How handling extreme C-reactive protein (CRP) values and regularization influences CRP and depression criteria associations in network analyses

Label-free electrochemical detection of glycated hemoglobin (HbA1c) and C-reactive protein (CRP) to predict the maturation of coronary heart disease due to diabetes

The pathophysiological link between diabetes and heightened propensity for the development of coronary heart disease (CHD) is well-established. Prevailing evidence confirms that small increases in low concentrations of high-sensitivity C reactive protein (hs-CRP) in the human body can determine the tendency of developing CHD. Additionally, glycated hemoglobin (HbA1c) is a well-recognized biomarker to evaluate diabetes progression. Given the positive correlation between diabetes and CHD, this research presents a notably unprecedented label-free electrochemical approach for the dual detection of %HbA1c regarding Total Hb and hs-CRP, facilitating early CHD prediction and cost-effective point-of-care diagnostics. Furthermore, a novel redox probe O-(4-Nitrophenylphosphoryl)choline (C11H17N2O6P) was used for the electrochemical detection of CRP, a method not documented in scientific literature before. The calibration curves demonstrate a limit of detection (LOD) of 5 mg/mL in PBS (pH 8) and 6 mg/mL in simulated blood (SB) for a linear range of 0-30 mg/mL of HbA1c. Conjointly, a LOD of 0.007 mg/mL and 0.008 mg/mL for measurement in PBS (pH 7.4) and SB are reported for a linear range of 0-0.05 mg/mL of CRP. The electrochemical systems presented could accurately quantify HbA1c and CRP in mixed samples, demonstrating reasonable specificity and practical applicability for complex biological samples.

Associations of depression and perceived physical fatigability with white matter integrity in older adults

BACKGROUNDS

Fatigability is prevalent in older adults. However, it is often associated with depressed mood. We aim to investigate these two psychobehavioral constructs by examining their underpinning of white matter structures in the brain and their associations with different medical conditions.

METHODS

Twenty-seven older adults with late-life depression (LLD) and 34 cognitively normal controls (CN) underwent multi-shell diffusion MRI. Fatigability was measured with the Pittsburgh Fatigability Scale. We examined white matter integrity by measuring the quantitative anisotropy (QA), a fiber tracking parameter with better accuracy than the traditional imaging technique.

RESULTS

We found those with LLD had lower QA in the 2nd branch of the left superior longitudinal fasciculus (SLF-II), and those with more physical fatigability had lower QA in more widespread brain regions. In tracts associated with more physical fatigability, the lower QA in left acoustic radiation and left superior thalamic radiation correlated with higher blood glucose (r = - 0.46 and - 0.49). In tracts associated with depression, lower QA in left SLF-II correlated with higher bilirubin level (r = - 0.58).

DISCUSSION

Depression and fatigability were associated with various white matter integrity changes, which correlated with biochemistry biomarkers all related to inflammation.

Characterizing the hierarchical depression phenotype in sexually diverse individuals

INTRODUCTION

Sexual diverse individuals are at high risk for internalizing psychopathologies, such as depression. Understanding how symptom profiles of heterogeneous psychiatric disorders such as depression differ for sexually diverse vs. heterosexual individuals is thus critical to advance precision psychiatry and maximize our ability to effectively treat members of this population. Research has failed to consider the possibility of hierarchical phenotypes, wherein sexual orientation status may be uniquely and simultaneously associated with both depression broadly and with individual symptoms.

METHOD

To address these issues, we conducted a moderated nonlinear factor analysis in Wave IV of the Add Health study, using sexual diversity status as a predictor of (a) latent depression, (b) factor loadings, and (c) individual symptoms, with and without controlling for race.

RESULTS

Sexual diversity status was positively and simultaneously associated with latent depression, concentration difficulties, and happiness.

DISCUSSION

These findings suggest that sexually diverse populations not only face greater depression, broadly defined, but are disproportionately more likely to experience concentration difficulties and be happier compared to heterosexual counterparts. Methodologically, these models indicate that the CES-D is scalar noninvariant as a function of sexual diversity status (i.e., identical scores on the CES-D may represent different manifestations of depression for sexually diverse and heterosexual participants). Studies examining disparities in depression across heterosexual and sexually diverse samples should thus consider depression broadly as well as specific symptoms. Further, it is critical to examine whether these relations function via different mechanisms.

Ketamine's mechanism of action with an emphasis on neuroimmune regulation: can the complement system complement ketamine's antidepressant effects?

Over 300 million people worldwide suffer from major depressive disorder (MDD). Unfortunately, only 30-40% of patients with MDD achieve complete remission after conventional monoamine antidepressant therapy. In recent years, ketamine has revolutionized the treatment of MDD, with its rapid antidepressant effects manifesting within a few hours as opposed to weeks with conventional antidepressants. Many research endeavors have sought to identify ketamine's mechanism of action in mood disorders; while many studies have focused on ketamine's role in glutamatergic modulation, several studies have implicated its role in regulating neuroinflammation. The complement system is an important component of the innate immune response vital for synaptic plasticity. The complement system has been implicated in the pathophysiology of depression, and studies have shown increases in complement component 3 (C3) expression in the prefrontal cortex of suicidal individuals with depression. Given the role of the complement system in depression, ketamine and the complement system's abilities to modulate glutamatergic transmission, and our current understanding of ketamine's anti-inflammatory properties, there is reason to suspect a common link between the complement system and ketamine's mechanism of action. This review will summarize ketamine's anti- inflammatory roles in the periphery and central nervous system, with an emphasis on complement system regulation.

Networks of C-reactive protein and depression symptoms in patients with stable coronary heart disease: Findings from the Heart and Soul Study

OBJECTIVE

Research addressing the associations between C-reactive protein (CRP) and depression among patients with stable coronary heart disease (CHD) has produced inconsistent results. This might be attributable to varying associations of CRP with specific depression symptom profiles. We responded to this challenge using various network analysis techniques.

METHODS

A total of 967 outpatients with documented CHD were drawn from the baseline cross-sectional data of the Heart and Soul Study. We first estimated mixed graphical models that included CRP and individual depression symptoms, before and after adjusting for relevant covariates, to explore whether CRP is correlated with specific facets of depression. We also investigated whether CRP levels moderated the associations between specific depression symptoms using moderated network models. Finally, we performed a network comparison test and compared the symptom network properties between non-elevated and elevated CRP groups.

RESULTS

In the network model without covariates, CRP was positively associated with fatigue, appetite changes, and psychomotor problems. CRP maintained its negative association with concentration difficulty regardless of covariate adjustment. Few symptom-symptom associations, especially those involving appetite changes, were moderated by CRP. Further, the elevated CRP group showed greater overall symptom connectivity as compared to the non-elevated group.

CONCLUSION

This study segues into CRP-depression relationship with sophisticated methodology.

Identification of Relationships Among Resilience Factors Using Network Analysis: A Pilot Study

BACKGROUND

Although college life can be fulfilling, it can be stressful, particularly for health professional students. In addition, they may have had Adverse Childhood Experience (ACE) that increases their sensitivity to academic stress. Yet, students need to overcome challenges to become successful professionals. The literature suggests the following factors may be associated with resilience: ACE and academic stress as the antecedents; ego-resilience, emotion regulation, resources, social support, inflammatory markers, and genes as the defining attributes; and mental health and sense of coherence (SOC) as the consequences.

AIMS

The purpose is to identify the relationships among factors associated with resilience using network analysis.

METHODS

A total of 70 college students participated in this cross-sectional pilot study. They completed measures of psychosocial variables and provided saliva samples, which were analyzed for Serotonin Transporter-Linked Promoter Region (5-HTTLPR)/rs25531 and inflammatory markers. Mixed graphical models including all variables were estimated using the R-package mgm.

RESULTS

Network analysis revealed positive associations between (1) mental health and SOC; (2) mental health and resources; (3) mental health and social support; (4) SOC and reappraisal of emotion regulation; (5) resources and reappraisal of emotion regulation; and (6) resources and social support. In addition, SOC and academic stress were negatively associated. Furthermore, the short variant of 5-HTTLPR/rs25531 was associated with stronger suppression of emotion regulation and fewer resources compared with the long variant.

CONCLUSION

Resilience may be influenced by biopsychosocial factors, notably SOC and 5-HTTLPR/rs25531. However, longitudinal research is needed with a larger sample size to better understand how these and other factors may affect resilience.

A network analysis of depressive symptoms and metabolomics

BACKGROUND

Depression is associated with metabolic alterations including lipid dysregulation, whereby associations may vary across individual symptoms. Evaluating these associations using a network perspective yields a more complete insight than single outcome-single predictor models.

METHODS

We used data from the Netherlands Study of Depression and Anxiety (N = 2498) and leveraged networks capturing associations between 30 depressive symptoms (Inventory of Depressive Symptomatology) and 46 metabolites. Analyses involved 4 steps: creating a network with Mixed Graphical Models; calculating centrality measures; bootstrapping for stability testing; validating central, stable associations by extra covariate-adjustment; and validation using another data wave collected 6 years later.

RESULTS

The network yielded 28 symptom-metabolite associations. There were 15 highly-central variables (8 symptoms, 7 metabolites), and 3 stable links involving the symptoms Low energy (fatigue), and Hypersomnia. Specifically, fatigue showed consistent associations with higher mean diameter for VLDL particles and lower estimated degree of (fatty acid) unsaturation. These remained present after adjustment for lifestyle and health-related factors and using another data wave.

CONCLUSIONS

The somatic symptoms Fatigue and Hypersomnia and cholesterol and fatty acid measures showed central, stable, and consistent relationships in our network. The present analyses showed how metabolic alterations are more consistently linked to specific symptom profiles.

Mediation of the Association Between Vascular Risk Factors and Depressive Symptoms by C-Reactive Protein

Background

This study examined whether C-reactive protein (CRP), a marker of low-grade systemic inflammation, mediates the association between vascular risk factor (VRF) burden and depressive symptoms.

Methods

We drew on the prospective design of the UK Biobank to include participants with longitudinal data on VRF burden, CRP, and depressive symptoms. Total, direct, and indirect effects were estimated using regression-based mediation models while controlling for confounding by sociodemographic factors, baseline CRP, and baseline depression. Sensitivity analyses probed the robustness of results to unmeasured confounding.

Results

We analyzed data from 10,470 participants from the UK Biobank (mean age = 56.75 years at baseline). Net of covariates, VRFs at baseline were associated with higher depressive symptoms at follow-up (total effect = 0.099; 95% CI, 0.002-0.163). CRP mediated this association (indirect effect = 0.010; 95% CI, 0.004-0.017), accounting for 10.0% (95% CI, 0.3%-30.0%) of the total effect of VRF burden on depressive symptoms. Exploratory analyses suggested that the total and indirect effects pertained to somatic depressive symptoms (tiredness and appetite).

Conclusions

These results suggest that inflammation-promoting effects of VRFs may contribute to depressive symptoms in mid- and later life. However, the mediating pathway via CRP explains only a small part of the association between VRFs and depression after accounting for important covariates and may pertain to specific depressive symptoms. Future studies leveraging similar longitudinal designs are needed to further disentangle the time-varying effects between VRFs, inflammation, and certain depressive symptoms while addressing important confounders.

Exploring the multiverse: the impact of researchers' analytic decisions on relationships between depression and inflammatory markers

In recent years, a replication crisis in psychiatry has led to a growing focus on the impact of researchers' analytic decisions on the results from studies. Multiverse analyses involve examining results across a wide array of possible analytic decisions (e.g., log-transforming variables, number of covariates, or treatment of outliers) and identifying if study results are robust to researchers' analytic decisions. Studies have begun to use multiverse analysis for well-studied relationships that have some heterogeneity in results/conclusions across studies.We examine the well-studied relationship between peripheral inflammatory markers (PIMs; e.g., white blood cell count (WBC) and C-reactive protein (CRP)) and depression severity in the large NHANES dataset (n = 25,962). Specification curve analyses tested the impact of 9 common analytic decisions (comprising of 58,000+ possible combinations) on the association of PIMs and depression severity. Relationships of PIMs and total depression severity are robust to analytic decisions (based on tests of inference jointly examining effect sizes and p-values). However, moderate/large differences are noted in effect sizes based on analytic decisions and the majority of analyses do not result in significant findings, with the percentage of analyses with statistically significant results being 46.1% for WBC and 43.8% for CRP. For associations of PIMs with specific symptoms of depression, some associations (e.g., sleep, appetite) in males (but not females) were robust to analytic decisions. We discuss how multiverse analyses can be used to guide research and also the need for authors, reviewers, and editors to incorporate multiverse analyses to enhance replicability of research findings.

Prospective network analysis of proinflammatory proteins, lipid markers, and depression components in midlife community women

BACKGROUND

Vulnerability theories propose that suboptimal levels of lipid markers and proinflammatory proteins predict future heightened depression. Scar models posit the reverse association. However, most studies that tested relationships between non-specific immune/endocrine markers and depression did not separate temporal inferences between people and within-person and how different immunometabolism markers related to unique depression symptoms. We thus used cross-lagged prospective network analyses (CLPN) to investigate this topic.

METHODS

Community midlife women (n = 2224) completed the Center for Epidemiologic Studies-Depression scale and provided biomarker samples across five time-points spanning 9 years. CLPN identified significant relations (edges) among components (nodes) of depression (depressed mood, somatic symptoms, interpersonal issues), lipid markers [insulin, fasting glucose, triglycerides, low-density lipoprotein-cholesterol (LDL), high-density lipoprotein-cholesterol (HDL)], and proinflammatory proteins [C-reactive protein (CRP), fibrinogen], within and across time-points. All models adjusted for age, estradiol, follicle-stimulating hormone, and menopausal status.

RESULTS

In within-person temporal networks, higher CRP and HDL predicted all three depression components (d = 0.131-2.112). Increased LDL preceded higher depressed mood and interpersonal issues (v. somatic symptoms) (d = 0.251-0.327). Elevated triglycerides predicted more somatic symptoms (v. depressed mood and interpersonal problems) (d = 0.131). More interpersonal problems forecasted elevated fibrinogen and LDL levels (d = 0.129-0.331), and stronger somatic symptoms preceded higher fibrinogen levels (d = 0.188).

CONCLUSIONS

Results supported both vulnerability and scar models. Long-term dysregulated immunometabolism systems, social disengagement, and related patterns are possible mechanistic accounts. Cognitive-behavioral therapies that optimize nutrition and physical activity may effectively target depression.

The future is dynamic: A call for intensive longitudinal data in immunopsychiatry

The long-term value of immunopsychiatry will be based on its ability to translate basic science into effective clinical interventions. In this article, we discuss a key obstacle to achieving this important translational goal-namely, the preponderance of studies that are cross-sectional, or that have months-to-years long follow-up periods. Immunopsychiatric processes such as stress, inflammation, and depression symptoms are inherently dynamic and fluctuate over hours, days, and weeks. This fact suggests that higher-density data collection with only days between measurements is necessary to capture-with adequate resolution-the actual dynamics of these systems, determine optimal time lags with which to observe associations between variables of interest, and maximize the translational potential of these data. To illustrate these points, we use pilot data from our own intensive longitudinal immunopsychiatric study. We then conclude by making several recommendations for future research. By learning how to better use existing data for dynamically informative studies as well as collecting intensive longitudinal data, we believe immunopsychiatry will be much better positioned to advance our causal understanding of the interplay between the immune system and health.

Ultrasensitive Terahertz Biodetection Enabled by Quasi-BIC-Based Metasensors

Advanced sensing devices, highly sensitive, and reliable in detecting ultralow concentrations of circulating biomarkers, are extremely desirable and hold great promise for early diagnostics and real-time progression monitoring of diseases. Nowadays, the most commonly used clinical methods for diagnosing biomarkers suffer from complicated procedures and being time consumption. Here, a chip-based portable ultra-sensitive THz metasensor is reported by exploring quasi-bound states in the continuum (quasi-BICs) and demonstrate its capability for sensing low-concentration analytes. The designed metasensor is made of the designed split-ring resonator metasurface which supports magnetic dipole quasi-BIC combining functionalized gold nanoparticles (AuNPs) conjugated with the specific antibody. Attributed to the strong near-field enhancement near the surface of the microstructure enabled by the quasi-BICs, light-analyte interactions are greatly enhanced, and thus the device's sensitivity is boosted significantly. The system sensitivity slope is up to 674 GHz/RIU, allowing for repeatable resolving detecting ultralow concentration of C-reactive protein (CRP) and Serum Amyloid A (SAA), respectively, down to 1 pM. The results touch a range that cannot be achieved by ordinary immunological assays alone, offering a novel non-destructive and rapid trace measured approach for next-generation biomedical quantitative detection systems.

Higher immune-related gene expression in major depression is independent of CRP levels: results from the BIODEP study

Compelling evidence demonstrates that some individuals suffering from major depressive disorder (MDD) exhibit increased levels of inflammation. Most studies focus on inflammation-related proteins, such as serum or plasma C-reactive protein (CRP). However, the immune-related modifications associated with MDD may be not entirely captured by CRP alone. Analysing mRNA gene expression levels, we aimed to identify broader molecular immune-related phenotypes of MDD. We examined 168 individuals from the non-interventional, case-control, BIODEP study, 128 with a diagnosis of MDD and 40 healthy controls. Individuals with MDD were further divided according to serum high-sensitivity (hs)CRP levels (n = 59 with CRP <1, n = 33 with CRP 1-3 and n = 36 with CRP >3 mg/L). We isolated RNA from whole blood and performed gene expression analyses using RT-qPCR. We measured the expression of 16 immune-related candidate genes: A2M, AQP4, CCL2, CXCL12, CRP, FKBP5, IL-1-beta, IL-6, ISG15, MIF, GR, P2RX7, SGK1, STAT1, TNF-alpha and USP18. Nine of the 16 candidate genes were differentially expressed in MDD cases vs. controls, with no differences between CRP-based groups. Only CRP mRNA was clearly associated with serum CRP. In contrast, plasma (proteins) IL-6, IL-7, IL-8, IL-10, IL-12/IL-23p40, IL-16, IL-17A, IFN-gamma and TNF-alpha, and neutrophils counts, were all differentially regulated between CRP-based groups (higher in CRP >3 vs. CRP <1 and/or controls), reflecting the gradient of CRP values. Secondary analyses on MDD individuals and controls with CRP values <1 mg/L (usually interpreted as 'no inflammation') confirmed MDD cases still had significantly different mRNA expression of immune-related genes compared with controls. These findings corroborate an immune-related molecular activation in MDD, which appears to be independent of serum CRP levels. Additional biological mechanisms may then be required to translate this mRNA signature into inflammation at protein and cellular levels. Understanding these mechanisms will help to uncover the true immune abnormalities in depression, opening new paths for diagnosis and treatment.

Sex differences in childhood maltreatment, inflammation, and adulthood depression: A network analysis

Background

Efforts to improve treatment for adults with major depression (MD) and childhood maltreatment (CM) have identified inflammation as a potential target to improve health. Network models have emerged as a new way to understand the relationship between depressive symptoms and inflammation. However, none have accounted for the role of childhood maltreatment in the link between depressive symptoms and inflammation, or sex differences commonly found in these constructs.

Methods

Data from two waves of the Midlife Development in the United States study were used in this study (N = 1917). The Center for Epidemiological Studies Depression (CES-D) scale and Childhood Trauma Questionnaire, and six inflammation markers served as nodes in an undirected psychometric network analysis. Edges between nodes were calculated using partial Spearman's correlation. Separate networks were modeled for males and females.

Results

The total network revealed several associations between nodes of CM, MD, and inflammation, with emotional abuse having a strong association with somatic complaints. Network comparison testing revealed male-female network invariance, with several edge differences between male and female networks. Males and females showed differences in associations across inflammatory markers and depressive symptom clusters, particularly among somatic complaints and interpersonal difficulties.

Conclusions

Specific associations between dimensions of inflammation, CM, and MD may represent important targets for treatment. Network models disaggregated by sex showed that males and females may have fundamentally different associations between these constructs, suggesting that future studies should consider sex-specific interventions.

Racial Differences in C-Reactive Protein, Depression Symptoms, and Social Relationships in Older Adults: A Moderated Network Analysis

INTRODUCTION

We introduce moderated network analysis as an integrative approach to assess the moderation effects of race on the relationship between C-reactive protein (CRP) and depression symptoms in older adults. This study further explores how the observed relationships differ adjusting for social relationships.

METHODS

This secondary analysis of cross-sectional data from the National Social Life, Health, and Aging Project (2010-2011) includes 2,880 older adults. We used different depression symptom domains (depressed affect, low positive affect, somatic symptoms, and interpersonal problems) from the Center for Epidemiologic Studies-Depression Scale. Social relationships were assessed with measures of social integration, social support, and social strain. The moderated networks were constructed using the R-package mgm. The racial moderator was coded as White/African American racial groups.

RESULTS

In the moderated networks of CRP and depression symptoms, CRP-"interpersonal problems" edge was present only among African Americans. CRP-"somatic symptoms" edge was present in both racial groups with equal edge weights. After adjusting for social relationships, the aforementioned patterns remained the same, but the edge weights were attenuated. We additionally observed CRP-social strain and social integration-"depressed affect" edges only in African Americans.

DISCUSSION

Race may moderate the relationship between the CRP and depression symptoms in older adults and social relationships might be important covariates to consider while analyzing them. This study as an initiation point; future network investigations would benefit from leveraging more contemporary cohorts of older adults, gaining a large sample size with diverse racial/ethnic backgrounds, and important covariates. Several important methodological issues of the current study are addressed.

Exploring Associations between C-Reactive Protein and Self-Reported Interoception in Major Depressive Disorder: A Bayesian Analysis

Major depressive disorder (MDD) is associated with dysfunctional self-reported interoception (i.e., abnormal perception of the body's physiological state) and systemic inflammation, both of which adversely affect treatment response. In this study, we explored associations between C-reactive protein (CRP) and self-reported interoception, to gain more insight into the pathophysiology of interoceptive impairments in MDD. We also aimed to replicate previous findings on the associations of depression and fatigue severity with CRP. The study included 97 depressed individuals, who completed self-administered questionnaires (Multidimensional Assessment of Interoceptive Awareness (MAIA-2); Beck Depression Inventory-II, Multidimensional Fatigue Inventory). CRP concentrations were analyzed in the serum using a particle-enhanced turbidimetric immunoassay. We applied Bayesian inference to estimate robust effect parameters from posterior distributions based on MCMC sampling, and computed Bayes factors (BF₁₀) as indices of relative evidence. The bivariate analysis supported evidence against associations between CRP and self-reported interoception (BF₁₀ ≤ 0.32), except for one dimension (Not-Distracting: r = 0.11, BF₁₀ > 0.43, absence of evidence). Positive correlations with overall depression (r = 0.21, BF₁₀ = 3.19), physical fatigue (r = 0.28, BF₁₀ = 20.64), and reduced activity (r = 0.22, BF₁₀ = 4.67) were found. The multivariate analysis showed moderate evidence that low-grade inflammation predicted higher scores on the MAIA-2 Not-Worrying scale (β = 0.28, BF₁₀ = 3.97), after controlling for relevant confounders. Inflammatory responses, as measured by CRP, may not be involved in the pathophysiology of dysfunctional self-reported interoception. However, systemic low-grade inflammation could potentially exert a protective effect against worries about pain or discomfort sensations. An immunological involvement in interoceptive impairments cannot be ruled out until future studies considering additional biomarkers of inflammation replicate our findings.

Sociodemographic, lifestyle and clinical characteristics of energy-related depression symptoms: A pooled analysis of 13,965 depressed cases in 8 Dutch cohorts

BACKGROUND

In a substantial subgroup of depressed patients, atypical, energy-related depression symptoms (e.g. increased appetite/weight, hypersomnia, loss of energy) tend to cluster with immuno-metabolic dysregulations (e.g. increased BMI and inflammatory markers). This clustering is proposed to reflect a more homogeneous depression pathology. This study examines to what extent energy-related symptoms are associated and share sociodemographic, lifestyle and clinical characteristics.

METHODS

Data were available from 13,965 participants from eight Dutch cohorts with DSM-5 lifetime major depression assessed by the Lifetime Depression Assessment Self-report (LIDAS) questionnaire. Information on four energy-related depression symptoms were extracted: energy loss, increased appetite, increased weight, and hypersomnia. Tetrachoric correlations between these symptoms, and associations of these symptoms with sociodemographic (sex, age, education), lifestyle (physical activity, BMI, smoking) and clinical characteristics (age of onset, episode duration, history, treatment and recency, and self-reported comorbidity) were computed.

RESULTS

Correlations between energy-related symptoms were overall higher than those with other depression symptoms and varied from 0.90 (increased appetite vs increased weight) to 0.11 (increased appetite vs energy loss). All energy-related symptoms were strongly associated with higher BMI and a more severe clinical profile. Patients with increased appetite were more often smokers, and only patients with increased appetite or weight more often had a self-reported diagnosis of PTSD (OR = 1.17, p = 2.91E-08) and eating disorder (OR = 1.40, p = 4.08E-17).

CONCLUSIONS

The symptom-specific associations may have consequences for a profile integrating these symptoms, which can be used to reflect immuno-metabolic depression. They indicate the need to study immuno-metabolic depression at individual symptom resolution as a starting point.

Hierarchical Inflammatory Phenotypes of Depression: A Novel Approach Across Five Independent Samples and 27,730 Adults

BACKGROUND

Although characterizing associations between inflammation and depression may prove critical for informing theory, research, and treatment decisions, extant research has been limited by ignoring the possibility that inflammation may be simultaneously associated with depression broadly and with a subset of symptoms. This lack of direct comparison has hampered attempts to understand inflammatory phenotypes of depression and critically fails to consider that inflammation might be uniquely associated with both depression broadly and individual symptoms.

METHODS

We used moderated nonlinear factor analysis in 5 NHANES (National Health and Nutrition Examination Survey) cohorts (N = 27,730, 51% female, mean age = 46 years).

RESULTS

C-reactive protein (CRP) is simultaneously associated with latent depression, appetite, and fatigue. Specifically, CRP was associated with latent depression in all 5 samples (rs: 0.044-0.089; ps: < .001-.002) and was associated with both appetite (significant rs: 0.031-0.049, significant ps: .001-.007) and fatigue (significant rs: 0.030-0.054, significant ps: < .001-.029) in 4 samples. These results were largely robust to covariates.

CONCLUSIONS

Methodologically, these models indicate that the Patient Health Questionnaire-9 is scalar noninvariant as a function of CRP (i.e., identical Patient Health Questionnaire-9 scores may represent different constructs in those with high vs. low CRP levels). Therefore, mean comparisons of depression total scores and CRP might be misleading without accounting for symptom-specific associations. Conceptually, these findings indicate that studies investigating inflammatory phenotypes of depression should examine how inflammation is simultaneously related both to depression broadly and to specific symptoms, and whether these relations function via different mechanisms. This has the potential to yield new theoretical insights and may lead to the development of novel therapies for reducing inflammation-related symptoms of depression.

C-Reactive Protein and Specific Depression Symptoms Among Older Adults: An Exploratory Investigation of Multi-Plane Networks Using Cross-Sectional Data From NHANES (2017-2020)

INTRODUCTION

Studies investigating the association between C-reactive protein (CRP) and depression among older adults have yielded inconsistent results. We suspect that this may be due to varying associations between CRP and particular depression symptom criteria, and we addressed this challenge using network analysis.

METHODS

We used cross-sectional data from prepandemic National Health and Nutrition Examination Survey questionnaires (2017-2020) and included a sample of 1698 adults aged 65 years or older. Depression symptoms were assessed using the Patient Health Questionnaire-9. Unregularized Mixed Graphical Models were estimated using the R package mgm before and after adjusting for relevant sociodemographic, clinical, and lifestyle covariates.

RESULTS

In the model with no covariates, the only symptom criterion associated with CRP was "appetite problems." This association remained robust after controlling for all covariates. Although not associated with CRP, other criteria such as "fatigue" and "concentration difficulty" showed associations with important covariates for older adults such as white blood cell count or hemoglobin, respectively.

DISCUSSION

The CRP-related variability in the depression symptom network that we have demonstrated may help explain the reported inconsistencies. The present study stands as exploratory, and future research should focus on applying longitudinal designs and including several other inflammatory proteins and covariates that were not measured in the current network model.

Women with lower systemic inflammation demonstrate steeper cognitive decline with age: Results from a large prospective, longitudinal sample

Background

Men and women experience large disparities in prevalence, detection, and clinical course of neurodegenerative diseases. Inflammation has been implicated in the pathogenesis of neurodegenerative diseases, yet there is a paucity of literature documenting sex differences in this phenomenon in prospective, longitudinal studies.

Methods

Participants were 4217 non-smoking individuals (62.2% female; aged 46–91 at enrollment) enrolled in the Health and Retirement Study who provided dried blood spots and completed a standardized assessment of cognitive function 3 times across 8 years. Inflammation was indexed using C-reactive protein (CRP).

Results

Higher CRP was associated with lower concurrent cognitive function, b = −0.13 (SE = 0.06), p < .05, but less decline in cognitive function over time, b = 0.02 (SE = 0.01), p < .05. Sex moderated the association between CRP and decline in total cognitive function, b = 0.02 (SE = 0.01), p < .05, such that the steepest declines in cognitive function were observed among women with the lowest CRP concentrations.

Conclusions

Women with lower systemic inflammation as measured by CRP may be at risk of going undetected for neurodegenerative disease, especially given their overall higher cognitive scores. This may perpetuate sex-related disparities in prevention and clinical course. Attention to the underlying biological mechanisms explaining the link between lower CRP and risk for cognitive decline for women and its potential clinical implications are needed.

•

Sex differences in links between inflammation and cognitive function are under-explored.

•

Higher CRP was associated with lower concurrent cognitive function, only in men.

•

Women with lower CRP showed the steepest declines in cognitive functioning.

Youth depression and inflammation: Cross-sectional network analyses of C-Reactive protein, interleukin-6 and symptoms in a population-based sample

BACKGROUND

Inflammation-related proteins constitute a promising avenue in studying biological correlates of major depressive disorder (MDD). However, MDD is a heterogeneous condition - a crucial aspect to be considered in association studies. We examined whether inflammatory proteins are associated with categorical diagnosis, a dimensional total sum-score, and specific depressive symptoms among youths.

METHODS

We analyzed data from the 1993 Pelotas Birth Cohort, a population-based study in Brazil that followed individuals up to age 22 years. Categorical psychiatric diagnoses were derived using adapted modules of the Mini International Neuropsychiatric Interview (MINI). Dimensional symptomatology was assessed using the Brazilian Portuguese version of the Center for Epidemiological Studies-Depression Scale-Revised (CESD-R). We estimated network structures that included individual depressive symptoms as measured by CESD-R items, peripheral inflammatory markers (C-Reactive Protein [CRP] and Interleukin-6 [IL-6]), as well as relevant covariates.

RESULTS

We evaluated 2586 participants (mean age = 22.5[SD = 0.33]) There were no associations between concentrations of inflammatory proteins and categorical diagnosis of MDD or with CESD-R total sum-scores. In symptom-specific analysis, CRP and IL-6 were positively connected to somatic and cognitive items.

DISCUSSION

We found cross-sectional connections of two commonly studied inflammatory proteins and specific depressive symptoms. Conducting symptom-specific analyses in relation to biological markers might advance our understanding of the heterogeneity of MDD.

C-Reactive protein concentrations in reproductive-aged women with major mood disorders

To examine associations between high sensitivity C-reactive protein (CRP) concentrations and depressive symptoms in reproductive-aged women with mood disorders. Women (N = 86) with major depressive or bipolar disorder in a specialized mood disorders program provided plasma samples which were analyzed for CRP concentrations and categorized by tertiles (T1, low; T2, middle; T3 high). Depressive symptoms were assessed with the Inventory of Depressive Symptoms. We hypothesized that CRP concentrations would be significantly associated with the following: (1) depressive symptoms; (2) pregnancy, (3) body mass index, and (4) counts of white blood cells and absolute neutrophils and percentage of segmented neutrophils. The distribution of CRP concentrations was highly skewed with a median of 2.45 mg/L and an interquartile range 0.90 - 8.17 mg/L. Elevated plasma levels of CRP were not associated with depressive symptoms, which did not differ by tertile group either before or after adjusting for BMI, pregnancy status, and their interactions. Women in T3 had 5 times greater odds of pregnancy compared to women in T1 (p = .021). However, women in T2 had 11% greater BMI on average (p = 0.023), and women in T3 had 47% greater BMI compared to those in T1 (p < 0.001). Women in T3 had higher mean white blood cell counts than those in T1 and T2, the percentage of neutrophils was higher in T2 and T3 compared to T1, and women in T3 had higher absolute neutrophil counts compared to T1. CRP concentrations varied widely and were significantly elevated in reproductive-aged women with high BMI and current pregnancy, but not with depressive symptoms in this sample of depressed women.

Diagnoses Based on C-Reactive Protein Point-of-Care Tests

C-reactive protein (CRP) is an important part of the immune system's reaction to various pathological impulses such as bacterial infections, systemic inflammation, and internal organ failures. An increased CRP level serves to diagnose the mentioned pathological states. Both standard laboratory methods and simple point-of-care devices such as lateral flow tests and immunoturbidimetric assays serve for the instrumental diagnoses based on CRP. The current method for CRP has many flaws and limitations in its use. Biosensor and bioassay analytical devices are presently researched by many teams to provide more sensitive and better-suited tools for point-of-care tests of CRP in biological samples when compared to the standard methods. This review article is focused on mapping the diagnostical relevance of CRP, the applicability of the current analytical methods, and the recent innovations in the measurement of CRP level.

Unconsidered issues of measurement noninvariance in biological psychiatry: A focus on biological phenotypes of psychopathology

There is increasing appreciation that certain biological processes may not be equally related to all psychiatric symptoms in a given diagnostic category. Research on the biological phenotyping of psychopathology has begun examining the etiological and treatment implications of identified biotypes; however, little attention has been paid to a critical methodological implication of these results: measurement noninvariance. Measurement invariance is the ability of an instrument to measure the same construct, the same way, across different people, or across different time points for the same individual. If what a measure quantifies differs across different people (e.g., those with or without a particular biotype) or time points, then it is invalid to directly compare means on that measure. Using a running example of inflammatory phenotypes of depression, we first describe the biological phenotyping of psychopathology. Second, we discuss three types of measurement invariance. Third, we demonstrate how differential biology-symptom associations invariably creates measurement noninvariance using a theoretical example and simulated data (for which code is provided). We also show how this issue can lead to false conclusions about the broader diagnostic construct. Finally, we provide several suggestions for addressing these important issues to help advance the field of biological psychiatry.

Association of inflammation with depression and anxiety: evidence for symptom-specificity and potential causality from UK Biobank and NESDA cohorts

We examined whether inflammation is uniformly associated with all depressive and anxiety symptoms, and whether these associations are potentially causal. Data was from 147,478 individuals from the UK Biobank (UKB) and 2,905 from the Netherlands Study of Depression and Anxiety (NESDA). Circulating C-reactive protein (CRP) was measured in both cohorts and interleukin-6 (IL-6) in NESDA. Genetic instruments for these proteins were obtained from published GWAS and UKB. Depressive and anxiety symptoms were assessed with self-report questionnaires. In NESDA, neurovegetative (appetite, sleep, psychomotor) symptoms were disaggregated as increased vs. decreased. In joint analyses, higher CRP was associated with depressive symptoms of depressed mood (OR = 1.06, 95% CI = 1.05-1.08), altered appetite (OR = 1.25, 95%CI = 1.23-1.28), sleep problems (OR = 1.05, 95%CI = 1.04-1.06), and fatigue (OR = 1.12, 95% CI = 1.11-1.14), and with anxiety symptoms of irritability (OR = 1.06, 95% CI = 1.05-1.08) and worrying control (OR = 1.03, 95% CI = 1.02-1.04). In NESDA, higher IL-6 was additionally associated with anhedonia (OR = 1.30, 95% CI = 1.12-1.52). Higher levels of both CRP (OR = 1.27, 95% CI = 1.13-1.43) and IL-6 (OR = 1.26, 95% CI = 1.07-1.49) were associated with increased sleep. Higher CRP was associated with increased appetite (OR = 1.21, 95% CI = 1.08-1.35) while higher IL-6 with decreased appetite (OR = 1.45, 95% CI = 1.18-1.79). In Mendelian Randomisation analyses, genetically predicted higher IL-6 activity was associated with increased risk of fatigue (estimate = 0.25, SE = 0.08) and sleep problems (estimate = 0.19, SE = 0.07). Inflammation was associated with core depressive symptoms of low mood and anhedonia and somatic/neurovegetative symptoms of fatigue, altered sleep and appetite changes. Less consistent associations were found for anxiety. The IL-6/IL-6R pathway could be causally linked to depression. Experimental studies are required to further evaluate causality, mechanisms, and usefulness of immunotherapies for depressive symptoms.

Difficulties in psychosocial functioning due to current depressive symptoms: What can C-Reactive protein tell us?

Background

Multiple empirical studies and meta-analyses have examined how inflammation may be associated with various aspects of major depression, with older adults being particularly at risk for the effects of inflammation-related depression. Despite this wide area of research, no study has examined how depression-related inflammation impacts psychosocial functioning.

Methods

Data from the National Health and Nutrition Examination Survey, years 2007–2008, were utilized to examine whether adults over the age of 40 experienced difficulty in their work, taking care of things at home, or getting along with other people due to current depressive symptoms through a logistic regression analysis. We selected C-reactive protein (CRP), a common marker of immune system activation, as our primary predictor of interest while controlling for relevant covariates.

Results

Greater CRP was positively associated with a greater risk for individuals experiencing difficulties in psychosocial functioning due to depressive symptoms. While current number and severity of depressive symptoms was also found to be significant in the model, comparison of effect sizes identified that CRP appears to be a more relevant marker for experiencing difficulty than a number of relevant biopsychosocial covariates.

Conclusion

Inflammation as measured by CRP may be a helpful tool in understanding how depressive symptoms are associated with an individual's ability to successfully navigate their social environment. Results here demonstrate the emerging utility of CRP in helping to assess the risk for negative outcomes in those experiencing depressive symptoms, especially as it pertains to older adults.

•

Aimed to evaluate the role of CRP in psychosocial functioning of older adults experiencing current depressive symptoms.

•

Higher CRP levels were positively associated with risk for experiencing psychosocial difficulty due to depressive symptoms.

•

CRP levels above 10 mg/L were associated with a 13.7–55.6% increased risk for experiencing psychosocial difficulties.

Building a replicable and clinically-impactful immunopsychiatry: Methods, phenotyping, and theory integration

Immunopsychiatry is a subfield of psychoneuroimmunology that integrates immunological and psychopathological processes with promise for improving the classification, identification, and treatment of psychopathology. Using research on the relationship between inflammation and depression as a running example, this mini-review will discuss three areas of work that should be emphasized in future research to maximize the replicability and clinical impact of the field: 1) methodology with respect to planning data collection and statistical analyses with measurement properties and conceptually important sources of variance in mind, 2) characterizing inflammatory phenotypes of psychopathology, and 3) the integration of inflammatory processes into robust, extant psychosocial theoretical frameworks of psychopathology risk. Consistent, parallel growth in all three areas will ensure immunopsychiatry research is replicable, contributes to understanding of how (and for whom) the immune system is associated with psychiatric symptoms, and increases the flexibility and power of personalized treatment planning.

Shift work, inflammation and musculoskeletal pain-The HUNT Study

BACKGROUND

Studies have indicated that shift work, in particular night work, is associated with chronic musculoskeletal pain but the mechanisms are unclear. It has been suggested that sleep disturbance, a common complaint among shift and night workers, may induce low-grade inflammation as well as heightened pain sensitivity.

AIMS

Firstly, this study was aimed to examine the cross-sectional associations between shift work, C-reactive protein (CRP) level and chronic musculoskeletal pain, and secondly, to analyse CRP as a mediator between shift work and chronic musculoskeletal pain.

METHODS

The study included 23 223 vocationally active women and men who participated in the HUNT4 Survey of the Trøndelag Health Study (HUNT). Information was collected by questionnaires, interviews, biological samples and clinical examination.

RESULTS

Regression analyses adjusted for sex, age and education revealed significant associations between shift work and odds of any chronic musculoskeletal pain (odd ratio [OR] 1.11, 95% confidence interval [CI] 1.04-1.19), between shift work and CRP level (OR 1.09, 95% CI 1.03-1.16) and between CRP level 3.00-10 mg/L and any chronic musculoskeletal pain (OR 1.38, 95% CI 1.27-1.51). Shift work and CRP were also associated with number of chronic pain sites. Mediation analysis indicated that shift work was indirectly associated with any chronic musculoskeletal pain through CRP (OR 1.03, 95% CI 1.01-1.06).

CONCLUSIONS

The results support the hypothesis that shift work is associated with chronic musculoskeletal pain, and that systemic inflammation may be a biological mechanism linking shift work to chronic pain.

Lost in translation. The quest for definitions of treatment-resistant depression with a focus on inflammation-related gene expression

Approximately one third of individuals with major depressive disorder (MDD) do not respond to antidepressant treatments; but what does treatment-resistant depression (TRD) mean? With this article, I aim to provide an overview of the clinical and operational criteria currently used to define TRD, highlighting core gaps in knowledge and open questions to be addressed in order to drive future research in the field. Importantly, a better definition of TRD must include a better characterization of the biological and molecular correlates of non-response. Among these potential biomarkers, compelling evidence reveals a potential role of inflammation-related gene expression signatures. A more accurate clinical and etiopathological characterization of TRD subjects may help to identify biologically based MDD clinical phenotypes to be targeted in future research and finally achieve better outcomes.

Major Depressive Disorder in Older Patients as an Inflammatory Disorder: Implications for the Pharmacological Management of Geriatric Depression

Depression is a common and highly disabling condition in older adults. It is a heterogenous disorder and there is emerging evidence of a link between inflammation and depression in older patients, with a possible inflammatory subtype of depression. Persistent low-level inflammation, from several sources including psychological distress and chronic disease, can disrupt monoaminergic and glutaminergic systems to create dysfunctional brain networks. Despite the evidence for the role of inflammation in depression, there is insufficient evidence to recommend use of any putative anti-inflammatory agent in the treatment of depression in older adults at this stage. Further characterisation of markers of inflammation and stratification of participants with elevated rates of inflammatory markers in treatment trials is needed.

Inflammatory phenotype of depression symptom structure: A network perspective

BACKGROUND

There has been increasing interest in classifying inflammatory phenotypes of depression. Most investigations into inflammatory phenotypes only have tested whether elevated inflammation is associated with elevated levels of depression symptoms, or risk for a diagnosis. This study expanded the definition of phenotype to include the structure of depression symptoms as a function of inflammation.

METHODS

Network models of depression symptoms were estimated in a sample of 4157 adults (mean age = 47.6, 51% female) from the 2015-2016 National Health and Nutrition Examination Survey (NHANES). Analyses included comparisons of networks between those with elevated (C-reactive protein (CRP) values ≥ 3.0 mg/L; N = 1696) and non-elevated CRP (N = 2841) as well as moderated network models with CRP group status and raw CRP values moderating the associations between depression symptoms.

RESULTS

Differences emerged at all levels of analysis (global, symptom-specific, symptom-symptom associations). Specifically, the elevated CRP group had greater symptom connectivity (stronger total associations between symptoms). Further, difficulty concentrating and psychomotor difficulties had higher expected influence (concordance with other symptoms) in the elevated CRP group. Finally, there was evidence that several symptom-symptom associations were moderated by CRP.

CONCLUSIONS

This study provides consistent evidence that the structure of depression symptoms varies as a function of CRP levels. Greater symptom connectivity might contribute to why elevated CRP is associated with treatment-resistant depression. Additionally, differences in symptom structure might highlight different maintenance mechanisms and treatment targets for individuals with compared to those without elevated CRP. Finally, differences in symptom structure as a function of CRP highlight a potential misalignment of standard depression measures (the structure of which are evaluated on groups unselected for CRP levels) and the presentation of depression symptoms in those with elevated CRP.

Personality pathways to mortality: Interleukin-6 links conscientiousness to mortality risk

Personality is associated consistently with mortality hazards, but the physiological pathways are not yet clear. Immune system dysregulation may be one such pathway due to its role in age-related morbidity and mortality. In this preregistered study, we tested whether interleukin-6 (IL-6) and C-reactive protein (CRP) mediated the associations between personality traits and mortality hazards. The sample included 957 participants (M ± SD = 58.65 ± 11.51 years; range = 35-86 years) from the Midlife in the United States Survey that had 14 years of follow-up. Higher conscientiousness was associated with lower mortality hazards, with each one standard deviation higher conscientiousness associated with a 35% lower mortality risk. IL-6, but not CRP, partially mediated this association, with IL-6 accounting for 18% of this association in the fully adjusted model. While there was initial evidence that the biomarkers mediated both neuroticism and agreeableness and mortality risk, the indirect effects were not significant when controlling for the sociodemographic variables. Taken together, higher conscientiousness may lead to a longer life partially as a result of lower IL-6. This work highlights the importance of biological pathways that link personality to future mortality risk.

Treatment-Resistant Depression Revisited: A Glimmer of Hope

Major Depressive Disorder (MDD) is a highly prevalent psychiatric disorder worldwide. It causes individual suffering, loss of productivity, increased health care costs and high suicide risk. Current pharmacologic interventions fail to produce at least partial response to approximately one third of these patients, and remission is obtained in approximately 30% of patients. This is known as Treatment-Resistant Depression (TRD). The burden of TRD exponentially increases the longer it persists, with a higher risk of impaired functional and social functioning, vast losses in quality of life and significant risk of somatic morbidity and suicidality. Different approaches have been suggested and utilized, but the results have not been encouraging. In this review article, we present new approaches to identify and correct potential causes of TRD, thereby reducing its prevalence and with it the overall burden of this disease entity. We will address potential contributory factors to TRD, most of which can be investigated in many laboratories as routine tests. We discuss endocrinological aberrations, notably, hypothalamic-pituitary-adrenal (HPA) axis dysregulation and thyroid and gonadal dysfunction. We address the role of Vitamin D in contributing to depression. Pharmacogenomic testing is being increasingly used to determine Single Nucleotide Polymorphisms in Cytochrome P450, Serotonin Transporter, COMT, folic acid conversion (MTHFR). As the role of immune system dysregulation is being recognized as potentially a major contributory factor to TRD, the measurement of C-reactive protein (CRP) and select immune biomarkers, where testing is available, can guide combination treatments with anti-inflammatory agents (e.g., selective COX-2 inhibitors) reversing treatment resistance. We focus on established and emerging test procedures, potential biomarkers and non-biologic assessments and interventions to apply personalized medicine to effectively manage treatment resistance in general and TRD specifically.