Exposure to stressful life events during pregnancy predicts psychotic experiences via behaviour problems in childhood

Examining the association between prenatal and perinatal adversity and the psychotic experiences in childhood

BACKGROUND

Prenatal and perinatal complications are established risk factors for psychotic disorder, but far less is known about these measures and psychotic experiences (PEs). We investigated the longitudinal effect of prenatal risk factors (maternal behavior, medication complications) and perinatal risk factors (birth weight, medical complications) on frequency of PEs. We also examined the cumulative risk of prenatal/perinatal risk factors, and differences between transient PE, persistent PE, and controls.

METHODS

The Adolescent Brain Cognitive Development study is a large child cohort (age 9-10 at baseline; n = 11 872 with PE data). PEs were measured longitudinally using the Prodromal Questionnaire-Brief, Child version, and included only if reported as distressing. Mixed-effects models were used for analysis, controlling for random effects, and a substantial number of fixed-effects covariates.

RESULTS

Urinary tract infection (β = 0.11, 95% confidence interval [CI] 0.03-0.19) and severe anemia (β = 0.18, 95% CI 0.07-0.29) increased frequency of distressing PEs in childhood. Number of prenatal complications increased frequency of PEs (β = 0.03, 95% CI 0.01-0.06) and risk of persistent PEs (odds ratio [OR] = 1.08, 95% CI 1.01-1.15). Maternal smoking was associated with an increased frequency of PEs (β = 0.11, 95% CI 0.04-0.18) and persistent PEs (OR = 1.31, 95% CI 1.04-1.66). Maternal substance use was a risk factor for a 48% increased risk of persistent PEs (OR = 1.48, 95% CI 1.08-2.01). Perinatal complications showed no effect on PEs.

CONCLUSIONS

This study provides evidence that certain prenatal medical complications (severe nausea, severe anemia), cumulative number of prenatal medical complications, and maternal behaviors (smoking during pregnancy), increased frequency of distressing PEs in childhood. Maternal smoking and substance use, as well as cumulative number of prenatal complications increased risk of persistent PEs.

A consideration of the increased risk of schizophrenia due to prenatal maternal stress, and the possible role of microglia

Schizophrenia is caused by interaction of a combination of genetic and environmental factors. Of the latter, prenatal exposure to maternal stress is reportedly associated with elevated disease risk. The main orchestrators of inflammatory processes within the brain are microglia, and aberrant microglial activation/function has been proposed to contribute to the aetiology of schizophrenia. Here, we evaluate the epidemiological and preclinical evidence connecting prenatal stress to schizophrenia risk, and consider the possible mediating role of microglia in the prenatal stress-schizophrenia relationship. Epidemiological findings are rather consistent in supporting the association, albeit they are mitigated by effects of sex and gestational timing, while the evidence for microglial activation is more variable. Rodent models of prenatal stress generally report lasting effects on offspring neurobiology. However, many uncertainties remain as to the mechanisms underlying the influence of maternal stress on the developing foetal brain. Future studies should aim to characterise the exact processes mediating this aspect of schizophrenia risk, as well as focussing on how prenatal stress may interact with other risk factors.

Protective Effect of the MCP-1 Gene Haplotype against Schizophrenia

While cytokines and their genetic variants have been intensively studied in schizophrenia, little attention has been focused on chemokines in the last years. The monocyte chemoattractant protein 1 (MCP-1) is known to attract peripheral monocytes to the brain during an inflammatory reaction and to affect the T helper (Th) cell development by stimulating Th2 polarization. Owing to the neuroinflammation in schizophrenia and the variable level of MCP-1 in these patients' sera, we proposed to analyze the impact of functional genetic variants of the MCP-1 gene (MCP-1-2518A/G (rs1024611), MCP-1-362G/C (rs2857656), and MCP-1 int1del554-567 (rs3917887)) in schizophrenic patients. We conducted a case-control study on a Tunisian population composed of 200 patients and 200 controls using RFLP-PCR. Our results indicated that the minor alleles (-2518G and Del554-567) were significantly more prevalent in controls than in patients (P=0.001/adjusted OR = 0.42, P=0.04/adjusted OR = 0.64), whereas, for -362C minor allele, increased risk of schizophrenia was revealed (P=0.001, adjusted OR = 2.38). In conclusion, we have identified the haplotype combination -2581G/-362G/int1del554-567 that could mediate protection against schizophrenia (P=0.0038, OR = 0.19) and the effect could result more strongly from the MCP-1 -2582G with -362G variants, whereas the effect of int1del554-567 may in part be explained by its LD with -362.

A cross-lagged panel analysis of children's sleep, attention, and mood in a prenatally stressed cohort: The QF2011 Queensland flood study

BACKGROUND

It is well recognized that childhood sleep, attention and mood problems increase risk for multiple adverse outcomes across the life-span; therefore, understanding factors, such as prenatal maternal stress, that underlie these types of childhood problems is critical for developing interventions that may optimize longer-term functioning. Our goal was to determine the association between disaster-related stress in pregnancy and young children's sleep, attention, and anxious/depressed symptoms.

METHODS

Soon after a major flood in Australia in 2011, we assessed various aspects of disaster-related prenatal maternal stress (PNMS) in women who had been pregnant at the time. Mothers rated several domains of their children's development with the Child Behavior Checklist (CBCL) at ages 2½ (n = 134) and 4 years (n = 118).

RESULTS

The primary finding was that more severe objective flood-related hardship in pregnancy predicted higher sleep problem scores at 2½ years, and that a negative maternal cognitive appraisal of the flood predicted lower attention problem scores at 2½ years. A cross-lagged panel analysis examined the association between children's sleep, attention, and anxious/depressed symptoms within and across ages. Results showed that these problems were likely to co-occur at each age, and that they were stable from 2½ to 4 years. Additionally, anxious/depressed scores at age 2½ predicted sleep problem scores at 4 years, all else being equal.

LIMITATIONS

Limitations of the study include a relatively small sample size and the children's outcome data relied on maternal report using the CBCL, rather than independent observation of the children's functioning, which may have introduced reporter bias.

CONCLUSIONS

These findings highlight the importance of early intervention for these childhood problems to optimize long-term mental health, particularly under conditions of prenatal stress.

Validation of the importance of continua in representing delusional ideation in the general population

BACKGROUND

Previous studies have examined the distribution of psychotic like experiences (PLE) with the aim of informing the debate concerning the categorical versus continuous nature of psychosis. We extend this research by subjecting a number of competing models of delusional ideation to validation analysis to further examine previous findings.

METHODS

We constructed latent variable models representing the factor structure of delusional ideation reported previously, using self-reported delusional ideation (Peter's Delusional Inventory; PDI) at age 21 in a general population prospective birth cohort study. After firstly eliminating models which exhibited poor fit we performed a longitudinal validation analyses among the competing models to investigate whether increasing levels of ideation were associated with developmental antecedents, correlates and distal indicators of psychotic disorder.

RESULTS

Four latent variable models were found to adequately represent the delusional ideation data, two comprised exclusively of continua (a multidimensional 5 factor model and a bifactor model with 1 general and 4 specific factors), and two which included both categories and continua (two factor mixture models, each with 3 classes and 1 factor per class, but with varying levels of parameter restrictions). Exclusively categorical latent models obtained poor fit and the categorical components of hybrid models failed to discriminate on psychotic illness, while among the models incorporating continuous latent factors validation analyses did not clearly identify any model as better than the others.

CONCLUSION

We provide novel evidence of the importance of continua in adequately and validly representing delusional ideation in the general population. Beyond this, our data suggests it is not possible to further refine the structure of delusional ideation in the general population.

Barbara Fish and a Short History of the Neurodevelopmental Hypothesis of Schizophrenia

The neurodevelopmental hypothesis of schizophrenia has become a paradigm broadly accepted in today's research in schizophrenia and its spectrum. This article traces the historical development of the neurodevelopmental hypothesis of schizophrenia up until the time of its explicit formulation in 1987, by Weinberger and by Murray and Lewis, with a main focus on the seminal contribution of Barbara Fish to its conception and elaboration.

Schizophrenia and reelin: a model based on prenatal stress to study epigenetics, brain development and behavior

Schizophrenia is a severe psychiatric disorder that results in a significant disability for the patient. The disorder is characterized by impairment of the adaptive orchestration of actions, a cognitive function that is mainly dependent on the prefrontal cortex. This behavioral deficit, together with cellular and neurophysiological alterations in the prefrontal cortex, as well as reduced density of GABAergic cells and aberrant oscillatory activity, all indicate structural and functional deficits of the prefrontal cortex in schizophrenia. Among the several risk factors for the development of schizophrenia, stress during the prenatal period has been identified as crucial. Thus, it is proposed that prenatal stress induces neurodevelopmental alterations in the prefrontal cortex that are expressed as cognitive impairment observed in schizophrenia. However, the precise mechanisms that link prenatal stress with the impairment of prefrontal cortex function is largely unknown. Reelin is an extracellular matrix protein involved in the development of cortical neural connectivity at embryonic stages, and in synaptic plasticity at postnatal stages. Interestingly, down-regulation of reelin expression has been associated with epigenetic changes in the reelin gene of the prefrontal cortex of schizophrenic patients. We recently showed that, similar to schizophrenic patients, prenatal stress induces down-expression of reelin associated with the methylation of its promoter in the rodent prefrontal cortex. These alterations were paralleled with altered prefrontal cortex functional connectivity and impairment in prefrontal cortex-dependent behavioral tasks. Therefore, considering molecular, cellular, physiological and behavioral evidence, we propose a unifying framework that links prenatal stress and prefrontal malfunction through epigenetic alterations of the reelin gene.

The hidden price and possible benefit of repeated traumatic exposure

There is a growing evidence showing that first-responders who are frequently exposed to traumatic events as part of their occupational routine may pay a hidden price. Although they display low to moderate levels of post-traumatic stress disorder (PTSD) symptoms, similar to individuals with full-blown PTSD, they show impaired ability to process and react according to contextual demands. We aimed to test whether this impairment affects performance on simple unrelated tasks and its association with cumulative traumatic exposure and level of PTSD symptoms. Thirty-nine trauma-exposed criminal scene investigator police and 35 unexposed civilians matched for age, gender, and education performed a simple discrimination task in the presence of aversive pictures with low or high intensity. We predicted and found that trauma-exposed individuals failed to modify their behavior in accordance with levels of negative intensity. Hence they were equally distracted in both low and high negative intensity conditions, compared to unexposed controls who showed improved performance in low intensity conditions. Importantly, performance of trauma-exposed individuals on conditions of low intensity negatively correlated with their levels of PTSD symptoms. These results highlight the maladaptive tendency of individuals with repeated traumatic exposure to maintain the same behavior in low-intensity contextual conditions when it is no longer adequate. Interestingly however, in high-intensity conditions trauma-exposed individuals outperformed unexposed controls. Specifically, when completing simple tasks in high intensity conditions. The results suggest that repeated traumatic exposure has both positive and negative consequences on the way individuals interpret and react to their environment.

Systematic Review of the Neurobiological Relevance of Chemokines to Psychiatric Disorders

Psychiatric disorders are highly prevalent and disabling conditions of increasing public health relevance. Much recent research has focused on the role of cytokines in the pathophysiology of psychiatric disorders; however, the related family of immune proteins designated chemokines has been relatively neglected. Chemokines were originally identified as having chemotactic function on immune cells; however, recent evidence has begun to elucidate novel, brain-specific functions of these proteins of relevance to the mechanisms of psychiatric disorders. A systematic review of both human and animal literature in the PubMed and Google Scholar databases was undertaken. After application of all inclusion and exclusion criteria, 157 references were remained for the review. Some early mechanistic evidence does associate select chemokines with the neurobiological processes, including neurogenesis, modulation of the neuroinflammatory response, regulation of the hypothalamus–pituitary–adrenal axis, and modulation of neurotransmitter systems. This early evidence however does not clearly demonstrate any specificity for a certain psychiatric disorder, but is primarily relevant to mechanisms which are shared across disorders. Notable exceptions include CCL11 that has recently been shown to impair hippocampal function in aging – of distinct relevance to Alzheimer’s disease and depression in the elderly, and pre-natal exposure to CXCL8 that may disrupt early neurodevelopmental periods predisposing to schizophrenia. Pro-inflammatory chemokines, such as CCL2, CCL7, CCL8, CCL12, and CCL13, have been shown to drive chemotaxis of pro-inflammatory cells to the inflamed or injured CNS. Likewise, CX3CL has been implicated in promoting glial cells activation, pro-inflammatory cytokines secretion, expression of ICAM-1, and recruitment of CD4+ T-cells into the CNS during neuroinflammatory processes. With further translational research, chemokines may present novel diagnostic and/or therapeutic targets in psychiatric disorders.

[The effect of childhood stress on the development of mental disorders in adults]

There is evidence that not only severe stressful events, but also common low-threat events, in particular chronic ones, may cause or provoke some mental disorders. The literature data on the degree of pathogenicity of stress factors are insufficient. Authors attempted to summarize the established facts in the following aspects: current conceptions on the physiology and pathology of stress in the frames of the problem of psychosomatic disorders, deprivation in childhood, neurobiological consequences of childhood stress, psychiatric consequences of stress in childhood. Authors believe that this problem demands further investigation to find possible predictors of mental disorders in patients who had experienced stressful life events in childhood.