Stress sensitization in schizophrenia

Post-intervention neuroimaging effects of psychosocial interventions aimed at promoting resilience in children and adolescents under psychological stress: A systematic review

Childhood and adolescence are neurodevelopmentally critical periods, during which psychological adversity can increase the risk of subsequent mental health difficulties. However, the increased neuroplasticity during this window also confers potential for developing resilience, which is now seen as a dynamic process of adapting to adversity. This pre-registered systematic review (PROSPERO-CRD42024537715) summarises the post-intervention neuroimaging outcomes of non-invasive, non-pharmacological interventions aimed at promoting resilience in samples with a mean age of < 25 years exposed to any explicit psychological stress. Studies involving traumatic or focal brain lesions were excluded. MEDLINE, PsycINFO and CENTRAL databases were searched from inception to 14/7/2024. Magnetic Resonance Imaging (MRI) outcomes were the primary focus. Risk of bias was assessed against adapted Joanna Briggs Institute checklist items. A narrative synthesis was conducted due to study heterogeneity. We identified 13 eligible studies: 1 reporting structural and diffusion-weighted MRI (performed after 2 years of intervention), 1 resting-state fMRI (14 years after end of intervention) and 11 task-based fMRI metrics (ranging from immediately post-intervention to 8 years after end of intervention). Resilience interventions reduce limbic activity (thalamus, amygdala and right anterior insula) in task-based fMRI. In older adolescents, social, mindfulness, and exercise interventions strengthen Prefrontal Cortex(PFC)-limbic connectivity, decreasing limbic activity. Evidence in younger adolescents is sparse, showing mixed effects on PFC-limbic connectivity. Five studies were at high risk of bias; the most common limitation was no pre-intervention MRI scans. Overall, this study summarises promising mechanisms, as demonstrated on neuroimaging, through which resilience can be enhanced in stressed youth through psychosocial interventions.

The moderating role of hair cortisol in the association of early and recent stress with stress-related phenotypes

Background

Increased hair cortisol concentrations (HCC) have been found in clinical samples of schizophrenia, first episode psychosis and clinical risk for psychosis, but evidence of such is scarce in schizotypy. High HCC are supposed to reflect elevated chronic stress. However, HCC were not directly associated with adversity measures and stress-related phenotypes in previous research. This study tested whether HCC moderated the association between a comprehensive range of psychosocial stressors with several stress-related phenotypes in a sample of nonclinical young adults. It was expected that stressors, either distal (i.e., early-life) or recent, would be associated with subclinical features, particularly for those with elevated HCC, reflecting the effects of a potential biological sensitization to stress.

Methods

The sample comprised 132 nonclinical young adults belonging to the Barcelona Longitudinal Investigation of Schizotypy Study (BLISS). Participants completed a questionnaire of childhood adversity and two complementary measures of recent life events, tapping threatening vs. more general life events. Both the frequency and subjective impact (positive vs. negative) of general life events were also assessed. Psychotic (i.e., schizotypy, suspiciousness) and non-psychotic (i.e., depression, anxiety) subclinical features as well as appraisals of perceived stress were examined. Hierarchical linear regressions and simple slope analyses were computed.

Results

HCC moderated the effects of both early and recent stress on suspiciousness as well as the effects of recent life events on perceived stress, such that those with higher HCC presented increased suspiciousness and perceived stress at higher levels of stress exposure. Positive, but not negative, recent life events were associated with decreased perceived stress and depression, and these associations were moderated by low HCC, indicating a buffering effect for those with a non-impaired HPA axis.

Conclusion

In line with the neural diathesis-stress model, results highlight the role of the interplay between the HPA axis and exposure to stressful experiences in exacerbating psychosis features and extend evidence to the nonclinical expression of the psychosis continuum. In addition, findings support the protective effect of positive experiences in decreasing stress appraisals and affective disturbances, which is consistent with emerging research about the relevance of positive factors in reducing the likelihood of psychopathological outcomes.

Basic symptoms of schizophrenia are related to symptoms of traumatic stress: A pivotal role of sensitization. An observational study

INTRODUCTION

Subjective cognitive deficits have been broadly reported in schizophrenia and described by Huber as basic symptoms. It remains unclear however to what extent they may be related to psychosocial stressors including trauma.

METHODS

We assessed basic symptoms using the Frankfurt Complaint Questionnaire (FCQ) in a sample of 40 patients with schizophrenia. Trauma-related symptoms were assessed concurrently using the Trauma Symptom Checklist-40, symptoms of dissociation using the Dissociative Experiences Scale, and sensitization phenomena using the Complex Partial Seizure-like Symptoms Inventory and Limbic System Checklist-33. Psychotic symptoms were measured by Health of the Nation Outcome Scales. The dosage of antipsychotic medication was assessed in terms of equivalents of chlorpromazine, and antidepressant medication in terms of equivalents of fluoxetine. Spearman correlations were performed to explore the relationship between FCQ and other trauma-related measures. To determine the relative contributions of trauma-related symptoms to basic symptoms a linear regression analysis was performed.

RESULTS

The results showed that higher levels of basic symptoms of schizophrenia were associated with greater levels of symptoms of dissociation, traumatic stress, and sensitization or kindling-like processes in schizophrenia. Among the trauma-related variables, sensitization phenomena assessed with Complex Partial Seizure-like Symptoms Inventory were closely associated with basic symptoms.

DISCUSSION

These results indicate that basic symptoms measured by FCQ might be related to trauma. The potential of trauma to influence neurodevelopmental hypotheses of schizophrenia is discussed.

Psychosocial Stress, Epileptic-Like Symptoms and Psychotic Experiences

Background

Current research suggests that stressful life experiences and situations create a substantive effect in the development of the initial manifestations of psychotic disorders and may influence temporo-limbic epileptic-like activity manifesting as cognitive and affective seizure-like symptoms in non-epileptic conditions.

Methods

The current study assessed trauma history, hair cortisol levels, epileptic-like manifestations and other psychopathological symptoms in 56 drug naive adult young women experiencing their initial occurrence of psychosis.

Results

Hair cortisol levels among patients experiencing their initial episode of psychosis, were significantly correlated with stress symptoms measured by Trauma Symptom Checklist-40 (r = − 0.48, p < 0.01), and complex partial seizure-like symptoms measured by the Complex Partial Seizure-Like Symptoms Inventory (r = − 0.33, p < 0.05) and LSCL-33 (r = − 0.33, p < 0.05). Hair cortisol levels were not found to be significantly correlated with symptoms of anxiety and depression measured by Beck depression Inventory and Zung Anxiety Scale.

Conclusion

These findings suggest a significant relationship between epileptic-like symptoms and stress responses demonstrated by patients in their first psychotic episode. These findings may suggest the potential for research to explore usefulness of anticonvulsant treatment in patients who do not respond to usual psychotropic medication.

Myelin Deficits Caused by Olig2 Deficiency Lead to Cognitive Dysfunction and Increase Vulnerability to Social Withdrawal in Adult Mice

Oligodendrocyte (OL) and myelin development are crucial for network integration and are associated with higher brain functions. Accumulating evidence has demonstrated structural and functional impairment of OLs and myelin in serious mental illnesses. However, whether these deficits contribute to the brain dysfunction or pathogenesis of such diseases still lacks direct evidence. In this study, we conditionally deleted Olig2 in oligodendroglial lineage cells (Olig2 cKO) and screened the behavioral changes in adult mice. We found that Olig2 ablation impaired myelin development, which further resulted in severe hypomyelination in the anterior cingulate cortex. Strikingly, Olig2 cKO mice exhibited an anxious phenotype, aberrant responses to stress, and cognitive deficits. Moreover, Olig2 cKO mice showed increased vulnerability to social avoidance under the mild stress of social isolation. Together, these results indicate that developmental deficits in OL and myelin lead to cognitive impairment and increase the risk of phenotypes reminiscent of mental illnesses.

The Fragile Brain: Stress Vulnerability, Negative Affect and GABAergic Neurocircuits in Psychosis

Persons with schizophrenia exhibit sensitivity to stress and negative affect (NA), both strongly correlated with poor functional outcome. This theoretical review suggests that NA reflects a "fragile brain," ie, vulnerable to stress, including events not experienced as stressful by healthy individuals. Based on postmortem evidence of altered gamma-aminobutyric acid (GABA) function in parvalbumin positive interneurons (PVI), animal models of PVI abnormalities and neuroimaging data with GABAergic challenge, it is suggested that GABAergic disruptions weaken cortical regions, which leads to stress vulnerability and excessive NA. Neurocircuits that respond to stressful and salient environmental stimuli, such as the hypothalamic-pituitary-adrenal axis and the amygdala, are highly dysregulated in schizophrenia, exhibiting hypo- and hyper-activity. PVI abnormalities in lateral prefrontal cortex and hippocampus have been hypothesized to affect cognitive function and positive symptoms, respectively; in the medial frontal cortex (dorsal anterior cingulate cortex and dorsal medial prefrontal cortex), these abnormalities may lead to vulnerability to stress, NA and dysregulation of stress responsive systems. Given that postmortem PVI disruptions have been identified in other conditions, such as bipolar disorder and autism, stress vulnerability may reflect a transdiagnostic dimension of psychopathology.

Visuospatial and Sensory Integration Tasks in Patients With Schizophrenia or Schizoaffective Disorder: Relationship to Body Mass Index and Smoking

Neurological soft signs (NSSs) are highly prevalent among patients with schizophrenia, but their pathophysiological significance remains unclear. The present study employed perceptual-motor and visuospatial processing tests that have not yet been attempted in this patient population. Patients with schizophrenia or schizoaffective disorder (n = 42) and mentally healthy subjects (n = 10) were administered Copy Figure Test, Detection and Recognition of an Object Test and Road Map Test. As compared to controls, schizophrenic and schizoaffective patients displayed significantly poorer ability to copy three-dimensional figures (namely, Necker- and hidden line elimination cubes) and to orient in space on a road-map test; group differences in copying two-dimensional figures and on objects' recognition against a background noise were not apparent. In the schizophrenia/schizoaffective group, more mistakes on the hidden line elimination cube was associated with greater body mass index and greater severity of nicotine dependence measured via the Fagerstrom Test of Nicotine Dependence. The above findings replicate those of prior reports and extend them to the tasks that do not involve motivational and attentional confounds. Furthermore, the present data support the hypothesis that subtle cerebral cortical abnormalities detected with specific NSSs tests may be related to some aspects of metabolic and motivational function in patients with schizophrenia/schizoaffective disorder.

Sexual dimorphism of the planum temporale in schizophrenia: A MRI study

OBJECTIVE

Anatomical alterations in the superior temporal gyrus have been consistently reported in patients with schizophrenia, and they have mostly been linked to positive symptoms, including hallucinations and thought disorders. The superior temporal gyrus is considered one of the most asymmetric and lateralized structure of the human brain, and the process of lateralization seems to vary according to gender in the normal population. However, although it has been consistently suggested that patients with schizophrenia did not show normal brain lateralization in several regions, only few studies investigated it in the superior temporal gyrus and its sub-regions considering the effects of gender. In this context, the aim of this study was to evaluate sexual dimorphism in superior temporal gyrus volumes in a sample of patients with schizophrenia compared to age- and gender-matched healthy controls.

METHODS

A total of 72 right/left-handed males (40 schizophrenia patients and 32 healthy controls) and 45 right/left-handed females (18 schizophrenia patients and 27 healthy controls) underwent clinical evaluation and a 1.5T magnetic resonance imaging scan. Gray and white matter volumes of regions of interest within the superior temporal gyrus were manually detected, including the Heschl's gyrus and the planum temporale.

RESULTS

Female patients with schizophrenia presented a reduction in left planum temporale gray matter volumes ( F = 4.58, p = 0.03) and a lack of the normal planum temporale asymmetry index ( t = 0.27; p = 0.79) compared to female controls ( t = 5.47; p = 0.001). No differences were found between males for any volumes or laterality indices. Finally, in female patients with schizophrenia, Heschl's gyrus gray and white matter volumes negatively correlated with positive symptoms ( r = -0.56, p = 0.01).

CONCLUSION

Our results showed that sexual dimorphism plays a key role on planum temporale in schizophrenia, underlining the importance of gender as a modulator of brain morphology and lateralization of schizophrenia.

Influence of early trauma on features of schizophrenia

AIM

This proof-of-concept study examined if early trauma influences features of schizophrenia, consistent with hypothalamic-pituitary-adrenal (HPA) axis activation.

METHODS

Early trauma and current perceived stress were assessed in 28 treated schizophrenia cases, along with salivary cortisol, brain volumes, cognition and symptoms.

RESULTS

Early trauma predicted more positive (r = .66, P = .005) and dysthymia symptoms (r -.65, P = .007), but less negative symptoms (r = -.56, P = .023), as well as reduced whole brain volumes (r = .50, P = .040) and increased amygdala to whole brain volume ratios (r = .56, P = .018). Larger volume reductions accompanied cortisol levels: evening values predicted smaller whole brain and hippocampal volumes whereas afternoon levels only significantly predicted smaller brain volumes in women. Sex differences were demonstrated between early trauma and cognition, with better cognition in traumatized women than other women and no male effects. Current perceived stress was related to dysthymia (especially in women) and diminished sense of purpose and social drive (especially in men).

CONCLUSIONS

These results suggest that early trauma and current stress impact features of schizophrenia, consistent with stress sensitization and increased dopamine activity for treatment refractory positive symptoms, as well as the cascade of increased morning cortisol, reduced brain volumes, and depressive and deficit symptoms. Conversely, cognitive deficits and negative symptoms may arise from a distinct diathesis. The sex differences accord with the literature on human HPA function and stress responses. Early trauma may be a stressor in the aetiopathophysiology of schizophrenia, particularly for cases with treatment refractory positive symptoms, and may guide future treatment development.

Effect of a socıal defeat experıence on prefrontal actıvıty ın schızophrenıa

The social defeat (SD) hypothesis of schizophrenia posits that repeated experiences of SD may lead to sensitization of the mesolimbic dopaminergic system and to precipitation of psychosis. Based on previous definitions adapted to a human experimental paradigm, we prepared a computer simulation of SD to mimic this subjective experience. We measured prefrontal cortex (PFC) activity in subjects with schizophrenia and healthy controls during exposure to a single SD experience with functional near infrared spectroscopy. PFC activity declined in both groups. Compared with the control condition, SD exposure was associated with a broader decline in left ventromedial, right medial and right lateral PFC activity in healthy controls (n=25), and a sharper decline in right ventrolateral PFC activity in subjects with schizophrenia (n=25). The activity in the right ventrolateral PFC, was significantly lower in patients compared with controls. This may be due to a deficiency in emotion regulation or self-control, or it may be related to impaired empathy in schizophrenia. Different patterns of brain activity during the SD experience in subjects with schizophrenia versus healthy controls may provide indirect evidence regarding the SD hypothesis of schizophrenia.

Subclinical psychotic experiences in healthy young adults: associations with stress and genetic predisposition

Stress has been identified as a common trigger for psychosis. Dopamine pathways are suggested to be affected by chronic and severe stress and to play an important role in psychosis. This pilot study investigates the potential relationship of stress and psychosis in subclinical psychotic experiences. It was hypothesized that single-nucleotide polymorphisms (SNPs) previously found to be associated with psychiatric disorders would be associated with both stress and subclinical psychotic experiences. University students (N=182) were genotyped for 17 SNPs across 11 genes. Higher stress reporting was associated with rs4680 COMT, rs13211507 HLA region, and rs13107325 SLC39A8. Reports of higher subclinical psychotic experiences were associated with DRD2 SNPs rs17601612 and rs658986 and an AKT1 SNP rs2494732. Replication studies are recommended to further pursue this line of research for identification of markers of psychosis for early diagnosis and intervention.

The neurobiology of relapse in schizophrenia

Dopamine's proposed role in psychosis proved a starting point in our understanding of the neurobiology of relapse, fitting given the central role positive symptoms play. This link is reflected in early work examining neurotransmitter metabolite and drug (e.g. amphetamine, methylphenidate) challenge studies as a means of better understanding relapse and predictors. Since, lines of investigation have expanded (e.g. electrophysiological, immunological, hormonal, stress), an important step forward if relapse per se is the question. Arguably, perturbations in dopamine represent the final common pathway in psychosis but it is evident that, like schizophrenia, relapse is heterogeneous and multidimensional. In understanding the neurobiology of relapse, greater gains are likely to be made if these distinctions are acknowledged; for example, efforts to identify trait markers might better be served by distinguishing primary (i.e. idiopathic) and secondary (e.g. substance abuse, medication nonadherence) forms of relapse. Similarly, it has been suggested that relapse is 'neurotoxic', yet individuals do very well on clozapine after multiple relapses and the designation of treatment resistance. An alternative explanation holds that schizophrenia is characterized by different trajectories, at least to some extent biologically and/or structurally distinguishable from the outset, with differential patterns of response and relapse. Just as with schizophrenia, it seems naïve to conceptualize the neurobiology of relapse as a singular process. We propose that it is shaped by the form of illness and in place from the outset, modified by constitutional factors like resilience, as well as treatment, and confounded by secondary forms of relapse.

Stress and neurodevelopmental processes in the emergence of psychosis

The notion that stress plays a role in the etiology of psychotic disorders, especially schizophrenia, is longstanding. However, it is only in recent years that the potential neural mechanisms mediating this effect have come into sharper focus. The introduction of more sophisticated models of the interplay between psychosocial factors and brain function has expanded our opportunities for conceptualizing more detailed psychobiological models of stress in psychosis. Further, scientific advances in our understanding of adolescent brain development have shed light on a pivotal question that has challenged researchers; namely, why the first episode of psychosis typically occurs in late adolescence/young adulthood. In this paper, we begin by reviewing the evidence supporting associations between psychosocial stress and psychosis in diagnosed patients as well as individuals at clinical high risk for psychosis. We then discuss biological stress systems and examine changes that precede and follow psychosis onset. Next, research findings on structural and functional brain characteristics associated with psychosis are presented; these findings suggest that normal adolescent neuromaturational processes may go awry, thereby setting the stage for the emergence of psychotic syndromes. Finally, a model of neural mechanisms underlying the pathogenesis of psychosis is presented and directions for future research strategies are explored.

Perceived stress predicts altered reward and loss feedback processing in medial prefrontal cortex

Stress is a significant risk factor for the development of psychopathology, particularly symptoms related to reward processing. Importantly, individuals display marked variation in how they perceive and cope with stressful events, and such differences are strongly linked to risk for developing psychiatric symptoms following stress exposure. However, many questions remain regarding the neural architecture that underlies inter-subject variability in perceptions of stressors. Using functional magnetic resonance imaging (fMRI) during a Monetary Incentive Delay (MID) paradigm, we examined the effects of self-reported perceived stress levels on neural activity during reward anticipation and feedback in a sample of healthy individuals. We found that subjects reporting more uncontrollable and overwhelming stressors displayed blunted neural responses in medial prefrontal cortex (mPFC) following feedback related to monetary gains as well monetary losses. This is consistent with preclinical models that implicate the mPFC as a key site of vulnerability to the noxious effects of uncontrollable stressors. Our data help translate these findings to humans, and elucidate some of the neural mechanisms that may underlie stress-linked risk for developing reward-related psychiatric symptoms.

From epidemiology to daily life: linking daily life stress reactivity to persistence of psychotic experiences in a longitudinal general population study

Subclinical psychotic experiences at the level of the general population are common, forming an extended psychosis phenotype with clinical psychosis. Persistence of subclinical experiences is associated with transition to later mental disorder. Increased daily life stress reactivity is considered an endophenotype for psychotic disorders. We examined, in a longitudinal framework, whether baseline momentary assessment markers of stress reactivity would predict persistence of subclinical psychotic experiences over time. In a general population sample of female twins (N = 566), the Experience Sampling Method (ESM; repetitive random sampling of momentary emotions, psychotic experiences and context) was used to assess (emotional and psychotic) daily life stress reactivity. Persistence of subclinical psychotic experiences was based on the Community Assessment of Psychic Experiences (CAPE), assessed three times over 14 months post-baseline. It was investigated whether baseline daily life emotional and psychotic stress reactivity predicted persistence of psychotic experiences over time. Higher levels of emotional stress reactivity (a decrease in positive and an increase in negative affect in response to stress), and increased psychotic reactivity to daily stress was found in individuals with persistent psychotic experiences over time compared to individuals with transient psychotic experiences. The results suggest that markers of daily life stress reactivity may predict “macro-level” persistence of normally transient expression of psychotic liability over time. Linking daily life markers of altered reactivity in terms of emotions and psychotic experiences to longitudinal persistence of psychotic experiences, associated with increased risk of transition to overt mental disorder, may contribute to earlier and more accurate diagnosis of risk.

Adversity and psychosis: a 10-year prospective study investigating synergism between early and recent adversity in psychosis

OBJECTIVE

Recent studies have suggested that early adverse events, such as childhood trauma, may promote enduring liability for psychosis whereas more recent adverse events may act as precipitants. Examination of these environmental dynamics, however, requires prospective studies in large samples. This study examines whether the association between recent adverse events and psychosis is moderated by exposure to early adversity.

METHOD

A random regional representative population sample of 3021 adolescents and young adults in Munich, Germany, was assessed three times over a period of up to 10 years, collecting information on sociodemographic factors, environmental exposures, and measures of psychopathology and associated clinical relevance. Evidence of statistical non-additivity between early adversity (two levels) and more recent adversity (four levels) was assessed in models of psychotic symptoms. Analyses were a priori corrected for age, gender, cannabis use, and urbanicity.

RESULTS

Early and recent adversity were associated with each other (RR = 1.32, 95% CI 1.06-1.66; P = 0.014) and displayed statistical non-additivity at the highest level of exposure to recent adversity (χ(2) = 4.59; P = 0.032).

CONCLUSION

The findings suggest that early adversity may impact on later expression of psychosis either by increasing exposure to later adversity and/or by rendering individuals more sensitive to later adversity if it is severe.

Increased stress-induced dopamine release in psychosis

BACKGROUND

A pathologic response to common life stressors, in which a hyperresponsive dopaminergic system is thought to play a key role, is a potential etiologic factor in the triggering and relapse of psychosis. However, there is no direct evidence that brain dopaminergic response to stress is exaggerated in psychosis.

METHODS

Using the ability of endogenous dopamine (DA) to compete with [(11)C]-(+)-PHNO binding, as measured with positron emission tomography, we examined stress-induced DA release in response to a validated psychosocial stress task. We studied 12 clinical high-risk (CHR), 10 antipsychotic-naive subjects with schizophrenia (SCZ), and 12 matched healthy volunteers (HV). Stress-induced DA release was estimated as the percent change in binding potential between conditions (stress and control scan) in the striatal subdivisions: limbic striatum (LST), associative striatum (AST), and sensorimotor striatum (SMST).

RESULTS

We found a significant difference between groups in the AST (F = 8.13, df = 2,31, p = .001), and at the SMST (F = 3,64, df = 2,31, p = .03) but not in the LST (F = .43, df = 2,31, p = .40) with CHR and SCZ having larger [(11)C]-(+)-PHNO displacement in response to the stress. Bonferroni-corrected comparisons confirmed that HV displacement (-2.86%) in the AST was significantly different in CHR (6.97%) and SCZ (11.44%) (with no significant difference between CHR and SCZ).

CONCLUSIONS

This study reveals a sensitized dopaminergic response to stress in a psychiatric condition and may have important theoretical and clinical implications regarding efforts to abort or delay relapse and/or conversion to psychosis.

Early intervention in psychosis: Insights from Korea

Subjects at clinical high risk (CHR) for psychosis have been the focus of clinical attention in psychiatry for the last 15 years, leading to the development of valid and reliable diagnostic instruments to detect these individuals early in the course of their illness. These efforts have resulted in research into optimal preventive measures. Our experiences at and data from the Seoul Youth Clinic support the validity of the CHR concept and its underlying neurobiological basis and provide valuable information related to the determination of appropriate clinical interventions. The limitations of the current criteria for CHR, such as the relatively low transition rates to psychosis and the "false-positive" problem, are also common critical issues in Korea. Additionally, concerns about social stigmatization and the potential side effects of pharmacotherapy render individuals at CHR reluctant to visit clinical settings. Therefore, further investigations using a combination of predictive markers based on clinical and neurobiological studies of those at CHR are needed to refine the diagnostic criteria, overcome their current limitations including ethical issues, and develop phase-specific and individualized therapeutic interventions.

Self-assessment of psychological stress in schizophrenia: Preliminary evidence of reliability and validity

Heightened stress sensitivity is a common characteristic of schizophrenia and may be predictive of clinical and functional outcomes. However, systematic assessment is not part of routine clinical practice. This study investigated the reliability and predictive values of two versions of a new scale for the assessment of psychological stress in psychosis (Psychological Stress Index; PSI). Thirty-seven patients with schizophrenia/schizoaffective disorder and 30 healthy controls completed a battery of self-report measures at baseline and 4-8 weeks for test-retest. Thirty-four patients were followed up at 12 months. Both of the 18-item and 9-item PSI demonstrated good levels of reliability and could significantly discriminate patients from healthy controls. Both versions showed moderate convergence with self-report and clinician ratings of depression and anxiety, and superior predictive validity of 12-month follow-up clinical and functional outcomes compared to an existing measure of stress (Perceived Stress Scale). The clinical usefulness of the PSI is supported by its predictive power on cross-sectional and longitudinal outcome. The PSI-9 performed as well as, if not better than, the PSI-18 in this study, but further evaluation is warranted for more conclusive comparison.

The role of the nucleus accumbens in the acquisition and expression of conditioned defeat

When Syrian hamsters (Mesocricetus auratus) are defeated by a larger, more aggressive hamster, they subsequently exhibit submissive and defensive behavior, instead of their usual aggressive and social behavior, even toward a smaller, non-aggressive opponent. This change in behavior is termed conditioned defeat, and we have found that the amygdala, bed nucleus of the stria terminalis, and ventral hippocampus, among others, are crucial brain areas for either the acquisition and/or expression of this behavioral response to social stress. In the present study, we tested the hypothesis that the nucleus accumbens is also a necessary component of the circuit mediating the acquisition and expression of conditioned defeat. We found that infusion of the GABA(A) agonist muscimol into the nucleus accumbens prior to defeat training failed to affect acquisition of conditioned defeat, but infusion prior to testing significantly decreased submissive behavior and significantly increased aggressive behavior directed toward the non-aggressive intruder. These data indicate that, unlike the basolateral complex of the amygdala, the nucleus accumbens is not a critical site for the plasticity underlying conditioned defeat acquisition, but it does appear to be an important component of the circuit mediating the expression of the behavioral changes that are produced in response to a previous social defeat. Of note, this is the first component of the putative "conditioned defeat neural circuit" wherein we have found that pharmacological manipulations are effective in restoring the territorial aggressive response in previously defeated hamsters.

Beyond the first episode: candidate factors for a risk prediction model of schizophrenia

Many early psychosis services are financially compromised and cannot offer a full tenure of care to all patients. To maintain viability of services it is important that those with schizophrenia are identified early to maximize long-term outcomes, as are those with better prognoses who can be discharged early. The duration of untreated psychosis remains the mainstay in determining those who will benefit from extended care, yet its ability to inform on prognosis is modest in both the short and medium term. There are a number of known or putative genetic and environmental risk factors that have the potential to improve prognostication, though a multivariate risk prediction model combining them with clinical characteristics has yet to be developed. Candidate risk factors for such a model are presented, with an emphasis on environmental risk factors. More work is needed to corroborate many putative factors and to determine which of the established factors are salient and which are merely proxy measures. Future research should help clarify how gene-environment and environment-environment interactions occur and whether risk factors are dose-dependent, or if they act additively or synergistically, or are redundant in the presence (or absence) of other factors.

Sensitization, epileptic-like symptoms and local synchronization in patients with paranoid schizophrenia

Recent findings indicate that changes in synchronization of neural activities underlying sensitization and kindling could be more comprehensively understood using nonlinear methods. With this aim we have examined local synchronization using novel measure of coarse-grained information rate (CIR) in 8 EEG signals recorded at different cortical areas in 44 patients with paranoid schizophrenia. The values of local synchronization that could reflect sensitization related changes in EEG activities of cortical sites were then related to psychometric measures of epileptic-like symptoms and positive and negative schizophrenia symptoms (PANSS). While no significant correlations between CIR and positive and negative symptoms have been found, statistically significant relationships described by Spearman correlation coefficients between CIR indices and results of LSCL-33 have been observed in 7 (of 8) EEG channels (r in the range from 0.307 to 0.374, p<0.05). Results of this study provide first supportive evidence for the relationship between local synchronization measured by CIR and epileptic-like symptoms in schizophrenia.

Psychosocial stress and psychosis. A review of the neurobiological mechanisms and the evidence for gene-stress interaction

This article presents evidence suggesting that psychosocial stress may increase risk for psychosis, especially in the case of cumulative exposure. A heuristically useful framework to study the underlying mechanisms is the concept of "behavioral sensitization" that stipulates that exposure to psychosocial stress--such as life events, childhood trauma, or discriminatory experiences--may progressively increase the behavioral and biological response to subsequent exposures. The neurobiological substrate of sensitization may involve dysregulation of the hypothalamus-pituitary-adrenal axis, contributing to a hypothesized final common pathway of dopamine sensitization in mesolimbic areas and increased stress-induced striatal dopamine release. It is argued that, in order to reconcile genetic and environmental influences on the development of psychosis, gene-environment interactions may be an important mechanism in explaining between-subject differences in risk following (cumulative) exposure to psychosocial stress. To date, most studies suggestive of gene-stress interaction have used proxy measures for genetic vulnerability such as a family history of psychosis; studies investigating interactions between molecular genetic measures and psychosocial stressors are still relatively scarce. Preliminary evidence suggests that polymorphisms within the catechol-O-methyltransferase and brain-derived neurotrophic factor genes may interact with psychosocial stress in the development of psychosis; however, extensive further investigations are required to confirm this.

Schizophrenia, "Just the Facts": what we know in 2008 part 1: overview

For every disorder, there is a set of established findings and accepted constructs upon which further understanding is built. The concept of schizophrenia as a disease entity has been with us for a little more than a century, although descriptions resembling this condition predate this conceptualization. In 1988, for the inaugural issue of Schizophrenia Research, at the invitation of the founding editors, a senior researcher, since deceased (RJ Wyatt) published a summary of generally accepted ideas about the disorder, which he termed "the facts" of schizophrenia. Ten years later, in conjunction with two of the authors (MSK, RT), he compiled a more extensive set of "facts" for the purpose of evaluating conceptual models or theoretical constructs developed to understand the nature of schizophrenia. On the 20th anniversary of this journal, we update and substantially expand our effort to periodically summarize the current body of information about schizophrenia. We compile a body of seventy-seven representative major findings and group them in terms of their specific relevance to schizophrenia -- etiologies, pathophysiology, clinical manifestations, and treatments. We rate each such "fact" on a 0-3 scale for measures of reproducibility, whether primary to schizophrenia, and durability over time. We also pose one or more critical questions with reference to each "fact", answers to which might help better elucidate the meaning of that finding for our understanding of schizophrenia. We intend to follow this paper with the submission to the journal of a series of topic-specific articles, critically reviewing the evidence.