergic system, and monoaminergic neurotransmission, affecting cognition and emotional behavior. Inflammatory cytokines have been postulated to be the possible link and culprit in the disruption of these systems. In addition, evidence from different studies suggests that impairment of glial functions appears to be a major contributor as well. Thus, the intricate role between glia, namely microglia and astrocytes, and the central nervous system's (CNSs) immune response is briefly discussed, highlighting the kynurenine pathway as a pivotal player. Moreover, evaluations of different treatment strategies targeting the inflammatory response are considered. The immuno-modulatory properties of vitamin D receptor (VDR) suggest that vitamin D is an attractive and plausible candidate in spite of controversial findings. Further research investigating the role of VDR in mood disorders is warranted.

Interleukin-6 as a predictor of symptom resolution in psychological distress: a cohort study

BACKGROUND

Elevated levels of interleukin-6 (IL-6) have been associated with the development of common mental disorders, such as depression, but its role in symptom resolution is unclear.

METHOD

We examined the association between IL-6 and symptom resolution in a non-clinical sample of participants with psychological distress.

RESULTS

Relative to high IL-6 levels, low levels at baseline were associated with symptom resolution at follow-up [age- and sex-adjusted risk ratio (RR) = 1.15, 95% confidence interval (CI) 1.06-1.25]. Further adjustment for covariates had little effect on the association. Symptomatic participants with repeated low IL-6 were more likely to be symptom-free at follow-up compared with those with repeated high IL-6 (RR = 1.21, 95% CI 1.03-1.41). Among the symptomatic participants with elevated IL-6 at baseline, IL-6 decreased along with symptom resolution.

CONCLUSIONS

IL-6 is potentially related to the mechanisms underlying recovery from symptoms of mental ill health. Further studies are needed to examine these mechanisms and to confirm the findings in relation to clinical depression.

Increased cerebrospinal fluid fibrinogen in major depressive disorder

Major depressive disorder (MDD) presumably includes heterogeneous subgroups with differing pathologies. To obtain a marker reflecting such a subgroup, we analyzed the cerebrospinal fluid (CSF) levels of fibrinogen, which has been reported to be elevated in the plasma of patients with MDD. Three fibrinogen-related proteins were measured using aptamer-based analyses and CSF samples of 30 patients with MDD and 30 controls. The numbers of patients with an excessively high level (>99 percentile of the controls) was significantly increased (17 to 23%). Measurement reproducibility of these results was confirmed by an ELISA for fibrinogen (Pearson’s r = 0.77). In an independent sample set from 36 patients and 30 controls, using the ELISA, results were similar (22%). When these two sample sets were combined, the number of patients with a high fibrinogen level was significantly increased (15/66; odds ratio 8.53; 95% confidence interval 1.9–39.1, p = 0.0011). By using diffusion tensor imaging, we found white matter tracts abnormalities in patients with a high fibrinogen level but not those patients with a normal fibrinogen level, compared with controls. Plasma fibrinogen levels were similar among the diagnostic groups. Our results point to a subgroup of MDD represented by increased CSF fibrinogen and white matter tract abnormalities.

Elevated Serum Levels of Neopterin at Admission Predicts Depression After Acute Ischemic Stroke: a 6-Month Follow-Up Study

Inflammation and cell-mediated immune activation are attributed to the pathogenesis and pathophysiology in depression. Our aim was to test the possible association between serum levels of neopterin and the development of post-stroke depression (PSD) in Chinese patients. The subjects were first-ever acute ischemic stroke patients who were hospitalized at the First Affiliated Hospital of Xinxiang Medical University during the period from December 2012 to December 2013. Clinical information and stroke severity were collected at admission. Neurological and neuropsychological evaluations were conducted at the 6-month follow-up. Serum neopterin levels were measured using fluorometry and a high performance liquid chromatography (HPLC) method. Multivariate analyses were performed using logistic regression models. During the study period, 226 patients were included and finished the 6-month follow-up. Sixty-nine patients (30.5 %) were diagnosed as having major depression at 6 months. Patients with major depression showed higher levels of serum neopterin (21.6[IQR, 18.9-25.7]nmol/L vs. 14.6[IQR, 12.2-18.4]nmol/L, P < 0.0001) at admission. In multivariate analyses, serum neopterin was an independent predictor of PSD at 6 months [odds ratio (OR): 1.952 (95 % CI, 1.358-2.805), P < 0.0001]. With an AUC of 0.850 (95 % CI, 0.797-0.902), neopterin showed a significantly greater discriminatory ability as compared with high-sensitivity C-reactive protein, age, body mass index, and National Institutes of Health and Stroke Scale score. Neopterin is a novel, independent predictor of the development of depression 6 months after stroke. This indicated that the elevated neopterin levels may play a significant role in the pathology of depression and that the pathways leading to inflammation and cell-mediated immune activation warrant further exploration.

Serum Levels of High-sensitivity C-Reactive Protein at Admission Are More Strongly Associated with Poststroke Depression in Acute Ischemic Stroke than Homocysteine Levels

Inflammatory processes have fundamental roles in depression. The primary purpose of this study was to assess the serum levels of high-sensitivity C-reactive protein (Hs-CRP) and homocysteine (HCY) at admission to the presence of poststroke depression (PSD). From December 2012 to December 2013, first-ever acute ischemic stroke patients who were admitted to the hospital within the first 24 h after stroke onset were consecutively recruited and followed up for 6 months. Serum levels of Hs-CRP and HCY were tested at admission. Based on the symptoms, diagnoses of depression were made in accordance with DSM-IV criteria for depression at 6 months after stroke. Ninety-five patients (42.0%) showed depression (major + minor) at 6 months after admission, and in 69 patients (30.5%), this depression was classified as major. In the 69 patients with major depression, our results showed significantly higher Hs-CRP and HCY levels at admission than patients without major depression. After adjusting all other possible covariates, Hs-CRP and HCY still were independent predicators of PSD with adjusted OR of 1.332 (95% CI, 1.230-1.452; P < 0.001) and 1.138 (95% CI, 1.072-1.274; P < 0.001), respectively. The area under the receiver operating characteristic curve values of Hs-CRP and HCY were 0.765 (95% CI, 0.701-0.9825) and 0.684 (95% CI, 0.610-0.757) for PSD, respectively. The prognostic accuracy of combined model (HCY and Hs-CRP) was higher compared to those biomarkers alone and other markers. Elevated serum levels of Hs-CRP and HCY at admission were found to be associated with depression 6 months after stroke, suggesting that these alterations might participate in the pathophysiology of depression symptoms in stroke patients.

The poly(I:C)-induced maternal immune activation model in preclinical neuropsychiatric drug discovery

Increasing epidemiological and experimental evidence implicates gestational infections as one important factor involved in the pathogenesis of several neuropsychiatric disorders. Corresponding preclinical model systems based upon maternal immune activation (MIA) by treatment of the pregnant female have been developed. These MIA animal model systems have been successfully used in basic and translational research approaches, contributing to the investigation of the underlying pathophysiological mechanisms at the molecular, cellular and behavioral levels. The present article focuses on the application of a specific MIA rodent paradigm, based upon treatment of the gestating dam with the viral mimic polyinosinic-polycytidilic acid (Poly(I:C)), a synthetic analog of double-stranded RNA (dsRNA) which activates the Toll-like receptor 3 (TLR3) pathway. Important advantages and constraints of this animal model will be discussed, specifically in light of gestational infection as one vulnerability factor contributing to the complex etiology of mood and psychotic disorders, which are likely the result of intricate multi-level gene×environment interactions. Improving our currently incomplete understanding of the molecular pathomechanistic principles underlying these disorders is a prerequisite for the development of alternative therapeutic approaches which are critically needed in light of the important drawbacks and limitations of currently available pharmacological treatment options regarding efficacy and side effects. The particular relevance of the Poly(I:C) MIA model for the discovery of novel drug targets for symptomatic and preventive therapeutic strategies in mood and psychotic disorders is highlighted in this review article.

Indirect associations of combat exposure with post-deployment physical symptoms in U.S. soldiers: roles of post-traumatic stress disorder, depression and insomnia

OBJECTIVE

To characterize the indirect associations of combat exposure with post-deployment physical symptoms through shared associations with post-traumatic stress disorder (PTSD), depression and insomnia symptoms.

METHODS

Surveys were administered to a sample of U.S. soldiers (N = 587) three months after a 15-month deployment to Iraq. A multiple indirect effects model was used to characterize direct and indirect associations between combat exposure and physical symptoms.

RESULTS

Despite a zero-order correlation between combat exposure and physical symptoms, the multiple indirect effects analysis did not provide evidence of a direct association between these variables. Evidence for a significant indirect association of combat exposure and physical symptoms was observed through PTSD, depression, and insomnia symptoms. In fact, 92% of the total effect of combat exposure on physical symptoms scores was indirect. These findings were evident even after adjusting for the physical injury and relevant demographics.

CONCLUSION

This is the first empirical study to suggest that PTSD, depression and insomnia collectively and independently contribute to the association between combat exposure and post-deployment physical symptoms. Limitations, future research directions, and potential policy implications are discussed.

A review of the neuro- and systemic inflammatory responses in post concussion symptoms: Introduction of the "post-inflammatory brain syndrome" PIBS

Post-concussion syndrome is an aggregate of symptoms that commonly present together after head injury. These symptoms, depending on definition, include headaches, dizziness, neuropsychiatric symptoms, and cognitive impairment. However, these symptoms are common, occurring frequently in non-head injured controls, leading some to question the existence of post-concussion syndrome as a unique syndrome. Therefore, some have attempted to explain post-concussion symptoms as post-traumatic stress disorder, as they share many similar symptoms and post-traumatic stress disorder does not require head injury. This explanation falls short as patients with post-concussion syndrome do not necessarily experience many key symptoms of post-traumatic stress disorder. Therefore, other explanations must be sought to explain the prevalence of post-concussion like symptoms in non-head injury patients. Many of the situations in which post-concussion syndrome like symptoms may be experienced such as infection and post-surgery are associated with systemic inflammatory responses, and even neuroinflammation. Post-concussion syndrome itself has a significant neuroinflammatory component. In this review we examine the evidence of neuroinflammation in post-concussion syndrome and the potential role systemic inflammation plays in post-concussion syndrome like symptoms. We conclude that given the overlap between these conditions and the role of inflammation in their etiologies, a new term, post-inflammatory brain syndromes (PIBS), is necessary to describe the common outcomes of many different inflammatory insults. The concept of post-concussion syndrome is in its evolution therefore, the new term post-inflammatory brain syndromes provides a better understanding of etiology of its wide-array of symptoms and the wide array of conditions they can be seen in.

A meta-analysis of cytokines in suicidal behavior

BACKGROUND

We conducted the first meta-analysis of studies comparing the plasma and CSF concentrations of cytokines in suicidal patients vs. non-suicidal patients or healthy controls.

METHODS

We searched Medline, Web of Science, and PsycINFO from 1965 to November 2014 for relevant studies. Manual searches of references and unpublished data were also included. Suicidal patients included severe suicide ideators and suicide attempters.

RESULTS

Eleven articles were available for the meta-analysis, for a total sample size of 494 suicidal patients, 497 non-suicidal patients and 398 healthy controls. Levels of 6 independent plasma cytokines (IL2, IL6, TNFalpha, IFNgamma, IL4, TGFbeta) were meta-analyzed for plasma studies comparing suicidal vs. both controls. IL8 level was meta-analyzed for cerebrospinal fluid studies comparing suicidal patients with healthy controls. We reported with medium effect size, that suicidal patients had: (1) lower IL2 plasma levels than both non-suicidal patients and healthy controls (medium effect size); (2) lower IL4 and higher TGFbeta plasma levels than healthy controls.

CONCLUSION

Our results promote the hypothesis of altered inflammatory markers in suicidal patients, for both pro-inflammatory (IL2) and anti-inflammatory (IL4 and TGFbeta) cytokines.

Inflammatory biomarkers as differential predictors of antidepressant response

Although antidepressants are generally effective in the treatment of major depressive disorder (MDD), it can still take weeks before patients feel the full antidepressant effects. Despite the efficacy of standard treatments, approximately two-thirds of patients with MDD fail to respond to pharmacotherapy. Therefore, the identification of blood biomarkers that can predict the treatment response to antidepressants would be highly useful in order to improve this situation. This article discusses inflammatory molecules as predictive biomarkers for antidepressant responses to several classes of antidepressants, including the N-methyl-d-aspartate (NMDA) receptor antagonist ketamine.

Depression sum-scores don't add up: why analyzing specific depression symptoms is essential

Most measures of depression severity are based on the number of reported symptoms, and threshold scores are often used to classify individuals as healthy or depressed. This method--and research results based on it--are valid if depression is a single condition, and all symptoms are equally good severity indicators. Here, we review a host of studies documenting that specific depressive symptoms like sad mood, insomnia, concentration problems, and suicidal ideation are distinct phenomena that differ from each other in important dimensions such as underlying biology, impact on impairment, and risk factors. Furthermore, specific life events predict increases in particular depression symptoms, and there is evidence for direct causal links among symptoms. We suggest that the pervasive use of sum-scores to estimate depression severity has obfuscated crucial insights and contributed to the lack of progress in key research areas such as identifying biomarkers and more efficacious antidepressants. The analysis of individual symptoms and their causal associations offers a way forward. We offer specific suggestions with practical implications for future research.

Low-grade inflammation differentiates between symptoms of apathy and depression in community-dwelling older individuals

BACKGROUND

Systemic low-grade inflammation has repeatedly been associated with depression in old age, but the relationship with apathy is less clear. The present study assessed whether C-reactive protein (CRP) is differentially associated with symptoms of apathy and depression.

METHODS

A population-based cohort study was carried-out. At baseline and after two and four years of follow-up, CRP levels were assessed and symptoms of apathy and depression were measured using the 15-item Geriatric Depression Scale. Logistic regression analysis was used to investigate the cross-sectional and longitudinal associations of CRP with symptoms of apathy and depression.

RESULTS

Two thousand forty-seven community-dwelling participants (70-78 years) without a history of cardiovascular disease or stroke were studied. A cross-sectional association was found between CRP and apathy symptoms at three time points (odds ratio (OR) per natural log unit increase in CRP: baseline visit = 1.40, 95% CI = 1.12-1.75; two-year follow-up visit = 1.62, 95% CI = 1.17-2.25; four-year follow-up visit = 1.51, 95% CI = 1.03-2.21). This did not change after adjustment for demographics and depressive symptoms, and was slightly attenuated after adjustment for cardiovascular risk factors. No cross-sectional association was found with depressive symptoms. Baseline CRP did not predict incident apathy or depressive symptoms during four years of follow-up.

CONCLUSIONS

Increased CRP levels are associated with apathy symptoms but not with depressive symptoms. This suggests a differential effect of inflammation on apathy and depression. In older persons, symptoms of apathy may be a behavioral manifestation of concurrent low-grade inflammation.

Unhealthy lifestyle may increase later depression via inflammation in older women but not men

Depression and inflammatory markers have a reliable cross-sectional association although less is known about the prospective relationship. The current study investigated whether pro-inflammatory markers are prospectively associated with depression, and whether indicators of unhealthy lifestyle, physical health and psychosocial functioning may drive this association. Participants were drawn from the Hunter Community Study, a community-dwelling cohort of individuals aged 55-85 years (N = 1410). Participants completed baseline physiological assessment, health-related questionnaires, and blood sampling for the analysis of inflammatory markers, C-reactive protein (CRP) and interleukin (IL)-6. Participants completed the same depressive symptom questionnaire again after 3.5-5.5 years. Depression outcomes at follow-up were analysed dichotomously using established scale cut-off scores and continuously as a "residual score", representing the variation in follow-up depressive symptoms not explained by baseline symptoms and age. Analyses were conducted on males and females separately. At baseline, indicators of unhealthy lifestyle, physical health and psychosocial functioning were associated with depressive symptoms and inflammatory markers. For males, there were no relationships between inflammatory markers and follow-up depression outcomes. In females, IL-6 was significantly associated with depression outcomes in univariate, but not multivariate analyses. However, IL-6 significantly mediated the association between the predictors of waist-to-hip ratio, smoking and psychological coping at baseline, and follow-up depression outcomes. The results support the inflammatory hypothesis of depression, although females may be more vulnerable to effects. The findings raise the possibility that unhealthy lifestyle and psychosocial stress may drive inflammation and subsequent depressive symptoms.

Inflammation and neuronal plasticity: a link between childhood trauma and depression pathogenesis

During the past two decades, there has been increasing interest in understanding and characterizing the role of inflammation in major depressive disorder (MDD). Indeed, several are the evidences linking alterations in the inflammatory system to Major Depression, including the presence of elevated levels of pro-inflammatory cytokines, together with other mediators of inflammation. However, it is still not clear whether inflammation represents a cause or whether other factors related to depression result in these immunological effects. Regardless, exposure to early life stressful events, which represent a vulnerability factor for the development of psychiatric disorders, act through the modulation of inflammatory responses, but also of neuroplastic mechanisms over the entire life span. Indeed, early life stressful events can cause, possibly through epigenetic changes that persist over time, up to adulthood. Such alterations may concur to increase the vulnerability to develop psychopathologies. In this review we will discuss the role of inflammation and neuronal plasticity as relevant processes underlying depression development. Moreover, we will discuss the role of epigenetics in inducing alterations in inflammation-immune systems as well as dysfunction in neuronal plasticity, thus contributing to the long-lasting negative effects of stressful life events early in life and the consequent enhanced risk for depression. Finally we will provide an overview on the potential role of inflammatory system to aid diagnosis, predict treatment response, enhance treatment matching, and prevent the onset or relapse of Major Depression.

Influence of depression on cardiometabolic responses to a lifestyle intervention in at-risk individuals

BACKGROUND

Cardiometabolic diseases and depression are public health problems that are often related. The benefits of behavioral interventions on lifestyle are well documented. However, the influence of depression in these interventions is unclear.

OBJECTIVE

To evaluate whether depression affects the impact of a lifestyle intervention on cardiometabolic response in an at-risk sample.

METHODS

129 individuals identified by the public health system to be at risk for cardiometabolic disease were allocated to 18-month interventions on diet and physical activity. Socio-demographic and clinical data were obtained. Depressive symptoms were assessed by the Beck Depression Inventory. Changes by at least 10% in each of 6 cardiometabolic risk factors were used to define responses to intervention. Logistic regression models were employed for each gender.

RESULTS

Approximately 42% of individuals had depressive symptoms. They had higher adiposity, cholesterol, and blood pressure levels and lower quality of life and physical activity levels than non-depressed individuals. In adjusted models, only women with depression at baseline had lower chance of improving plasma glucose (OR: 0.32) and lower chance of improving mean blood pressure (OR: 0.29) after the follow-up, compared with non-depressed women.

LIMITATIONS

The small sample size may have diminished the power of the results and the instrument used to measure depression does not provide clinical diagnosis according to DSM criteria.

CONCLUSION

Depression at baseline of lifestyle interventions predicted a lower chance of improving long-term cardiometabolic risk, particularly in women, suggesting that screening and management of depression as part of lifestyle interventions can potentially improve cardiometabolic risk profile.

Association of inflammatory biomarkers with depressive symptoms and cognitive decline in a community-dwelling healthy older sample: a 3-year follow-up study

BACKGROUND

The relationship between the pathophysiology of dementia and neuroinflammation is well-known. The number of reports stating that depression is a risk factor for dementia has recently been increasing. These epidemiological findings suggest the possibility that both depression and dementia have common pathophysiological backgrounds of neuroinflammation.

METHODS

The sample consists of 64 non-demented community-dwelling older participants aged 65 years or over. Participants were assessed at baseline (2004-2006) and 3 years later (2007-2009). Plasma concentration of markers of inflammation (interleukins (IL)-1β, IL-2, IL-6, soluble interleukin-2 receptor (sIL-2R), soluble interleukin-6 receptor (sIL-6R), high sensitivity C-reactive protein (hsCRP) and tumor necrosis factor (TNF)-α) were measured at baseline. Depression symptoms were assessed with the Beck Depression Inventory (BDI) and cognitive decline was assessed with the Mini-Mental State Examination (MMSE), Frontal Assessment Battery (FAB) and Clock Drawing Test (CDT) at baseline and follow-up. All analyses were adjusted for age, gender and years of education.

RESULTS

In the cross-sectional analysis, the present study found soluble IL-2 receptor (sIL-2R) to be associated only with the MMSE score at baseline in men. In the longitudinal analysis, none of our inflammatory biomarkers were associated with either depressive symptoms or cognitive decline.

LIMITATIONS

The present study consists of small number of participants and body mass index (BMI) scores were not obtained.

CONCLUSIONS

Our findings suggest that sIL-2R is associated with current cognitive function in men. None of our inflammatory markers predicted future depressive state or cognitive decline in our community-dwelling healthy older sample.

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.