The role of substance use, smoking, and inflammation in risk for suicidal behavior

Suicide, neuroinflammation and other physiological alterations

Suicide is considered one of the major public health problems worldwide, being the second leading cause of death in the 15-29 age group. It is estimated that every 40s someone in the world commits suicide. The social taboo surrounding this phenomenon as well as the fact that suicide prevention measures currently fail to avoid deaths from this cause, means that more research is needed to understand its mechanisms. The present narrative review on suicide tries to point out several important aspects, such as risk factors or the dynamics of suicide, as well as the current findings in the field of physiology that could offer advances in the understanding of suicide. Subjective measures of risk such as scales and questionnaires are not effective alone, whereas the objective measures can be addressed from physiology. Thus, an increased neuroinflammation in people who take their own lives has been found, with an increase in inflammatory markers such as interleukin-6 and other cytokines in plasma or cerebrospinal fluid. Also, the hyperactivity of the hypothalamic-pituitary-adrenal axis and a decrease in serotonin or in vitamin D levels seems to also be involved. In conclusion, this review could help to understand which factors can trigger an increased risk of dying by suicide, as well as pointing out those alterations that occur in the body when someone attempt to commit suicide or succeeds in taking their own life. There is a need for more multidisciplinary approaches that address suicide to help to raise awareness of the relevance of this problem that causes the death of thousands of people every year.

Role of machine learning algorithms in suicide risk prediction: a systematic review-meta analysis of clinical studies

OBJECTIVE

Suicide is a complex and multifactorial public health problem. Understanding and addressing the various factors associated with suicide is crucial for prevention and intervention efforts. Machine learning (ML) could enhance the prediction of suicide attempts.

METHOD

A systematic review was performed using PubMed, Scopus, Web of Science and SID databases. We aim to evaluate the performance of ML algorithms and summarize their effects, gather relevant and reliable information to synthesize existing evidence, identify knowledge gaps, and provide a comprehensive list of the suicide risk factors using mixed method approach.

RESULTS

Forty-one studies published between 2011 and 2022, which matched inclusion criteria, were chosen as suitable. We included studies aimed at predicting the suicide risk by machine learning algorithms except natural language processing (NLP) and image processing. The neural network (NN) algorithm exhibited the lowest accuracy at 0.70, whereas the random forest demonstrated the highest accuracy, reaching 0.94. The study assessed the COX and random forest models and observed a minimum area under the curve (AUC) value of 0.54. In contrast, the XGBoost classifier yielded the highest AUC value, reaching 0.97. These specific AUC values emphasize the algorithm-specific performance in capturing the trade-off between sensitivity and specificity for suicide risk prediction. Furthermore, our investigation identified several common suicide risk factors, including age, gender, substance abuse, depression, anxiety, alcohol consumption, marital status, income, education, and occupation. This comprehensive analysis contributes valuable insights into the multifaceted nature of suicide risk, providing a foundation for targeted preventive strategies and intervention efforts.

CONCLUSIONS

The effectiveness of ML algorithms and their application in predicting suicide risk has been controversial. There is a need for more studies on these algorithms in clinical settings, and the related ethical concerns require further clarification.

Suicide mortality following the implementation of tobacco packaging and pricing policies in Korea: an interrupted time-series analysis

BACKGROUND

To prevent tobacco use in Korea, the national quitline number was added to tobacco packages in December 2012, tobacco prices were raised by 80% in January 2015, and graphic health warning labels were placed on tobacco packages in December 2016. This study evaluated the association of these tobacco packaging and pricing policies with suicide mortality in Korea.

METHODS

Monthly mortality from suicide was obtained from Cause-of-Death Statistics in Korea from December 2007 to December 2019. Interrupted time-series analysis was performed using segmented Poisson regression models. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated adjusted for suicide prevention strategies.

RESULTS

Suicide mortality was 20 per 1,000,000 in December 2007 and showed a downward trend over the study period. After the implementation of tobacco packaging and pricing policies, suicide mortality immediately declined by - 0.09 percent points (95% CI =  - 0.19 to 0.01; P > 0.05) for the national quitline number, - 0.22 percent points (95% CI =  - 0.35 to - 0.09; P < 0.01) for tobacco prices, and - 0.30 percent points (95% CI =  - 0.49 to - 0.11; P < 0.01) for graphic health warning labels. The corresponding RRs for these post-implementation changes compared with the pre-implementation level were 0.91 (95% CI = 0.83 to 1.00), 0.80 (95% CI = 0.70 to 0.91), and 0.74 (95% CI = 0.61 to 0.90), respectively. Significant associations between tobacco control policies and suicide mortality were observed even when stratified by sex and region.

CONCLUSIONS

The findings of this study provide new evidence for an association between tobacco control policies and deaths by suicide. An array of effective tobacco control policies should be considered for prevention programs targeting suicide.

Sex difference in association between suicide attempts and lipid profile in first-episode and drug naive patients with major depressive disorder

BACKGROUND

The relationship between suicide attempts and lipid profiles in patients with major depressive disorder (MDD) remains uncertain. The purpose of this study was to investigate sex differences in the relationship between suicide attempts and plasma lipid profiles in a large sample of first-episode and drug naive (FEDN) MDD patients.

METHODS

We recruited 1718 FEDN MDD patients and gathered demographic, clinical, and blood lipid data. The Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale and the Positive and Negative Syndrome Scale were used to assess the symptoms of patients.

RESULTS

There was no significant difference in the prevalence of suicide attempts between male and female MDD patients. The suicide attempt group had higher levels of depression, anxiety, psychotic symptoms, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C), but lower levels of high-density lipoprotein cholesterol (HDL-C) levels than the non-suicide attempt group. Binary logistic regression showed that TC levels were significantly correlated with suicidal attempts in both male and female patients. Correlation analysis revealed that the levels of TC, HDL-C and LDL-C were significantly associated with the number of suicide attempts in both male and female patients. Further multiple linear regression revealed that TC levels were significantly associated with the number of suicide attempts in male patients only.

CONCLUSIONS

Lipid biomarkers, particularly high TC levels, are associated with suicide attempts in both male and female MDD patients. However, there is gender difference in association between lipid biomarkers, especially TC levels, and the number of suicide attempts in MDD patients.

Association of combined healthy lifestyle with general and abdominal obesity

Background

Data linking joint healthy lifestyle factors to general and abdominal obesity are scarce, in particular in the Middle East. The aim of this study was to examine the association of combined healthy lifestyle factors with general and abdominal obesity in a large population of Iranian adults.

Methods

This cross-sectional study was done on 3,172 Iranian adults aged ≥18 years. We constructed healthy lifestyle score using information on dietary intakes, physical activity, smoking status, and psychological distress. To evaluate components of healthy lifestyle, we applied a validated 106-item semi-quantitative Food Frequency Questionnaire (FFQ), General Practice Physical Activity Questionnaire (GPPAQ), General Health Questionnaire (GHQ), and other pre-tested questionnaires. General obesity was defined as having a body mass index (BMI) ≥30 kg/m2 and abdominal obesity as a waist circumference (WC) of ≥102 cm in men and ≥88 cm in women.

Results

Mean age of participants was 36.54 ± 7.97 years. General and abdominal obesity were prevalent among 8.7% and 21.5% of study participants, respectively. Linear analysis showed a significant positive relationship between healthy lifestyle score and BMI among men (β: 0.30, 95% CI: 0.05, 0.54). However, no significant association was found between healthy lifestyle and abdominal obesity in men. Among women, one score increase in healthy lifestyle score was associated with a reduction of 0.65 cm in WC. In terms of individual components of healthy lifestyle, we found that low-distressed women had lower odds of abdominal obesity compared with high-distressed women.

Conclusion

We found a significant inverse association between healthy lifestyle and WC among women. However, healthy lifestyle was positively associated with BMI among men.

Impulsivity across severe mental disorders: a cross-sectional study of immune markers and psychopharmacotherapy

BACKGROUND

Impulsivity is a transdiagnostic feature linked to severe clinical expression and a potential target for psychopharmacological strategies. Biological underpinnings are largely unknown, but involvement of immune dysregulation has been indicated, and the effects of psychopharmacological agents vary. We investigated if impulsivity was associated with circulating immune marker levels and with a range of psychopharmacological treatment regimens in severe mental disorders.

METHODS

Impulsivity was assessed in a sample (N = 657) of patients with schizophrenia or schizophreniform disorder (SCZ) (N = 116) or bipolar disorder (BD) (N = 159) and healthy participants (N = 382) using the Barratt Impulsiveness Scale (BIS-11) questionnaire. Plasma levels of systemic immune markers (RANTES, IL-1RA, IL-18, IL-18BP, sTNFR-1) were measured by enzyme immunoassays. Patients underwent thorough clinical assessment, including evaluation of psychotropic medication. Associations were assessed using linear regressions.

RESULTS

Impulsivity  was positively associated with SCZ (p < 0.001) and BD (p < 0.001) diagnosis and negatively associated with age (p < 0.05), but not significantly associated with any of the circulating immune markers independently of diagnostic status. Among patients, impulsivity was negatively associated with lithium treatment (p = 0.003) and positively associated with antidepressant treatment (p = 0.011) after controlling for diagnosis, psychotropic co-medications, manic symptoms, and depressive symptoms.

CONCLUSIONS

We report elevated impulsivity across SCZ and BD but no associations to systemic immune dysregulation based on the current immune marker selection. The present study reveals associations between impulsivity in severe mental disorders and treatment with lithium and antidepressants, with opposite directions. Future studies are warranted to determine the causal directionality of the observed associations with psychopharmacotherapy.

Network analysis of comorbid depression, suicidality and biomarkers on HPA axis among mood disorder patients to psychiatric emergency services

Rapid assessment and intervention of suicide risk are common and challenging in psychiatric emergency departments (PED). It is unclear whether distinct pathophysiological processes exist among depressive patients with suicidality. This study examined the network structures of biomarkers on Hypothalamic-Pituitary-Adrenal (HPA) axis, such as Adrenocorticotropic hormone (ACTH) and Corticosterone (Cort), as well as suicidality and depressive symptoms in mood disorder patients in PED. Mood disorder patients in PED were assessed with the measurements of suicidality and depressive symptoms, respectively. A network analysis was performed to identify central symptoms and bridge symptoms of this network and their links to ACTH and Cort. Network stability was examined using the case-dropping procedure. The Network Comparison Test (NCT) was conducted to evaluate whether network characteristics differed by gender. A total of 1815 mood disorder patients were recruited. The prevalence of SI was 31.2% (95% CI: 28.15-34.21%), SP was 30.4% (95% CI: 27.39-33.41%), SA was 30.62% (95% CI: 27.61-33.64%) among psychiatric outpatients. The mean score of HAMD-24 was 13.87 ± 8.02. Network analysis revealed that 'Somatic anxiety' had the highest expected centrality, followed by 'Hopelessness' and 'Suicide attempt'. 'Corticosterone' and 'Retardation' may be the main bridge symptoms between depressive symptoms and the suicidality community. The network model showed a high degree of stability. Gender did not significantly influence the network structure. The central symptoms and key bridge symptoms identified could be potential targets for interventions of the HPA axis, which is designed for regular screening of a range of suicidal activity. In the light of this, timely treatment should be provided for psychiatric emergency care.

Plasma and cerebrospinal fluid inflammatory markers and human aggression

A growing body of work suggests that individuals with aggressive behavior and/or aggressive tendencies have evidence of chronic, low level, inflammation as manifested by elevated circulating levels of acute phase reactant proteins and pro-inflammatory cytokines. While animal studies report that direct application of pro-inflammatory proteins in brain increase aggressive behavior, there is no data on the relationship of central levels of these proteins and aggression in human subjects. We simultaneously measured levels of both plasma and lumbar cerebrospinal fluid (CSF) C-Reactive Protein (CRP) and IL-6, IL-8, and TNF-α in 77 medically healthy, drug-free, individuals with varying degrees of aggression including 22 individuals with DSM-5 Intermittent Explosive Disorder (IED). Aggression was assessed using the Life History of Aggression (LHA) and the Buss-Perry Aggression Questionnaire (BPAQ). Plasma and CSF levels of CRP, IL-8, and TNF-α, but not IL-6, correlated significantly with each other. Aggressive individuals with IED displayed elevated plasma, but not CSF, levels of proinflammatory markers and this relationship was specific to IED. Similarly, composite aggression scores correlated significantly with plasma, but not CSF, pro-inflammatory markers. Aggressive behavior in humans is correlated with Plasma, but not CSF, proinflammatory markers despite the observation that these two sets of markers are significantly correlated. Since the direct application of proinflammatory proteins in brains of animals increase aggressive behavior, proinflammatory proteins likely influence brain-based behavior in a manner not reflected in lumbar CSF.

A moderated mediation analysis of the association between smoking and suicide attempts among adolescents in 28 countries

Globally, evidence has shown that many adolescents are victims of substance use, mainly cigarette smoking, and it has been associated with suicidal ideation. However, the mechanisms underlying this association are poorly understood. This study examines whether truancy mediates and gender moderates the association of cigarette smoking with suicide attempts among adolescents in 28 countries. Data from the Global School-Based Student Health Survey were used. Hierarchical multiple logistic regression analyses were used to estimate the effect-modification of gender on cigarette smoking and suicide attempt. The mediating effect of truancy on the association between cigarette smoking and suicidal attempt was assessed using the generalized decomposition method. Cigarette smoking was associated with suicide attempts after adjusting for several confounding variables (aOR = 1.21; 95% CI = 1.09-1.33). The bootstrap results from the generalized decomposition analysis indicated that truancy partially mediated the association of cigarette smoking with a suicide attempt, contributing 21% of the total effect among in-school adolescents. Hierarchical regression analyses suggested that gender moderated the effect of cigarette smoking on suicidal attempts: female adolescents who smoked had 36% higher odds of suicidal attempts compared to male adolescents. The findings suggest possible pathways for designing and implementing interventions to address adolescents' cigarette smoking and truancy to prevent suicidal attempts.

Hyper-inflammation of astrocytes in patients of major depressive disorder: Evidence from serum astrocyte-derived extracellular vesicles

Astrocyte-derived extracellular vesicles (ADEs) allow the in vivo probing of the inflammatory status of astrocytes practical. Serum sample and ADEs were used to test the inflammatory hypothesis in 70 patients with major depressive disorder (MDD) and 70 matched healthy controls (HCs). In serum, tumor necrosis factor α (TNF-α) and interleukin (IL)-17A were significantly increased, where as IL-12p70 was significantly reduced in the MDD patients compared with HCs. In ADEs, all inflammatory markers (Interferon-γ, IL-12p70, IL-1β, IL-2, IL-4, IL-6, TNF-α, and IL-17A) except IL-10 were significantly increased in the MDD patients, the Hedge's g values of elevated inflammatory markers varied from 0.48 to 1.07. However, there were no differences of all inflammatory markers whether in serum or ADEs between MDD-drug free and medicated subgroups. The association of inflammatory biomarkers between ADEs and serum did not reach statistically significance after multi-comparison correction neither in the HCs nor MDD patients. The spearman coefficients between inflammatory factors and clinical characteristics in the MDD patients, such as onset age, disease course, current episode duration, and severity of depression, were nonsignificant after multi-comparison correction. In the receiver operating characteristic curves analysis, the corrected partial area under the curve (pAUC) of each inflammatory markers in ADEs ranged from 0.522 to 0.696, and the combination of these inflammatory factors achieved a high pAUC (>0.9). Our findings support the inflammatory glial hypothesis of depression, and suggests that in human ADEs could be a useful tool to probe the in vivo astrocyte status.

Increased burden of cardiovascular risk among youth suicide attempters

BACKGROUND

Suicide and cardiovascular disease rank among the leading causes of disability and premature mortality worldwide. Young adult suicide attempters are at increased risk of mortality from cardiovascular disease even compared to those with major depressive disorder suggesting an increased burden of cardiovascular risk factors. We compared the cardiovascular risk burden between youth attempters and other high-risk individuals.

METHODS

Participants were from the Collaborative Psychiatric Epidemiology Surveys (CPES), a U.S. population-based study, aged 18-30 years [suicide attempt (SA): n = 303; suicidal ideation (SI): n = 451; controls: n = 3671]; and psychiatric inpatients admitted for a SA (n = 38) or SI (n = 40) and healthy controls (n = 37) aged 15-30 years. We computed a cardiovascular risk score and high- and low-risk latent classes based on risk factors of high blood pressure, obesity, and smoking.

RESULTS

Suicide attempters showed an increased cardiovascular risk score (CPES: B = 0.43, 95% confidence interval (CI) 0.31-0.54, p < 0.001; inpatient sample: B = 1.61, 95% CI 0.53-2.68, p = 0.004) compared to controls. They were also more likely to be classified in the high cardiovascular risk group (CPES: odds ratio (OR) 3.36, 95% CI 1.67-6.78, p = 0.001; inpatient sample: OR 9.89, 95% CI 1.38-85.39, p = 0.03) compared to those with SI (CPES: OR 1.15, 95% CI 0.55-2.39, p = 0.71; inpatient sample: OR 1.91, 95% CI 0.25-15.00, p = 0.53).

CONCLUSIONS

Youth attempters show an increased burden for cardiovascular risk compared to other high-risk individuals in inpatient and population-based samples. Clinicians should pay particular attention to cardiovascular risk factors among suicide attempters in order to reduce their risk for cardiovascular events.

Sibling alcohol use disorder is associated with increased risk for suicide attempt

The association between having a sibling diagnosed with alcohol use disorder (AUD) and risk for suicide attempt may be attributable to shared genetic liability between AUD and suicidal behavior, effects of environmental exposure to a sibling's AUD, or both. To distinguish between these alternatives, we conducted a series of Cox regression models using data derived from Swedish population-based registers with national coverage. Among full sibling pairs (656,807 males and 607,096 females), we found that proband risk for suicide attempt was significantly elevated when their sibling was affected by AUD, even after accounting for the proband's AUD status. Further, risk for proband suicide attempt was consistently higher when the sibling's AUD registration had occurred more recently. Our findings provide evidence for exposure to sibling AUD as an environmental risk factor for suicide attempt and suggest that clinical outreach may be warranted following a sibling's diagnosis with AUD.

Suicidal ideation and behavior in youth in low- and middle-income countries: A brief review of risk factors and implications for prevention

Although global rates of suicide have dropped in the last 30 years, youth in low- and middle-income countries (LMICs) continue to be highly represented in suicide statistics yet underrepresented in research. In this review we present the epidemiology of suicide, suicidal ideation, and suicide attempts among youth in LMICs. We also describe population-level (attitudes toward suicide, socioeconomic, and societal factors) and individual-level clinical and psychosocial risk factors, highlighting specific considerations pertaining to youth in LMICs. These specific considerations in risk factors within this population can inform how multi-level prevention strategies may be targeted to meet their specific needs. Prevention and intervention strategies relying on the stepped-care framework focusing on population-, community-, and individual level targets while considering locally- and culturally relevant practices are key in LMICs. In addition, systemic approaches favoring school-based and family-based interventions are important among youth. Cross-culturally adapted multimodal prevention strategies targeting the heterogeneity that exists in healthcare systems, suicide rates, and risk factors in these countries should be accorded a high priority to reduce the burden of suicide among youth in LMICs.

Resting mononuclear cell NR3C1 and SKA2 expression levels predict blunted cortisol reactivity to combat training stress among elite army cadets exposed to childhood adversity

Childhood adversity (CA) may alter reactivity to stress throughout life, increasing risk for psychiatric and medical morbidity, yet long-term correlates of milder CA levels among high functioning healthy adolescents are less studied. The current study examined the prevalence and impact of CA exposure among a cohort of healthy motivated elite parachute unit volunteers, prospectively assessed at rest and at the height of an intensive combat-simulation exposure. We found significantly reduced gene expression levels in resting mononuclear cell nuclear receptor, subfamily 3, member 1 (NR3C1), and its transactivator spindle and kinetochore-associated protein 2 (SKA2), that predict blunted cortisol reactivity to combat-simulation stress among CA exposed adolescents. Long-term alterations in endocrine immune indices, subjective distress, and executive functions persist among healthy high functioning adolescents following milder CA exposure, and may promote resilience or vulnerability to later real-life combat exposure.

Association and Genetic Expression between Genes Involved in HPA Axis and Suicide Behavior: A Systematic Review

BACKGROUND

Suicide behavior (SB) has been highly associated with the response to stress and the hypothalamic-pituitary-adrenal (HPA) axis. The aim of this study was to summarize the results obtained in genetic studies that analyzed the HPA axis-stress pathway and SB through a systematic review.

METHODS

We performed an online search in PubMed, EBSCO, Web of Science, Scopus, and PsycoInfo databases up to May 2021. We followed the PRISMA guidelines for systematic reviews. We included case-control and expression studies that provided data on mRNA expression and single-nucleotide polymorphisms of genes associated with SB.

RESULTS

A total of 21,926 individuals participated across 41 studies (not repeats); 34 studies provided data on single-nucleotide polymorphisms in 21,284 participants and 11 studies reported data on mRNA expression in 1034 participants. Ten genes were identified: FKBP5, CRH, CRHBP, CRHR1, CRHR2, NR3C1, NR3C2, SKA2, MC2R, and POMC.

CONCLUSIONS

Our findings suggest that key stress pathway genes are significantly associated with SB and show potential as biomarkers for SB.

A genetically informed study on the association of cannabis, alcohol, and tobacco smoking with suicide attempt

Use of substances such as cannabis, alcohol, and tobacco, has been associated with increased risk of suicide attempt in several observational studies. However, establishing whether these associations are causal is challenging when using observational designs. To evaluate the potential causal contributions of cannabis use, alcohol use, and tobacco smoking to suicide attempt, we applied two-sample Mendelian randomization, an instrumental variable approach using single-nucleotide polymorphisms (SNPs) as instrumental variables for three exposures: lifetime cannabis use (yes/no; 42 instrument SNPs; GWAS sample size [N] = 162,082), alcohol use (drinks-per-week; 53 instrument SNPs; N = 941,280), and tobacco smoking (initiation, yes/no; 156 instrument SNPs; N = 1,232,091; heaviness; 27 instrument SNPs; N = 337,334). The main outcome was suicide attempt measured from hospital records (N = 50,264). All data come from publicly available summary statistics of genome-wide association studies of participants of European ancestry. We found evidence supporting a possible causal role of cannabis (OR = 1.18; 95% CI = 1.01-1.37, P = 0.032), alcohol (OR = 1.95; 95% CI = 1.15-3.32, P = 0.013), and smoking (initiation, OR = 1.90; 95% CI = 1.54-2.34, P < 0.001; heaviness, OR = 2.13; 95% CI = 1.13-3.99; P = 0.019) on suicide attempt. Using multivariable Mendelian randomization, we found that only cannabis showed a direct pathway to suicide attempt (P = 0.001), suggesting that the effect of alcohol and smoking was mediated by the other substance use phenotypes. No evidence was found for reverse causation, i.e., associations of suicide attempt on cannabis (P = 0.483), alcohol (P = 0.234), smoking initiation (P = 0.144), and heaviness (P = 0.601). In conclusion, evidence from this quasi-experimental study based on genetic data from large-scale GWASs are consistent with a causal role of cannabis, alcohol, and tobacco smoking on suicide attempt.

Psychosocial Correlates of Suicidal Behavior among Adolescents under Confinement Due to the COVID-19 Pandemic in Aguascalientes, Mexico: A Cross-Sectional Population Survey

Background: Suicide and suicidal behaviors were already a global public health problem, producing preventable injuries and deaths. This issue may worsen due to the COVID-19 pandemic and may differentially affect vulnerable groups in the population, including children, adolescents, and young adults. The current study evaluated the association of affective variables (depression, hopelessness, and anxiety), drug use (alcohol, tobacco, and others), emotional intelligence, and attachment with suicidal behaviors. Methods: A state-wide survey included 8033 students (51% female, 49% male; mean age of 16 years) from science and technology high-schools using a standardized questionnaire that was distributed online. Multinomial logistic regression models tested associations between suicidal behaviors and several covariates. The analyses accommodated the complex structure of the sample. Results: Approximately 21% of all students reported a suicidal behavior (11% with a low-lethality suicide attempt, 6% with self-injuries, and 4% with a high-lethality suicide attempt). Variables associated with higher odds of suicidal behavior included: female sex, depression, hopelessness, anxiety, alcohol and tobacco use, childhood trauma, and having to self-rely as issues affecting attachment, and low self-esteem. Security of attachment was associated with lower odds of suicidal behavior. Conclusions: The complexity of suicidal behavior makes it clear that comprehensive programs need to be implemented.

The role of gene polymorphisms, and analysis of peripheral and central levels of interleukins in suicidal behavior: A systematic review

In terms of the physiological characteristics of suicidal behavior (SB) disorder, an increase inflammation response has been reported in these individuals. Therefore, the pro-inflammatory and anti-inflammatory activities of interleukins are adequate markers to research in order to understand the pathogenesis of SB. For that reason, the aim of this systematic review was to evaluate the role of interleukins in individuals with suicidal behavior disorder. A systematic search was performed in PubMed, Scopus and EBSCO databases up to July 2019. We used the words "interleukin" AND "suicide", "interleukin" AND "suicidal", and "IL-". Articles where interleukins concentrations were measured in individuals with SB and/or genetic studies addressing interleukins genes variants as possible markers to SB were included. A total of 54 articles were included. Articles that measured interleukin levels comprised 1111 cases and 1588 controls; whereas the genetic studies comprised 3082 cases and 5148 controls. These studies evaluated the concentrations of IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-10, sIL-2R in serum, plasma. The pro-inflammatory interleukins concentrations were higher in cases than in controls; however, we observed heterogeneity in the measurements and sample sources. Whereas, 9 polymorphisms of IL-1α, IL-1β, IL-6, IL-1β-8 genes were analyzed in association with suicide behavior disorder, though no conclusive outcomes were attained. Our results suggest that individuals with suicide risk undergo continuous stress that could trigger the release and circulation of pro-inflammatory interleukins and therefore their concentration in plasma. However, more studies are necessary in order to reach conclusively outcomes.

Predictive inflammatory biomarkers for change in suicidal ideation in major depressive disorder and panic disorder: A 12-week follow-up study

Previous studies have investigated the role of inflammatory markers in suicidality of patients with major depressive disorder (MDD) or panic disorder (PD). However, few studies have investigated associations between serum inflammatory cytokine levels and suicidality. We hypothesized that MDD and PD status might be significantly associated with serum inflammatory cytokines and that we could predict levels of improvement in suicide ideation intensity using serum inflammatory biomarkers in patients with MDD and PD. For this study, 41 patients with MDD, 52 patients with PD, and 59 healthy control (HC) subjects were enrolled. Psychological measurements and serum inflammatory markers such as interleukin (IL) -6, -10, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and C reactive protein (CRP) were examined. A total of five visits were completed during 12 weeks. After controlling for confounding factors, log-transformed IL-6 (ln_IL-6) at baseline (MDD: 0.297 ± 0.626; PD: 0.342 ± 0.723; HC: -0.121 ± 0.858; p = 0.007, >0.0017, 0.05/30) and mean ln_IL-6 (MDD: 0.395 ± 0.550, PD: 0.249 ± 0.544, HC: -0.139 ± 0.622, p = 0.002, >0.0017, 0.05/30) levels were trends towards significantly higher in patients with MDD and PD than in HC. In MDD patients, a higher level of basal ln_TNF-α was a significant predictor of ΔSSI (changes in SSI scores between baseline and week 12) even after controlling for changes of depression symptoms and baseline SSI scores (standardized β = 0.541, p = 0.002 < 0.0028, 0.05/18). In conclusion, we could predict ΔSSI using baseline inflammatory biomarkers for patients with MDD.

The role of psychiatric symptoms and environmental vulnerability factors in explaining the relationship between child maltreatment and suicidality: A prospective investigation

BACKGROUND

Childhood maltreatment has been associated with suicide thoughts and attempts; however, few longitudinal studies have assessed risk of suicidality into adulthood. Fewer have examined potential mediators (psychiatric symptoms and environmental vulnerability factors).

METHODS

Prospective cohort design. Children with documented cases of maltreatment (N = 495, ages 0-11) were matched with non-maltreated children (N = 395) and followed up into adulthood. Psychiatric symptoms (depression, anxiety, dysthymia, post-traumatic stress,antisocial personality,and substance use) and environmental vulnerability (social isolation, physical disability/illness, and homelessness) were assessed at mean age 29 and suicide thoughts and attempts at 39. Structural equation models tested for mediation, controlling for age, sex, race, and IQ.

RESULTS

Childhood maltreatment predicted suicide attempts (Beta = 0.44, p<0.001), but not suicide thoughts only.Individuals with only suicide thoughts differed significantly from those with suicide attempts in psychiatric symptoms, physical disability/ illness, and homelessness. There were significant paths from child maltreatment to suicide attempts through psychiatric symptoms (0.18, p<0.001), ASPD (0.13, p<0.001), substance use (0.07, p<0.01), and homelessness (0.10, p<0.05).

LIMITATIONS

Court cases of child maltreatment may not generalize to middle- or upper- class and non-reported cases.Effect sizes were small but significant.

CONCLUSIONS

Psychiatric risk factors for suicide are well recognized. These new results provide strong evidence that environmental vulnerability factors, particularly homelessness, are associated with increased risk for suicide attempts and warrant attention.Although many people report suicide thoughts, maltreated children with more psychiatric symptoms and experience homelessness are more likely to attempt suicide and warrant targeted interventions.

Increased vulnerability to impulsive behavior after streptococcal antigen exposure and antibiotic treatment in rats

RATIONALE

The inflammation induced by Group A Streptococcus (GAS) infection has been viewed as a vulnerability factor in mental disorders characterized by inhibitory control deficits, such as attention-deficit/hyperactivity disorder or obsessive-compulsive disorder. Antibiotic treatment reduces GAS symptoms; however, its effects on impulsivity have not been fully assessed.

OBJECTIVES

We investigated whether GAS exposure during early adolescence might be a vulnerability factor for adult impulsivity, if antibiotic treatment acts as a protective factor, and whether these differences are accompanied by changes in the inflammatory cytokine frontostriatal regions.

METHODS

Male Wistar rats were exposed to the GAS antigen or to vehicle plus adjuvants at postnatal day (PND) 35 (with two boosts), and they received either ampicillin (supplemented in the drinking water) or water alone from PND35 to PND70. Adult impulsivity was assessed using two different models, the 5-choice serial reaction time task (5-CSRT task) and the delay discounting task (DDT). The levels of interleukin-6 (IL-6) and IL-17 were measured in the prefrontal cortex (PFc), and the tumor necrosis factor α levels (TNFα) were measured in the PFc and nucleus accumbens (NAcc).

RESULTS

GAS exposure and ampicillin treatment increased the waiting impulsivity by a higher number of premature responses when the animals were challenged by a long intertrial interval during the 5-CSRT task. The GAS exposure revealed higher impulsive choices at the highest delay (40 s) when tested by DDT, while coadministration with ampicillin prevented the impulsive choice. GAS exposure and ampicillin reduced the IL-6 and IL-17 levels in the PFc, and ampicillin treatment increased the TNFα levels in the NAcc. A regression analysis revealed a significant contribution of GAS exposure and TNFα levels to the observed effects.

CONCLUSIONS

GAS exposure and ampicillin treatment induced an inhibitory control deficit in a different manner depending on the form of impulsivity measured here, with inflammatory long-term changes in the PFc and NAcc that might increase the vulnerability to impulsivity-related neuropsychiatric disorders.

The role of childhood maltreatment in cortisol in the hypothalamic-pituitary-adrenal (HPA) axis in methamphetamine-dependent individuals with and without depression comorbidity and suicide attempts

BACKGROUND

The hypothalamic-pituitary-adrenal (HPA) axis dysregulation which was found to have an important role in the pathophysiology of depression, suicide, and substance dependence, may be influenced by childhood maltreatment (CM). The present study aimed to investigate the relationship between CM and cortisol changes in methamphetamine-dependent individuals.

METHODS

In a cross-sectional study, methamphetamine-dependent individuals (n = =195) with or without both comorbid major depressive disorder (MDD) and a history of suicide attempts were selected and completed the Childhood Trauma Questionnaire-Short Form (CTQ-SF), the Beck Scale for Suicide Ideation (BSSI), and the Beck Depression Inventory-II (BDI-II). To assess cortisol levels, saliva samples were collected at six time intervals for two consecutive days.

RESULTS

A history of CM significantly predicted wake-up cortisol level, cortisol awakening response (CAR), and diurnal cortisol slope. Methamphetamine-dependent individuals with both MDD and lifetime suicide attempts had higher CM and higher cortisol levels with a blunted diurnal cortisol slope than individuals who were merely methamphetamine-dependent. Individuals with high CM showed higher cortisol levels with a blunted diurnal slope than those with low or without CM.

LIMITATIONS

Cross-sectional data and use of self-report scales, especially retrospective measurements (e.g., the CTQ-SF), were important limitations of this study.

CONCLUSION

Findings suggest that methamphetamine-dependent individuals with adverse psychological factors such as CM, MDD, and suicide attempts may show dysregulation in biological factors including cortisol level. In addition, CM and its effects on cortisol in the HPA axis may emerge as important factors regarding psychopathological use of methamphetamine.

Post-trauma anhedonia is associated with increased substance use in a recently-traumatized population

Recreational substance use (SU) can emerge or worsen in the aftermath of psychological trauma. Anhedonia is one reason for this problematic SU. Symptoms of posttraumatic stress disorder (PTSD) that represent anhedonia (post-trauma anhedonia; PTA) have been consistently linked to SU disorders. However, no prospective studies have examined whether changes in PTA over time are associated with problematic SU in recently-traumatized people, which was the goal of this study. 165 men and women were recruited as part of a prospective PTSD study in the emergency department of a Level 1 trauma center. Clinical assessments of PTSD and SU were administered at three and six months post-trauma. Compared to participants with minimal SU at six months post-trauma, high substance users at six months post-trauma showed significant increases in PTA during the three to six month time period. This relationship was significant even after accounting for variance associated with other factors, including PTSD symptoms such as re-experiencing and hyperarousal. Participants who demonstrated increases in SU during this time also showed significant increases in PTA, unlike those who demonstrated consistently minimal/no SU during this time. These findings indicate that PTA may be a mechanism through which SU problems emerge in recently-traumatized individuals.