Replication and reproducibility issues in the relationship between C-reactive protein and depression: A systematic review and focused meta-analysis

Does Emotional Distress Predict Worse Glycemic Control Over Time? Results From the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE)

OBJECTIVE

To evaluate whether baseline levels of depressive symptoms and diabetes-specific distress are associated with glycemic control in Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE), a large randomized controlled trial comparing the metabolic effects of four common glucose-lowering medications when combined with metformin in individuals with type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

The primary and secondary outcomes were defined as an HbA1c value ≥7%, subsequently confirmed, and an HbA1c value >7.5%, subsequently confirmed, respectively. Separate Cox proportional hazards models assessed the association between baseline levels of each exposure of interest (depressive symptoms measured with the eight-item Patient Health Questionnaire and diabetes distress measured with the Diabetes Distress Scale) and the subsequent risk of metabolic outcomes.

RESULTS

This substudy included 1,739 participants (56% of whom were non-Hispanic White, 18% non-Hispanic Black, 17% Hispanic, and 68% male; mean [SD] age 58.0 [10.2] years, diabetes duration 4.2 [2.8] years, and HbA1c 7.5% [0.48%]). A total of 1,157 participants reached the primary outcome, with time to event of 2.1 years on average, while 738 participants reached the secondary outcome at 3 years on average. With adjustment for sex, race/ethnicity, treatment group, baseline age, duration of T2DM, BMI, and HbA1c, there were no significant associations between the depressive symptoms or diabetes distress and the subsequent risk of the primary or secondary outcomes.

CONCLUSIONS

The current findings suggest that, at least for individuals with diabetes of relatively short duration, baseline levels of emotional distress are not associated with glycemic control over time.

Increased C-Reactive Protein in Patients with Post-Stroke Depression: A Meta-analysis of Cohort Study

Background

Pathophysiological mechanisms and related biological markers for post-stroke depression (PSD) are unknown. Some studies have noted that C-reactive protein (CRP) is activated in the serum of PSD patients. We aim to quantitatively summarize the concentrations of CRP in PSD patients compared to non-PSD patients.

Methods

Original studies evaluating the association between CRP and PSD were searched in 4 specific databases from the establishment of the databases to March 2023. RevMan 5.20 and Stata 11.0 statistical software were used for meta-analysis. Publication bias was tested by Egger's test. The CRP level were combined by standardized mean difference (SMD) with 95% confidence interval (CI).

Results

A total of 43 relevant literatures were retrieved, while 13 cohort studies were collected. The heterogeneity test result of the level of CRP in patients with PSD vs. non-PSD was (Q = 98.38, P < .001, I2 = 88%). The combined value of the estimated effect was [SMD = 0.34, 95% CI (0.12-0.56); P = .003]. Sensitivity analysis indicated that no study had a remarkable influence on the result of the pooled estimate. Egger's test was used to test the bias and the result was (Egger's test, P = .548), suggesting that there was no publication bias, and the results were credible. We found that different depression evaluation criteria (P = .035) and stroke types (P = .024) were considered as influencing factors for potential sources of heterogeneity.

Conclusion

In conclusion, compared to those without depressive symptoms, patients with post-stroke depression have higher concentrations of CRP in the blood.

The association between lymphocyte to high-density lipoprotein ratio and depression: Data from NHANES 2015-2018

INTRODUCTION

The relationship of lymphocyte to high-density lipoprotein ratio (LHR) with depression remains uncertain. We aimed to evaluate the association between LHR and depression in US adults.

METHODS

In this cross-sectional study, a total of 4216 participants were enrolled from the National Health and Nutrition Examination Survey (2015-2018). Depressive symptoms were measured with the Patient Health Questionnaire-9 (PHQ-9). Participants were classified as having depression if PHQ-9 scores were ≥10. Multiple logistic regression models were used to explore the relationship between the LHR and depression.

RESULTS

Overall, the LHR was significantly associated with depression (per standard deviation increment; adjusted odds ratio (OR), 1.31; 95% confidence interval (CI) [1.14, 1.50]) after adjusted potential variables. Interactions between LHR with metabolic syndrome (MetS) and body mass index (BMI) on the risk of depression were found in stratified analysis (p for interaction < .05).

CONCLUSIONS

A higher level of LHR was significantly associated with higher odds of having depression in US adults, and it was strengthened in participants with MetS or BMI ranging from 25 to 30 kg/m2 .

Mood and microbes: a comprehensive review of intestinal microbiota's impact on depression

Depression is considered a multifaceted and intricate mental disorder of growing concern due to its significant impact on global health issues. The human gut microbiota, also known as the "second brain," has an important role in the CNS by regulating it through chemical, immunological, hormonal, and neurological processes. Various studies have found a significant bidirectional link between the brain and the gut, emphasizing the onset of depression therapies. The biological and molecular processes underlying depression and microbiota are required, as the bidirectional association may represent a novel study. However, profound insights into the stratification and diversity of the gut microbiota are still uncommon. This article investigates the emerging evidence of a bacterial relationship between the gut and the brain's neurological system and its potential pathogenicity and relevance. The interplay of microbiota, immune system, nervous system neurotransmitter synthesis, and neuroplasticity transitions is also widely studied. The consequences of stress, dietary fibers, probiotics, prebiotics, and antibiotics on the GB axis are being studied. Multiple studies revealed the processes underlying this axis and led to the development of effective microbiota-based drugs for both prevention and treatment. Therefore, the results support the hypothesis that gut microbiota influences depression and provide a promising area of research for an improved knowledge of the etiology of the disease and future therapies.

Longitudinal associations between dimensions of maltreatment and internalizing symptoms in late adolescence: The role of inflammation during the COVID-19 pandemic

Childhood adversity and depression have been linked with heightened inflammation. However, few longitudinal studies examine how dimensions of maltreatment (i.e., abuse and neglect) differentially impact pathways to heightened inflammation and internalizing symptoms. The present study examined effects of abuse and neglect on (1) internalizing symptoms through inflammation, and (2) on inflammation through internalizing symptoms across 3 years of adolescence in the context of the COVID-19 pandemic. In a sample of 78 adolescents, significant indirect effects revealed that childhood abuse, not neglect, significantly predicted future internalizing symptoms, which predicted future heighted C-reactive protein (CRP). Using prospective longitudinal data, these findings emphasize the importance of examining distinct forms of maltreatment in understanding the developmental pathways connecting early adversity, internalizing symptoms, and inflammation.

Monomeric C-reactive protein as a biomarker for major depressive disorder

Neuroinflammation has been postulated to be a key factor in the pathogenesis of major depressive disorder (MDD). With this is mind, there has been a wave of research looking into pro-inflammatory mediators as potential biomarkers for MDD. One such mediator is the acute phase protein, C-reactive protein (CRP). While several studies have investigated the potential of CRP as a biomarker for MDD, the results have been inconsistent. One explanation for the lack of consistent findings may be that the high-sensitivity CRP tests utilized in these studies only measure the pentameric isoform of CRP (pCRP). Recent research, however, has indicated that the monomeric isoform of CRP (mCRP) is responsible for the pro-inflammatory function of CRP, while pCRP is weakly anti-inflammatory. The objective of this minireview is to re-examine the evidence of CRP involvement in MDD with a view of mCRP as a potential biomarker.

The effects of childhood maltreatment on social support, inflammation, and depressive symptoms in adulthood

RATIONALE

Social Safety Theory (SST) suggests that social threats increase inflammation, exacerbating health risks, but that social support may decrease inflammatory signaling. One of the key health problems affected by both social forces and inflammation is major depression.

OBJECTIVE

The present study sought to test aspects of the SST, to understand how social support and inflammation may mediate the effects of childhood maltreatment on depressive symptoms in adulthood.

METHODS

This study utilized data from the national Midlife Development in the United States study (n = 1969; mean age 53; 77.2% White; 53.6% female) to model the effects of childhood maltreatment on depressive symptoms in adulthood and the potential serial mediating effects of social support and inflammation. Analyses were conducted via structural equation modeling, using the four subscales of the Center for Epidemiologic Studies Depression Scale to indicate depressive symptoms, the five subscales of the Childhood Trauma Questionnaire to indicate childhood maltreatment, and the Positive Relations Scale and a network level measure of support as indicators of social support. Inflammation was indexed using C-reactive protein (CRP). The model was estimated via maximum likelihood with robust standard errors and significance of indirect effects were assessed via a Sobel test.

RESULTS

Childhood maltreatment was associated with increased depressive symptoms and CRP but decreased social support. Social support was associated with decreased depressive symptoms while CRP was associated with increased depressive symptoms. Assessing indirect effects yielded no serial mediation effect; however, a significant indirect effect from childhood maltreatment to depressive symptoms through social support was identified.

CONCLUSIONS

Analyses indicate mixed support for the SST with respect to depressive symptoms. Results highlight the role of social support in mitigating the effects depressive symptoms in adulthood; although, alternative strategies may be needed to decrease the effects of childhood maltreatment on inflammation as indexed by CRP.

Association between psychosocial factors and C-reactive protein across income, race, and sex

OBJECTIVE

A health disparity is a health difference that adversely affects disadvantaged populations, and thus could plausibly be due to social factors. Biopsychosocial processes that contribute to health disparities are not well-understood. Establishing whether candidate biomarkers are similarly associated with biologically relevant psychosocial constructs across health disparity groups is a current gap in our understanding.

METHOD

This study examined associations between perceived stress, depressive symptoms, and social support with C-reactive protein (CRP) and whether associations varied by race, sex, or income in 24,395 Black and White adults aged 45 years or older from the REGARDS population-based national cohort.

RESULTS

The association between depressive symptoms and CRP was slightly larger at higher (vs. lower) income levels and larger for men (vs. women) but did not vary by race. Associations between stress and CRP and social support and CRP were not moderated by income, race, or sex. An interaction between race and income, evidenced that higher income was more strongly associated with lower CRP in White participants compared to Black participants, consistent with the idea of "diminishing returns" of income for the health of Black Americans.

CONCLUSIONS

Basic associations between these psychosocial factors and CRP are small and generally similar across income, race, and sex. Black and lower-income Americans likely evidence higher CRP due to greater exposure to psychosocial risk factors rather than increased biological vulnerability to these exposures. Additionally, given small associations, CRP should not be used as a proxy for the construct of psychosocial stress. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Social Media Use and Its Concurrent and Subsequent Relation to a Biological Marker of Inflammation: Short-Term Longitudinal Study

BACKGROUND

Although many studies have examined the impact of social media use (SMU) on mental health, very few studies have examined the association of SMU with health-relevant biomarkers.

OBJECTIVE

Addressing this gap, we conducted a short-term longitudinal study examining the link between SMU and C-reactive protein (CRP), a biological marker of systemic inflammation predictive of major depression, chronic diseases, and mortality.

METHODS

We measured college students' weekly amount of SMU for 5 consecutive weeks objectively via the Screen Time app and collected blood samples at baseline and 5 weeks later.

RESULTS

In separate cross-sectional analyses conducted at phase 1 (baseline) and at phase 2 (5 weeks after baseline), objective SMU had a positive, concurrent association with CRP at both time points. Critically, in a longitudinal analysis, more SMU between phase 1 and phase 2 predicted increased CRP between these time points, suggesting that increased SMU led to heightened inflammation during that period.

CONCLUSIONS

Although more research is needed to understand why SMU led to higher inflammation, the association between objective SMU and a marker of a biological process critical to physical health presents an intriguing opportunity for future research on social media effects.

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.

Incorporating causal inference perspectives into psychoneuroimmunology: A simulation study highlighting concerns about controlling for adiposity in immunopsychiatry

Psychoneuroimmunology and immunopsychiatry are quickly approaching a critical point where the clinical translatability of their evidence base will be tested. To maximize chances for translational success, we believe researchers must adopt causal inference techniques that augment the causal relevance of estimates given theorized causal structures. To illustrate the utility of incorporating causal inference perspectives into psychoneuroimmunology, we applied directed acyclic graphs and a combination of empirical and simulated data to demonstrate the consequences of controlling for adiposity when testing the association between inflammation and depression under the plausible causal structure of increases in adipose tissue leading to greater inflammation that in turn promotes depression. Effect size estimates were pulled from a dataset combining the Midlife in the United States 2 (MIDUS-2) and MIDUS Refresher datasets. Data were extracted and used to simulate data reflecting an adiposity → inflammation → depression causal structure. Next, a Monte Carlo simulation study with 1,000 iterations and three sample size scenarios (Ns = 100, 250, and 500) was conducted testing whether controlling for adiposity when estimating the relation between inflammation and depression influenced the precision of this estimate. Across all simulation scenarios, controlling for adiposity reduced precision of the inflammation → depression estimate, suggesting that researchers primarily interested in quantifying inflammation → depression associations should not control for adiposity. This work thus underscores the importance of incorporating causal inference approaches into psychoneuroimmunological research.

Association between platelet to lymphocyte ratio and depression and symptom severity among adults in the United States: A cross-sectional study

Background

The pathogenesis of depression has not yet been fully understood. The association between platelet to lymphocyte ratio (PLR) and depression has been investigated in previous studies, however, the results were controversial. The objective of the study was to explore the potential relationship between PLR and depression and symptom severity.

Methods

A cross-sectional study was conducted based on the National Health and Nutrition Examination Survey (NHANES) data from 2005 to 2018. Totally 30,032 adults were analyzed, and 2480 reported depression. Depression and symptom severity were assessed with the Patient Health Questionnaire (PHQ-9). PLR was calculated as the ratio of platelets to lymphocytes. Multivariable weighted-logistic regression models and generalized additive model (GAM) were employed to evaluate the linear and nonlinear association between PLR and depression and symptom severity.

Results

There was a negative association for Q3 (odds ratio [OR]: 0.82, 95% confidence interval [CI]: 0.68 to 0.99) when comparing participants for Q1 between 10-PLR and depression after fully adjusting the covariates; however, there was no significant association between 10-PLR and symptom severity. GAM showed that 10-PLR was associated with depression and symptom severity in a nonlinear manner. The inflection points were at 12.15. Subgroup analyses showed nonlinear relationships only in specific subgroups. Conclusions: PLR is associated with depression among adults in the United States. U-shaped nonlinear relationships and threshold effects were observed between 10-PLR and depression and symptom severity. Additionally, inflammatory mechanisms vary in different sociodemographic subgroups.

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.

Interpersonal Life Stress and Inflammatory Reactivity as Prospective Predictors of Suicide Attempts in Adolescent Females

Adolescents' suicidal behavior frequently is preceded by interpersonal stress, but not all who experience distress attempt to end their lives. Recent theories have posited individual differences in stress-related inflammatory reactivity may be associated with psychopathology risk; this study examined inflammatory reactivity as a moderator of the prospective association between interpersonal stress and adolescents' suicidal behavior. Participants included 157 at-risk adolescent females (ages 12 to 16 years) and assessed individual differences in proinflammatory cytokine responses to a brief laboratory-based social stressor, both interpersonal and non-interpersonal life events, and suicidal behavior over an 18-month follow-up period. Measuring levels of the key proinflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) before and after an experimentally-induced social stressor, results revealed that blunted cytokine reactivity heightened the effect of high interpersonal stress exposure on risk for suicidal behaviors over the subsequent 9 months. Significant effects were not revealed for non-interpersonally themed stress. Finding highlight the urgent need for more research examining inflammation reactivity among adolescents.

Association between neutrophil to lymphocyte ratio and erectile dysfunction among US males: a population-based cross-sectional study

Objective

The purpose of the study was to investigate the relationship between neutrophil-to-lymphocyte ratio (NLR) and erectile dysfunction (ED) in adult American males using a large database.

Methods

We adopted a series of statistical analyses of the relationship between NLR indices and ED prevalence among participants in the 2001-2004 National Health and Nutrition Examination Survey (NHANES) database using the R software.

Results

The study included a total of 3012 participants, of whom 570 (18.9%) presented with ED. NLR levels were 2.13 (95% CI: 2.08,2.17) in those without ED and 2.36 (95% CI: 2.27,2.45) in those with ED. After adjusting for confounding variables, NLR levels were higher in patients with ED, (β, 1.21, 95% CI, 1.09-1.34, P < 0.001). In addition, a U-shaped relationship between NLR and ED was observed after controlling for all confounders. A more significant correlation (β, 1.35, 95% CI, 1.19 to 1.53, P < 0.001) existed to the right of the inflection point (1.52).

Conclusion

The results of the large cross-sectional study showed a statistically significant association between the occurrence of ED and NLR, a simple, inexpensive, and readily available parameter of inflammation, in US adults. Further studies are still needed in the future to validate and replicate our findings and to investigate the specific mechanisms involved.

Eveningness chronotype and depressive affective temperament associated with higher high-sensitivity C-reactive protein in unipolar and bipolar depression

BACKGROUND

Several studies investigated the role of inflammation in the etiopathogenesis of mood disorders. The aim of our cross-sectional study is evaluating baseline high-sensitivity C-reactive-protein (hsCRP) levels in a cohort of unipolar and bipolar depressive inpatients, in relation with psychopathological, temperamental and chronotype features.

METHODS

Among 313 screened inpatients, we retrospectively recruited 133 moderate-to-severe depressive patients who were assessed for hsCRP levels, chronotype with Morningness-Eveningness Questionnaire (MEQ) and affective temperament with Temperament Evaluation of Memphis, Pisa, Paris and San Diego (TEMPS).

LIMITATIONS

The cross-sectional and retrospective design of the study, the small sample size, the exclusion of hypomanic, maniac and euthymic bipolar patients.

RESULTS

hsCRP levels were significantly higher among those with previous suicide attempt (p = 0.05), death (p = 0.018) and self-harm/self-injury thoughts (p = 0.011). Linear regression analyses, adjusted for all covariates, demonstrated that higher scores at the TEMPS-M depressive, while lower scores at the hyperthymic and irritable affective temperaments [F = 88.955, R² = 0.710, p < 0.001] and lower MEQ scores [F = 75.456, R² = 0.405, p < 0.001] statistically significantly predicted higher hsCRP.

CONCLUSION

Eveningness chronotype and a depressive affective temperament appeared to be associated with higher hsCRP levels during moderate-to-severe unipolar and bipolar depression. Further longitudinal and larger studies should better characterise patients with mood disorders by investigating the influence of chronotype and temperament.

Inflammation, stress and depression: An exploration of ketamine's therapeutic profile

Well-established animal models of depression have described a proximal relationship between stress and central nervous system (CNS) inflammation - a relationship mirrored in the peripheral inflammatory biomarkers of individuals with depression. Evidence also suggests that stress-induced proinflammatory states can contribute to the neurobiology of treatment-resistant depression. Interestingly, ketamine, a rapid-acting antidepressant, can partially exert its therapeutic effects via anti-inflammatory actions on the hypothalamic-pituitary adrenal (HPA) axis, the kynurenine pathway or by cytokine suppression. Further investigations into the relationship between ketamine, inflammation and stress could provide insight into ketamine's unique therapeutic mechanisms and stimulate efforts to develop rapid-acting, anti-inflammatory-based antidepressants.

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.

Lack of bidirectional association between C-reactive protein and depressive symptoms in middle-aged and older adults: Results from a nationally representative prospective cohort study

Depression is associated with low quality of life and increased health burdens for middle-aged and older adults in resource-limited settings. Although inflammation plays an etiological role in the development and progression of depression, the directionality of the inflammation-depression relationship is unclear, especially in non-Western populations. To examine this relationship among community-dwelling Chinese middle-aged and older adults, we obtained data from the 2011, 2013, and 2015 China Health and Retirement Longitudinal Study (CHARLS). The participants were aged 45 years or above at baseline in 2011 and completed the follow-up survey in 2013 and 2015. Depressive symptoms were measured using the 10-item Center for Epidemiologic Studies Depression Scale (CESD-10), and the C-reactive protein (CRP) level was used to measure individual inflammation levels. Cross-lagged regression analyses examined the inflammation-depression relationship. Cross-group analyses were performed to test for model invariance across the sexes. Pearson's correlations revealed no concurrent correlations between depression and CRP for both 2011 and 2015 (ps > 0.05, ranging 0.07-0.36) studies. Cross-lagged regression path analyses revealed that the paths from baseline CRP to depression in 2013 (ß_std  = -0.01, p = 0.80), from baseline CRP to depression in 2015 (ß_std  = 0.02, p = 0.47), from baseline depression to CRP in 2015 (ß_std  = -0.02, p = 0.40), and from depression at 2013 to CRP in 2015 (ß_std  = 0.03, p = 0.31) were not statistically significant. Additionally, the autoregressive model did not vary across the sexes (△χ ² = 78.75, df = 54, p = 0.02, △ comparative fit index (CFI) <0.01). We failed to find a bidirectional association between the CRP levels and depressive symptoms in our sample.

Associations of perceived stress, depressive symptoms, and caregiving with inflammation: a longitudinal study

OBJECTIVES

Higher inflammation has been linked to poor physical and mental health outcomes, and mortality, but few studies have rigorously examined whether changes in perceived stress and depressive symptoms are associated with increased inflammation within family caregivers and non-caregivers in a longitudinal design.

DESIGN

Longitudinal Study.

SETTING

REasons for Geographic And Racial Differences in Stroke cohort study.

PARTICIPANTS

Participants included 239 individuals who were not caregivers at baseline but transitioned to providing substantial and sustained caregiving over time. They were initially matched to 241 non-caregiver comparisons on age, sex, race, education, marital status, self-rated health, and history of cardiovascular disease. Blood was drawn at baseline and approximately 9.3 years at follow-up for both groups.

MEASUREMENTS

Perceived Stress Scale, Center for Epidemiological Studies-Depression, inflammatory biomarkers, including high-sensitivity C-reactive protein, D dimer, tumor necrosis factor alpha receptor 1, interleukin (IL)-2, IL-6, and IL-10 taken at baseline and follow-up.

RESULTS

Although at follow-up, caregivers showed significantly greater worsening in perceived stress and depressive symptoms compared to non-caregivers, there were few significant associations between depressive symptoms or perceived stress on inflammation for either group. Inflammation, however, was associated with multiple demographic and health variables, including age, race, obesity, and use of medications for hypertension and diabetes for caregivers and non-caregivers.

CONCLUSIONS

These findings illustrate the complexity of studying the associations between stress, depressive symptoms, and inflammation in older adults, where these associations may depend on demographic, disease, and medication effects. Future studies should examine whether resilience factors may prevent increased inflammation in older caregivers.

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.

The Link Between Positive and Negative Parenting Behaviors and Child Inflammation: A Systematic Review

Children's inflammation may be an important link between parenting behaviors and health outcomes. The aims of this systematic review were to: (1) describe associations between parenting behaviors and child inflammatory markers, and (2) evaluate the relevance of existing literature to the review question. Database searches identified 19 studies that included a measure of positive or negative parenting behaviors and a marker of child inflammation, 53% of which measured parental responsiveness/warmth. Greater parental responsiveness/warmth was associated with lower levels of child pro-inflammatory markers in 60% of studies. Across studies, the association between parenting and child inflammation varied as a function of parenting construct, inflammatory measure, and sample characteristics. Studies were highly relevant, with 42% rated 5 + out of 6 for study's ability to address links between parenting behavior and child inflammation. If future research uncovers causal effects of parenting behaviors on inflammation, parenting interventions could be employed as a preventative tool.

Adolescent Psychological Assets and Cardiometabolic Health Maintenance in Adulthood: Implications for Health Equity

Background Positive cardiometabolic health (CMH) is defined as meeting recommended levels of multiple cardiometabolic risk factors in the absence of manifest disease. Prior work finds that few individuals-particularly members of minoritized racial and ethnic groups-meet these criteria. This study investigated whether psychological assets help adolescents sustain CMH in adulthood and explored interactions by race and ethnicity. Methods and Results Participants were 3478 individuals in the National Longitudinal Study of Adolescent Health (49% female; 67% White, 15% Black, 11% Latinx, 6% other [Native American, Asian, or not specified]). In Wave 1 (1994-1995; mean age=16 years), data on 5 psychological assets (optimism, happiness, self-esteem, belongingness, and feeling loved) were used to create a composite asset index (range=0-5). In Waves 4 (2008; mean age=28 years) and 5 (2016-2018; mean age=38 years), CMH was defined using 7 clinically assessed biomarkers. Participants with healthy levels of ≥6 biomarkers at Waves 4 and 5 were classified as maintaining CMH over time. The prevalence of CMH maintenance was 12%. Having more psychological assets was associated with better health in adulthood (odds ratio [OR]_{linear trend}, 1.12 [95% CI, 1.01-1.25]). Subgroup analyses found substantive associations only among Black participants (OR, 1.35 [95% CI, 1.00-1.82]). Additionally, there was some evidence that racial and ethnic disparities in CMH maintenance may be less pronounced among participants with more assets. Conclusions Youth with more psychological assets were more likely to experience favorable CMH patterns 2 decades later. The strongest associations were observed among Black individuals. Fostering psychological assets in adolescence may help prevent cardiovascular disease and play an underappreciated role in shaping health inequities.

C-Reactive Protein (CRP): A Potent Inflammation Biomarker in Psychiatric Disorders

An increasing number of studies have investigated the role of inflammation in psychiatric disorders, by demonstrating how an altered/dysfunctional immunological and inflammatory system may underpin a psychiatric condition. Particularly, several studies specifically investigated the role of a neuroinflammatory biomarker, named C-reactive protein (CRP), in psychiatric disorders. Overall, even though scientific literature so far published still does not appear definitive, CRP is more likely reported to be elevated in several psychiatric disorders, including schizophrenia, mood disorders, anxiety disorders and post-traumatic stress disorder. Moreover, a low-grade inflammation (CRP >3 mg/L) has been more likely observed in a subgroup of patients affected with a more severe psychopathological symptomatology, more treatment resistance and worst clinical mental illness course, strengthening the hypothesis of the need for a different clinical and prognostic characterization based on this concomitant neuroinflammatory predisposition. However, even though further research studies are needed to confirm this preliminary evidence, CRP may represent a potential clinical routine biomarker which could be integrated in the clinical routine practice to better characterize clinical picture and course as well as address clinicians towards a personalized treatment.

Association between neutrophil to lymphocyte ratio and depression among US adults: From a large population-based cross-sectional study

OBJECTIVE

The study aims to determine the association between neutrophil to lymphocyte ratio (NLR) and depression and severity.

METHODS

We conducted a cross-sectional analysis of the National Health and Nutrition Examination Survey (NHANES). The Patient Health Questionnaire (PHQ-9) was administered to assess depression and its severity. NLR was calculated as a neutrophil count-to-lymphocyte count ratio.

RESULTS

The study included 22,207 adults (mean age, 44.43 years; women, 51.05%), and 1671 (6.54%) reported depression. The association between NLR and depression was not significant (odds ratio [OR], 1.06, 95% confidence interval [CI], 0.98 to 1.15, p = 0.12) after fully adjusting the covariates, and similar results (Q1 reference Vs Q2: OR, 0.87, 95%CI, 0.70 to 1.07 Vs Q3: OR, 0.99, 95%CI, 0.80 to 1.21 Vs Q4: OR, 1.08, 95%CI, 0.86 to 1.35, p for trend 0.21) when NLR as a categorical variable. After controlling for all confounding variables, a U-shaped relationship between NLR and depression severity was observed, and the inflection point was 1.78. Subgroup analyses showed a significant association among Mexican American/other Hispanic (OR, 1.13, 95%CI, 1.00 to 1.28, p = 0.04), non-Hispanic blacks (OR, 1.18, 95%CI, 1.07 to 1.32, p = 0.002), the subjects with poverty income ratio above four (OR, 1.24, 95%CI, 1.00 to 1.53, p = 0.048) between NLR and depression. The results from the sensitivity analyses remained stable.

CONCLUSION

The association between NLR and depression is not general across depressed populations among US adults. This association may be specific to subgroups. The relationship between NLR and depression severity is non-linear.

The pro-inflammatory factors contribute to the EEG microstate abnormalities in patients with major depressive disorder

Pro-inflammatory factors may be associated with abnormalities in functional brain networks, which may be a mechanism in the pathogenesis of major depressive disorder (MDD). Electroencephalogram (EEG) microstates reflect the functioning of brain networks. However, the relationship between pro-inflammatory factors and the microstate abnormalities in patients with MDD is poorly understood. 24 MDD patients and 24 age-and sex-matched healthy controls (HC) were recruited. Montgomery-Asberg Depression Rating Scale(MADRS) were assessed. Serum (interleukin- 2(IL- 2), tumor necrosis factor-α (TNF-α) and hs-C-reactive protein (CRP)and EEG data were collected. K-means clustering was performed to characterize different microstates. For each microstate, duration, occurrence and coverage were estimated. Four microstates (e.g. A, B, C, D) were characterized, MDD group showed lower duration, occurrence and coverage of microstate B and microstate D, while higher duration of microstate A and microstate C and levels of IL-2, TNF-α, hs-CRP than HC group. The duration, occurrence and coverage of microstate D were negatively correlated with levels of pro-inflammatory factors (IL-2, TNF- α and hs- CRP) (all P < 0.05). Serum pro-inflammatory induced the abnormalities of microstate D. Together, these findings add to the understanding of the pathophysiology of MDD and point to pro-inflammatory factors contribute to EEG microstate abnormalities in patients with MDD.

Salivary immune markers are not associated with self-reported childhood maltreatment or psychopathology in adults

BACKGROUND

Psychological stress has repeatedly been found to be associated with pro-inflammatory markers in blood, and neuro-inflammation may play a role in the development of psychopathology after early life stress. Salivary immune testing is a novel method to non-invasively assess immune functioning. We examined a large range of salivary immune markers in relation to self-reported childhood maltreatment and psychopathology in an adult sample.

METHODS

Participants (N = 118, 51% female, mean age = 46.6 yrs, range 22-64) were drawn from a cross-sectional three-generation study, and supplied 2 ml of saliva via passive drool. They reported on childhood maltreatment experiences and on psychopathological symptoms in the last 6 months. Hair cortisol was additionally assessed in a subsample (n = 68). Levels of IL1ß, IL6, IL8, IFNγ, TNFα, tIgE, sIgA, FLCƛ, and FLCƙ were assessed.

RESULTS

Linear mixed model analyses showed that several salivary immune markers were associated with age (sIgA and IgE), BMI (sIgA, IL1ß, and IL6), sex (FLCs and IgE), and bad health (IL6, IL8, TNFα). No associations with (anti-inflammatory) medication use or oral health problems were found. Notably, no associations between the immune markers and self-reported childhood maltreatment, psychopathology, or hair cortisol were found.

CONCLUSIONS

Salivary immune measures were found to be sensitive to individual differences in age, sex, health and BMI. However. in the current sample there was no indication of inflammation in relation to chronic psychological stress. Larger studies, including participants with higher stress levels, are needed to further examine associations between salivary immune markers and psychological stress.

C-Reactive protein and the kynurenic acid to quinolinic acid ratio are independently associated with white matter integrity in major depressive disorder

Kynurenic acid (KynA) and quinolinic acid (QA) are neuroactive kynurenine pathway (KP) metabolites that have neuroprotective and neurotoxic properties, respectively. At least partly as a result of immune activation, the ratio of KynA to QA in the blood is reduced in major depressive disorder (MDD) and has been reported to be positively correlated with gray matter volume in depression. This study examined whether the inflammatory mediator, C-reactive protein (CRP) and the putative neuroprotective index, KynA/QA, were associated with white matter integrity in MDD, and secondly, whether any such associations were independent of each other or whether the effect of CRP was mediated by KynA/QA. One hundred and sixty-six participants in the Tulsa 1000 study with a DSM-V diagnosis of MDD completed diffusion tensor imaging and provided a serum sample for the quantification of CRP, KynA, and QA. Correlational tractography was performed using DSI Studio to map the specific white matter pathways that correlated with CRP and KynA/QA. CRP was negatively related to KynA/QA (standardized beta coefficient, SBC = -0.35 with standard error, Std.E = 0.13, p < 0.01) after controlling for nine possible confounders, i.e., age, sex, body mass index (BMI), medication status, lifetime alcohol use, severity of depression, severity of anxiety, length of illness, and smoking status. Higher concentrations of CRP were associated with decreased white matter integrity (fractional anisotropy, FA) of the bilateral cingulum and fornix after controlling for the nine potential confounders (SBC = -0.43, Std.E = 0.13, p = 0.002). Greater serum KynA/QA was associated with increased white matter integrity of the bilateral fornix, bilateral superior thalamic radiations, corpus callosum, and bilateral cingulum bundles after controlling for the same possible confounders (SBC = 0.26, Std.E = 0.09, p = 0.005). The relationship between CRP and FA was not mediated by KynA/QA. Exploratory analyses also showed that KynA/QA but not CRP was associated with self-reported positive affect, attentiveness, and fatigue measured with the PANASX (SBCs = 0.17-0.23). Taken together, these results are consistent with the hypothesis that within a subgroup of MDD patients, a higher level of systemic inflammation alters the balance of KP metabolism but also raise the possibility that CRP and neuroactive KP metabolites represent independent molecular mechanisms underlying white matter alterations in MDD.

Does the moderator matter? Identification of multiple moderators of the association between peripheral inflammatory markers and depression severity in a large racially diverse community cohort

Depressive symptomology has been linked to low-grade peripheral inflammatory markers (PIMs), specifically C-reactive protein (CRP) and white blood cell count (WBC). However, such associations may be affected by multiple moderators (including race/ethnicity), though few well-powered and racially diverse studies have examined this. We examined 31 moderators of PIM-depression relationships in a large racially diverse cohort (n = 21,570). We also examined if associations between PIM and depression severity were dependent on clinical cutpoints for moderate depressive symptoms and elevated CRP. We found several positive moderators of PIM-depression relationships for both WBC and CRP: ongoing medication use (antidepressant, statin, or any prescription drug), presence of sleep concerns, and poor health status (β's = 0.06-0.21, p's < 0.05). For both WBC and CRP, individuals of non-Hispanic White race/ethnicity were found to have stronger PIM-depression associations overall relative to minoritized groups (B's = 0.14 to 1.01, p's < 0.05). For CRP, stronger PIM-depression relationships existed for individuals with moderate (or greater) depression severity or elevated CRP (B's = 0.27 to 0.49, p's < 0.05). Thus, a wide range of moderators appears to affect PIM-depression associations. These results could help identify participants with strong coupling of PIM-depression severity, to guide future research and personalized treatments for depression and to indicate gaps in the applicability of widely referenced theoretical models among racial/ethnic minoritized groups.

Psychiatric symptoms are not associated with circulating CRP concentrations after controlling for medical, social, and demographic factors

Elevated serum concentrations (>3 mg/L) of the acute-phase protein, C-reactive protein (CRP), is used as a clinical marker of inflammation and is reported to be a strong risk factor for cardiovascular disease. In psychiatric populations, CRP concentration is reported to be higher in depressed versus healthy individuals. Positive associations between CRP and depression have been established in both clinical and community samples, but effect sizes are attenuated after controlling for confounding variables. Similarly, emerging research has begun to draw a link between inflammation, symptoms of anxiety, and substance abuse. Given the high level of comorbid anxiety and substance use disorders in many depressed populations, this study examined whether depression (Patient Health Questionnaire 9 [PHQ-9]) and substance use-related (Drug Abuse Screening Test [DAST]) symptoms were associated with CRP concentrations in the blood after adjusting for relevant medical, social, and demographic covariates in a large sample undergoing screening for several transdiagnostic psychiatric research studies. A total of 1,724 participants were analyzed for association of CRP with variables using multivariate linear regression. An unadjusted model with no covariates showed that PHQ-9 was significantly associated with CRP in All (β = 0.125), Female (β = 0.091), and Male (β = 0.154) participants, but DAST was significantly associated with CRP in males only (β = 0.120). For the adjusted model, in both males and females, mood-stabilizer treatment (β = 0.630), opioid medication (β = 0.360), body mass index (β = 0.244), percent body fat (β = 0.289), nicotine use (β = 0.063), and self-reported sleep disturbance (β = 0.061) were significantly associated with increased CRP concentrations. In females, oral contraceptive use (β = 0.576), and waist-to-hip ratio (β = 0.086), and in males, non-steroidal anti-inflammatory drug use (β = 0.367) were also associated with increased CRP concentrations. There was no significant association between CRP and individual depressive, anxiety, or substance use-related symptoms when covariates were included in the regression models. These results suggest that associations between circulating CRP and the severity of psychiatric symptoms are dependent on the type of covariates controlled for in statistical analyses.

Association of depression and obesity with C-reactive protein in Germany: A large nationally representative study

INTRODUCTION

Depression and obesity often occur comorbidly, and once both are present, they further increase the risk of developing other medical comorbidities, likely due to the underlying chronic low-grade inflammation. We investigated to what extent depression and obesity are associated with levels of high-sensitivity C-reactive protein (hsCRP) in a nationally representative sample of the German adult population.

METHODS

We analyzed data from the German Health Interview and Examination Survey for Adults (DEGS1, N = 7115), and its mental health module (DEGS1-MH; N = 4483). Two different depression measures were used: current depressive symptoms assessed by the self-administered German version of the Patient Health Questionnaire-9 and major depressive disorder (MDD) in the last 12 months assessed by a modified German version of the Composite International Diagnostic Interview. Obesity was defined by body mass index calculated from measured data. Associations with log(x + 1)-transformed hsCRP levels were analyzed using multivariable linear regression models.

RESULTS

Obese participants with depressive symptoms had significantly higher hsCRP compared to non-obese participants with depressive symptoms adjusted for sociodemographic and behavioral variables and medication use. In non-obese individuals, depressive symptoms were inversely associated with hsCRP, whereas MDD was not associated with hsCRP after adjustment for covariates. Additional analyses suggested symptom-specific associations of hsCRP as higher levels were linked to fatigue (β = 0.10, p <.001) while lower levels were linked to cognitive problems (β = -0.09, p <.001). Low SES, current smoking, lower levels of physical exercise, and the use of anti-inflammatory/anti-rheumatic medication and antidepressants were additional determinants of hsCRP in the fully adjusted models.

CONCLUSIONS

Our data suggest that obesity status is more strongly associated with increased inflammation than depressive symptoms or MDD. The relationship between depression and hsCRP in our population-based sample is substantially influenced by obesity status as well as other medical factors, lifestyle, and socioeconomic status. Furthermore, our findings suggest that the association between hsCRP and depression is symptom-specific rather than generalized.

The association of physical illness and low-grade inflammatory markers with depressive symptoms in a large NHANES community sample: Dissecting mediating and moderating effects

BACKGROUND

Both low-grade elevation in peripheral inflammatory markers (e.g., white blood count (WBC) and C-reactive protein (CRP)) and physical illness (both chronic and acute) have been associated with depressive symptomology. However, it is unclear if low-grade elevation in inflammatory markers mediates relationships between physical illness and depression or if physical illness positively moderates relationships between inflammatory markers and depression.

METHODS

In a well-powered, racially diverse cohort (n = 21,525) from NHANES datasets, we examined if inflammatory markers (CRP and WBC) and physical illnesses (acute and chronic) were independently associated with depression severity. We also examined if associations between physical illness and depression severity were mediated by inflammatory markers and if physical illness moderated associations between inflammatory markers and depression.

RESULTS

We found that both inflammatory markers and physical illness were associated with depression severity, even after considering a wide range of potential confounders (e.g., age, gender, body mass index). Inflammatory markers mediated a marginal portion (<5%; p < 0.001) of potential effects of physical illness on depression severity. In moderation analyses, associations between inflammatory markers and depression severity were significantly stronger in participants with chronic physical illness than those without. This moderating effect was not present for acute physical illness.

CONCLUSIONS

Inflammatory markers and physical illness appear independently linked to depression severity and, in individuals with chronic physical illness, inflammatory markers are more tightly connected to depressive symptomology. Such findings could help guide future individualized treatment research for depression based on both inflammatory marker level and physical illness burden.

Immune–Inflammatory Biomarkers Predict Cognition and Social Functioning in Patients With Type 2 Diabetes Mellitus, Major Depressive Disorder, Bipolar Disorder, and Schizophrenia: A 1-Year Follow-Up Study

Background

Systemic, low-grade immune–inflammatory activity, together with social and neurocognitive performance deficits are a transdiagnostic trait of people suffering from type 2 diabetes mellitus (T2DM) and severe mental illnesses (SMIs), such as schizophrenia (SZ), major depressive disorder (MDD), and bipolar disorder (BD). We aimed to determine if immune–inflammatory mediators were significantly altered in people with SMIs or T2DM compared with healthy controls (HC) and whether these biomarkers could help predict their cognition and social functioning 1 year after assessment.

Methods

We performed a prospective, 1-year follow-up cohort study with 165 participants at baseline (TB), including 30 with SZ, 42 with BD, 35 with MDD, 30 with T2DM, and 28 HC; and 125 at 1-year follow-up (TY), and determined executive domain (ED), global social functioning score (GSFS), and peripheral blood immune–inflammatory and oxidative stress biomarkers.

Results

Participants with SMIs and T2DM showed increased peripheral levels of inflammatory markers, such as interleukin-10 (p < 0.01; η²p = 0.07) and tumor necrosis factor-α (p < 0.05; η²p = 0.08); and oxidative stress biomarkers, such as reactive oxygen species (ROS) (p < 0.05; η²p = 0.07) and mitochondrial ROS (p < 0.01; η²p = 0.08). The different combinations of the exposed biomarkers anticipated 46–57.3% of the total ED and 23.8–35.7% of GSFS for the participants with SMIs.

Limitations

Participants' treatment, as usual, was continued without no specific interventions; thus, it was difficult to anticipate substantial changes related to the psychopharmacological pattern.

Conclusion

People with SMIs show significantly increased levels of peripheral immune–inflammatory biomarkers, which may contribute to the neurocognitive and social deficits observed in SMIs, T2DM, and other diseases with systemic immune–inflammatory activation of chronic development. These parameters could help identify the subset of patients who could benefit from immune–inflammatory modulator strategies to ameliorate their functional outcomes.

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: Marker of risk for post-traumatic stress disorder and its potential for a mechanistic role in trauma response and recovery

Increasing evidence indicates that inflammation plays a role in PTSD and stress disorder pathophysiology. PTSD is consistently associated with higher circulating inflammatory protein levels. Rodent models demonstrate that inflammation promotes enduring avoidance and arousal behaviors after severe stressors (e.g., predator exposure and social defeat), suggesting that inflammation may play a mechanistic role in trauma disorders. C-reactive protein (CRP) is an innate acute phase reactant produced by the liver after acute infection and chronic disease. A growing number of investigations report associations with PTSD diagnosis and elevated peripheral CRP, CRP gene mutations, and CRP gene expression changes in immune signaling pathways. CRP is reasonably established as a potential marker of PTSD and trauma exposure, but if and how it may play a mechanistic role is unclear. In this review, we discuss the current understanding of immune mechanisms in PTSD with a particular focus on the innate immune signaling factor, CRP. We found that although there is consistent evidence of an association of CRP with PTSD symptoms and risk, there is a paucity of data on how CRP might contribute to CNS inflammation in PTSD, and consequently, PTSD symptoms. We discuss potential mechanisms through which CRP could modulate enduring peripheral and CNS stress responses, along with future areas of investigation probing the role of CRP and other innate immune signaling factors in modulating trauma responses. Overall, we found that CRP likely contributes to central inflammation, but how it does so is an area for further study.

C-reactive protein is related to a distinct set of alterations in resting-state functional connectivity contributing to a differential pathophysiology of major depressive disorder

BACKGROUND

Several studies in major depressive disorder (MDD) have found inflammation, especially C-reactive protein (CRP), to be consistently associated with MDD and network dysfunction. The aim was to investigate whether CRP is linked to a distinct set of resting-state functional connectivity (RSFC) alterations.

METHODS

For this reason, we investigated the effects of diagnosis and elevated blood plasma CRP levels on the RSFC in 63 participants (40 females, mean age 31.4 years) of which were 27 patients with a primary diagnosis of MDD and 36 healthy control-subjects (HC), utilizing a seed-based approach within five well-established RSFC networks obtained using fMRI.

RESULTS

Of the ten network pairs examined, five showed increased between-network RSFC-values unambiguously connected either to a diagnosis of MDD or elevated CRP levels. For elevated CRP levels, increased RSFC between DMN and AN was found. Patients showed increased RSFC within DMN areas and between the DMN and ECN and VAN, ECN and AN and AN and DAN.

CONCLUSIONS

The results of this study show dysregulated neural circuits specifically connected to elevated plasma CRP levels and independent of other alterations of RSFC in MDD. This dysfunction in neural circuits might in turn result in a certain immune-inflammatory subtype of MDD.

Going beyond risk factor: Childhood maltreatment and associated modifiable targets to improve life-long outcomes in mood disorders

Childhood maltreatment increases risk for mood disorders and is associated with earlier onset-and more pernicious disease course following onset-of mood disorders. While the majority of studies to date have been cross-sectional, longitudinal studies are emerging and support the devastating role(s) childhood maltreatment has on development of, and illness course in, mood disorders. This manuscript extends prior reviews to emphasize more recent work, highlighting longitudinal data, and discusses treatment studies that provide clues to mechanisms that mediate disease risk, course, relapse, and treatment response. Evidence suggesting systemic inflammation, alterations in hypothalamic-pituitary-adrenal (HPA) axis function and corticotropin-releasing factor (CRF) neural systems, genetic and other familial factors as mechanisms that mediate risk and onset of, and illness course in, mood disorders following childhood maltreatment is discussed. Risky behaviors following maltreatment, e.g., substance use and unhealthy lifestyles, may further exacerbate alterations in the HPA axis, CRF neural systems, and systematic inflammation to contribute to a more pernicious disease course. More research on sex differences and the impact of maltreatment in vulnerable populations is needed. Future research needs to be aimed at leveraging knowledge on modifiable targets, going beyond childhood maltreatment as a risk factor, to inform prevention and treatment strategies and foster trauma-informed care.

Progress and challenges in research of the mechanisms of anhedonia in major depressive disorder

There is an increasing heavy disease burden of major depressive disorder (MDD) globally. Both high diagnostic heterogeneity and complicated pathological mechanisms of MDD pose significant challenges. There is much evidence to support anhedonia as a core feature of MDD. In the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, anhedonia is further emphasised as a key item in the diagnosis of major depression with melancholic features. Anhedonia is a multifaceted symptom that includes deficits in various aspects of reward processing, such as anticipatory anhedonia, consummatory anhedonia, and decision-making anhedonia. Anhedonia is expected to become an important clinicopathological sign for predicting the treatment outcome of MDD and assisting clinical decision making. However, the precise neurobiological mechanisms of anhedonia in MDD are not clearly understood. In this paper, we reviewed (1) the current understanding of the link between anhedonia and MDD; (2) the biological basis of the pathological mechanism of anhedonia in MDD; and (3) challenges in research on the pathological mechanisms of anhedonia in MDD. A more in-depth understanding of anhedonia associated with MDD will improve the diagnosis, prediction, and treatment of patients with MDD in the future.

Social Media Use and Its Link to Physical Health Indicators

Social media use has become an integral part of many young adults' daily lives. Although much research has examined how social media use relates to psychological well-being, little is known about how it relates to physical health. To address this knowledge gap, the present research investigated how the amount of social media people use relates to various indices of physical health. Young adults provided a blood sample that was analyzed for C-reactive protein (CRP), a marker of chronic inflammation. They also completed self-report measures of social media use, somatic symptoms, illness-related physician or health center visits, and whether they sought medical care for infection-related illnesses in the last 3 months. Social media use was positively correlated with higher levels of CRP, more somatic symptoms, and more visits to the doctor or health centers for an illness. Although directionally consistent, the correlation with likelihood of seeking medical care for infection-related illnesses was nonsignificant (p = 0.061). All of these results held after controlling for factors such as sociodemographic information and depressive symptoms. Given the prevalence of social media use in daily life, these findings underscore the need for more research examining how social media use relates to physical health.

C-Reactive Protein as a Biomarker for Major Depressive Disorder?

The etiopathogenesis of depression is not entirely understood. Several studies have investigated the role of inflammation in major depressive disorder. The present work aims to review the literature on the association between C-Reactive Protein (CRP) and depression. A systematic review was performed for the topics of ‘CRP’ and ‘depression’ using the PubMed database from inception to December 2021. Fifty-six studies were identified and included in the review. Evidence suggested the presence of dysregulation in the inflammation system in individuals with depression. In most studies, higher blood CRP levels were associated with greater symptom severity, a specific pattern of depressive symptoms, and a worse response to treatment. Moreover, about one-third of depressed patients showed a low-grade inflammatory state, suggesting the presence of a different major depressive disorder (MDD) subgroup with a distinct etiopathogenesis, clinical course, treatment response, and prognosis, which could benefit from monitoring of CRP levels and might potentially respond to anti-inflammatory treatments. This work provides robust evidence about the potential role of CRP and its blood levels in depressive disorders. These findings can be relevant to developing new therapeutic strategies and better understanding if CRP may be considered a valuable biomarker for depression.

Is the Therapeutic Mechanism of Repetitive Transcranial Magnetic Stimulation in Cognitive Dysfunctions of Depression Related to the Neuroinflammatory Processes in Depression?

The lifetime prevalence of depression is reported to be >10%, and it is an important illness that causes various disabilities over a long period of life. Neuroinflammation process is often reported to be closely linked to the pathophysiology of depression. Approximately one-third of depression is known to be treatment-resistant depression (TRD), in which the symptoms are refractory to adequate treatment. Cognitive dysfunction is one of the most important symptoms of depression that impedes the rehabilitation of patients with depression. Repetitive transcranial magnetic stimulation (rTMS) is a minimally invasive and effective treatment for TRD and is also known to be effective in cognitive dysfunction in depression. Since the details of the therapeutic mechanism of rTMS are still unknown, we have been conducting studies to clarify the therapeutic mechanism of rTMS, especially focusing on cognitive dysfunction in depression. In the present review, we present our latest results and discuss them from the standpoint of the neuroinflammation hypothesis of depression, while citing relevant literature.

Elevated Systemic Inflammation Is Associated with Reduced Corticolimbic White Matter Integrity in Depression

(1) Background: Growing evidence indicates that inflammation can induce neural circuit dysfunction and plays a vital role in the pathogenesis of major depressive disorder (MDD). Nevertheless, whether inflammation affects the integrity of white matter pathways is only beginning to be explored. (2) Methods: We computed quantitative anisotropy (QA) from diffusion magnetic resonance imaging as an index of white matter integrity and regressed QA on C-reactive protein (CRP), controlling for age, sex, and BMI, in 176 participants with MDD. (3) Results: The QA values of several white matter tracts were negatively correlated with CRP concentration (standardized beta coefficient = -0.22, 95%CI = -0.38--0.06, FDR < 0.05). These tracts included the bilateral cortico-striatal tracts, thalamic radiations, inferior longitudinal fasciculi, corpus callosum (the forceps minor portion and the tapetum portion), cingulum bundles, and the left superior longitudinal fasciculus III. Importantly, the association remained robust after regressing up to twelve potential confounders. The bilateral fornix and a small portion of the thalamic radiation showed a positive association with CRP levels, but these associations did not remain significant after adjusting for confounders. (4) Conclusions: Peripheral inflammation may contribute to the etiology of MDD by impacting the microstructural integrity of brain corticolimbic white matter pathways.

Association Between Systemic Inflammation and Individual Symptoms of Depression: A Pooled Analysis of 15 Population-Based Cohort Studies

OBJECTIVE

Evidence from anti-inflammatory drug trials for the treatment of depression has been inconsistent. This may be ascribed to the differing symptom-specific effects of inflammation. Accordingly, the authors explored the associations between systemic inflammation and an array of individual symptoms of depression across multiple studies.

METHODS

This random-effects pooled analysis included 15 population-based cohorts and 56,351 individuals age 18 years and older. Serum or plasma concentrations of C-reactive protein (CRP) and interleukin-6 (IL-6) were measured at baseline. Using validated self-report measures, 24 depressive symptoms were ascertained in 15 cross-sectional studies, and, in seven cohorts, were also assessed at follow-up (mean follow-up period, 3.2 years).

RESULTS

The prevalence of depressive symptoms ranged from 1.1% (suicidal ideation) to 21.5% (sleep problems). In cross-sectional analyses, higher concentrations of CRP were robustly associated with an increased risk of experiencing four physical symptoms (changes in appetite, felt everything was an effort, loss of energy, sleep problems) and one cognitive symptom (little interest in doing things). These associations remained after adjustment for sociodemographic variables, behavioral factors, and chronic conditions; in sex- and age-stratified analyses; in longitudinal analyses; when using IL-6 as the inflammatory marker of interest; in depressed individuals; and after excluding chronically ill individuals. For four exclusively emotional symptoms (bothered by things, hopelessness about the future, felt fearful, life had been a failure), the overall evidence was strongly against an association with inflammation.

CONCLUSIONS

These findings suggest symptom-specific rather than generalized effects of systemic inflammation on depression. Future trials exploring anti-inflammatory treatment regimens for depression may benefit from targeting individuals presenting with symptom profiles characterized by distinct inflammation-related physical and cognitive symptoms.

Elevated C-reactive protein levels across diagnoses: The first comparison among inpatients with major depressive disorder, bipolar disorder, or obsessive-compulsive disorder

OBJECTIVE

We addressed elevated C-reactive protein level (eCRP) specificity comparing, for the first time, eCRP (i.e., serum CRP > 3 and ≤10 mg/L) in patients with major depressive disorder (MDD), bipolar disorder (BD), or obsessive-compulsive disorder (OCD). We also assessed to what extent multiple variables that can potentially increase inflammation may have influenced eCRP in our sample.

METHODS

We performed a retrospective, observational, cross-sectional study using information documented in the electronic medical records (EMRs) of patients hospitalized for a 4-week psychiatric rehabilitation program. We collected all information according to the standardized procedures of the hospital's clinical practice and applied a logistic regression model (α = 0.05).

RESULTS

We included 388 inpatients, that is, 156 (40.2%) with MDD, 135 (34.8%) with BD, and 97 (25.0%) with OCD, and found considerable eCRP rates among them (36.5%, 47.4%, and 29.9% in MDD, BD, and OCD, respectively) but without significant differences across groups. In the whole sample, eCRP variations were only partially attributable (approximately for one-third) to potential confounders. All groups presented considerable rates of cardiovascular risk factors, and we classified most patients as having medium or high CRP-based cardiovascular risk.

CONCLUSION

This first study comparing eCRP in MDD, BD, and OCD suggests that eCRP may be a transdiagnostic feature of different psychiatric disorders, and other mechanisms beyond the effects of multiple confounders may explain the presence of eCRP in a substantial portion of psychiatric patients. Therefore, we encourage the routine measurement of CRP in psychiatric clinical practice.

Inflammatory burden in adolescents with prolonged parent-child separation

BACKGROUND

Prolonged parent-child separation is associated with a broad array of poor developmental outcomes. A potential pathway may be through changes in inflammatory processes. However, relatively little is known about the relationship between parent-child separation pattern (timing and duration) and inflammatory burden. The aim of this study was to investigate whether parent-child separation since birth is associated with inflammatory burden in adolescents.

METHODS

A total of 574 adolescents (mean age 12.07 years, SD: 0.62) were enrolled from rural areas of Chizhou, Anhui Province, China. Parent-child separation was reported mainly by primary caregivers, and other adverse childhood adversities (ACEs) were derived from adolescents semi-structured interview or questionnaire. Blood samples were collected from venepuncture for C-reactive protein (CRP) as well as soluble urokinase plasminogen activator receptor (suPAR).

RESULTS

Nearly 40% (232/574) participants experienced parent-child separation, among which more than 1 of 4 persistently separated from both parents since birth. Both CRP and suPAR levels were significantly higher among adolescents persistently separated from both parents, compared with those who did not separate from both parents (CRP: 1.75 vs. 1.36 mg/L, P < 0.001; suPAR: 2.85 ng/mL vs. 2.55 ng/mL, P < 0.001). After adjusted for demographic covariates, body mass index, ACEs as well as parental characteristics, persistent parent-child separation was associated with elevated suPAR (B = 0.30; 95% CI, 0.12-0.48) and CRP (B = 1.34; 95% CI, 1.02-1.75). No similar associations were observed between inflammatory burden with current or early childhood parent-child separation groups. Adolescents who exposed to persistent parent-child separation were more likely to have elevated suPAR levels even if they did not have elevated CRP levels (aOR, 4.26, 95% CI, 1.23-14.80; P = 0.022).

CONCLUSION

Elevated inflammatory burden observed in persistent parent-child separation adolescents highlights the need to support children and adolescents undergoing separation from both parents in order to minimize the long-term impact on disease vulnerability.

Depression in type 2 diabetes: A systematic review and meta-analysis of blood inflammatory markers

The prevalence of depression is higher among people with type 2 diabetes (T2DM). Individually, both conditions are associated with systemic inflammation. This study aimed to summarize the clinical data comparing peripheral inflammatory markers in blood between people with T2DM, with and without comorbid depression. From 2187 records, we identified 20 original peer-reviewed articles from which blood inflammatory marker concentrations could be combined and compared between people with T2DM and comorbid depression (D) vs. no depression (ND) as standardized mean differences (SMD) in random effects meta-analysis. Concentrations of C-reactive protein (CRP; ND/NND = 1742/15244, SMD = 0.31 95% confidence interval [0.16, 0.45], Z16 = 4.03, p < 0.01; I2 = 84.0%) and interleukin-6 (IL-6; ND/NND = 677/4349, SMD = 0.17 [0.04, 0.30], Z4 = 2.58, p = 0.01; I2 = 48.1%), were higher, and concentrations of brain derived neurotrophic factor (BDNF; ND/NND = 358/1512, SMD = -0.37 95% confidence interval [-0.64,-0.10], Z2 = -2.68, p = 0.01; I2 = 61.2%) were lower, among those with depression. Depression in T2DM was associated with systemic inflammation and lower peripheral blood BDNF concentrations. Inconsistency between studies suggests the need to explore further population heterogeneity and pathophysiological elements. PROSPERO (CRD42020188509).

Confounders in Identification and Analysis of Inflammatory Biomarkers in Cardiovascular Diseases

Proinflammatory biomarkers have been increasingly used in epidemiologic and intervention studies over the past decades to evaluate and identify an association of systemic inflammation with cardiovascular diseases. Although there is a strong correlation between the elevated level of inflammatory biomarkers and the pathology of various cardiovascular diseases, the mechanisms of the underlying cause are unclear. Identification of pro-inflammatory biomarkers such as cytokines, chemokines, acute phase proteins, and other soluble immune factors can help in the early diagnosis of disease. The presence of certain confounding factors such as variations in age, sex, socio-economic status, body mass index, medication and other substance use, and medical illness, as well as inconsistencies in methodological practices such as sample collection, assaying, and data cleaning and transformation, may contribute to variations in results. The purpose of the review is to identify and summarize the effect of demographic factors, epidemiological factors, medication use, and analytical and pre-analytical factors with a panel of inflammatory biomarkers CRP, IL-1b, IL-6, TNFa, and the soluble TNF receptors on the concentration of these inflammatory biomarkers in serum.