C-reactive protein is elevated in atypical but not nonatypical depression: data from the National Health and Nutrition Examination survey (NHANES) 1999-2004

Low-Grade Inflammation Associated with Major Depression Subtypes: A Cross-Sectional Study

Major depressive disorder (MDD) is associated with inflammation and a high level of comorbidities. Atypical depression (AD) is a MDD subtype based on DSM criteria, that could have specific underlying biological mechanisms. AD is associated with elevated cardiovascular (CVD) comorbidities, higher risk of suicide attempts, hypersomnia, and anxiety disorder. In this study, we aim to investigate if AD and polysomnographic parameters could be associated with low-grade inflammation (LGI). LGI is defined by a range from 3 to 10 mg/L of C-reactive protein levels. We carried out a retrospective cohort study in which 765 individuals with MDD were split into two groups: with and without LGI. Our results exhibit differences between the groups for the polysomnographic parameters, with the LGI group showing parameters already associated with inflammation such as reduced rapid eye movement sleep and elevated hypoxemia markers (identified as CVD risk factor). We found that AD is associated with LGI (OR 1.48; p = 0.047) after adjustment. Likewise, we found an LGI prevalence in AD higher (34.8%) than in MDD without atypical features (26.8%). Overall, these results confirm the low-grade inflammation feature of AD and highlight polysomnographic parameters associated with LGI that could also act as risk factors in this context.

Sub-chronic and mild social defeat stress exposure to C57BL/6J mice increases visceral fat mass and causes accumulation of cholesterol and bile acids in the liver

Major depressive disorder is accompanied by a high metabolic illness comorbidity and patients with atypical depression are a subgroup with particularly high risk of obesity, dyslipidemia, and metabolic syndrome; however, the underlying mechanisms have not been fully elucidated. In this study, we examined visceral fat deposition, lipid profiles in the liver, and gut microbiota in sub-chronic and mild social defeat stress (sCSDS)-exposed C57BL/6J mice, which exhibit atypical depression-like phenotypes, i.e., increased body weight and food and water intake. We found that visceral fat mass and levels of hepatic cholesterol and bile acids in sCSDS-exposed mice were significantly increased compared to those in controls. The expression of hepatic small heterodimer partner, a negative regulator of cholesterol metabolism, was significantly elevated in sCSDS-exposed mice. We also found that gut microbial diversity and composition including lower relative abundance of Bacteroides spp. and Bifidobacterium spp. in sCSDS-exposed mice were different from those in controls. In addition, relative abundance of Bacteroides spp. and Bifidobacterium spp. was significantly and negatively correlated with body weight, visceral fat mass, and hepatic cholesterol and bile acids levels. These results indicate that sCSDS-exposure induces dysbiosis, and thereby contributes to metabolic disorder development.

Cross-sectional analysis of depressive symptom profiles and serum C-reactive protein levels: data from the Northern Finland 1966 birth cohort

PURPOSE

Individuals with depression exhibit significantly higher levels of systemic inflammation than those without depression, particularly among those with atypical depression. However, this association has been less convincing at the population level among individuals without a formal depression diagnosis but with suggestive symptoms. Our aim was to clarify this association.

MATERIALS AND METHODS

In a large birth cohort sample of the Finnish general population, we examined the cross-sectional association between high-sensitivity C-reactive protein (hsCRP) levels in venous blood samples and atypical/non-atypical depressive symptoms using the Beck Depression Inventory-II to screen 5443 middle-aged participants.

RESULTS

As expected, depressive symptoms associated to elevated hsCRP-levels compared to non-depressed. Participants with the atypical subtype of depressive symptoms (n = 84) had an odds ratio (OR) of 2.59 (95% CI 1.40-4.81) for elevated hsCRP levels compared to the non-depressed group. Similarly, our findings indicate that participants with non-atypical symptoms (n = 440) also showed an OR of 1.42 (95% CI 1.05-1.92) when compared to the non-depressed group (n = 4919).

CONCLUSIONS

These results provide additional support for previous research linking depression and inflammation and add to the field with a unique and sizeable study population. Furthermore, the current results support the notion that different types of depressive symptoms may be associated with inflammatory markers in slightly different ways.

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.

Peripheral inflammatory markers in melancholic versus non-melancholic depression

BACKGROUND

Peripheral inflammation has been associated with major depression, however there is a paucity of studies examining whether inflammatory profiles differ across depressive subtypes. The current study sought to compare peripheral inflammatory markers in patients with melancholic versus non-melancholic depression and with healthy controls.

METHOD

Eighty outpatients with a current major depressive episode (MDE) were assigned as having a melancholic or a non-melancholic depressive subtype based on clinician diagnosis and the Sydney Melancholic Prototypic Index (SMPI). Participants provided peripheral venous blood from which plasma levels of cytokines and other inflammatory markers (C-reactive protein (CRP), neutrophil/lymphocyte ratio, plasma cytokines) were compared across the two patient groups and also to a group of 81 age-matched healthy controls.

RESULTS

Patients with melancholic and non-melancholic depression demonstrated increased CRP and decreased interferon-gamma (IFN-γ) levels compared to controls. Using clinician diagnosis of subtype, interleukin-12 (IL-12) and interleukin-10 (IL-10) levels were elevated in melancholic patients versus non-melancholic and control groups, with no differences found for the other measured markers of inflammation.

CONCLUSION

Study findings demonstrate shared inflammatory changes across certain inflammatory markers (CRP and IFN-γ) and increases in IL-12 and IL-10 levels specific to melancholic depression. While generally supportive of previous work, our peripheral inflammation findings in melancholic depression are relatively novel and suggest this subgroup may benefit from anti-inflammatory therapies. Further studies are required to replicate these findings.

Associations between individual depressive symptoms and immunometabolic characteristics in major depression

Inflammation and metabolic dysregulations are likely to underlie atypical, energy-related depressive symptoms such as appetite and sleep alterations. Indeed, increased appetite was previously identified as a core symptom of an immunometabolic subtype of depression. The aim of this study was 1) to replicate the associations between individual depressive symptoms and immunometabolic markers, 2) to extend previous findings with additional markers, and 3) to evaluate the relative contribution of these markers to depressive symptoms. We analyzed data from 266 persons with major depressive disorder (MDD) in the last 12 months from the German Health Interview and Examination Survey for Adults and its mental health module. Diagnosis of MDD and individual depressive symptoms were determined by the Composite International Diagnostic Interview. Associations were analyzed using multivariable regression models, adjusting for depression severity, sociodemographic/behavioral variables, and medication use. Increased appetite was associated with higher body mass index (BMI), waist circumference (WC), insulin, and lower high-density lipoprotein. In contrast, decreased appetite was associated with lower BMI, WC, and fewer metabolic syndrome (MetS) components. Insomnia was associated with higher BMI, WC, number of MetS components, triglycerides, insulin, and lower albumin, while hypersomnia was associated with higher insulin. Suicidal ideation was associated with higher number of MetS components, glucose, and insulin. None of the symptoms were associated with C-reactive protein after adjustment. Appetite alterations and insomnia were most important symptoms associated with metabolic markers. Longitudinal studies should investigate whether the candidate symptoms identified here are predicted by or predict the development of metabolic pathology in MDD.

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.

Importance of immunometabolic markers for the classification of patients with major depressive disorder using machine learning

BACKGROUND

Although there is scientific evidence of the presence of immunometabolic alterations in major depression, not all patients present them. Recent studies point to the association between an inflammatory phenotype and certain clinical symptoms in patients with depression. The objective of our study was to classify major depression disorder patients using supervised learning algorithms or machine learning, based on immunometabolic and oxidative stress biomarkers and lifestyle habits.

METHODS

Taking into account a series of inflammatory and oxidative stress biomarkers (C-reactive protein (CRP), tumor necrosis factor (TNF), 4-hydroxynonenal (HNE) and glutathione), metabolic risk markers (blood pressure, waist circumference and glucose, triglyceride and cholesterol levels) and lifestyle habits of the participants (physical activity, smoking and alcohol consumption), a study was carried out using machine learning in a sample of 171 participants, 91 patients with depression (71.42% women, mean age = 50.64) and 80 healthy subjects (67.50% women, mean age = 49.12). The algorithm used was the support vector machine, performing cross validation, by which the subdivision of the sample in training (70%) and test (30%) was carried out in order to estimate the precision of the model. The prediction of belonging to the patient group (MDD patients versus control subjects), melancholic type (melancholic versus non-melancholic patients) or resistant depression group (treatment-resistant versus non-treatment-resistant) was based on the importance of each of the immunometabolic and lifestyle variables.

RESULTS

With the application of the algorithm, controls versus patients, such as patients with melancholic symptoms versus non-melancholic symptoms, and resistant versus non-resistant symptoms in the test phase were optimally classified. The variables that showed greater importance, according to the results of the area under the ROC curve, for the discrimination between healthy subjects and patients with depression were current alcohol consumption (AUC = 0.62), TNF-α levels (AUC = 0.61), glutathione redox status (AUC = 0.60) and the performance of both moderate (AUC = 0.59) and vigorous physical exercise (AUC = 0.58). On the other hand, the most important variables for classifying melancholic patients in relation to lifestyle habits were past (AUC = 0.65) and current (AUC = 0.60) tobacco habit, as well as walking routinely (AUC = 0.59) and in relation to immunometabolic markers were the levels of CRP (AUC = 0.62) and glucose (AUC = 0.58). In the analysis of the importance of the variables for the classification of treatment-resistant patients versus non-resistant patients, the systolic blood pressure (SBP) variable was shown to be the most relevant (AUC = 0.67). Other immunometabolic variables were also among the most important such as TNF-α (AUC = 0.65) and waist circumference (AUC = 0.64). In this case, sex (AUC = 0.59) was also relevant along with alcohol (AUC = 0.58) and tobacco (AUC = 0.56) consumption.

CONCLUSIONS

The results obtained in our study show that it is possible to predict the diagnosis of depression and its clinical typology from immunometabolic markers and lifestyle habits, using machine learning techniques. The use of this type of methodology could facilitate the identification of patients at risk of presenting depression and could be very useful for managing clinical heterogeneity.

Irrational beliefs, depression and anxiety, in relation to 10-year cardiovascular disease risk: the ATTICA Epidemiological Study

BACKGROUND AND OBJECTIVES

Various bio-psychosocial mechanisms underlying the link between anxiety, depression and cardiovascular disease risk, remain unknown. We investigated the role of irrational beliefs in conjunction with anxiety and depression in the 10-year cardiovascular disease (CVD) incidence, and the effect of biochemical and socio-behavioral factors.

DESIGN

853[453 men (45 ± 13 years) and 400 women (44 ± 18 years)] from the ATTICA study (2002-2012) and without evidence of CVD were assessed.

METHODS

The Irrational Beliefs Inventory (IBI), the Zung Self-Rating-Depression-Scale (ZDRS) and the State-Trait-Anxiety-Inventory (STAI) were used for the assessments. Incidence of CVD was defined according to the International Coding Diseases (ICD)-10 criteria.

RESULTS

Participants with high irrational beliefs and anxiety symptoms had a 138% greater risk of developing CVD during the 10-year follow-up (2.38; 95%CI 1.75, 3.23) as compared to those without anxiety. Among others, C-reactive protein, interleukin-6 and total antioxidant capacity were mediators in the tested association. Interaction of irrational beliefs and depression was not associated with the 10-year CVD in all models.

CONCLUSIONS

Inflammation and oxidative stress, partially explained the associations between irrational beliefs and anxiety in predicting CVD risk. These findings advance psychological research in the area of primary prevention of mental health and cardiovascular diseases.

Peripheral Inflammatory Markers in Subtypes and Core Features of Depression: A Systematized Review

INTRODUCTION

The aim of this work was to summarize relationships between two subtypes of major depressive disorder (melancholic and atypical) and four core features of depression that reflect the domains identified consistently in previous studies of major depressive disorder endophenotypes (exaggerated reactivity to negative information, altered reward processing, cognitive control deficits, and somatic symptoms) on the one hand and selected peripheral inflammatory markers (C-reactive protein [CRP], cytokines, and adipokines) on the other.

METHODS

A systematized review was conducted. The database used for searching articles was PubMed (MEDLINE).

RESULTS

According to our search, most peripheral immunological markers associated with major depressive disorder are not specific to a single depressive symptom group. The most evident examples are CRP, IL-6, and TNF-α. The strongest evidence supports the connection of peripheral inflammatory markers with somatic symptoms; weaker evidence indicates a role of immune changes in altered reward processing. The least amount of evidence was found for the role of peripheral inflammatory markers in exaggerated reactivity to negative information and cognitive control deficits. Regarding the depression subtypes, a tendency for higher CRP and adipokines was observed in atypical depression; increased IL-6 was found in melancholic depression.

CONCLUSION

Somatic symptoms of depression could be a manifestation of a specific immunological endophenotype of depressive disorder. Melancholic and atypical depression may be characterized by different profiles of immunological markers.

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.

Goldilocks at work: Just the right amount of job demands may be needed for your sleep health

OBJECTIVES

It has been reported that job demands affect sleep, but how different levels of job demands affect sleep remains unclear. We examined whether curvilinear relationships exist between job demands and multiple sleep health outcomes.

DESIGN

Cross-sectional analyses with linear and quadratic effects, using self-administered survey data.

SETTING

A national sample of US adults.

PARTICIPANTS

Workers from Midlife in the United States Study (MIDUS2; n = 2927).

MEASUREMENTS

The Job Content Questionnaire assessed overall and 5 specific aspects of job demands (intensity, role conflict, work overload, time pressure, and interruptions). Habitual sleep health patterns across 5 dimensions (regularity, satisfaction/quality, daytime alertness, efficiency, and duration) were assessed. Age, sex, race/ethnicity, marital/partnered status, education, job tenure, work hours, body mass index, smoking status, and study sample were covariates.

RESULTS

There were significant linear and quadratic relationships between job demands and sleep outcomes. Specifically, the linear effects indicated that participants with higher job demands had worse sleep health, such as shorter duration, greater irregularity, greater inefficiency, and more sleep dissatisfaction. The quadratic effects, however, indicated that sleep regularity and efficiency outcomes were the best when participants' job demands were moderate rather than too low or too high. These effects were found for overall job demands as well as for specific aspects of job demands. Stratified analyses further revealed that these curvilinear associations were mainly driven by participants with low job control.

CONCLUSIONS

Moderate levels of job demands, especially if combined with adequate job control, are related to optimal sleep health.

Associations of polygenic risks, depression, and obesity-related traits in Taiwan Biobank

BACKGROUND

The comorbidity of obesity and major depressive disorder (MDD) may be attributable to a bidirectional relationship and shared genetic influence. We aimed to examine the polygenic associations between obesity and MDD and to characterize their corresponding impacts on the obesity mechanism.

METHODS

Genome-wide genotyping was available in 106,604 unrelated individuals from Taiwan Biobank. Polygenic risk score (PRS) for body mass index (BMI) and MDD was derived to evaluate their effects on obesity-related traits. Stratified analyses were performed for the modified effect of depression on the polygenic associations.

RESULTS

The MDD PRS was positively associated with waistline (beta in per SD increase in PRS = 0.12), hipline (beta = 0.08), waist-hip ratio (WHR) (beta = 0.05), body fat rate (beta = 0.08), BMI (beta = 0.05), overweight (OR = 1.02 for BMI ≥ 25), and obesity (OR = 1.05 for BMI ≥ 30). For the synergism between depression and BMI PRS, the presence of active depression symptoms defined by the PHQ-4 (p for interaction < 0.05 for waistline, WHR, and BMI) was more salient than lifetime MDD.

LIMITATIONS

Limitations include recall bias for MDD due to a retrospective self-reporting questionnaire, a low response rate of the PHQ-4 for evaluating active psychological symptoms, and limited generalizability to non-Taiwanese ancestries.

CONCLUSIONS

The shared genetic etiology of obesity and depression was demonstrated. The amplified effect of BMI polygenic effect on obesity for individuals with active depressive symptoms was also characterized. The study may be helpful for designing public health interventions to reduce the disease burden caused by obesity and depression.

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.

Neurobiological Markers for Predicting Treatment Response in Patients with Bipolar Disorder

Predictive neurobiological markers for prognosis are essential but underemphasized for patients with bipolar disorder (BD), a neuroprogressive disorder. Hence, we developed models for predicting symptom and functioning changes. Sixty-one patients with BD were recruited and assessed using the Young Mania Rating Scale (YMRS), Montgomery−Åsberg Depression Rating Scale (MADRS), Positive and Negative Syndrome Scale (PANSS), UKU Side Effect Rating Scale (UKU), Personal and Social Performance Scale (PSP), and Global Assessment of Functioning scale both at baseline and after 1-year follow-up. The models for predicting the changes in symptom and functioning scores were trained using data on the brain morphology, functional connectivity, and cytokines collected at baseline. The correlation between the predicted and actual changes in the YMRS, MADRS, PANSS, and UKU scores was higher than 0.86 (q < 0.05). Connections from subcortical and cerebellar regions were considered for predicting the changes in the YMRS, MADRS, and UKU scores. Moreover, connections of the motor network were considered for predicting the changes in the YMRS and MADRS scores. The neurobiological markers for predicting treatment-response symptoms and functioning changes were consistent with the neuropathology of BD and with the differences found between treatment responders and nonresponders.

Störungsspezifische und transdiagnostische Veränderung der Inflammationsaktivität bei psychischen Störungen

Zusammenfassung. Theoretischer Hintergrund: Empirische Befunde deuten vermehrt auf eine erhöhte Entzündungsaktivität im Zusammenhang mit psychischen Störungen hin. Inwieweit sich inflammatorische Veränderungen über Störungen hinweg unterscheiden bzw. ob Inflammation ein transdiagnostisches Korrelat psychischer Störungen darstellt, ist bisher jedoch noch nicht eindeutig beantwortet. Fragestellung: Liegen spezifische inflammatorische Marker (z. B. Zytokine) über psychische Störungen hinweg verändert vor und/oder gibt es störungsspezifische Zytokinveränderungen bei Major Depression (MDD), Bipolarer Störung, Schizophrenie und Angststörungen inkl. Posttraumatischer Belastungsstörung (PTBS). Methode: Basierend auf einer Literaturrecherche werden aktuelle metaanalytische Befunde, die Studien bei Patient_innen mit MDD, Bipolarer Störung, Schizophrenie oder Angststörungen inkl. PTBS im Vergleich zu gesunden Kontrollen betrachten, zusammengetragen und vergleichend dargestellt. Ergebnisse: Aktuelle Evidenz verweist relativ konsistent auf Veränderungen des Immunsystems, wobei v. a. das Zytokin Interleukin (IL–) 6 und das C-reaktive Protein (CRP) störungsübergreifend leicht erhöht sind. Schlussfolgerungen: Perspektivisch könnten Patient_innen mit chronisch inflammatorischen Erkrankungen und psychischen Störungen von psychotherapiebegleitenden antiinflammatorischen Maßnahmen wie bspw. körperlicher Aktivität, antiinflammatorischer Ernährung und Entspannungsverfahren profitieren.

Associations of somatic depressive symptoms with body mass index, systemic inflammation, and insulin resistance in primary care patients with depression

The somatic depressive symptom cluster (including appetite and sleep disturbances) is more strongly associated with insulin resistance (a diabetes risk marker) than other depressive symptom clusters. Utilizing baseline data from 129 primary care patients with depression but no diabetes in the eIMPACT trial (M_age = 59 years, 78% female, 50% Black), we examined associations of somatic depressive symptoms with insulin resistance (HOMA-IR), body mass index (BMI), and high-sensitivity C-reactive protein (hsCRP). We tested BMI and hsCRP as mediators and race as a moderator of these relationships. Hyperphagia was positively associated HOMA-IR (β = 0.19, p = .048) and BMI (β = 0.30, p < .001); poor appetite was negatively associated with HOMA-IR (β = -0.24, p = .02); hypersomnia was positively associated with HOMA-IR (β = 0.28, p = .003), BMI (β = 0.26, p = .003), and hsCRP (β = 0.23, p = .01); and disturbed sleep was positively associated with hsCRP (β = 0.21, p = .04). BMI partially mediated hyperphagia and hypersomnia's associations with HOMA-IR; hsCRP partially mediated the hypersomnia-HOMA-IR association; and race moderated the hyperphagia-HOMA-IR association (positive for White participants but null for Black participants). People with depression experiencing hyperphagia and/or hypersomnia may be a subgroup with greater insulin resistance; BMI and hsCRP are likely pathways in these relationships. This study highlights the importance of considering the direction of somatic depressive symptoms in the context of cardiometabolic disease risk.

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.

Associations between heart rate variability, peripheral inflammatory markers and major depressive disorder

BACKGROUND

Measures for the irregularity of the heartbeat, for example respiratory sinus arrhythmia, have been implicated as a measure for restorative functions of the vegetative nervous system.

METHODS

In the current observational study, we investigated 265 subjects, 70 of whom had a lifetime history of major depression, with a plethysmographic heartbeat monitor, blood sampling, as well as a range of psychiatric questionnaires.

RESULTS

Subjects with a history of MDE had significantly reduced respiratory sinus arrhythmia (RSA) as compared to never-depressed controls; in the whole sample, higher RSA went with lower anxiety/fear variables, especially in subscores related to cardiac symptoms as well as being afraid of dying. A reduced RSA was also associated with an increased concentration of cytokines (TNFa, IL1a, IL6, IFNg) and thyroid-stimulating hormone in the serum, pointing to a possible triangular relationship between immune system, vegetative nervous system, and emotional dysregulation.

LIMITATIONS

We used a plethysmographic device for the measurement of heartbeat instead of an electrocardiogram, and had a single time point only.

CONCLUSIONS

This data corroborate the idea that a disequilibrium of the vegetative nervous, especially if accompanied by a dysregulation system in immune function, can increase the risk for depression. Conversely, vagal stimulation and anti-inflammatory treatments may support the treatment with antidepressants.

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.

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.

The menace of obesity to depression and anxiety prevalence

The incidence of depression and anxiety is amplified by obesity. Mounting evidence reveals that the psychiatric consequences of obesity stem from poor diet, inactivity, and visceral adipose accumulation. Resulting metabolic and vascular dysfunction, including inflammation, insulin and leptin resistance, and hypertension, have emerged as key risks to depression and anxiety development. Recent research advancements are exposing the important contribution of these different corollaries of obesity and their impact on neuroimmune status and the neural circuits controlling mood and emotional states. Along these lines, this review connects the clinical manifestations of depression and anxiety in obesity to our current understanding of the origins and biology of immunometabolic threats to central nervous system function and behavior.

The dietary inflammatory index is inversely associated with depression, which is minimally mediated by C-reactive protein

Depression affects 8% of adults in America and is one of the leading causes of disability in Western countries. The dietary inflammatory index (DII) has previously been reported to be associated with inflammation and depression. However, no study to date has looked at the potential mediating effect of inflammation on the association of DII and depression. We hypothesized that the association of DII and depression would be both statistically and clinically mediated substantially by inflammation. We assessed these associations using the cross-sectional National Health and Nutrition Examination Survey (NHANES) 2005-2010 database. Our analysis included 10,022 participants aged 20 years and older. Inflammation was assessed with C-reactive protein (CRP) levels. Diet was measured using two 24 hour dietary recalls. Depression was assessed using the 9-item Patient Health Questionnaire (PHQ-9), which has a score range of 0 to 27, with the higher score showing more severe depressive symptoms. Comparing the highest to lowest DII quartiles, the mean score difference for depression was 0.47 units (95% CI 0.24-0.70, P-trend <.001) in the multivariable adjusted model. In the sex-stratified models, the results remained significant only among females, with the mean score difference of 0.72 (95% CI 0.34-1.10, P-trend <.001). CRP mediated 3.6% of the association between DII and depression in the total population in the fully adjusted model, which was statistically significant (P-trend <.001) but not clinically significant. No mediation association was found in the sex-stratified models. Further studies are needed to assess the associations with various inflammatory biomarkers in larger and more diverse populations.

Associations of somatic depressive symptoms with food attentional bias and eating behaviors

Recent evidence suggests that atypical major depressive disorder (MDD) - whose key features include the reversed somatic symptoms of hyperphagia (increased appetite) and hypersomnia (increased sleep) - is a stronger predictor of future obesity than other MDD subtypes. The mechanisms underlying this relationship are unclear. The present study sought to elucidate whether the individual symptoms of hyperphagia, hypersomnia, poor appetite, and disturbed sleep have differential relationships with food attentional bias, emotional eating, external eating, and restrained eating. This cross-sectional laboratory study involved 103 young adults without obesity (mean age = 20 years, 79% female, 26% non-White, mean BMI = 23.4 kg/m²). We measured total depressive symptom severity and individual symptoms of hyperphagia, poor appetite, and disturbed sleep using the Hopkins Symptom Checklist-20 (SCL-20) and added an item to assess hypersomnia; food attentional bias using a Food Stroop task; and self-reported eating behaviors using the Dutch Eating Behavior Questionnaire. Hyperphagia was positively associated with emotional eating but negatively associated with food attentional bias. Hypersomnia was negatively associated with emotional eating. Poor appetite was negatively associated with emotional eating. Disturbed sleep was positively associated with food attentional bias and emotional eating. An aggregate of the remaining 15 depressive symptoms (SCL-15) was positively associated with emotional and restrained eating. Our findings highlight the importance of examining the direction of somatic depressive symptoms, and they set the stage for future research to identify subgroups of people with depression at greatest risk for obesity (e.g., those with hyperphagia and/or disturbed sleep) and the mechanisms responsible for this elevated risk (e.g., emotional eating).

Inflammatory phenotype of depression symptom structure: A network perspective

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Linking atypical depression and insulin resistance-related disorders via low-grade chronic inflammation: Integrating the phenotypic, molecular and neuroanatomical dimensions

Insulin resistance (IR) and related disorders, such as T2DM, increase the risk of major depressive disorder (MDD) and vice versa. Current evidence indicates that psychological stress and overeating can induce chronic low-grade inflammation that can interfere with glutamate metabolism in MDD as well as insulin signaling, particularly in the atypical subtype. Here we first review the interactive role of inflammatory processes in the development of MDD, IR and related metabolic disorders. Next, we describe the role of the anterior cingulate cortex in the pathophysiology of MDD and IR-related disorders. Furthermore, we outline how specific clinical features of atypical depression, such as hyperphagia, are more associated with inflammation and IR-related disorders. Finally, we examine the regional specificity of the effects of inflammation on the brain that show an overlap with the functional and morphometric brain patterns activated in MDD and IR-related disorders.

Associations between depressive symptom profiles and immunometabolic characteristics in individuals with depression and their siblings

OBJECTIVES

The present study examined associations between immunometabolic characteristics (IMCs) and depressive symptom profiles (DSPs) in probands with lifetime diagnoses of depression and/or anxiety disorders and their siblings.

METHODS

Data were from the Netherlands Study of Depression and Anxiety, comprising 256 probands with lifetime diagnoses of depression and/or anxiety and their 380 siblings. Measured IMCs included blood pressure, waist circumference, and levels of glucose, triglycerides, HDL cholesterol, CRP, TNF-α and IL-6. DSPs included mood, cognitive, somatic and atypical-like profiles. We cross-sectionally examined whether DSPs were associated with IMCs within probands and within siblings, and whether DSPs were associated with IMCs between probands and siblings.

RESULTS

Within probands and within siblings, higher BMI and waist circumference were associated with higher somatic and atypical-like profiles. Other IMCs (IL-6, glucose and HDL cholesterol) were significantly related to DSPs either within probands or within siblings. DSPs and IMCs were not associated between probands and siblings.

CONCLUSIONS

The results suggest that there is a familial component for each trait, but no common familial factors for the association between DSPs and IMCs. Alternative mechanisms, such as direct causal effects or non-shared environmental risk factors, may better fit these results.

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

Increasingly, it has been recognized that analysis at the symptom, rather than diagnostic, level will drive progress in the field of immunopsychiatry. Network analysis offers a useful tool in this pursuit with the ability to identify associations between immune markers and individual symptoms, independent of all other variables modeled. However, investigation into how methodological decisions (i.e., including vs. excluding participants with C-reactive protein (CRP) >10 mg/L, regularized vs. nonregularized networks) influence results is necessary to establish best practices for the use of network analysis in immunopsychiatry. In a sample of 3,464 adult participants from the 2015-2016 National Health and Nutrition Examination Survey dataset, this study found consistent support for associations between CRP and fatigue and changes in appetite and some support for additional CRP-criterion associations. Methodologically, results consistently demonstrated that including individuals with CRP >10 mg/L and estimating nonregularized networks provided better estimates of these associations. Thus, we recommend considering the use of nonregularized networks in immunopsychiatry and inclusion of cases with CRP values >10 mg/L when testing the association between CRP and depression criteria, unless contraindicated by the research question being tested. Additionally, results most consistently suggest that CRP is uniquely related to fatigue and changes in appetite, supporting their inclusion in an immunometabolic phenotype of depression. Finally, these associations suggest that fatigue and changes in appetite might be particularly receptive to anti-inflammatory treatments. However, future research with more nuanced measures is necessary to parse out whether appetite increases or decreases drive this association. Further, longitudinal research is an important next step to test how these relationships manifest over time.

Using Precision Medicine with a Neurodevelopmental Perspective to Study Inflammation and Depression

PURPOSE OF REVIEW

To consider various precision medicine approaches to further elucidate the relationship between inflammation and depression and to illustrate how a neurodevelopmental perspective can help in this regard.

RECENT FINDINGS

Inflammation associates most strongly with phenotypes of depression that reflect illness behavior and/or metabolic dysfunction and obesity. A separate body of research has shown that maternal inflammation during pregnancy can alter brain circuitry important for mood regulation and/or reward in the developing fetus. Our research group is finding that maternal CRP levels differentially predict positive and negative affect in children assessed at age 4 years, depending on the timing of plasma sampling during pregnancy and the sex of the child. Recent authors have stressed the need to use a variety of precision medicine approaches to refine our understanding of inflammation-depression links. Adding a neurodevelopmental perspective may help to address some of the methodological challenges in this active area of study.

Peripheral Markers of Depression

Major Depressive Disorder (MDD) is a leading cause of disability worldwide, creating a high medical and socioeconomic burden. There is a growing interest in the biological underpinnings of depression, which are reflected by altered levels of biological markers. Among others, enhanced inflammation has been reported in MDD, as reflected by increased concentrations of inflammatory markers-C-reactive protein, interleukin-6, tumor necrosis factor-α and soluble interleukin-2 receptor. Oxidative and nitrosative stress also plays a role in the pathophysiology of MDD. Notably, increased levels of lipid peroxidation markers are characteristic of MDD. Dysregulation of the stress axis, along with increased cortisol levels, have also been reported in MDD. Alterations in growth factors, with a significant decrease in brain-derived neurotrophic factor and an increase in fibroblast growth factor-2 and insulin-like growth factor-1 concentrations have also been found in MDD. Finally, kynurenine metabolites, increased glutamate and decreased total cholesterol also hold promise as reliable biomarkers for MDD. Research in the field of MDD biomarkers is hindered by insufficient understanding of MDD etiopathogenesis, substantial heterogeneity of the disorder, common co-morbidities and low specificity of biomarkers. The construction of biomarker panels and their evaluation with use of new technologies may have the potential to overcome the above mentioned obstacles.

Depression Heterogeneity and Its Biological Underpinnings: Toward Immunometabolic Depression

Epidemiological evidence indicates the presence of dysregulated homeostatic biological pathways in depressed patients, such as increased inflammation and disrupted energy-regulating neuroendocrine signaling (e.g., leptin, insulin). Alterations in these biological pathways may explain the considerable comorbidity between depression and cardiometabolic conditions (e.g., obesity, metabolic syndrome, diabetes) and represent a promising target for intervention. This review describes how immunometabolic dysregulations vary as a function of depression heterogeneity by illustrating that such biological dysregulations map more consistently to atypical behavioral symptoms reflecting altered energy intake/expenditure balance (hyperphagia, weight gain, hypersomnia, fatigue, and leaden paralysis) and may moderate the antidepressant effects of standard or novel (e.g., anti-inflammatory) therapeutic approaches. These lines of evidence are integrated in a conceptual model of immunometabolic depression emerging from the clustering of immunometabolic biological dysregulations and specific behavioral symptoms. The review finally elicits questions to be answered by future research and describes how the immunometabolic depression dimension could be used to dissect the heterogeneity of depression and potentially to match subgroups of patients to specific treatments with higher likelihood of clinical success.

Associations between systemic inflammation and somatic depressive symptoms: Findings from the Moli-sani study

BACKGROUND

The link between systemic inflammation and depression has been deeply investigated, but relatively few studies explored symptom-specific associations, mostly focusing on common inflammatory biomarkers like C-reactive protein (CRP) levels.

METHODS

We investigated associations of low-grade inflammation with depressive symptoms assessed through a reduced version of Patient Health Questionnaire 9 (PHQ-9) in a large population-based cohort of adult Italians (N = 13 301). We built logistic regressions between each depressive symptom and composite index of systemic inflammation based on four circulating biomarkers, namely CRP, Plt, WBC, and GLR (INFLA)-score, a composite blood-based inflammation index, and with its component biomarkers, namely CRP, platelets count (Plt), white blood cells count (WBC), and granulocyte-to-lymphocyte ratio (GLR).

RESULTS

We observed a strong association of the altered appetite/eating symptom with standardized INFLA-score (OR [95% CI] = 1.19 [1.12-1.26]; corrected p = 3.0 × 10-7 ), CRP (1.28 [1.20-1.36]; p = 1.9 × 10-13 ), and WBC (1.13 [1.06-1.20]; p = 2.3 × 10-3 ), and of tiredness/low energy with GLR (1.11 [1.05-1.17]; p = 9.4 × 10-3 ). These associations remained stable within nondepressed participants (PHQ-9 < 10), and after adjustment for the use of antidepressants, main chronic conditions, and lifestyle factors; while they were notably attenuated within depressed participants (PHQ-9 ≥ 10) and-for altered appetite only-by adjustment for obesity.

CONCLUSIONS

This study provides a robust replication of the association previously reported between CRP and altered appetite in a large US population cohort, and supports a link between systemic inflammation, altered appetite, and tiredness. Moreover, it extends this evidence to inflammatory markers other than CRP and suggests new targets for the treatment of atypical depression.

Depression profilers and immuno-metabolic dysregulation: Longitudinal results from the NESDA study

BACKGROUND

Major depressive disorder (MDD) is linked to higher cardio-metabolic comorbidity that may in part be due to the low-grade inflammation and poorer metabolic health observed in MDD. Heterogeneity of MDD is however large, and immune-inflammatory and metabolic dysregulation is present in only part of the MDD cases. We examined the associations of four depression dimensional profilers (atypical energy-related symptom dimension, melancholic symptom dimension, childhood trauma severity, and anxious distress symptom dimension) with immuno-metabolic outcomes, both cross-sectionally and longitudinally.

METHODS

Three waves covering a 6-year follow-up (>7000 observations) of the Netherlands Study of Depression and Anxiety (NESDA) were used. Depression profilers were based on the Inventory of Depressive Symptomatology, the Beck Anxiety Inventory, and the Childhood Trauma index. An inflammatory index (based on IL-6 and CRP), a metabolic syndrome index (based on the five metabolic syndrome components), and a combination of these two indices were constructed. Mixed models were used for cross-sectional and longitudinal models, controlling for covariates.

RESULTS

Of the four depression profilers, only the atypical, energy-related symptom dimension showed robust associations with higher scores on the inflammatory, metabolic syndrome and combined inflammatory-metabolic indexes cross-sectionally, as well as at follow-up. The melancholic symptom dimension was associated with lower scores on the metabolic syndrome index both cross-sectionally and longitudinally.

CONCLUSION

The atypical energy-related symptom dimension was linked to poorer immune-inflammatory and metabolic health, while the melancholic symptom dimension was linked to relatively better metabolic health. Persons with high atypical energy-related symptom burden, representing an immuno-metabolic depression, may be the most important group to target in prevention programs for cardiometabolic disease, and may benefit most from treatments targeting immuno-metabolic pathways.

Adiposity, depression and anxiety: interrelationship and possible mediators

OBJECTIVES

To explore the association between adiposity, major depressive disorder and generalized anxiety disorder, and to assess the role of inflammation, diet quality and physical activity in this association.

METHODS

We used data from 2,977 individuals from the 1993 Pelotas Cohort (Brazil) who attended the 18- and 22-year follow-ups. We assessed general obesity using body mass index, fat mass index, and abdominal obesity using waist circumference. Major Depressive Disorder and generalized anxiety disorder were assessed using the mini-international neuropsychiatric interview. C-reactive protein and interleukin-6 (IL-6) levels were used as a measure of inflammation; diet quality was estimated using the revised diet quality index, and physical activity was assessed by the International physical activity questionnaire (IPAQ, min/day). The association between adiposity and major depressive disorder and generalized anxiety disorder was assessed using logistic regression, and the natural indirect effect via the mediators was estimated using G-computation.

RESULTS

General obesity assessed by body mass index (OR: 2.3; 95% CI:1.13; 4.85), fat mass index (OR: 2.6; 95%CI: 1.37; 4.83), and abdominal obesity (OR: 2.5; 95%CI: 1.18; 5.39) were associated with higher odds of major depressive disorder, whereas major depressive disorder was only associated with obesity assessed by body mass index (OR=1.9; 95% CI: 1.09; 3.46). Obesity and generalized anxiety disorder were not associated. C-reactive protein, diet quality and physical activity did not mediate the effect of obesity on major depressive disorder, and C-reactive protein mediated about 25% of the effect of major depressive disorder on adiposity.

CONCLUSIONS

Depression, but not generalized anxiety disorder, is associated with adiposity in both directions, with a stronger evidence for the direction obesity-depression. Inflammation explains part of the effect of major depressive disorder on obesity but not the other way around. Further research should explore other mechanisms that could be involved in the association between obesity and depression.

The brain-adipocyte-gut network: Linking obesity and depression subtypes

Major depressive disorder (MDD) and obesity are dominant and inter-related health burdens. Obesity is a risk factor for MDD, and there is evidence MDD increases risk of obesity. However, description of a bidirectional relationship between obesity and MDD is misleading, as closer examination reveals distinct unidirectional relationships in MDD subtypes. MDD is frequently associated with weight loss, although obesity promotes MDD. In contrast, MDD with atypical features (MDD-AF) is characterised by subsequent weight gain and obesity. The bases of these distinct associations remain to be detailed, with conflicting findings clouding interpretation. These associations can be viewed within a systems biology framework-the psycho-immune neuroendocrine (PINE) network shared between MDD and metabolic disorders. Shared PINE subsystem perturbations may underlie increased MDD in overweight and obese people (obesity-associated depression), while obesity in MDD-AF (depression-associated obesity) involves more complex interactions between behavioural and biomolecular changes. In the former, the chronic PINE dysfunction triggering MDD is augmented by obesity-dependent dysregulation in shared networks, including inflammatory, leptin-ghrelin, neuroendocrine, and gut microbiome systems, influenced by chronic image-associated psychological stress (particularly in younger or female patients). In MDD-AF, behavioural dysregulation, including hypersensitivity to interpersonal rejection, fundamentally underpins energy imbalance (involving hyperphagia, lethargy, hypersomnia), with evolving obesity exaggerating these drivers via positive feedback (and potentially augmenting PINE disruption). In both settings, sex and age are important determinants of outcome, associated with differences in emotional versus cognitive dysregulation. A systems biology approach is recommended for further research into the pathophysiological networks underlying MDD and linking depression and obesity.

Anxiety, C-reactive protein, and obesity in NHANES 1999-2004

The inflammatory marker C-reactive protein has been linked to anxiety across a number of studies. This paper uses data for 1,439 participants of the National Health and Nutrition Examination Survey (NHANES) 1999–2004 to examine the association between anxiety and C-reactive protein (CRP), and the potential for moderation by body mass index. No association was found between anxiety or depression and CRP in unadjusted or multivariable-adjusted logistic regression analyses, nor was there evidence of moderation by continuous BMI, BMI class, or obesity. Future studies on the relationship between anxiety and CRP should utilize larger general population samples or populations with a high prevalence of anxiety. There is also a need for prospective studies in this area to better discern the temporal relationships between anxiety and inflammation.

Involvement of inflammatory gene expression pathways in depressed patients with hyperphagia

The pathophysiology of major depressive disorder (MDD) is highly heterogeneous. Previous evidence at the DNA level as well as on the serum protein level suggests that the role of inflammation in MDD pathology is stronger in patients with hyperphagia during an active episode. Which inflammatory pathways differ in MDD patients with hyperphagia inflammatory pathways in terms of gene expression is unknown. We analyzed whole-blood gene expression profiles of 881 current MDD cases and 331 controls from the Netherlands Study of Depression and Anxiety (NESDA). The MDD patients were stratified according to patients with hyperphagia (characterized by increased appetite and/or weight, N = 246) or hypophagia (characterized by decreased appetite and/or weight, N = 342). Using results of differential gene expression analysis between controls and the MDD subgroups, enrichment of curated inflammatory pathways was estimated. The majority of the pathways were significantly (FDR < 0.1) enriched in the expression profiles of MDD cases with hyperphagia, including top pathways related to factors responsible for the onset of inflammatory response ('caspase', 'GATA3', 'NFAT', and 'inflammasomes' pathways). Only two pathways ('adaptive immune system' and 'IL-8- and CXCR2-mediated signaling') were enriched in the MDD with hypophagia subgroup, these were also enriched in the total current MDD group and the group with hyperphagia. This confirms the importance of inflammation in MDD pathology of patients with hyperphagia, and suggests that distinguishing more uniform MDD phenotypes can help in finding their pathophysiological basis.

Depression and obesity: evidence of shared biological mechanisms

Depression and obesity are common conditions with major public health implications that tend to co-occur within individuals. The relationship between these conditions is bidirectional: the presence of one increases the risk for developing the other. It has thus become crucial to gain a better understanding of the mechanisms responsible for the intertwined downward physiological spirals associated with both conditions. The present review focuses specifically on shared biological pathways that may mechanistically explain the depression-obesity link, including genetics, alterations in systems involved in homeostatic adjustments (HPA axis, immuno-inflammatory activation, neuroendocrine regulators of energy metabolism including leptin and insulin, and microbiome) and brain circuitries integrating homeostatic and mood regulatory responses. Furthermore, the review addresses interventional opportunities and questions to be answered by future research that will enable a comprehensive characterization and targeting of the biological links between depression and obesity.

Treatment-resistant depression and peripheral C-reactive protein

BACKGROUND

C-reactive protein (CRP) is a candidate biomarker for major depressive disorder (MDD), but it is unclear how peripheral CRP levels relate to the heterogeneous clinical phenotypes of the disorder.AimTo explore CRP in MDD and its phenotypic associations.

METHOD

We recruited 102 treatment-resistant patients with MDD currently experiencing depression, 48 treatment-responsive patients with MDD not currently experiencing depression, 48 patients with depression who were not receiving medication and 54 healthy volunteers. High-sensitivity CRP in peripheral venous blood, body mass index (BMI) and questionnaire assessments of depression, anxiety and childhood trauma were measured. Group differences in CRP were estimated, and partial least squares (PLS) analysis explored the relationships between CRP and specific clinical phenotypes.

RESULTS

Compared with healthy volunteers, BMI-corrected CRP was significantly elevated in the treatment-resistant group (P = 0.007; Cohen's d = 0.47); but not significantly so in the treatment-responsive (d = 0.29) and untreated (d = 0.18) groups. PLS yielded an optimal two-factor solution that accounted for 34.7% of variation in clinical measures and for 36.0% of variation in CRP. Clinical phenotypes most strongly associated with CRP and heavily weighted on the first PLS component were vegetative depressive symptoms, BMI, state anxiety and feeling unloved as a child or wishing for a different childhood.

CONCLUSIONS

CRP was elevated in patients with MDD, and more so in treatment-resistant patients. Other phenotypes associated with elevated CRP included childhood adversity and specific depressive and anxious symptoms. We suggest that patients with MDD stratified for proinflammatory biomarkers, like CRP, have a distinctive clinical profile that might be responsive to second-line treatment with anti-inflammatory drugs.Declaration of interestS.R.C. consults for Cambridge Cognition and Shire; and his input in this project was funded by a Wellcome Trust Clinical Fellowship (110049/Z/15/Z). E.T.B. is employed half time by the University of Cambridge and half time by GlaxoSmithKline; he holds stock in GlaxoSmithKline. In the past 3 years, P.J.C. has served on an advisory board for Lundbeck. N.A.H. consults for GlaxoSmithKline. P.d.B., D.N.C.J. and W.C.D. are employees of Janssen Research &amp; Development, LLC., of Johnson &amp; Johnson, and hold stock in Johnson &amp; Johnson. The other authors report no financial disclosures or potential conflicts of interest.

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

One of the most common inflammatory markers examined in depression is C-reactive protein (CRP). However, the magnitude of the association between CRP and depression when controlling for potentially confounding factors such as age, sex, socio-economic status, body mass index, medication and other substance use, and medical illness, is unclear. Inconsistencies in other methodological practices, such as sample collection, assaying, and data cleaning and transformation, may contribute to variations in results. We aggregate studies that examined the association between CRP and depression in two ways. First, a systematic review summarizes how studies of CRP and depression have reported on methodological issues. Second, a tiered meta-analysis aggregates studies that have adhered to various levels of methodological rigor. Findings from the systematic review indicate a lack of protocol detail provided. The effect between depression and CRP was small, but highly significant across all stages of the meta-analysis (p < 0.01). The effect size in the most methodologically rigorous stage of the meta-analysis, which included studies controlling for age, sex, obesity, medical conditions and substance, medication, or psychosocial factors, was small (r = 0.05). There were also only 26 articles in this stage (13% of studies from the systematic review), suggesting that more studies that consistently account for these confounding factors are needed. Additionally, an a priori quality score of methodological rigor was a significant moderator in this stage of the meta-analysis. The effect size was strikingly attenuated (r = 0.005) and non-significant in studies with higher quality scores. We describe a set of recommended guidelines for future research to consider, including sample collection and assaying procedures, data cleaning and statistical methods, and control variables to assess.

Interleukin, tumor necrosis factor-α and C-reactive protein profiles in melancholic and non-melancholic depression: A systematic review

OBJECTIVE

The current diagnostic criteria for major depressive disorder (MDD) do not allow prediction of prognosis and therapeutic response. A possible strategy to improve this situation is the identification of depression subtypes on the bases of biomarkers reflecting underlying pathological processes such as neuro-inflammation.

METHODS

The PubMed/Medline database was searched until Apr 25th, 2017. In the initial search 1018 articles were retrieved, which were subsequently screened and only selected when the inclusion and exclusion criteria were fulfilled.

RESULTS

Eight eligible studies were found. Overall, serum interleukin-6 and 1β values were increased in the melancholic MDD subtype compared to controls and the non-melancholic MDD subtype. C-reactive protein was increased in non-melancholic MDD in 2 out of 4 studies, while there was no difference for tumor necrosis factor-α and interleukin-2 and 10.

CONCLUSION

Given the paucity of eligible studies the tentative conclusion must be drawn that peripheral inflammation markers have limited added value thus far to distinguish between melancholic and non-melancholic depression. To allow for a more definitive conclusion, further research is warranted using a broader panel of inflammatory markers in MDD subtypes, preferably based on a general consensus regarding diagnostic criteria and subtype definitions.

CRP genetic variants are associated with mortality and depressive symptoms in chronic heart failure patients

OBJECTIVE

Heart failure (HF) is a complex medical condition with a multitude of genetic and other factors being involved in the pathogenesis. Emerging evidence points to an involvement of inflammatory mechanisms at least in subgroups of patients. The same is true for depression and depressive symptoms, which have a high prevalence in HF patients and are risk factors for the development and outcomes of cardiovascular disease.

METHODS

In 936 patients of the Interdisciplinary Network Heart Failure (INH) program, CRP and IL-6 protein blood levels were measured and genetic variants (single nucleotide polymorphisms) of the CRP and IL6 gene analyzed regarding their influence on mortality.

RESULTS

Less common recessive genotypes of two single nucleotide polymorphisms in the CRP gene (rs1800947 and rs11265263) were associated with significantly higher mortality risk (p < 0.006), higher CRP levels (p = 0.029, p = 0.006) and increased depressive symptoms in the PHQ-9 (p = 0.005, p = 0.003). Variants in the IL-6 gene were not associated with mortality.

CONCLUSION

Our results hint towards an association of less common CRP genetic variants with increased mortality risk, depressive symptoms and peripheral CRP levels in this population of HF patients thereby suggesting a possible role of the inflammatory system as link between poor prognosis in HF and depressive symptoms.

Metabolic and inflammatory markers: associations with individual depressive symptoms

BACKGROUND

Literature has shown that obesity, metabolic syndrome and inflammation are associated with depression, however, evidence suggests that these associations are specific to atypical depression. Which of the atypical symptoms are driving associations with obesity-related outcomes and inflammation is unknown. We evaluated associations between individual symptoms of depression (both atypical and non-atypical) and body mass index (BMI), metabolic syndrome components and inflammatory markers.

METHODS

We included 808 persons with a current diagnosis of depression participating in the Netherlands Study of Depression and Anxiety (67% female, mean age 41.6 years). Depressive symptoms were derived from the Composite International Diagnostic Interview and the Inventory of Depressive Symptomatology. Univariable and multivariable regression analyses adjusting for sex, age, educational level, depression severity, current smoking, physical activity, anti-inflammatory medication use, and statin use were performed.

RESULTS

Increased appetite was positively associated with BMI, number of metabolic syndrome components, waist circumference, C-reactive protein and tumor necrosis factor-α. Decreased appetite was negatively associated with BMI and waist circumference. Psychomotor retardation was positively associated with BMI, high-density lipoprotein cholesterol and triglycerides, and insomnia with number of metabolic syndrome components.

CONCLUSION

Increased appetite - in the context of a depressive episode - was the only symptom that was associated with both metabolic as well as inflammatory markers, and could be a key feature of an immuno-metabolic form of depression. This immuno-metabolic depression should be considered in clinical trials evaluating effectiveness of compounds targeting metabolic and inflammatory pathways or lifestyle interventions.

Mood disorders and circulating levels of inflammatory markers in a longitudinal population-based study

BACKGROUND

There has been increasing evidence that chronic low-grade inflammation is associated with mood disorders. However, the findings have been inconsistent because of heterogeneity across studies and methodological limitations. Our aim is to prospectively evaluate the bi-directional associations between inflammatory markers including interleukin (IL)-6, tumor necrosis factor (TNF)-α and high sensitivity C-reactive protein (hsCRP) with mood disorders.

METHODS

The sample consisted of 3118 participants (53.7% women; mean age: 51.0, s.d. 8.8 years), randomly selected from the general population, who underwent comprehensive somatic and psychiatric evaluations at baseline and follow-up (mean follow-up duration = 5.5 years, s.d. 0.6). Current and remitted mood disorders including bipolar and major depressive disorders (MDD) and its subtypes (atypical, melancholic, combined atypical and melancholic, and unspecified) were based on semi-structured diagnostic interviews. Inflammatory biomarkers were analyzed in fasting blood samples. Associations were tested by multiple linear and logistic regression models.

RESULTS

Current combined MDD [β = 0.29, 95% confidence interval (CI) 0.03-0.55] and current atypical MDD (β = 0.32, 95% CI 0.10-0.55) at baseline were associated with increased levels of hsCRP at follow-up. There was little evidence for inflammation markers at baseline predicting mood disorders at follow-up.

CONCLUSIONS

The prospective unidirectional association between current MDD subtype with atypical features and hsCRP levels at follow-up suggests that inflammation may be a consequence of this condition. The role of inflammation, particularly hsCRP that is critically involved in cardiovascular diseases, warrants further study. Future research that examines potential influences of medications on inflammatory processes is indicated.

Cardiovascular Risk Factors as Differential Predictors of Incident Atypical and Typical Major Depressive Disorder in US Adults

OBJECTIVE

Although the association between major depressive disorder (MDD) and future cardiovascular disease (CVD) is established, less is known about the relationship between CVD risk factors and future depression, and no studies have examined MDD subtypes. Our objective was to determine whether hypertension, tobacco use, and body mass index (BMI) differentially predict atypical and typical MDD in a national sample of US adults.

METHODS

We examined prospective data from 22,915 adults with no depressive disorder history at baseline who participated in Wave 1 (2001-2002) and Wave 2 (2004-2005) of the National Epidemiologic Survey on Alcohol and Related Conditions. CVD risk factors (Wave 1) and incident MDD subtypes (Wave 2) were determined by structured interviews.

RESULTS

There were 252 patients with atypical MDD and 991 patients with typical MDD. In fully adjusted models, baseline hypertension (odds ratio [OR] = 0.57, 95% confidence interval [CI] = 0.43-0.76), former tobacco use (OR = 1.46, 95% CI = 1.20-1.78), and BMI (OR = 1.32, 95% CI = 1.25-1.40; all p < .001) predicted incident atypical MDD versus no MDD, whereas no CVD risk factor predicted incident typical MDD. Baseline hypertension (OR = 0.52, 95% CI = 0.39-0.70), former tobacco use (OR = 1.53, 95% CI = 1.22-1.93), and BMI (OR = 1.26, 95% CI = 1.18-1.36; all p < .001) also predicted incident atypical MDD versus typical MDD.

CONCLUSIONS

Our study is the first to report that CVD risk factors differentially predict MDD subtypes, with hypertension (protective factor), former tobacco use (risk factor), and BMI (risk factor) being stronger predictors of incident atypical versus typical MDD. Such evidence could provide insights into the etiologies of MDD subtypes and inform interventions tailored to MDD subtype.

Atypical depression and double depression predict new-onset cardiovascular disease in U.S. adults

BACKGROUND

Although depression is a risk factor for cardiovascular disease (CVD), it is unknown whether this risk varies across depressive disorder subtypes. Thus, we investigated atypical major depressive disorder (MDD) and double depression as predictors of new-onset CVD in a nationally representative sample of U.S. adults.

METHODS

Prospective data from 28,726 adults initially free of CVD who participated in Wave 1 (2001-2002) and Wave 2 (2004-2005) of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) were examined. Lifetime depressive disorder subtypes (Wave 1) and incident CVD (Wave 2) were determined by structured interviews.

RESULTS

We identified 1,116 incident CVD cases. In demographics adjusted models, the atypical MDD group had a higher odds of incident CVD than the no depression history (OR = 2.19, 95% CI: 1.71-2.81, P < .001), dysthymic disorder only (OR = 1.61, 95% CI: 1.08-2.39, P = .019), and nonatypical MDD (OR = 1.46, 95% CI: 1.11-1.91, P = .006) groups. Likewise, the double depression group had a higher odds of incident CVD than the no depression history (OR = 2.17, 95% CI: 1.92-2.45, P < .001), dysthymic disorder only (OR = 1.59, 95% CI: 1.16-2.19, P = .004), and MDD only (OR = 1.46, 95% CI: 1.20-1.77, P < .001) groups. Relationships were similar but attenuated after adjustment for CVD risk factors and anxiety disorders.

CONCLUSIONS

Adults with atypical MDD or double depression may be subgroups of the depressed population at particularly high risk of new-onset CVD. Thus, these subgroups may (a) be driving the overall depression-CVD relationship and (b) be in need of earlier and/or more intense CVD primary prevention efforts to reduce their excess CVD burden.

The relationships of current suicidal ideation with inflammatory markers and heart rate variability in unmedicated patients with major depressive disorder

Studies investigating inflammatory status and autonomic functioning simultaneously in depressed patients with current suicidal ideation (SI) are lacking. We recruited 58 unmedicated depressed patients with current SI but without lifetime history of suicidal behavior, as well as 61 equally depressed patients without lifetime history of SI or suicidal behavior. We measured serum cortisol, high-sensitivity C-reactive protein (hs-CRP), erythrocyte sedimentation rate (ESR), and autonomic functioning evaluated by frequency-domain measures of heart rate variability (HRV). The intensity of current SI was rated with the Columbia Suicide Severity Rating Scale. Chronic psychological stress was assessed using the Chinese version of the Perceived Stress Scale (PSS). Patients with current SI showed higher hs-CRP and ESR but lower variance (total HRV), low frequency (LF), and high frequency (HF) HRV than those without lifetime history of SI. We found no differences in cortisol levels and PSS scores. The intensity of current SI was negatively correlated with variance, LF, and HF but positively correlated with hs-CRP. Our results help improve the understanding of the relationships among current SI, inflammation, and autonomic functioning in depressed patients. The combined use of inflammatory markers and HRV indices may one day be applied in predicting and monitoring patients' suicide risk.

Depressive Disorder Subtypes as Predictors of Incident Obesity in US Adults: Moderation by Race/Ethnicity

We compared the relative importance of atypical major depressive disorder (MDD), nonatypical MDD, and dysthymic disorder in predicting 3-year obesity incidence and change in body mass index and determined whether race/ethnicity moderated these relationships. We examined data from 17,787 initially nonobese adults in the National Epidemiologic Survey on Alcohol and Related Conditions waves 1 (2001-2002) and 2 (2004-2005) who were representative of the US population. Lifetime subtypes of depressive disorders were determined using a structured interview, and obesity outcomes were computed from self-reported height and weight. Atypical MDD (odds ratio (OR) = 1.68, 95% confidence interval (CI): 1.43, 1.97; P < 0.001) and dysthymic disorder (OR = 1.66, 95% CI: 1.29, 2.12; P < 0.001) were stronger predictors of incident obesity than were nonatypical MDD (OR = 1.11, 95% CI: 1.01, 1.22; P = 0.027) and no history of depressive disorder. Atypical MDD (B = 0.41 (standard error, 0.15); P = 0.007) was a stronger predictor of increases in body mass index than were dysthymic disorder (B = -0.31 (standard error, 0.21); P = 0.142), nonatypical MDD (B = 0.007 (standard error, 0.06); P = 0.911), and no history of depressive disorder. Race/ethnicity was a moderator; atypical MDD was a stronger predictor of incident obesity in Hispanics/Latinos (OR = 1.97, 95% CI: 1.73, 2.24; P < 0.001) than in non-Hispanic whites (OR = 1.54, 95% CI: 1.25, 1.91; P < 0.001) and blacks (OR = 1.72, 95% CI: 1.31, 2.26; P < 0.001). US adults with atypical MDD are at particularly high risk of weight gain and obesity, and Hispanics/Latinos may be especially vulnerable to the obesogenic consequences of depressions.

Oxidative stress, inflammation and treatment response in major depression

OBJECTIVE

Increased inflammation and oxidative stress have been shown in Major Depressive Disorder (MDD), although there is significant heterogeneity across studies. Whether markers of inflammation and oxidative stress are associated with antidepressant treatment response in MDD is currently unclear. The goals of the present study are to investigate markers of inflammation and oxidative stress in unmedicated MDD subjects and controls and test the relationship between these markers and antidepressant response in MDD subjects.

METHODS

Interleukin (IL)-6, tumor necrosis factor (TNF)-α, C-reactive protein, F2-isoprostanes, 8-OH 2-deoxyguanosine (8-OHdG), glutathione peroxidase, glutathione, and vitamin C were quantified in blood samples from 50 unmedicated MDD subjects and 55 healthy controls. Depression symptom severity was rated with the 17-item Hamilton Depression Rating Scale (HDRS). All subjects were somatically healthy and free from medications that could interfere with inflammation and oxidative stress markers. A subgroup of 22 MDD subjects underwent open-label selective serotonin reuptake inhibitor (SSRI) antidepressant treatment for eight weeks, after which blood sampling and the HDRS were repeated. Antidepressant treatment "response" was defined as ≥50% decrease in HDRS ratings over 8 weeks of treatment.

RESULTS

After controlling for the effects of age, sex, body mass index and smoking, MDD subjects had significantly higher levels of IL-6 (p<0.001), TNF-α (p<0.001), 8-OHdG (p=0.018), and F2-isoprostanes (p=0.012). Compared to Responders, Non-responders to SSRI antidepressant treatment had higher levels of F2-isoprostanes at baseline (p=0.006), and after eight weeks of treatment (p=0.031). Non-responders showed a significant increase in 8-OHdG over the course of treatment (p=0.021), whereas Responders showed a significant decrease in IL-6 over the course of treatment (p=0.019).

CONCLUSION

Our results are in line with previous reports of increased levels of markers of inflammation and oxidative stress in MDD. Moreover, poorer antidepressant treatment response was related to higher baseline levels of the major oxidative stress marker, F2-isoprostanes, in vivo. Further, antidepressant response was associated with changes in oxidative (8-OHdG) and inflammatory (IL-6) markers.