Increased C-reactive protein concentrations were associated with suicidal behavior in patients with depressive disorders: a meta-analysis

Immunological alterations in patients with current and lifetime suicide ideation and attempts: Examining the relationship with depressive symptoms

Background

Suicidal ideation and attempt (SI/SA) have been associated with dysregulation of the immune response and inflammation. However, few studies have explored how innate and acquired cellular immunity impact on the peripheral immune response. Our study addresses this gap by examining the composition of peripheral immune cells and humoral markers among individuals with current SI/SA, individuals with a history of SI/SA, and healthy controls (HC). Additionally, we aim to explore whether depressive symptoms settle the relationship between inflammation and SI/SA.

Methods

This is a multicenter case-control study that included 105 participants. Clinical and demographic characterists together with hemogram parameters, soluble pro and anti-inflamatory factors, and specific innate and adaptive immune cell populations were compared among patients with current SI/SA (n = 21), a history of lifetime SI/SA (n = 42), and HC (n = 42).

Results

Patients with both current and lifetime SI/SA had a significant increase in the absolute count of monocytes and in the monocyte/lymphocyte ratio (MLR). Additionally, patients with current and lifetime SI/SA showed a significant increase in high-sensitivity C- reactive protein (hs-CRP), and patients with lifetime SI/SA also showed higher levels of Erythrocyte Sedimentation Rate (ESR). The cellular inflammatory status of patients with SI/SA was characterized by altered proportions of monocytes with higher levels of nonclassical and intermediate monocytes. No differences were observed in the number of lymphocytes and the proportion of CD4 and CD8 between patients and HC, but we found differences in markers of exhaustion of CD4 lymphocytes, with increased levels of Programmed cell death protein 1 (PD1) in Current SI/SA and Lymphocyte activation gene 3 (LAG3) in Current SI/SA and Lifetime SI/SA compared to HC. The plasmainflammatory status was marked by higher levels of soluble Triggering receptor expressed on myeloid cells 2 (sTREM2) in patients with lifetime SI/SA compared to HC. Finally, the multinomial analysis indicates that inflammation and depressive symptoms are independently associated with SI/SA.

Conclusion

This study highlights the association of immunological alterations with SI/SA. Furthremore, SI/SA is independently influenced by depressive symptoms and inflammation. This may have important therapeutic implications, as in these patients, it may be necessary to treat the inflammatory process beyond treating the depressive symptoms.

Analysis of risk factors of suicidal ideation in adolescent patients with depression and construction of prediction model

BACKGROUND

Major depressive disorder is a common mental illness among adolescents and is the largest disease burden in this age group. Most adolescent patients with depression have suicidal ideation (SI); however, few studies have focused on the factors related to SI, and effective predictive models are lacking.

AIM

To construct a risk prediction model for SI in adolescent depression and provide a reference assessment tool for prevention.

METHODS

The data of 150 adolescent patients with depression at the First People's Hospital of Lianyungang from June 2020 to December 2022 were retrospectively analyzed. Based on whether or not they had SI, they were divided into a SI group (n = 91) and a non-SI group (n = 59). The general data and laboratory indices of the two groups were compared. Logistic regression was used to analyze the factors influencing SI in adolescent patients with depression, a nomogram prediction model was constructed based on the analysis results, and internal evaluation was performed. Receiver operating characteristic and calibration curves were used to evaluate the model's efficacy, and the clinical application value was evaluated using decision curve analysis (DCA).

RESULTS

There were differences in trauma history, triggers, serum ferritin levels (SF), high-sensitivity C-reactive protein levels (hs-CRP), and high-density lipoprotein (HDL-C) levels between the two groups (P < 0.05). Logistic regression analysis showed that trauma history, predisposing factors, SF, hs-CRP, and HDL-C were factors influencing SI in adolescent patients with depression. The area under the curve of the nomogram prediction model was 0.831 (95%CI: 0.763-0.899), sensitivity was 0.912, and specificity was 0.678. The higher net benefit of the DCA and the average absolute error of the calibration curve were 0.043, indicating that the model had a good fit.

CONCLUSION

The nomogram prediction model based on trauma history, triggers, ferritin, serum hs-CRP, and HDL-C levels can effectively predict the risk of SI in adolescent patients with depression.

Distinct correlation network of clinical characteristics in suicide attempters having adolescent major depressive disorder with non-suicidal self-injury

Suicidal behavior and non-suicidal self-injury (NSSI) are common in adolescent patients with major depressive disorder (MDD). Thus, delineating the unique characteristics of suicide attempters having adolescent MDD with NSSI is important for suicide prediction in the clinical setting. Here, we performed psychological and biochemical assessments of 130 youths having MDD with NSSI. Participants were divided into two groups according to the presence/absence of suicide attempts (SAs). Our results demonstrated that the age of suicide attempters is lower than that of non-attempters in participants having adolescent MDD with NSSI; suicide attempters had higher Barratt Impulsiveness Scale (BIS-11) impulsivity scores and lower serum CRP and cortisol levels than those having MDD with NSSI alone, suggesting levels of cortisol and CRP were inversely correlated with SAs in patients with adolescent MDD with NSSI. Furthermore, multivariate regression analysis revealed that NSSI frequency in the last month and CRP levels were suicidal ideation predictors in adolescent MDD with NSSI, which may indicate that the increased frequency of NSSI behavior is a potential risk factor for suicide. Additionally, we explored the correlation between psychological and blood biochemical indicators to distinguish suicide attempters among participants having adolescent MDD with NSSI and identified a unique correlation network that could serve as a marker for suicide attempters. Our research data further suggested a complex correlation between the psychological and behavioral indicators of impulsivity and anger. Therefore, our study findings may provide clues to identify good clinical warning signs for SA in patients with adolescent MDD with NSSI.

Impact of Toxoplasma gondii and Human Microbiome on Suicidal Behavior: A Systematic Review

BACKGROUND

Suicide remains a persistent global health challenge, resisting widespread prevention efforts. According to previous findings, toxoplasmosis is particularly associated with altered decision making, which could lead to risk-taking behavior, thereby increasing the likelihood for suicidal behavior (SB). In addition, discussion about the role of microbiome in psychiatric disorders has emerged lately, which also makes it relevant to investigate its role in the context of SB. Therefore, two systematic reviews are integrated in this paper, and the existing knowledge is comprehensively summarized regarding the association between microbial pathogens and SB.

METHODS

We conducted a systematic search with keywords including SB and Toxoplasma gondii (Suicid* AND Toxoplasm*) and microbiome (Suicid* AND Microbiome AND Microbiota) throughout PubMed and Scopus to retrieve related studies up to 9 November 2023, identifying 24 eligible records. The subjects of the included studies had to have fulfilled the criteria of an SB disorder as defined by DSM-5, and death cases needed to have been defined as suicide.

RESULTS

Most studies reported significant association between toxoplasmosis and SB, suggesting a higher likelihood of SB in the infected population. Regarding the microbiome, only very few studies investigated an association between SB and alterations in the microbiome. Based on six included studies, there were some indications of a link between changes in the microbiome and SB.

CONCLUSION

The cognitive aspects of decision making in T. gondii-infected individuals with SB should be further investigated to unravel the underlying mechanisms. Further sufficiently powered studies are needed to establish a link between SB and alterations in the microbiome.

Immune-related biomarkers and suicidal behaviors: A meta-analysis

Biomarkers that can differentiate between psychiatric disorders with and without suicidal behavior history from each other and from healthy volunteers may explain part of the pathogenesis of suicidal behavior. We conducted the hitherto largest meta-analysis comparing immune biomarkers between subjects with and without suicide attempt history or death by suicide. The study protocol was registered with PROSPERO, CRD42020212841. Standardized mean differences (SMD) were pooled with random-effects models. Heterogeneity between studies was assessed with the I2-statistic and publication bias was evaluated by the Egger test and funnel plots. Data were based on 36 studies including 2679 persons with suicidal behaviors and 6839 comparison subjects, and four immune-related biomarkers (CRP, IL-6, TNF-α and IL-1β). Suicidal behavior was associated with higher CRP blood levels compared with: healthy controls (SMD [95%CI] = 1.42[0.85-1.98]); patients with depression alone (SMD [95%CI] = 1.23[0.20-2.26]); and patients with any psychiatric disorders (SMD [95%CI] = 0.39[0.22-0.55]). IL-6 blood level was higher in patients with suicidal behaviors compared with healthy controls (SMD [95%CI] = 1.13[0.45-1.82]) and when compared with psychiatric patients without suicidal behaviors (SMD [95%CI] = 0.22 [0.11-0.33]). Meta-regression and subgroup analyses revealed that increased CRP in suicidal behavior is primarily driven by recent suicidal behavior. These results implicate the immune system and inflammatory response in suicidal behavior independent of a relationship to major psychiatric disorders, and that these biological measures are predominantly state-dependent markers. Future studies are needed to determine the cause-and-effect relationship of these immune system biomarkers with suicidal behavior, and their potential predictive properties.

Fight the Fire: Association of Cytokine Genomic Markers and Suicidal Behavior May Pave the Way for Future Therapies

The fight against suicide is highly challenging as it may be one of the most complex and, at the same time, most threatening among all psychiatric phenomena. In spite of its huge impact, and despite advances in neurobiology research, understanding and predicting suicide remains a major challenge for both researchers and clinicians. To be able to identify those patients who are likely to engage in suicidal behaviors and identify suicide risk in a reliable and timely manner, we need more specific, novel biological and genetic markers/indicators to develop better screening and diagnostic methods, and in the next step to utilize these molecules as intervention targets. One such potential novel approach is offered by our increasing understanding of the involvement of neuroinflammation based on multiple observations of increased proinflammatory states underlying various psychiatric disorders, including suicidal behavior. The present paper overviews our existing understanding of the association between suicide and inflammation, including peripheral and central biomarkers, genetic and genomic markers, and our current knowledge of intervention in suicide risk using treatments influencing inflammation; also overviewing the next steps to be taken and obstacles to be overcome before we can utilize cytokines in the treatment of suicidal behavior.

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.

Evaluation of inflammatory cytokines in drug-naïve major depressive disorder: A systematic review and meta-analysis

Objective: Altered levels of peripheral inflammatory and proinflammatory cytokine markers affect the different clinical stages of major depressive disorder (MDD). A concrete understanding of the causal mechanism of MDD is a prerequisite in developing treatment strategies and preventive plans. Here we aimed to conduct an updated systematic review and meta-analysis of studies assessing the association of C-reactive protein (CRP), INF-γ, MCP-1, and TNF-α in the peripheral fluid of drug-naïve MDD patients and healthy controls (HCs). Methods: We extracted articles from PubMed, ProQuest, PsycINFO, Web of Science, and Scopus databases from inception until 14 February 2021, to find relevant studies. In this meta-analysis, we included a total of 23 eligible studies (1,366 MDD patients and 1,342 controls) in the final meta-analysis. The Cochran's chi-square Q-test and I2-index were applied to measure the heterogeneity and inconsistency of all combined results. We selected a random-effect model during the analysis and measured publication biases using the funnel plot. We performed Bonferroni adjustment for multiple testing. Results: We found a high level of TNF-α in MDD patients than in control subjects Standardized Mean Difference (SMD) with a random-effects model: 1.04, 95% CI: 0.69-1.39, z = 5.84, p < 0.001). The levels of CRP (SMD with a random-effects model: 0.18, 95% CI: -0.85-1.23, z = 0.35, p = 0.73), INF-ɤ (SMD with a random-effects model: -0.05, 95% CI: -2.72-2.62, z = 0.03, p = 0.97), and MCP-1 (SMD with a random-effects model: 0.70, 95% CI: -0.09-1.49, z = 1.73, p = 0.08) were not significantly varies between MDD patients and HCs. Conclusion: The present study findings suggest the upregulated level of peripheral TNF-α but not CRP, INF-γ, and MCP-1 involve in depression. The elevated inflammatory cytokines confirmed the inflammatory state of depression. Therefore, inflammatory cytokines might serve as potential risk assessment markers in MDD.

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.

Increased immunological markers in female adolescents with non-suicidal self-injury

BACKGROUND

Nonsuicidal self-injury (NSSI) is a prevalent health problem among adolescents and commonly associated with psychological stressors such as childhood maltreatment and comorbid psychiatric disorders (e.g., depression). There is evidence that alterations of immunological markers may occur in the context of both environmental stress and psychopathological development.

METHOD

Here, we investigated differences in plasma/serum leukocytes, cortisol, c-reactive protein and interleukin-6 in a large sample of female adolescents with NSSI (n = 155) and healthy controls (HC, n = 42). Further, we assessed correlations between inflammatory markers, depression severity and the severity of childhood maltreatment.

RESULTS

The absolute number of leukocytes and the leukocyte/cortisol ratio (adjusted for body mass index and smoking) were significantly higher in NSSI as compared to HC, whereas interleukin-6 and CRP levels did not differ significantly between groups. Childhood maltreatment scores were significantly correlated with the leukocyte/cortisol ratio and depression severity was significantly correlated with both, absolute leukocyte numbers and the leukocyte/cortisol ratio.

CONCLUSIONS

Our results suggest that an immune activation can be detected in female adolescents with NSSI. Depression and childhood maltreatment, which are commonly reported in NSSI, may potentially underlie immune activation and partially explain group differences.

Inflammatory and oxidative stress markers in post-traumatic stress disorder: a systematic review and meta-analysis

Post-traumatic stress disorder (PTSD) has been associated with persistent, low-degree inflammation, which could explain the increased prevalence of autoimmune conditions and accelerated aging among patients. The aim of the present study is to assess which inflammatory and oxidative stress markers are associated with PTSD. We carried out a meta-analytic and meta-regression analysis based on a systematic review of studies comparing inflammatory and oxidative stress markers between patients with PTSD and controls. We undertook meta-analyses whenever values of inflammatory and oxidative stress markers were available in two or more studies. Overall, 28,008 abstracts were identified, and 54 studies were included, with a total of 8394 participants. The Newcastle-Ottawa Quality Assessment Scale was used to evaluate the quality of the studies. Concentrations of C-reactive protein (SMD = 0.64; 95% CI: 0.21 to 1.06; p = 0.0031; k = 12), interleukin 6 (SMD = 0.94; 95% CI: 0.36 to 1.52; p = 0.0014; k = 32), and tumor necrosis factor-α (SMD = 0.89; 95% CI: 0.23 to 1.55; p = 0.0080; k = 24) were significantly increased in patients with PTSD in comparison with healthy controls. Interleukin 1β levels almost reached the threshold for significance (SMD = 1.20; 95% CI: -0.04 to 2.44; p = 0.0569; k = 15). No oxidative stress marker was associated with PTSD. These findings may explain why PTSD is associated with accelerated aging and illnesses in which immune activation has a key role, such as cardiovascular diseases and diabetes. In addition, they pointed to the potential role of inflammatory markers as therapeutic targets.

Effects of stress on endophenotypes of suicide across species: A role for ketamine in risk mitigation

Suicide is a leading cause of death and morbidity worldwide, yet few interventions are available to mitigate its risk. Barriers to effective treatments involve a limited understanding of factors that predict the onset of suicidal thoughts and behaviors. In the context of suicide risk, stress is a precipitating factor that is largely overlooked in the literature. Indeed, the pathophysiology of stress and suicide are heavily interconnected, underscoring the need to target the stress system in suicide prevention. In this review, we integrate findings from the preclinical and clinical literature that links stress and suicide. We focus specifically on the effects of stress on underlying biological functions and processes associated with suicide, allowing for the review of research using animal models. Owing to the rapid anti-suicidal effects of (R,S)-ketamine, we discuss its ability to modulate various stress-related endophenotypes of suicide, as well as its potential role in preventing suicide in those with a history of chronic life stress (e.g., early life adversity). We highlight future research directions that could advance our understanding of stress-related effects on suicide risk, advocating a dimensional, endophenotype approach to suicide research.

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Suicide and chronic stress pathophysiology are interconnected.

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Chronic stress has profound impacts on several endophenotypes of suicide.

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Animal and human research points to stress as a precipitating factor in suicide.

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Ketamine modulates specific biological processes associated with stress and suicide.

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Suicide research into endophenotypes can help inform risk-mitigation strategies.

Suicide Biomarkers to Predict Risk, Classify Diagnostic Subtypes, and Identify Novel Therapeutic Targets: 5 Years of Promising Research

BACKGROUND

Suicide is a global health crisis. However, no objective biomarkers of suicide risk currently exist, and self-reported data can be unreliable, which limits prediction, diagnostic, and treatment efforts. Reliable biomarkers that can differentiate between diagnostic subgroups, predict worsening symptoms, or suggest novel therapeutic targets would be extremely valuable for patients, researchers, and clinicians.

METHODS

MEDLINE was searched for reports published between 2016 and 2021 using search terms (suicid*) AND (biomarker*) OR (indicat*). Reports that compared biomarkers between suicidal ideation, suicide attempt, death from suicide, or any suicide subgroup against other neuropsychiatric disorders were included. Studies exclusively comparing suicidal behavior or death from suicide with healthy controls were not included to ensure that biomarkers were specific to suicide and not other psychopathology.

RESULTS

This review summarizes the last 5 years of research into suicide-associated biomarkers and provides a comprehensive guide for promising and novel biomarkers that encompass varying presentations of suicidal ideation, suicide attempt, and death by suicide. The serotonergic system, inflammation, hypothalamic-pituitary-adrenal axis, lipids, and endocannabinoids emerged as the most promising diagnostic, predictive, and therapeutic indicators.

CONCLUSIONS

The utility of diagnostic and predictive biomarkers is evident, particularly for suicide prevention. While larger-scale studies and further in-depth research are required, the last 5 years of research has uncovered essential biomarkers that could ultimately improve predictive strategies, aid diagnostics, and help develop future therapeutic targets.

C-reactive protein as a potential biomarker in psychiatric practice: Are we there yet?

OBJECTIVES

Serum or plasma levels of C-reactive protein (CRP) and high-sensitivity CRP (hsCRP) are widely used clinical markers of inflammation in other branches of medicine, whereas its clinical use in psychiatry has been limited to research studies. We aimed to assess the possibility of using CRP/hsCRP in psychiatric practice. This is a review and evaluation of various lines of evidence supporting the concept of CRP as a biomarker for psychiatric disorders in certain conditions.

METHODS

We searched the literature for studies which assessed CRP/hsCRP levels in various psychiatric disorders.

RESULTS

The accumulating evidence from large studies and meta-analyses allows us to understand the role of CRP in major psychiatric disorders and increase our understanding of specific symptoms and subtypes of disorders. CRP may be considered a 'psychiatric biomarker' which can alert clinicians about neuroinflammation, adverse effects of medications, cardiometabolic status, co-morbidities, and may also predict clinical outcomes and guide optimal treatment.selection.

CONCLUSION

Although the underlying pathophysiological role of CRP and hsCRP is still elusive and the association between CRP and psychiatric disorders is inconsistent, CRP holds promise to become a psychiatric biomarker.

Inflammation and nitro-oxidative stress in current suicidal attempts and current suicidal ideation: a systematic review and meta-analysis

A meta-analysis showed a significant association between activated immune-inflammatory and nitro-oxidative (IO&NS) pathways and suicide attempts (SA). There is no data on whether recent suicidal ideation (SI) is accompanied by activated IO&NS pathways and whether there are differences between recent SA and SI. The current study searched PubMed, Google Scholar, and Web of Science, for articles published from inception until May 10, 2021, and systematically reviewed and meta-analysed the association between recent SA/SI (<3 months) and IO&NS biomarkers. We included studies which compared psychiatric patients with and without SA and SI and controls (either healthy controls or patients without SA/SI) and used meta-analysis (random-effect model with restricted maximum-likelihood) to delineate effect sizes with 95% confidence intervals (CI). Our search included 59 studies comprising 4.034 SA/SI cases and 12.377 controls. Patients with SA/SI showed activated IO&NS pathways (SMD: 0.299; CI: 0.200; 0.397) when compared to controls. The immune profiles were more strongly associated with SA than with SI, particularly when compared to healthy controls, as evidenced by activated IO&NS (SMD: 0.796; CI: 0.503; 1.089), immune (SMD: 1.409; CI: 0.637; 1.462), inflammatory (SMD: 1.200; CI: 0.584; 1.816), and neurotoxic (SMD: 0.904; CI: 0.431; 1.378) pathways. The effects sizes of the IO&NS, immune and inflammatory profiles were significantly greater in SA than in SI. In conclusion: activated IO&NS pathways are associated with recent SA and SI, and inflammation, T helper-1 activation, nitro-oxidative stress, lowered neuroprotection, and increased neurotoxicity explain at least in part why psychiatric patients show increased suicidal behaviours, especially SA.

Potential Role of Curcumin for the Treatment of Major Depressive Disorder

Curcumin is the major biologically active polyphenolic constituent in the turmeric plant (Curcuma longa) that has been shown to have antioxidant, anti-inflammatory, neuroprotective, anticancer, antimicrobial, and cardioprotective effects. Interest in curcumin as a treatment for mental health conditions has increased and there is an expanding body of preclinical and clinical research examining its antidepressant and anxiolytic effects. In this narrative review, human trials investigating the effects of curcumin for the treatment of depression or depressive symptoms are summarised. Using findings from in vitro, animal, and human trials, possible biological mechanisms associated with the antidepressant effects of curcumin are also explored. To increase the understanding of curcumin for the treatment of depression, directions for future research are proposed.

Suicide attempts are associated with activated immune-inflammatory, nitro-oxidative, and neurotoxic pathways: A systematic review and meta-analysis

BACKGROUND

Suicide attempts (SA) frequently occur in patients with mood disorders and schizophrenia, which are both accompanied by activated immune-inflammatory and nitro-oxidative (IO&NS) pathways.

METHODS

We searched PubMed, Google Scholar, and Web of Science, for articles published from inception until February 1, 2021. We included studies that compared blood biomarkers in psychiatric patients with (SA+) and without SA (SA-) and heathy controls and we combined different IO&NS biomarkers into immune, inflammatory, and neurotoxic profiles and used meta-analysis (random-effect model with restricted maximum-likelihood) to delineate effect sizes with 95% confidence interval (CI).

FINDINGS

Our search included 51 studies comprising 4.945 SA+ patients and 24.148 controls. We stratified the control group into healthy controls and SA- patients. SA+ patients showed significantly (p<0.001) increased immune activation (SMD: 1.044; CI: 0.599, 1.489), inflammation (SMD: 1.109; CI: 0.505, 1.714), neurotoxicity (SMD: 0.879; CI: 0.465, 1.293), and lowered neuroprotection (SMD: 0.648; CI: 0.354, 0.941) as compared with healthy controls. When compared with SA- patients, those with SA+ showed significant (p<0.001) immune activation (SMD: 0.290; CI: 0.183, 0.397), inflammation (SMD: 0.311; CI: 0.191, 0.432), and neurotoxicity (SMD: 0.315; CI: 0.198, 0.432), and lowered neuroprotection (SMD: 0.341; CI: 0.167, 0.515). Patients with current, but not lifetime, SA showed significant (p<0.001) levels of inflammation and neurotoxicity as compared with controls.

CONCLUSIONS

Patients with immune activation are at a higher risk of SA which may be explained by increased neurotoxicity due to inflammation and nitro-oxidative stress. This meta-analysis discovered new biomarkers of SA and therapeutic targets to treat individuals with SA.

Increased C-reactive protein concentration and suicidal behavior in people with psychiatric disorders: A systematic review and meta-analysis

OBJECTIVE

Suicide is a leading cause of death worldwide. Identifying factors associated with suicidality (suicidal ideation [SI]/suicidal behavior) could increase our understanding of the pathophysiological underpinnings of suicide and improve its prevention.

METHODS

We conducted a systematic review (PubMed/PsycInfo/Cochrane databases, up to September 2020) and random-effect meta-analysis including observational studies comparing peripheral C-reactive protein (CRP) levels in suicidal versus non-suicidal patients affected by any psychiatric disorder and healthy controls (HC). Primary outcome was the CRP standardized mean difference (SMD) between patients with high suicidality versus those with absent or low suicidality. Secondary outcomes were SMD of CRP levels between those with suicide attempt versus no suicide attempt, as well as between those with (high) versus low or absent SI. Quality of included studies was measured with Newcastle-Ottawa scale.

RESULTS

Out of initial 550 references, 21 observational studies involving 7682 subjects (7445 with mood disorders or first-episode psychosis, 237 HC) were included. A significant association of CRP levels with suicidality (SMD 0.688, 95% CI 0.476-0.9, p < 0.001) emerged. CRP levels were higher in individuals with high SI (SMD 1.145, 95% CI 0.273-2.018, p = 0.010) and in those with suicide attempt (SMD 0.549, 95%CI 0.363-0.735, p < 0.001) than non-suicidal individuals (either patients or HC). Main analyses were confirmed in sensitivity analysis (removing HC), and after adjusting for publication bias. The cross-sectional design of included studies, and the high heterogeneity of diagnosis and treatment limit the generalizability of these results. Median quality of included studies was high.

CONCLUSION

CRP is associated with higher suicidality in patients with mental disorders. Large cohort studies longitudinally monitoring CRP levels are needed to explore its longitudinal association with suicidality.