One Effect Size Does Not Fit All--Is the Depression-Inflammation Link Missing in Racial/Ethnic Minority Individuals?

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 and ethnic differences in the associations between social integration, C-reactive protein and depressive symptoms

This study evaluates whether the associations between social integration, inflammation, and depressive symptoms vary by race/ethnicity in the United States. Our study includes 5,634 respondents age 40 and older from the National Health and Nutrition Examination Survey for 2005-2008. We fit multivariate logistic regression models with interactions between C-reactive protein (CRP) and race/ethnicity as well as social integration and race/ethnicity to test our hypotheses. We find that social integration and CRP operate independently in their associations with depressive symptoms by race/ethnicity. Higher levels of social integration are associated with lower predicted probability of depressive symptoms for White and Black populations. This association is not statistically significant for the Hispanic population. CRP is associated with depressive symptoms for the White population, but not the Black or Hispanic populations. Our results suggest that studying depressive symptoms, and other mental health outcomes, among the US population without considering variation by race/ethnicity may restrict scholarly understanding of health disparities. Population-based assessments of associations between physiological processes or social integration should consider whether these variables operate differently by race/ethnicity and work to explain why differences may emerge. Furthermore, interventions aimed at social integration may improve mental health among older adults in the United States; especially for the least socially integrated.

Effects of exogenous ghrelin administration and ghrelin receptor blockade, in combination with alcohol, on peripheral inflammatory markers in heavy-drinking individuals: Results from two human laboratory studies

The ghrelin system has been garnering interest for its role in different neuropsychiatric disorders, including alcohol use disorder (AUD). Accordingly, targeting the ghrelin system is under investigation as a potential novel therapeutic approach. While alcohol provokes the immune system and inflammatory responses, ghrelin has potent immunomodulatory and anti-inflammatory properties. The present study aimed to shed light on the "crosstalk" between ghrelin and inflammation by examining the effects of exogenous ghrelin administration and ghrelin receptor blockade on peripheral inflammatory markers in the context of two human laboratory studies with alcohol administration. Non-treatment-seeking, heavy-drinking individuals with alcohol dependence, the majority of whom were African American males, were enrolled. In the first randomized, crossover, double-blind, placebo-controlled human laboratory study, participants underwent two experimental paradigms - an intravenous alcohol self-administration (IV-ASA) and an intravenous alcohol clamp (IV-AC) - each consisting of two counterbalanced sessions (ghrelin, placebo). A loading dose of intravenous ghrelin (3 mcg/kg) or placebo, followed by a continuous ghrelin (16.9 ng/kg/min) or placebo infusion was administered. In the second dose-escalating, single-blind, placebo-controlled human laboratory phase 1b study, participants were dosed with an oral ghrelin receptor blocker (PF-5190457) and underwent an oral alcohol challenge. Repeated blood samples were collected, and plasma concentrations of the following inflammatory markers were measured: C-reactive protein (CRP), interleukin (IL)-6, IL-10, IL-18, and tumor necrosis factor alpha (TNF-α). During the IV-ASA experiment, significant drug × time interaction effects were observed for IL-6 (F_3,36 = 3.345, p = 0.030) and IL-10 (F_3,53.2 = 4.638, p = 0.006), indicating that ghrelin, compared to placebo, significantly reduced blood concentrations of the proinflammatory cytokine IL-6, while increasing blood concentrations of the anti-inflammatory cytokine IL-10. No significant drug × time interaction effects were observed during the IV-AC experiment, possibly because of its much shorter duration and/or smaller sample. Treatment with PF-5190457, compared to placebo, had no significant effect on the inflammatory markers investigated. In conclusion, a supraphysiologic pharmacological challenge with exogenous ghrelin in heavy-drinking individuals produced anti-inflammatory effects in the context of intravenous alcohol administration. On the contrary, ghrelin receptor blockade did not lead to any change in the inflammatory markers included in this study. Mechanistic studies are required to better understand the interaction between ghrelin, alcohol, and inflammatory processes.

Depression and cardiovascular disease: Shared molecular mechanisms and clinical implications

Depression is a highly prevalent risk factor for both the onset of cardiovascular disease (CVD) and the mortality of CVD patients, and people suffering from CVD are more likely to develop depression than healthy individuals. The aim of this review is to summarize recent findings regarding the underlying relationship between CVD and depression. Literature search and review were conducted using PubMed, Google Scholar, Wanfang Med Online, and Baidu Scholar databases. CVD and depression are intimately related and researchers from around the world have proposed and validated various mechanisms that may potentially explain the comorbidity of CVD and depression. Recent studies have suggested that depression and CVD may manifest as two distinct clinical conditions in two different organs, the brain and the heart, respectively, but may also be linked by shared mechanisms. Of these, inflammation involving the immune system is thought to be a common mechanism of depression and heart disease, with specific inflammatory cytokines or pathways being potential targets for the prevention and treatment of the concurrent diseases. Therefore, inflammation may play an important role in bridging the link between depression and CVD, a finding that can have important clinical implications for the prevention and early intervention of these conditions.

Hair cortisol, allostatic load, and depressive symptoms in Australian Aboriginal and Torres Strait Islander people

Chronic stress and adversity are associated with poor mental health and are thought to contribute to the existing mental health gap between Aboriginal and Torres Strait Islander people and other Australians. Hair cortisol and allostatic load (AL) are indices of sustained stress and may be mediators of the effects of stress on health. The aim of this study was to examine the relationship between hair cortisol, AL, and depressive symptoms. This cross-sectional study comprised 329 Aboriginal and Torres Strait Islander adolescents and adults recruited at two health screening programs operating in three communities in north Queensland. We measured hair cortisol and calculated an AL index from 10 biomarkers. We assessed depressive symptoms with a version of the Patient Health Questionnaire-9 adapted for Aboriginal and Torres Strait Islander people (aPHQ-9). We found differences in cortisol and AL between the screening programs and communities, which were not explained by depressive symptoms. Overall aPHQ-9 scores were unrelated to hair cortisol (p = .25 and p = .94) and AL (p = .30 and p = .88) when age, gender and smoking were taken into account. However, anhedonia (p = .007) and insomnia (p = .006) sub-scores were each significantly associated with AL in one study site. Our present data did not demonstrate overall associations of stress biomarkers and multisystem dysregulation with depressive symptoms, which suggests that the relationship between cumulative stress and depression may be better explained by other factors in this population. The specific association between anhedonia and insomnia with AL indicates that chronic multisystem dysregulation plays a role in these features of depression in this population. Lay summary Our study investigated the relationship between symptoms of depression and two biological pathways thought to mediate depression risk - the stress hormone cortisol and allostatic load (AL) - in an Australian Aboriginal and Torres Strait Islander population. Overall, cortisol and AL were unrelated to depression. However, AL was selectively associated with anhedonia (lack of motivation or drive) and sleep disturbances. These results suggest that metabolic dysregulation measured as AL may be relevant to the depression risk in this population.

Baseline Body Mass Predicts Average Depressive Symptoms over the Next Two Decades for White but Not Black Older Adults

Background: Although obesity and depression have a bidirectional association, this link may vary based on race. The current study tested racial variation in bidirectional links between depressive symptoms and body mass index (BMI) over 24 years of follow-up in older adults over the age of 50 in the United States. We hypothesized weaker bidirectional links in Blacks compared to Whites. Methods: Data came from waves 1 to 12 (1990 to 2014) of the Health and Retirement Study (HRS), an ongoing state-of-the-art national cohort. The study followed a representative sample of Americans (n = 15,194; 2,200 Blacks and 12,994 Whites) over the age of 50. Dependent variables were average depressive symptoms and BMI over 24 years, based on measurements every other year, from 1990 to 2014. Independent variables included baseline depressive symptoms and BMI. Covariates included age, gender, marital status, veteran status, and activities of daily living. Structural equation models were fitted to the data for data analysis. Results: In the pooled sample, bidirectional associations were found between BMI and depressive symptoms as baseline BMI predicted average depressive symptoms over time and baseline depressive symptoms predicted average BMI over 24 years. Racial differences were found in the bidirectional association between BMI and depressive symptoms, with both directions of the associations being absent for Blacks. For Whites, baseline BMI predicted average depressive symptoms over the next 24 years. Conclusion: Reciprocal associations between BMI and depressive symptoms over a 24-year period among individuals over the age of 50 vary for Blacks and Whites. As these associations are stronger for Whites than Blacks, clinical and public health programs that simultaneously target comorbid obesity and depression may be more appropriate for Whites than Blacks.

Allostatic Load Biomarker Associations with Depressive Symptoms Vary among US Black and White Women and Men

The prevalence and severity of depression differ in women and men and across racial groups. Psychosocial factors such as chronic stress have been proposed as contributors, but causes of this variation are not fully understood. Allostatic load, a measure of the physiological burden of chronic stress, is known to be associated with depression. Using data from the National Health and Nutrition Examination Survey 2005–2010, we examined the associations of nine allostatic load biomarkers with depression among US black and white adults aged 18–64 years (n = 6431). Depressive symptoms were assessed using the Patient Health Questionaire-9; logistic models estimated adjusted odds of depression based on allostatic load biomarkers. High-risk levels of c-reactive protein were significantly associated with increased odds of depression among white women (adjusted odds ratio (aOR) = 1.7, 95% CI: 1.1–2.5) and men (aOR = 1.8, 95% CI: 1.1–2.8) but not black women (aOR = 0.8, 95% CI: 0.6–1.1) or men (aOR = 0.9, 95% CI: 0.5–1.5). Among black men, hypertension (aOR = 1.7, 95% CI: 1.1–2.7) and adverse serum albumin levels (aOR = 1.7, 95% CI: 1.0–2.9) predicted depression, while high total cholesterol was associated with depression among black women (aOR = 1.6, 95% CI: 1.0–2.7). The associations between allostatic load biomarkers and depression varies with gendered race, suggesting that, despite consistent symptomatology, underlying disease mechanisms may differ between these groups.

Depressive Symptoms and Self-Esteem in White and Black Older Adults in the United States

Background. Poor self-esteem is a core element of depression. According to recent research, some racial groups may vary in the magnitude of the link between depression and poor self-esteem. Using a national sample, we compared Black and White older Americans for the effect of baseline depressive symptoms on decline in self-esteem over time. Methods. This longitudinal study used data from the Religion, Aging, and Health Survey, 2001⁻2004. The study followed 1493 older adults (734 Black and 759 White) 65 years or older for three years. Baseline depressive symptoms (CES-D), measured in 2001, was the independent variable. Self-esteem, measured at the end of the follow up, was the dependent variable. Covariates included baseline demographic characteristics (age and gender), socioeconomic factors (education, income, and marital status), health (self-rated health), and baseline self-esteem. Race/ethnicity was the moderator. Linear multi-variable regression models were used for data analyses. Results. In the pooled sample, higher depressive symptoms at baseline were predictive of a larger decline in self-esteem over time, net of covariates. We found a significant interaction between race/ethnicity and baseline depressive symptoms on self-esteem decline, suggesting a weaker effect for Blacks compared to Whites. In race/ethnicity-specific models, high depressive symptoms at baseline was predictive of a decline in self-esteem for Whites but not Blacks. Conclusion. Depressive symptoms may be a more salient contributor to self-esteem decline for White than Black older adults. This finding has implications for psychotherapy and cognitive behavioral therapy of depression of racially diverse populations.

Positive and Negative Affect More Concurrent among Blacks than Whites

Background: While positive and negative affect are inversely linked, people may experience and report both positive and negative emotions simultaneously. However, it is unknown if race alters the magnitude of the association between positive and negative affect. The current study compared Black and White Americans for the association between positive and negative affect. Methods: We used data from MIDUS (Midlife in the United States), a national study of Americans with an age range of 25 to 75. A total number of 7108 individuals were followed for 10 years from 1995 to 2004. Positive and negative affect was measured at baseline (1995) and follow-up (2004). Demographic (age and gender), socioeconomic (education and income) as well as health (self-rated health, chronic medical conditions, and body mass index) factors measured at baseline were covariates. A series of linear regressions were used to test the moderating effect of race on the reciprocal association between positive and negative affect at baseline and over time, net of covariates. Results: In the pooled sample, positive and negative affect showed inverse correlation at baseline and over time, net of covariates. Blacks and Whites differed in the magnitude of the association between positive and negative affect, with weaker inverse associations among Blacks compared to Whites, beyond all covariates. Conclusion: Weaker reciprocal association between positive and negative affect in Blacks compared to Whites has implications for cross-racial measurement of affect and mood, including depression. Depression screening programs should be aware that race alters the concordance between positive and negative affect domains and that Blacks endorse higher levels of positive affect compared to Whites in the presence of high negative affect.

The Link between Mastery and Depression among Black Adolescents; Ethnic and Gender Differences

PURPOSE

Although the link between depression and lower levels of mastery is well established, limited information exists on ethnic and gender differences in the association between the two. The current study investigated ethnic, gender, and ethnic by gender differences in the link between major depressive disorder (MDD) and low mastery in the United States.

METHODS

We used data from the National Survey of American Life-Adolescent supplement (NSAL-A), 2003-2004. In total, 1170 Black adolescents entered the study. This number was composed of 810 African-American and 360 Caribbean Black youth (age 13 to 17). Demographic factors, socioeconomic status (family income), mastery (sense of control over life), and MDD (Composite International Diagnostic Interview, CIDI) were measured. Logistic regressions were used to test the association between mastery and MDD in the pooled sample, as well as based on ethnicity and gender.

RESULTS

In the pooled sample, a higher sense of mastery was associated with a lower risk of MDD. This association, however, was significant for African Americans but not Caribbean Blacks. Similarly, among African American males and females, higher mastery was associated with lower risk of MDD. Such association could not be found for Caribbean Black males or females.

CONCLUSION

Findings indicate ethnic rather than gender differences in the association between depression and mastery among Black youth. Further research is needed to understand how cultural values and life experiences may alter the link between depression and mastery among ethnically diverse Black youth.

Reciprocal Associations between Depressive Symptoms and Mastery among Older Adults; Black-White Differences

Purpose: Although higher levels of depressive symptoms and lower levels of sense of mastery tend to be comorbid, limited information exists on racial differences in the longitudinal associations between the two over time. The current study compared Black and White American older adults for the longitudinal links between depressive symptoms and mastery in the United States. Methods: Using data from the Religion, Aging, and Health Survey, 2001-2004, this longitudinal cohort study followed 1493 Black (n = 734) and White (n = 759) elderly individuals (age 66 or more) for 3 years. Depressive symptoms [Center for Epidemiological Studies-Depression scale (CES-D), 8 items] and mastery (Pearlin Mastery Scale, 7 items) were measured in 2001 and 2004. Demographics, socio-economics, and physical health were covariates and race was the focal moderator. Multi-group structural equation modeling was used for data analysis, where groups were defined based on race. Results: Among White but not Black older adults, higher levels of depressive symptoms at baseline predicted a greater decline in sense of mastery over 3 years of follow-up. Similarly among Whites but not Blacks, individuals with lower mastery at baseline developed more depressive symptoms over time. Conclusion: Findings are indicative of Black-White differences in reciprocal associations between depressive symptoms and mastery over time. Race alters how depression is linked to changes in evaluation of self (e.g., mastery) over time.

Systemic Inflammation in Midlife: Race, Socioeconomic Status, and Perceived Discrimination

INTRODUCTION

This study investigates social determinants of systemic inflammation, focusing on race, SES, and perceived discrimination.

METHODS

Data on 884 white and 170 black participants were obtained from the Survey of Midlife in the U.S., a cross-sectional observational study combining survey measures, anthropometry, and biomarker assay. Data, collected in 2004-2009, were analyzed in 2016. Main outcome measures were fasting blood concentrations of C-reactive protein, interleukin 6, fibrinogen, and E-selectin. For each biomarker, series of multivariate linear regression models were estimated for the pooled sample and separately for blacks and whites. Full models included social determinants; psychological, lifestyle, and health factors; and demographic covariates.

RESULTS

Bivariate analyses indicated higher concentrations of all inflammation markers among blacks compared with whites (p<0.001). In fully adjusted models using the pooled sample, racial differences persisted for interleukin 6 (p<0.001) and fibrinogen (p<0.01). For E-selectin and C-reactive protein, racial differences were explained after adjusting for covariates. Education was linked to lower fibrinogen concentration (p<0.05) in the fully adjusted model and C-reactive protein concentration (p<0.01) after adjusting for demographic factors and income. Lifetime perceived discrimination was related to higher concentrations of fibrinogen (p<0.05) in the fully adjusted model, and higher concentrations of E-selectin and interleukin 6 (p<0.05) after adjusting for socioeconomic status (SES) and demographic factors.

CONCLUSIONS

This study clarifies the contributions of race, SES, and perceived discrimination to inflammation. It suggests that inflammation-reducing interventions should focus on blacks and individuals facing socioeconomic disadvantages, especially low education.

Chronic Medical Conditions and Negative Affect; Racial Variation in Reciprocal Associations Over Time

BACKGROUND

The Black-White health paradox can be defined as lower frequency of depression despite higher prevalence of economic and social adversities as well as chronic medical conditions (CMC) among American Blacks compared to American Whites. Based on this paradox, the CMC - depressive symptoms link is expected to be weaker among Blacks than Whites. We conducted a 10-year longitudinal study to compare Blacks and Whites for bidirectional associations between number of CMC and negative affect over time.

METHODS

We used data from the MIDUS (Midlife in the United States), a nationally representative longitudinal study of American adults. A total number of 7,108 individuals with an age range of 25-75 years (N = 7,108) were followed for 10 years from 1995 to 2004. Age, gender, and socioeconomic status (education and income) were measured at baseline. Negative affect and CMC were measured at baseline (1995) and end of follow up (2004). Race was the moderator. Linear regression was used to test the moderating effect of race on the reciprocal associations between CMC and negative affect, net of covariates.

RESULTS

In the pooled sample, while baseline CMC was predictive of an increase in negative affect over time, baseline negative affect was also predictive of an increase in CMC. We found interactions between race and baseline CMC on change in depressive symptoms, as well as race with negative affect on CMC change, suggesting that the associations between CMC and negative affect are stronger for Whites in comparison to Blacks.

CONCLUSION

Blacks and Whites differ in reciprocal links between CMC and negative affect over time. This finding replicates recent studies on differential links between psychosocial factors and physical health based on race. Findings may help us better understand how Black-White health paradox develops across mid and later life.