Association between infection early in life and mental disorders among youth in the community: a cross-sectional study

Associations between soluble urokinase plasminogen activator receptor (suPAR) concentration and psychiatric disorders - A systematic review and meta-analysis

BACKGROUND

There is some evidence of an association between inflammation in the pathogenesis of mental disorders. Soluble urokinase plasminogen activator receptor (suPAR) is a biomarker of chronic inflammation, which provides a more stable index of systemic inflammation than more widely used biomarkers. This review aims to synthesise studies that measured suPAR concentrations in individuals with a psychiatric disorder, to determine if these concentrations are altered in comparison to healthy participants.

METHOD

Comprehensive literature searches from inception to October 2023 were conducted of five relevant databases (PubMed, Web of Science, Embase, Scopus, APA PsychInfo). Random-effects meta-analyses were performed to compare the standardised mean difference of blood suPAR levels (i.e. plasma or serum) for individuals with any psychiatric disorder relative to controls. Separate meta-analyses of suPAR levels were conducted for individuals with schizophrenia or other psychotic disorder and depressive disorder. Risk of bias was assessed using the Newcastle Ottawa Scale. Post-hoc sensitivity analyses included excluding studies at high risk of bias, and analyses of studies that measured suPAR concentrations either in serum or in plasma separately.

RESULTS

The literature search identified 149 records. Ten full-text studies were screened for eligibility and 9 studies were included for review. Primary analyses revealed no significant difference in suPAR levels between individuals with any psychiatric disorder compared to controls (k = 7, SMD = 0.42, 95 % CI [-0.20, 1.04]). However, those with depressive disorder had elevated suPAR levels relative to controls (k = 3, SMD = 0.61, 95 % CI [0.34, 0.87]). Similarly, secondary analyses showed no evidence of a significant difference in suPAR levels in individuals with any psychiatric disorder when studies at high risk of bias were excluded (k = 6, SMD = 0.54, 95 % CI [-0.14, 1.22]), but elevated suPAR concentrations for those with schizophrenia or other psychotic disorder were found (k = 3, SMD = 0.98, 95 % CI [0.39, 1.58]). Furthermore, studies that analysed plasma suPAR concentrations found elevated plasma suPAR levels in individuals with any psychiatric disorder relative to controls (k = 5, SMD = 0.84, 95 % CI [0.38, 1.29]), while studies measuring serum suPAR levels in any psychiatric disorder did not find a difference (k = 2, SMD = -0.61, 95 % CI [-1.27, 0.04]). For plasma, elevated suPAR concentrations were also identified for those with schizophrenia or other psychotic disorder (k = 3, SMD = 0.98, 95 % CI [0.39, 1.58]).

DISCUSSION

When studies measuring either only serum or only plasma suPAR were considered, no significant difference in suPAR levels were observed between psychiatric disorder groups, although significantly elevated suPAR levels were detected in those with moderate to severe depressive disorder. However, plasma suPAR levels were significantly elevated in those with any psychiatric disorder relative to controls, while no difference in serum samples was found. A similar finding was reported for schizophrenia or other psychotic disorder. The plasma findings suggest that chronic inflammatory dysregulation may contribute to the pathology of schizophrenia and depressive disorder. Future longitudinal studies are required to fully elucidate the role of this marker in the psychopathology of these disorders.

Imipramine Administration in Brucella abortus 2308-Infected Mice Restores Hippocampal Serotonin Levels, Muscle Strength, and Mood, and Decreases Spleen CFU Count

Brucellosis infection causes non-specific symptoms such as fever, chills, sweating, headaches, myalgia, arthralgia, anorexia, fatigue, and mood disorders. In mouse models, it has been associated with increased levels of IL-6, TNF-α, and IFN-γ, a decrease in serotonin and dopamine levels within the hippocampus, induced loss of muscle strength and equilibrium, and increased anxiety and hopelessness. Imipramine (ImiP), a tricyclic antidepressant, is used to alleviate neuropathic pain. This study evaluated the effects of ImiP on Balb/c mice infected with Brucella abortus 2308 (Ba) at 14- and 28-days post-infection. Serum levels of six cytokines (IFN-γ, IL-6, TNF-α, IL-12, MCP-1. and IL-10) were assessed by FACS, while the number of bacteria in the spleen was measured via CFU. Serotonin levels in the hippocampus were analyzed via HPLC, and behavioral tests were conducted to assess strength, equilibrium, and mood. Our results showed that mice infected with Brucella abortus 2308 and treated with ImiP for six days (Im6Ba14) had significantly different outcomes compared to infected mice (Ba14) at day 14 post-infection. The mood was enhanced in the forced swimming test (FST) (p < 0.01), tail suspension test (TST) (p < 0.0001), and open-field test (p < 0.0001). Additionally, there was an increase in serotonin levels in the hippocampus (p < 0.001). Furthermore, there was an improvement in equilibrium (p < 0.0001) and muscle strength (p < 0.01). Lastly, there was a decrease in IL-6 levels (p < 0.05) and CFU count in the spleen (p < 0.0001). At 28 days, infected mice that received ImiP for 20 days (Im20Ba28) showed preservation of positive effects compared to infected mice (Ba28). These effects include the following: (1) improved FST (p < 0.0001) and TST (p < 0.0001); (2) better equilibrium (p < 0.0001) and muscle strength (p < 0.0001); (3) decreased IL-6 levels (p < 0.05); and (4) reduced CFU count in the spleen (p < 0.0001). These findings suggest the potential for ImiP to be used as an adjuvant treatment for the symptoms of brucellosis, which requires future studies.

Examining the Relationships between the Incidence of Infectious Diseases and Mood Disorders: An Analysis of Data from the Global Burden of Disease Studies, 1990-2019

Mood disorders are among the commonest mental disorders worldwide. Epidemiological and clinical evidence suggests that there are close links between infectious diseases and mood disorders, but the strength and direction of these association remain largely unknown. Theoretical models have attempted to explain this link based on evolutionary or immune-related factors, but these have not been empirically verified. The current study examined cross-sectional and longitudinal associations between the incidence of infectious diseases and mood disorders, while correcting for climate and economic factors, based on data from the Global Burden of Disease Studies, 1990-2019. It was found that major depressive disorder was positively associated with lower respiratory infections, while bipolar disorder was positively associated with upper respiratory infections and negatively associated with enteric and tropical infections, both cross-sectionally and over a period of 30 years. These results suggest that a complex, bidirectional relationship exists between these disorders. This relationship may be mediated through the immune system as well as through the gut-brain and lung-brain axes. Understanding the mechanisms that link these groups of disorders could lead to advances in the prevention and treatment of both.

Relationship of herpesvirus (HSV1, EBV, CMV, HHV6) seropositivity with depressive disorder and its clinical aspects: The first study in children

Infections can lead to the onset of mood disorders in adults, partly through inflammatory mechanisms. However pediatric data are lacking. The aim of this study is to evaluate the relationship between depressive disorder and seropositivity of herpes virus infections in children. The sample group consisted of patients diagnosed with depressive disorder according to DSM-5 diagnostic criteria and healthy volunteers, being between 11 and 18 years with clinically normal mental capacity. All children completed DSM-5-Level-2 Depression Scale, DSM-5-Level-2 Irritability Scale, DSM-5-Level-2 Sleep Scale, DSM-5-Level-2 Somatic Symptoms Scale. The levels of anti-HSV1-IgG, anti-CMV-IgG, anti-EBNA, and anti-HHV6-IgG were examined in all participants. Patients with an antibody value above the cut-off values specified in the test kits were evaluated as seropositive. The mean age was 15.54 ± 1.57 years in the depression group (DG), 14.87 ± 1.76 years in the healthy control group (CG). There were 4 boys (11.2%), 32 girls (88.8%) in the DG, 9 boys (21.9%) and 32 girls (78.04%) in the CG. There was no statistically significant difference between the groups in terms of the presence of seropositivity of HSV1, CMV, EBV, and HHV6. HHV6 antibody levels were significantly higher in the DG (p = 0.000). A significant positive correlation was found between HHV6 antibodies and DSM-5 level-2 somatic symptoms scale score. HHV6 antibody levels were found to be significantly higher in patients with existing suicidal ideation in the DG (n = 13) compared to those without existing suicidal ideation in the DG (p = 0.043). HHV6 persistent infections may be responsible for somatic symptoms and etiology of suicidal ideation in childhood depressive disorder.

Back to the Future: The Role of Infections in Psychopathology. Focus on OCD

OBJECTIVE

Recently, there has been a resurgence of interest in the relationship between infections and psychopathology, given the increasing data on the neurotropism and neurological/psychiatric morbidity of the SARS-COV2 virus, responsible for the current worldwide pandemic. Although the majority of observations were those obtained in mood and schizophrenic disorders, a few data are also available on the presence of bacterial or viral infections in patients suffering from obsessive-compulsive disorder (OCD). Therefore, given the limited information, the present paper aimed at reviewing the most updated evidence of infections in neuropsychiatric disorders and their possible mechanisms of actions, with a narrow focus on microbes in OCD.

METHOD

This paper is a narrative review. The databases of PubMed, Scopus, Embase, PsycINFO and Google Scholar were accessed to research and collect English language papers published between 1 January 1980 and 31 December 2021. The data on PANDAS/PANS and those observed during severe brain infections were excluded.

RESULTS

Several pathogens have been associated with an increased risk to develop a broad spectrum of neuropsychiatric conditions, such as schizophrenia, mood disorders, autism, attention-deficit/hyperactivity disorder, anorexia nervosa, and post-traumatic stress disorder. Some evidence supported a possible role of infections also in the pathophysiology of OCD. Infections from Herpes simplex virus 1, Borna disease virus, Group A-Beta Hemolytic Streptococcus, Borrelia spp., and Toxoplasma gondii were actually found in patients with OCD. Although different mechanisms have been hypothesized, all would converge to trigger functional/structural alterations of specific circuits or immune processes, with cascade dysfunctions of several other systems.

CONCLUSIONS

Based on the current evidence, a possible contribution of different types of microbes has been proposed for different neuropsychiatric disorders including OCD. However, the currently available literature is meager and heterogeneous in terms of sample characteristics and methods used. Therefore, further studies are needed to better understand the impact of infectious agents in neuropsychiatric disorders. Our opinion is that deeper insights in this field might contribute to a better definition of biological underpinnings of specific clinical pictures, as well as to promote psychiatric precision medicine, with treatments based on altered pathological pathways of single patients. This might be particularly relevant in OCD, a disorder with a high proportion of patients who are resistant or do not respond to conventional therapeutic strategies.

Neonatal immune challenge influences the microbiota and behaviour in a sexually dimorphic manner

There is comorbidity between anxiety disorders and gastrointestinal disorders, with both linked to adverse early life events. The microbiome gut-brain-axis, a bidirectional communication system, is plastic throughout the neonatal period and is a possible mediator of this relationship. Here, we used a well-established neonatal rodent immune activation model to investigate the long-term effect of neonatal lipopolysaccharide (LPS) exposure on adult behaviour and the relationship to microbiome composition. Wistar rats were injected with LPS (0.05 mg/kg) or saline (equivolume) on postnatal days 3 and 5. In adulthood, behavioural tests were performed to assess anxiety-like behaviour, and microbiota sequencing was performed on stool samples. There were distinctly different behavioural phenotypes for LPS-exposed males and females. LPS-exposed males displayed typical anxiety-like behaviours with significantly decreased social interaction (F_(1,22) = 7.576, p = 0.009) and increased defecation relative to saline controls (F_(1,23) = 8.623, p = 0.005). LPS-exposed females displayed a different behavioural phenotype with significantly increased social interaction (F_(1,22) = 6.094, p = 0.018), and exploration (F_(1,24) = 6.359, p = 0.015), compared to saline controls. With respect to microbiota profiling data, Bacteroidota was significantly increased for LPS-exposed females (F_(1,14) = 4.931p = 0.035) and Proteobacteria was decreased for LPS-exposed rats of both sexes versus controls (F_(1,30) = 4.923p = 0.035). Furthermore, alterations in predicted functional pathways for neurotransmitters in faeces were observed with a decrease in the relative abundance of D-glutamine and D-glutamate metabolism in LPS exposed females compared to control females (p < 0.05). This suggests that neonatal immune activation alters both later life behaviour and adult gut microbiota in sex-specific ways. These findings highlight the importance of sex in determining the impact of neonatal immune activation on social behaviour and the gut microbiota.

Neuroimmunological investigations of cerebrospinal fluid in patients with recent onset depression - a study protocol

BACKGROUND

A proinflammatory response has been suggested to be involved in the pathophysiology of depression in a subgroup of patients. However, comprehensive largescale studies on neuroimmunological investigations of the cerebrospinal fluid (CSF) are lacking and no largescale longitudinal CSF studies comparing patients with depression to healthy controls currently exist.

METHODS

A longitudinal case-control study including at least 100 patients with first time depression (ICD-10: F32) within the past year with ongoing symptoms and at least 100 sex and age matched healthy controls with collection of CSF, blood, and fecal samples. All individuals will be evaluated by neurological examination including neurological soft signs, interviewed for psychopathology assessment and have symptomatology evaluated by relevant rating scales. Level of functioning and quality of life will be evaluated by a panel of interview questions and rating scales, and cognitive function assessed by a relevant test battery. In addition, a large number of potential confounders will be registered (BMI, smoking status, current medication etc.). Primary outcomes: CSF white cell count, CSF/serum albumin ratio, CSF total protein levels, IgG index, CSF levels of IL-6 and IL-8, and the prevalence of any CNS-reactive autoantibody in CSF and/or blood.

SECONDARY OUTCOMES

exploratory analyses of a wide range of neuroimmunological markers and specific autoantibodies. Power calculations are computed for all primary outcomes based on previous CSF studies including patients with depression and healthy controls.

DISCUSSION

This study will represent the hitherto largest investigation of CSF in patients with recent onset depression compared to healthy controls. We expect to elucidate neuroimmunological alterations in individuals with depression and characterize an immunological profile paving the way for the development of effective treatments based on biomarkers.

TRIAL REGISTRATION

The study is approved by The Regional Committee on Health Research Ethics (Capital Region, j.no: H-16030985) and The Danish Data Protection Agency (j.no: RHP-2016-020, I-Suite no.: 04945).

Association of severe childhood infections with depression and intentional self-harm in adolescents and young adults

Early-life infections have been linked with subsequent depression and self-harm. Examination of specific groups of infections and the role of familial factors may elucidate this observed relationship. We addressed these considerations in our investigations of the association of severe childhood infections with the risks of depression and self-harm in adolescence and early-adulthood. This population-based cohort study included all individuals born in Sweden between 1982 and 1996, with follow-up through 2013 (N = 1,506,070). Severe childhood infections were identified using inpatient and outpatient diagnoses from birth through age 12. Any infection as well as specific groups of infections were investigated. We examined diagnoses of depression and self-harm within inpatient and outpatient care and death by self-harm between ages 13 and 31. Cox proportional hazards regression models were used to estimate absolute risks, hazard ratios (HRs), and 95% CIs. When adjusting for sex and birth year, individuals exposed to any childhood infection demonstrated increased absolute risk differences for both outcomes (2.42% [95% CI, 0.41-4.43%] of being diagnosed with depression up until age 31, and 0.73% [-2.05% to 3.51%] of self-harm up until age 31) and increased relative risks (HR, 1.22 [1.20-1.24] for depression and HR, 1.29 [1.25-1.32] for self-harm). When controlling for unmeasured factors shared between family members by comparing discordant siblings, no strong association persisted. Our findings show that childhood infections may not be involved in the etiology of later depression and self-harm, and highlight the importance of identifying these genetic and environmental familial risk factors, which may serve as targets for interventions.

Increased incidence of childhood mental disorders following exposure to early life infection

Early life exposure to infectious diseases confers risk for adult psychiatric disorders but relatively few human population studies have examined associations with childhood mental disorder. Here we examined the effects of exposure to maternal infection during pregnancy, and child infectious diseases in early childhood (birth to age 4 years), in relation to first mental disorder diagnosis (age 5-13 years). The study sample comprised 71,841 children represented in a population cohort of children in New South Wales, Australia, followed from birth to early adolescence via linkage of administrative registers. Childhood exposure to infectious disease was determined during the prenatal period (i.e., maternal infection during gestation), and in early childhood (between birth and age 4 years) using the NSW Ministry of Health Admitted Patients data collection. Days to first diagnosis with a mental disorder was determined from recorded diagnoses between age 5-13 years in the NSW Ministry of Health's Admitted Patients, Emergency Department and Mental Health Ambulatory data collections. While crude hazard ratios for both prenatal infection and childhood infection exposures indicated significantly earlier diagnosis with mental disorders associated with both of these risk factors, only childhood infection exposure was associated with higher adjusted hazard ratios (aHR) for any diagnoses (aHR = 1.21, 95% CI = 1.11-1.32), externalising disorders (aHR = 1.45, 95% CI 1.18-1.79) and developmental disorders (aHR = 1.82, 95% CI 1.49-2.22) when the effects of maternal and early childhood (age < 5 years) mental disorders were taken into account. Exposure to infectious diseases during early childhood, but not prenatal infection exposure, appears to be associated with earlier diagnosis of mental disorders in childhood.

Association between common early-childhood infection and subsequent depressive symptoms and psychotic experiences in adolescence: a population-based longitudinal birth cohort study

BACKGROUND

Childhood infections are associated with adult psychosis and depression, but studies of psychotic experiences (PEs) and depressive symptoms in childhood, adolescence, and early-adulthood are scarce. Previous studies have typically examined severe infections, but studies of common infections are also scarce.

METHODS

Using data from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort, we examined associations of the number of infections in childhood from age 1.5 to 7.5 years with depressive symptom scores at age 10, 13, 14, 17, 18, and 19 years, and with PEs at 12 and 18 years. We performed additional analysis using infection burden ('low' = 0-4 infections, 'medium' = 5-6, 'high' = 7-9, or 'very high' = 10-22 infections) as the exposure.

RESULTS

The risk set comprised 11 786 individuals with childhood infection data. Number of childhood infections was associated with depressive symptoms from age 10 (adjusted beta = 0.14; standard error (s.e.) = 0.04; p = <0.01) to 17 years (adjusted beta = 0.17; s.e. = 0.08; p = 0.04), and with PEs at age 12 (suspected/definite PEs: adjusted odds ratio (OR) = 1.18; 95% confidence interval (CI) = 1.09-1.27). These effect sizes were larger when the exposure was defined as very high infection burden (depressive symptoms age 17: adjusted beta = 0.79; s.e. = 0.29; p = 0.01; suspected/definite PEs at age 12: adjusted OR = 1.60; 95% CI = 1.25-2.05). Childhood infections were not associated with depressive/psychotic outcomes at age 18 or 19.

CONCLUSIONS

Common early-childhood infections are associated with depressive symptoms up to mid-adolescence and with PEs subsequently in childhood, but not with these outcomes in early-adulthood. These findings require replication including larger samples with outcomes in adulthood.

Neuroimmune nexus of depression and dementia: Shared mechanisms and therapeutic targets

Dysfunctional immune activity is a physiological component of both Alzheimer's disease (AD) and major depressive disorder (MDD). The extent to which altered immune activity influences the development of their respective cognitive symptoms and neuropathologies remains under investigation. It is evident, however, that immune activity affects neuronal function and circuit integrity. In both disorders, alterations are present in similar immune networks and neuroendocrine signalling pathways, immune responses persist in overlapping neuroanatomical locations, and morphological and structural irregularities are noted in similar domains. Epidemiological studies have also linked the two disorders, and their genetic and environmental risk factors intersect along immune-activating pathways and can be synonymous with one another. While each of these disorders individually contains a large degree of heterogeneity, their shared immunological components may link distinct phenotypes within each disorder. This review will therefore highlight the shared immune pathways of AD and MDD, their overlapping neuroanatomical features, and previously applied, as well as novel, approaches to pharmacologically manipulate immune pathways, in each neurological condition. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

Immune activation in lactating dams alters sucklings' brain cytokines and produces non-overlapping behavioral deficits in adult female and male offspring: A novel neurodevelopmental model of sex-specific psychopathology

Early immune activation (IA) in rodents, prenatal through the mother or early postnatal directly to the neonate, is widely used to produce behavioral endophenotypes relevant to schizophrenia and depression. Given that maternal immune response plays a crucial role in the deleterious effects of prenatal IA, and lactation is a critical vehicle of immunological support to the neonate, we predicted that immune activation of the lactating dam will produce long-term abnormalities in the sucklings. Nursing dams were injected on postnatal day 4 with the viral mimic poly-I:C (4mg/kg) or saline. Cytokine assessment was performed in dams' plasma and milk 2h, and in the sucklings' hippocampus, 6h and 24h following poly-I:C injection. Male and female sucklings were assessed in adulthood for: a) performance on behavioral tasks measuring constructs considered relevant to schizophrenia (selective attention and executive control) and depression (despair and anhedonia); b) response to relevant pharmacological treatments; c) brain structural changes. Maternal poly-I:C injection caused cytokine alterations in the dams' plasma and milk, as well as in the sucklings' hippocampus. Lactational poly-I:C exposure led to sex-dimorphic (non-overlapping) behavioral abnormalities in the adult offspring, with male but not female offspring exhibiting attentional and executive function abnormalities (manifested in persistent latent inhibition and slow reversal) and hypodopaminergia, and female but not male offspring exhibiting despair and anhedonia (manifested in increased immobility in the forced swim test and reduced saccharine preference) and hyperdopaminergia, mimicking the known sex-bias in schizophrenia and depression. The behavioral double-dissociation predicted distinct pharmacological profiles, recapitulating the pharmacology of negative/cognitive symptoms and depression. In-vivo imaging revealed hippocampal and striatal volume reductions in both sexes, as found in both disorders. This is the first evidence for the emergence of long-term behavioral and brain abnormalities after lactational exposure to an inflammatory agent, supporting a causal link between early immune activation and disrupted neuropsychodevelopment. That such exposure produces schizophrenia- or depression-like phenotype depending on sex, resonates with notions that risk factors are transdiagnostic, and that sex is a susceptibility factor for neurodevelopmental psychopathologies.

The role of maternal anxiety and depressive disorders prior to and during pregnancy and perinatal psychopathological symptoms for early infant diseases and drug administration

BACKGROUND

Maternal mental health prior to and during pregnancy has been shown to be associated with inflammatory diseases and gastrointestinal complaints in the offspring. Unfortunately, many studies merely focused on perinatal distress without consideration of lifetime anxiety and depressive disorders.

AIMS

To prospectively investigate associations of anxiety and depressive disorders prior to and during pregnancy as well as perinatal distress with infants' inflammatory diseases, gastrointestinal complaints and corresponding drug administration.

STUDY DESIGN

Prospective-longitudinal study initiated in 2009/2010.

SUBJECTS

N=306 (expectant) mothers with and without DSM-IV lifetime anxiety and depressive disorders (Composite International Diagnostic Interview for Women) and low vs. high severity of psychopathological symptoms during pregnancy (Brief Symptom Inventory) enrolled in early pregnancy and repeatedly assessed during peripartum period.

OUTCOME MEASURES

Infant inflammatory diseases, gastrointestinal complaints and drug administration assessed via questionnaire (maternal report) at four months postpartum (n=279).

RESULTS

Severe psychopathological symptoms during pregnancy were associated with inflammatory diseases and anti-infective medication, whereas anxiety and depressive disorders prior to and during pregnancy were related to gastrointestinal complaints (diarrhea, colic complaints) and corresponding medication.

CONCLUSIONS

These results have to be discussed with caution, because information on infants' diseases were based exclusively on maternal self-reports. However, they suggest promising directions regarding our current knowledge about the relevance of maternal perinatal distress for infant inflammatory diseases (e.g. fetal programming). Moreover, the association between maternal anxiety and depressive disorders and infant gastrointestinal complaints may be explained by an anxious misinterpretation of 'normal' infant signals or a transmission of adverse gut microbiota, respectively.

Infectious, atopic and inflammatory diseases, childhood adversities and familial aggregation are independently associated with the risk for mental disorders: Results from a large Swiss epidemiological study

AIM

To examine the associations between mental disorders and infectious, atopic, inflammatory diseases while adjusting for other risk factors.

METHODS

We used data from PsyCoLaus, a large Swiss Population Cohort Study (n = 3720; age range 35-66). Lifetime diagnoses of mental disorders were grouped into the following categories: Neurodevelopmental, anxiety (early and late onset), mood and substance disorders. They were regressed on infectious, atopic and other inflammatory diseases adjusting for sex, educational level, familial aggregation, childhood adversities and traumatic experiences in childhood. A multivariate logistic regression was applied to each group of disorders. In a complementary analysis interactions with sex were introduced via nested effects.

RESULTS

Associations with infectious, atopic and other chronic inflammatory diseases were observable together with consistent effects of childhood adversities and familial aggregation, and less consistent effects of trauma in each group of mental disorders. Streptococcal infections were associated with neurodevelopmental disorders (men), and measles/mumps/rubella-infections with early and late anxiety disorders (women). Gastric inflammatory diseases took effect in mood disorders (both sexes) and in early disorders (men). Similarly, irritable bowel syndrome was prominent in a sex-specific way in mood disorders in women, and, moreover, was associated with early and late anxiety disorders. Atopic diseases were associated with late anxiety disorders. Acne (associations with mood disorders in men) and psoriasis (associations with early anxiety disorders in men and mood disorders in women) contributed sex-specific results. Urinary tract infections were associated with mood disorders and, in addition, in a sex-specific way with late anxiety disorders (men), and neurodevelopmental and early anxiety disorders (women).

CONCLUSION

Infectious, atopic and inflammatory diseases are important risk factors for all groups of mental disorders. The sexual dimorphism of the associations is pronounced.

Intestinal infection associated with future onset of an anxiety disorder: Results of a nationally representative study

Recent research involving mice suggests a possible relationship between intestinal infection and future anxiety-like behavior. However, there has been little epidemiological research showing such a connection in humans. This study uses the Medical Expenditure Panel Survey (MEPS) to assess longitudinally the association between intestinal infection and later onset of an anxiety disorder, through a nationally representative sample. Six 2-year panel datasets, each comprised of 5 consecutive rounds, were pooled from 2007 to 2013 to gather records for all respondents 18years of age or older that did not have an anxiety disorder in Round 1 (n=63, 133 people). Within the study sample, there were 2577 individuals with an intestinal infection in Round 1 and 4239 individuals with an anxiety disorder that began in Round 2, 3, 4, or 5. Overall, intestinal infection in Round 1 was associated with a 1.34 (P<0.01) odds ratio of having an anxiety disorder that began in Round 2, 3, 4, or 5. Separate analyses were performed to determine whether the association applied to other infection types, including respiratory infection, urinary tract infection, hepatitis infection, and skin infection. Respiratory infection was associated with a 1.36 (P<0.01) odds ratio of having an anxiety disorder that began in Round 2, 3, 4, or 5; no other infection type showed a significant association. More research on human populations is needed to examine the apparent association and explore potential mechanisms by which gut pathogens might influence anxiety.

Hospital admission for infection during early childhood influences developmental vulnerabilities at age 5 years

AIM

Childhood infectious diseases can be associated with later physical and psychological ill health, and the effects of this association may be evident during early childhood development. This study aimed to examine the effects of hospitalisation for early life infection on early childhood development.

METHODS

Hospital admission data for infection were obtained from the New South Wales Ministry of Health Admitted Patient Data Collection for 87 026 children, for whom the Australian Early Development Census (AEDC) was completed in their first year of formal schooling (age approximately 5 years). The AEDC provides estimates of each child's level of functioning on five domains of development spanning social and emotional skills, communication skills, numeracy and literacy and physical health. Multinomial logistic regressions were used to determine the relationship between exposure to hospital admissions for infectious disease prior to age 4 years and vulnerability on the AEDC. Models were adjusted for the effects of potential confounding factors related to the perinatal period, exposure to maltreatment and family characteristics.

RESULTS

Single and multiple hospitalisation(s) for infections were consistently associated with increased likelihood of being developmentally vulnerable on all AEDC domains, with odds ratios ranging from 1.02 to 1.28, after adjustment for confounding factors.

CONCLUSIONS

This study demonstrates a pervasive effect of early life infections that require hospital admission on multiple aspects of early child development, even after adjustment for potential confounding factors. Relatively, severe infection during early childhood constitutes a risk factor for developmental vulnerability by the time of entry to school.

Inflammatory insults and mental health consequences: does timing matter when it comes to depression?

It has become widely accepted that the immune system, and specifically increased levels of inflammation, play a role in the development of depression. However, not everyone with increased inflammation develops depression, and as with all other diseases, there are risk factors that may contribute to an increased vulnerability in certain individuals. One such risk factor could be the timing of an inflammatory exposure. Here, using a combination of PubMed, EMBASE, Ovid Medline and PsycINFO, we systematically reviewed whether exposure to medically related inflammation in utero, in childhood, and in adolescence, increases the risk for depression in adulthood. Moreover, we tried to determine whether there was sufficient evidence to identify a particular time point during the developmental trajectory in which an immune insult could be more damaging. While animal research shows that early life exposure to inflammation increases susceptibility to anxiety- and depressive-like behaviour, human studies surprisingly find little evidence to support the notion that medically related inflammation in utero and in adolescence contributes to an increased risk of developing depression in later life. However, we did find an association between childhood inflammation and later life depression, with most studies reporting a significantly increased risk of depression in adults who were exposed to inflammation as children. More robust clinical research, measuring direct markers of inflammation throughout the life course, is greatly needed to expand on, and definitively address, the important research questions raised in this review.

Hypermethylation of FOXP3 Promoter and Premature Aging of the Immune System in Female Patients with Panic Disorder?

Immunological abnormalities associated with pathological conditions, such as higher infection rates, inflammatory diseases, cancer or cardiovascular events are common in patients with panic disorder. In the present study, T cell receptor excision circles (TRECs), Forkhead-Box-Protein P3 gene (FOXP3) methylation of regulatory T cells (Tregs) and relative telomere lengths (RTLs) were investigated in a total and subsamples of 131 patients with panic disorder as compared to 131 age- and sex-matched healthy controls in order to test for a potential dysfunction and premature aging of the immune system in anxiety disorders. Significantly lower TRECs (p = 0.004) as well as significant hypermethylation of the FOXP3 promoter region (p = 0.005) were observed in female (but not in male) patients with panic disorder as compared to healthy controls. No difference in relative telomere length was discerned between patients and controls, but significantly shorter telomeres in females, smokers and older persons within the patient group. The presently observed reduced TRECs in panic disorder patients and FOXP3 hypermethylation in female patients with panic disorder potentially reflect impaired thymus and immunosuppressive Treg function, which might partly account for the known increased morbidity and mortality of anxiety disorders conferred by e.g. cancer and cardiovascular disorders.

Glia in the cytokine-mediated onset of depression: fine tuning the immune response

Major depressive disorder (MDD) is a mood disorder of multifactorial origin affecting millions of people worldwide. The alarming estimated rates of prevalence and relapse make it a global public health concern. Moreover, the current setback of available antidepressants in the clinical setting is discouraging. Therefore, efforts to eradicate depression should be directed towards understanding the pathomechanisms involved in the hope of finding cost-effective treatment alternatives. The pathophysiology of MDD comprises the breakdown of different pathways, including the hypothalamus-pituitary-adrenal (HPA) axis, the glutamatergic system, and monoaminergic neurotransmission, affecting cognition and emotional behavior. Inflammatory cytokines have been postulated to be the possible link and culprit in the disruption of these systems. In addition, evidence from different studies suggests that impairment of glial functions appears to be a major contributor as well. Thus, the intricate role between glia, namely microglia and astrocytes, and the central nervous system's (CNSs) immune response is briefly discussed, highlighting the kynurenine pathway as a pivotal player. Moreover, evaluations of different treatment strategies targeting the inflammatory response are considered. The immuno-modulatory properties of vitamin D receptor (VDR) suggest that vitamin D is an attractive and plausible candidate in spite of controversial findings. Further research investigating the role of VDR in mood disorders is warranted.

Comorbidity of physical and mental disorders in the neurodevelopmental genomics cohort study

OBJECTIVES

To examine patterns of associations between a broad range of mental and physical conditions by using a large, systematically obtained pediatric registry.

METHODS

The sample included 9014 youth ages 8 to 21 years (4349 males and 4665 females; 3585 aged <13 years, 3678 aged 13 to 18 years, and 1751 aged 19 to 21 years) from the Philadelphia Neurodevelopmental Cohort identified through pediatric clinics at the Children's Hospital of Philadelphia health care network by the Center for Applied Genomics. Measures were as follows: physical condition based on electronic medical records and interview data on 42 physical conditions of 14 organ systems/specialties and mental disorders based on an abbreviated version of the structured Kiddie-Schedule for Affective Disorders and Schizophrenia psychiatric diagnostic interview.

RESULTS

There was a direct association between the severity of the physical condition and most classes of mental disorders, as well as with functional impairment. Models adjusted for sociodemographic correlates, other physical and mental disorders, and false discovery and revealed broad patterns of associations between neurodevelopmental disorders with behavior disorders (odds ratio [OR]: 1.5; 95% confidence interval [CI]: 1.3-1.8; P < .004) and attention-deficit/hyperactivity disorder (OR: 3.1; 95% CI: 2.7-3.6; P < .0001), and neurologic/central nervous system conditions (OR: 1.3; 95% CI: 1.1-1.9; P < .05) with mood disorders and attention-deficit/hyperactivity disorder (OR: 1.3; 95% CI: 1.1-1.5; P < .001), and autoimmune/inflammatory conditions with mood disorders (OR: 1.4; 95% CI: 1.1-1.8, P < .05).

CONCLUSIONS

Findings show the strong overlap between physical and mental conditions and their impact on severity and functional impairment in youth. Specific patterns of comorbidity have important implications for etiology. Prospective tracking of cross-disorder morbidity will be important to establish more effective mechanisms for prevention and intervention.

The Role of Infections and Autoimmune Diseases for Schizophrenia and Depression: Findings from Large-Scale Epidemiological Studies

An immunologic component to schizophrenia and depression has been increasingly recognized, which has led to extensive research into the associations with infections and autoimmune diseases. Large-scale nationwide epidemiological studies have displayed an increased prevalence of both autoimmune diseases and infections among persons with schizophrenia and depression. Autoimmune diseases, and especially the number of infections requiring hospitalization, increase the risk of schizophrenia and depression in a dose–response relationship. Infections are a common exposure and a broad spectrum of infections are associated with schizophrenia and depression. Particularly the autoimmune diseases with a potential presence of brain-reactive antibodies were associated with psychiatric disorders. However, the associations seem to be bidirectional, since the risk of autoimmune diseases and infections is also increased after diagnosis with schizophrenia and depression. The risk of autoimmune diseases was particularly increased in individuals with prior hospital contacts for infections.

It has been suggested that inflammation and autoimmunity could be involved in the etiology and pathogenesis of some patients with symptoms of schizophrenia and depression. The psychiatric symptoms can be directly triggered by immune components, such as brain-reactive antibodies and cytokines, or infections reaching the central nervous system (CNS), or be secondary to systemic inflammation indirectly affecting the brain. However, the associations could also be caused by shared genetic factors, other environmental factors, or common etiological components. Nonetheless, autoimmune diseases and infections should be considered by clinicians in the treatment of individuals with psychiatric symptoms, since treatment would probably improve the psychiatric symptoms, quality of life, and the survival of the individuals.

Herpesviruses, inflammatory markers and incident depression in a longitudinal study of Detroit residents

BACKGROUND

Depression is predicted to become the leading cause of disability worldwide by 2030 and moreover, socioeconomic inequalities in depression persist. Herpesviruses, which are more prevalent among socioeconomically disadvantaged populations, subject to stress-induced reactivation and are associated with increased levels of pro-inflammatory cytokines implicated in the etiology of depression, may serve as novel risk factors for depression onset.

METHODS

Data are from individuals in the Detroit Neighborhood Health Study tested for herpes simplex virus-1 (HSV-1) and cytomegalovirus (CMV) seropositivity/immunoglobulin G (IgG) antibody levels (N=263) as well as interleukin-6 (IL-6) (N=245) and C-reactive protein (CRP) (N=236) levels and assessed for incident depression via the Patient Health Questionnaire-9. Linear and logistic regression models were used to examine associations between pathogen seropositivity/IgG antibody levels, pro-inflammatory markers and incident depression over approximately one-year of follow-up.

RESULTS

For every one unit increase in CMV IgG antibody level, the odds of incident depression increased by 26% and individuals with IgG antibody levels in the highest quartile had over three times greater odds of incident depression (odds ratio 3.87, 95% confidence interval 1.47, 10.19), compared to those in the lower three quartiles. Neither CMV or HSV-1 seropositivity nor HSV-1 IgG antibody level were associated with IL-6 or CRP levels at Wave 1, nor were IL-6 or CRP levels associated with incident depression at Wave 2.

CONCLUSIONS

Further examination of the biological pathways linking CMV and depression are warranted.

Comorbidity of infectious diseases and anxiety disorders in adults and its association with quality of life: a community study

Objective: Infectious diseases and anxiety disorders are common and both are associated with substantial burden to individual, families, and society. A better understanding of their association may be helpful in explicating possible etiological mechanisms related to both. The goal of the current study was to investigate the relationship between specific infectious diseases and anxiety disorders among adults in the community, and to examine whether the co-occurrence of the two is associated with poorer quality of life compared to subjects with one or neither condition.

Methods: We used data from the 1998 German Mental Health survey with 4181 subjects aged 18–65. Various infectious diseases (lifetime) and health-related quality of life were assessed via self-report questionnaires and anxiety disorders (past 12-months) were diagnosed using M-CIDI interviews. Logistic regression analyses were used to evaluate the association between infectious diseases and anxiety disorders; a linear model adjusted for sex was used to examine whether comorbidity of infectious diseases and anxiety disorders was associated with quality of life.

Results: Whooping cough [odds ratio (OR) = 1.69, 95% confidence intervals (CI) = 1.36–2.09], scarlet fever (OR = 1.31, 95% CI = 1.02–1.68), and diphtheria (OR = 1.79, 95% CI = 1.21–2.64) were associated with increased prevalence of any anxiety disorder. Subjects with both infectious diseases and anxiety disorders reported lower levels of both mental and physical quality of life, compared with subjects with only one or neither condition.

Conclusion: Extending prior research, this study suggests a relationship between specific infectious diseases and anxiety disorders in an adult community sample. Research targeting etiological mechanisms related to the interplay between infectious diseases and anxiety disorders is warranted.

The Prevention of Mental Disorders has a Bright Future

This article takes four looks at the status of prevention in psychiatry. The first glance is critical, shaped by disappointment at the slow progress in the understanding of psychiatric diseases and the lack of promise in prevention. The second look is less humble. It characterizes and acknowledges the efforts made so far. The third and the fourth perspectives optimistically announce a new age in research and prevention. Breakthroughs, whose contours are already appearing on the horizon today, will transform the prevention of psychiatric diseases into a success story within the next 10–15 years.