Environmental Risk Factors For Psychosis Research Articles

Cumulative Environmental Risk in Early Life: Associations With Schizotypy in Childhood.

Psychotic disorders are associated with a growing number of recognized environmental exposures. Cumulative exposure to multiple environmental risk factors in childhood may contribute to the development of different patterns of schizotypy evident in early life. Hypotheses were that distinct profiles of schizotypy would have differential associations with a cumulative score of environmental risk factors. We prospectively examined the relationship between 19 environmental exposures (which had demonstrated replicated associations with psychosis) measured from the prenatal period through to age 11 years, and 3 profiles of schizotypy in children (mean age = 11.9 years, n = 20 599) that have been established in population data from the New South Wales-Child Development Study. Multinomial logistic regression was used to examine associations between membership in each of 3 schizotypy profiles (true schizotypy, introverted schizotypy, and affective schizotypy) and exposure to a range of 19 environmental risk factors for psychosis (both individually and summed as a cumulative environmental risk score [ERS]), relative to children showing no risk. Almost all environmental factors were associated with at least 1 schizotypy profile. The cumulative ERS was most strongly associated with the true schizotypy profile (OR = 1.61, 95% CI = 1.52-1.70), followed by the affective (OR = 1.33, 95% CI = 1.28-1.38), and introverted (OR = 1.32, 95% CI = 1.28-1.37) schizotypy profiles. Consistent with the cumulative risk hypothesis, results indicate that an increased number of risk exposures is associated with an increased likelihood of membership in the 3 schizotypy profiles identified in middle childhood, relative to children with no schizotypy profile.

Do environmental risk factors for the development of psychosis distribute differently across dimensionally assessed psychotic experiences?

Psychotic experiences (PE) are associated with poorer functioning, higher distress and the onset of serious mental illness. Environmental exposures (e.g. childhood abuse) are associated with the development of PE. However, which specific exposures convey risk for each type or dimension of PE has rarely been explored. The Oxford Wellbeing Life and Sleep (OWLS) survey includes 22 environmental risk factors for psychosis and was designed to examine how environmental risks are associated with specific dimensions of PE. Multivariate logistic regression models were fit using these risk factors to predict six dimensions of PE (perceptual abnormalities, persecutory ideation, bizarre ideas, cognitive disorganisation, delusional mood and negative symptoms). Models were built using only 70% of the data, and then fit to the remaining data to assess their generalisability and quality. 1789 (27.2% men; mean age = 27.6; SD = 10.9) survey responses were analysed. The risk factors predictive of the most PE were anxiety, social withdrawal during childhood and trauma. Cannabis and depression predicted three dimensions with both predicting bizarre ideas and persecutory ideation. Psychological abuse and sleep quality each predicted two dimensions (persecutory ideation and delusional mood). Risk factors predicting one PE dimension were age (predicting cognitive disorganisation), physical abuse (bizarre ideas), bullying and gender (persecutory ideation); and circadian phase (delusional mood). These results lend support for a continuum of psychosis, suggesting environmental risks for psychotic disorders also increase the risk of assorted dimensions of PE. Furthermore, it advocates the use of dimensional approaches when examining environmental exposures for PE given that environmental risks distribute differently across dimensions.

Sleep-related memory consolidation in the psychosis spectrum phenotype

Sleep and memory processing impairments range from mild to severe in the psychosis spectrum. Relationships between memory processing and sleep characteristics have been described for schizophrenia, including unaffected first-degree relatives, but they are less clear across other high-risk groups within the psychosis spectrum. In this study, we investigated high-risk individuals with accumulated risk-factors for psychosis and subthreshold symptoms. Out of 1898 screened individuals, 44 age- and sex-matched participants were sub-grouped into those with substantial environmental risk factors for psychosis and subthreshold psychotic symptoms (high-risk group) and those without these phenotypes (low-risk controls). Four groups (high/low risk, morning/evening training) were trained and tested in the laboratory for sustained attention, motor skill memory (finger-tapping task) and declarative memory (word-pair learning task) immediately after training, again after a night of EEG-recorded sleep at home or a period of daytime wakefulness, and again after 24 h from training. No differences in sustained attention or in memory consolidation of declarative and motor skill memory were found between groups for any time period tested. However, a group difference was found for rapid-eye movement (REM) sleep in relation to motor skill memory: the longer the total sleep time, particularly longer REM sleep, the greater the performance gain, which occurred only in high-risk individuals. In conclusion, our results suggest a gain in motor skill performance with sufficient sleep opportunity for longer REM sleep in high-risk individuals with subthreshold psychotic symptoms. Declarative memory did not benefit from sleep consolidation above or beyond that of the control group.

Cannabinoid receptor CNR1 expression and DNA methylation in human prefrontal cortex, hippocampus and caudate in brain development and schizophrenia

Beyond being one the most widely used psychoactive drugs in the world, cannabis has been identified as an environmental risk factor for psychosis. Though the relationship between cannabis use and psychiatric disorders remains controversial, consistent association between early adolescent cannabis use and the subsequent risk of psychosis suggested adolescence may be a particularly vulnerable period. Previous findings on gene by environment interactions indicated that cannabis use may only increase the risk for psychosis in the subjects who have a specific genetic vulnerability. The type 1 cannabinoid receptor (CB1), encoded by the CNR1 gene, is a key component of the endocannabinoid system. As the primary endocannabinoid receptor in the brain, CB1 is the main molecular target of the endocannabinoid ligand, as well as tetrahydrocannabinol (THC), the principal psychoactive ingredient of cannabis. In this study, we have examined mRNA expression and DNA methylation of CNR1 in human prefrontal cortex (PFC), hippocampus, and caudate samples. The expression of CNR1 is higher in fetal PFC and hippocampus, then drops down dramatically after birth. The lifespan trajectory of CNR1 expression in the DLPFC differentially correlated with age by allelic variation at rs4680, a functional polymorphism in the COMT gene. Compared with COMT methionine158 carriers, Caucasian carriers of the COMT valine158 allele have a stronger negative correlation between the expression of CNR1 in DLPFC and age. In contrast, the methylation level of cg02498983, which is negatively correlated with the expression of CNR1 in PFC, showed the strongest positive correlation with age in PFC of Caucasian carriers of COMT valine158. Additionally, we have observed decreased mRNA expression of CNR1 in the DLPFC of patients with schizophrenia. Further analysis revealed a positive eQTL SNP, rs806368, which predicted the expression of a novel transcript of CNR1 in human DLPFC, hippocampus and caudate. This SNP has been associated with addiction and other psychiatric disorders. THC or ethanol are each significantly associated with dysregulated expression of CNR1 in the PFC of patients with affective disorder, and the expression of CNR1 is significantly upregulated in the PFC of schizophrenia patients who completed suicide. Our results support previous studies that have implicated the endocannabinoid system in the pathology of schizophrenia and provided additional insight into the mechanism of increasing risk for schizophrenia in the adolescent cannabis users.

M22. IGG ANTIBODIES TO TOXOPLASMA GONDII ARE ASSOCIATED WITH INCREASED LONG-TERM RISK FOR PSYCHOSIS IN INDIVIDUALS AT ULTRA-HIGH RISK FOR PSYCHOSIS

BackgroundThe prevalence of antibodies to Toxoplasma gondii, a ubiquitous parasitic protozoan causing the infectious disease toxoplasmosis, is increased in patients with psychotic disorders compared to the general population. We have previously shown that antibody titers for T.gondii correlate with the severity of positive symptoms in young people at ultra-high risk (UHR) for psychosis, suggesting that infection with T. gondii may be relevant to the manifestation of psychosis. However, it is unclear if T. gondii antibodies represent a risk factor for psychosis onset or non-psychotic outcome in UHR individuals. The aim of the present study was to examine whether seropositivity for T.gondii is associated with transition to psychosis and other outcomes in young people at UHR for psychosis.MethodsThe study sample consisted of 96 individuals at UHR for psychosis who were referred to the Personal Assistance and Crisis Evaluation (PACE) clinic in Melbourne, Australia, between 2001 and 2004, consented to optional blood tests for infectious agents and were followed up for up to 10 years after baseline (median (interquartile range) duration of follow-up: 7.15 (3.14 – 7.72) years). Serum IgG antibodies to six viral and parasitic pathogens (Toxoplasma gondii, Herpes Simplex Virus Type 1 and 2, Cytomegalovirus, Epstein Barr Virus, Varicella-Zoster Virus) were measured at baseline. Outcome measures included transition to psychosis, general psychiatric symptomatology and positive psychotic symptoms (BPRS), negative symptoms (SANS), depressive symptoms (HAM-D), anxiety symptoms (HAM-A) and functioning (SOFAS and GAF). Cox proportional hazards regression and linear regression models were used to examine the associations of seropositivity and antibody titers at baseline and transition to psychosis and other outcomes at follow-up.ResultsA total of 17 individuals (17.7%) were seropositive for Toxoplasma gondii at baseline. The rate of transition to psychosis was higher among seropositive (35.7%) compared to seronegative participants (14.6%), although this was not statistically significant (p=0.101). Antibody titers (IgG) for Toxoplasma gondii were significantly higher at baseline in participants who later transitioned to psychosis (1.34 ± 1.36 vs. 0.79 ± 0.73, p=0.027). Seropositivity for T.gondii IgG at baseline significantly predicted transition to psychosis within the follow-up duration (hazard ratio [HR]=3.61, 95%CI 1.08 – 12.00, p=0.036). Toxoplasma IgG at baseline were significantly associated with higher BPRS scores at follow-up in participants who were seropositive at baseline (Beta=6.38, 95%CI 0.43 – 12.34, p=0.038). No significant associations were found between antibodies to other pathogens and outcome, or between antibodies to Toxoplasma gondii and any other outcomes.DiscussionOur findings suggest that the presence of IgG class antibodies for Toxoplasma gondii is associated with a higher risk for psychosis transition in individuals at UHR for psychosis, but not with risk for other long-term outcomes. These observations provide support for the hypothesis that infection with Toxoplasma gondii may be an environmental risk factor for psychosis and suggest that IgG antibodies for Toxoplasma gondii in individuals at UHR for psychosis have prognostic relevance.

Childhood adverse traumatic experiences and schizophrenia

Εpidemiological research during last decades has demonstrated the association of certain environmental variables with psychosis. Ιn parallel with understanding environmental contributors to schizophrenia, identification of those at high risk of psychosis has become a priority. These risk factors include adverse traumatic experiences, such as discrimination, social environment adversities, bullying, emigration and childhood trauma. For many years the possibility of a relationship of adverse traumatic experiences with schizophrenia was minimized in favor of a biological paradigm. However, there is evidence supporting that childhood adversities is one of the most significant environmental risk factors for psychosis, if not the most significant. Studies have demonstrated the validity and the reliability of retrospective reports of adverse traumatic experiences in psychotic patients. The question on the causal relationship between adverse traumatic experiences and psychosis has been raised for many years, but it has not yet been answered. Researchers have focused on the study of dysfunctional cognitive schemes being formed due to childhood adversities and interpreting the world as unfriendly and threatening. According to social defeat hypothesis, the patients do not experience more stressful life events but they experience them as less controllable. Furthermore, researchers study the mediator psychopathology associated directly with adverse traumatic experiences, such as anxiety, mood, dissociative and adaptation disorders, which possibly predispose to psychosis. Cannabis use and childhood adversities may interact to increase the risk of psychotic symptoms in adolescence, according to research findings. Several publications have positively linked the number of traumatic adverse experiences with the severity of mental health and possibly with high risk of psychosis in a dose-response relationship model. Taking note that it is important to have a plausible hypothesis of the biological mechanisms involved with the relationship between adverse traumatic experiences and psychosis, the putative systems being explored are: (1) the hypothalamus-pituitary-adrenal (HPA) axis because it mediates the principal adaptive response to perceived psychological or physiological stress and (2) the dopamine system, which is considered to be important in the development of psychosis. The biological and environmental risk factors are both important in the etiology of psychosis but the effects of some forms of childhood adversity act largely independently of pre-existing genetic liability to increase the risk of psychosis. A supposed differentiation of psychosis associated with adverse traumatic experiences from the classic neurodegenerative model possibly should be considered seriously by the clinician in order to design the best therapeutic plan.

The Maudsley environmental risk score for psychosis.

Risk prediction algorithms have long been used in health research and practice (e.g. prediction of cardiovascular disease and diabetes). However, similar tools have not been developed for mental health. For example, for psychotic disorders, attempts to sum environmental risk are rare, unsystematic and dictated by available data. In light of this, we sought to develop a valid, easy to use measure of the aggregate environmental risk score (ERS) for psychotic disorders. We reviewed the literature to identify well-replicated and validated environmental risk factors for psychosis that combine a significant effect and large-enough prevalence. Pooled estimates of relative risks were taken from the largest available meta-analyses. We devised a method of scoring the level of exposure to each risk factor to estimate ERS. Relative risks were rounded as, due to the heterogeneity of the original studies, risk effects are imprecisely measured. Six risk factors (ethnic minority status, urbanicity, high paternal age, obstetric complications, cannabis use and childhood adversity) were used to generate the ERS. A distribution for different levels of risk based on simulated data showed that most of the population would be at low/moderate risk with a small minority at increased environmental risk for psychosis. This is the first systematic approach to develop an aggregate measure of environmental risk for psychoses in asymptomatic individuals. This can be used as a continuous measure of liability to disease; mostly relevant to areas where the original studies took place. Its predictive ability will improve with the collection of additional, population-specific data.

The role of self-disturbances and cognitive biases in the relationship between traumatic life events and psychosis proneness in a non-clinical sample

BackgroundTraumatic life events have been established as an environmental risk factor for psychosis. However, the exact mechanisms by which traumatic life events increase risk for psychosis are unknown. In the present study we tested an integrative model of traumatic life events being related to psychosis proneness via self-disturbances and cognitive biases. MethodsThe sample consisted of 653 healthy people. Traumatic life events, self-disturbances, cognitive biases and psychosis proneness were assessed with self-report questionnaires. The direct and an indirect model of the relationship between traumatic life events and psychosis proneness were compared using path analyses with structural equation modelling in a cross-sectional study. ResultsThere was a significant direct effect of traumatic life events on psychosis proneness. However, path analysis suggested better fit of the indirect model including paths from trauma to psychosis proneness via cognitive biases and self-disturbances. There were significant paths from traumatic life events to cognitive biases and self-disorders. Self-disorders significantly predicted cognitive biases. Finally, cognitive biases and self-disorders significantly predicted psychosis proneness. Exclusion of any paths, apart from direct path in the model, significantly reduced model fitness. DiscussionThe results revealed that a direct relationship between trauma and psychosis proneness became insignificant when taking into account the influence of self-disorders and cognitive biases. This suggests that the interactions between disrupted self-experience, impaired information processing and traumatic life events are of importance in psychosis proneness. This model should be further tested in a longitudinal study on a clinical sample.

Daily use of high-potency cannabis is associated with an increased risk of admission and more intervention after first-episode psychosis

ABSTRACT FROM: Schoeler T, Petros N, Di Forti M, et al . Effects of continuation, frequency, and type of cannabis use on relapse in the first 2 years after onset...

Deconstructing vulnerability for psychosis: Meta-analysis of environmental risk factors for psychosis in subjects at ultra high-risk

BackgroundSubjects at ultra high-risk (UHR) for psychosis have an enhanced vulnerability to develop the disorder but the risk factors accounting for this accrued risk are undetermined. MethodSystematic review of associations between genetic or environmental risk factors for psychosis that are widely established in the literature and UHR state, based on comparisons to controls. ResultsForty-four studies encompassing 170 independent datasets and 54 risk factors were included. There were no studies on association between genetic or epigenetic risk factors and the UHR state that met the inclusion criteria. UHR subjects were more likely to show obstetric complications, tobacco use, physical inactivity, childhood trauma/emotional abuse/physical neglect, high perceived stress, childhood and adolescent low functioning, affective comorbidities, male gender, single status, unemployment and low educational level as compared to controls. ConclusionsThe increased vulnerability of UHR subjects can be related to environmental risk factors like childhood trauma, adverse life events and affective dysfunction. The role of genetic and epigenetic risk factors awaits clarification.

Evaluation of oral assessment in pharmacy education at Charles Darwin University

Childhood trauma exposure is a robust environmental risk factor for psychosis. However, not all exposed individuals develop psychotic symptoms later in life. The Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism (rs6265) has been suggested to moderate the psychosis-inducing effects of childhood trauma in clinical and nonclinical samples. Our study aimed to explore the interaction effect between childhood trauma and the BDNF Val66Met polymorphism on subclinical psychotic experiences (PEs). This was explored in two nonclinical independent samples: an undergraduate and technical-training school student sample (n = 808, sample 1) and a female twin sample (n = 621, sample 2). Results showed that childhood trauma was strongly associated with positive and negative PEs in nonclinical individuals. A BDNF Val66Met x childhood trauma effect on positive PEs was observed in both samples. These results were discordant in terms of risk allele: while in sample 1 Val allele carriers, especially males, were more vulnerable to the effects of childhood trauma regarding PEs, in sample 2 Met carriers presented higher PEs scores when exposed to childhood trauma, compared with Val carriers. Moreover, in sample 2, a significant interaction was also found in relation to negative PEs. Our study partially replicates previous findings and suggests that some individuals are more prone to develop PEs following childhood trauma because of a complex combination of multiple factors. Further studies including genetic, environmental and epigenetic factors may provide insights in this field.

Childhood trauma, BDNF Val66Met and subclinical psychotic experiences. Attempt at replication in two independent samples

Childhood trauma exposure is a robust environmental risk factor for psychosis. However, not all exposed individuals develop psychotic symptoms later in life. The Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism (rs6265) has been suggested to moderate the psychosis-inducing effects of childhood trauma in clinical and nonclinical samples. Our study aimed to explore the interaction effect between childhood trauma and the BDNF Val66Met polymorphism on subclinical psychotic experiences (PEs). This was explored in two nonclinical independent samples: an undergraduate and technical-training school student sample (n = 808, sample 1) and a female twin sample (n = 621, sample 2). Results showed that childhood trauma was strongly associated with positive and negative PEs in nonclinical individuals. A BDNF Val66Met x childhood trauma effect on positive PEs was observed in both samples. These results were discordant in terms of risk allele: while in sample 1 Val allele carriers, especially males, were more vulnerable to the effects of childhood trauma regarding PEs, in sample 2 Met carriers presented higher PEs scores when exposed to childhood trauma, compared with Val carriers. Moreover, in sample 2, a significant interaction was also found in relation to negative PEs. Our study partially replicates previous findings and suggests that some individuals are more prone to develop PEs following childhood trauma because of a complex combination of multiple factors. Further studies including genetic, environmental and epigenetic factors may provide insights in this field.

Evaluating the impact of cannabis use on thalamic connectivity in youth at clinical high risk of psychosis.

BackgroundDisruptions in thalamic functional connectivity have been observed in people with schizophrenia and in youth at clinical high risk (CHR) of psychosis. However, the impact of environmental risk factors for psychosis on thalamic dysconnectivity is poorly understood. We tested whether thalamic dysconnectivity is related to patterns of cannabis use in a CHR sample.Methods162 CHR and 105 control participants were assessed on cannabis use severity, frequency, and age at onset of first use as part of the North American Prodrome Longitudinal Study and completed resting-state fMRI scans. Whole-brain thalamic functional connectivity maps were generated using individual subjects’ anatomically defined thalamic seeds.ResultsThalamic connectivity did not significantly correlate with current cannabis use severity or frequency in either CHR or controls. In CHR cannabis users, a significant correlation emerged between attenuated thalamic connectivity with left sensory/motor cortex and a younger age at onset of cannabis use. CHR who used cannabis before age 15 did not differ on thalamic connectivity as compared to CHR who used after age 15 or CHR who were cannabis naïve. No group differences in thalamic connectivity emerged when comparing CHR separated by moderate/high use frequency, low-frequency or cannabis naïve.ConclusionsAlthough a younger age at onset of cannabis use may be associated with disrupted thalamo-cortical coupling, cannabis use does not appear to be an identifying characteristic for thalamic connectivity in CHR with moderate/high use frequency compared to low-frequency users or CHR who are cannabis naïve.Electronic supplementary materialThe online version of this article (doi:10.1186/s12888-015-0656-x) contains supplementary material, which is available to authorized users.

Connecting the Brain and New Drug Targets for Schizophrenia

One thing we know for certain after decades of functional imaging in schizophrenia is that it is not a disorder that can simply be attributed to circumscribed lesions in the brain. It is, in other words, a disorder of the connectivity of the brain. In this overview, we will consider the power of connectivity analyses of functional MRI (and PET) data as tools for translational neuroscience. We describe the patterns of functional and effective disconnectivity seen in schizophrenia and particular psychotic symptoms, those that appear to be attributable to genetic and/or environmental risk factors for psychosis, the potential of these disconnectivities as trait and state biomarkers, and their sensitivity to drug effects. We conclude that substantial work needs to be done on standardising connectivity analyses across laboratories and that disconnectivity studies should be an integral part of drug discovery programmes.

Psychosis Rates Reflect Urban Life, Minority Status

Psychosis Rates Reflect Urban Life, Minority Status

Environmental risk factors for psychosis

Genetic factors are clearly important in the etiology of schizophrenia, but the environment in which an individual's genes find expression is also crucial to the development of the illness. In this review of environmental risk factors for schizophrenia, we consider risks operating prenatally and perinatally, during childhood, and then later in life prior to illness onset Some of these risk factors have been well documented, for example, early hazards causing fetal growth retardation or hypoxia, and hazards nearer the onset of illness like drug abuse and migration. Others are much less certain. The importance of interaction between genetic and environmental risk is, however, undoubtedly important and there is emerging evidence for this from a range of sources. As the etiology of schizophrenia is unraveled, the picture becomes more complex, but also more obviously relevant to the plight of the individual patient.