Increased stress-induced dopamine release in psychosis

Multiple measures of HPA axis function in ultra high risk and first-episode schizophrenia patients

INTRODUCTION

Abnormalities within hypothalamus-pituitary-adrenal (HPA) axis might interact with other neurobiological systems to enhance the risk of psychosis. Most of the neurodevelopmental and HPA axis changes occur in adolescence; this is also the period when prodromal and psychotic symptoms occur for the first time. More knowledge about how various stress components interact can advance understanding of the link between psychosis and the HPA axis.

METHOD

We examined 41 ultra high-risk (UHR) patients and 40 antipsychotic-naïve first-episode schizophrenia (FES) patients and compared them with 47 matched controls. The Perceived Stress Scale and the Recent Life Events Questionnaire were used to assess the stress levels. Day-time saliva samples were taken to measure cortisol. The pituitary gland volume was measured manually on the structural MRI using stereology.

RESULTS

Only the UHR patients, had a higher cortisol increase just after awakening (p = 0.009) compared to healthy controls. In UHR patients, we found a negative correlation between cortisol increase after awakening and symptom severity (p = 0.008). Pituitary gland volume and diurnal cortisol were not significantly different among the three groups. There was no correlation between pituitary gland volume, perceived stress/recent life events and any of the cortisol measures or symptoms.

CONCLUSION

Symptom severity during the very early phase of illness (UHR) seems to be associated with altered cortisol increase. Longitudinal studies in UHR patients would be useful to examine how stress levels affect the course of the illness.

Amphetamine-Induced Striatal Dopamine Release Measured With an Agonist Radiotracer in Schizophrenia

BACKGROUND

Receptor imaging studies have reported increased amphetamine-induced dopamine release in subjects with schizophrenia (SCH) relative to healthy control subjects (HCs). A limitation of these studies, performed with D2/3 antagonist radiotracers, is the failure to provide information about D2/3 receptors configured in a state of high affinity for the agonists (i.e., D2/3 receptors coupled to G proteins [D2/3 HIGH]). The endogenous agonist dopamine binds with preference to D2/3 HIGH receptors relative to D2/3 LOW receptors, making it critical to understand the status of D2/3 HIGH receptors in SCH.

METHODS

D2/3 agonist positron emission tomography radiotracer [11C]N-propyl-norapomorphine ([11C]NPA) binding potential (BPND) was measured in 14 off-medication subjects with SCH and 14 matched HCs at baseline and after the administration of 0.5 mg kg-1 oral D-amphetamine. The amphetamine-induced change in BPND (ΔBPND) was calculated as the difference between BPND in the postamphetamine condition and BPND in the baseline condition and was expressed as a percentage of BPND at baseline.

RESULTS

A trend-level increase was observed in comparing baseline [11C]NPA BPND (repeated-measures analysis of variance, F1,26 = 3.34, p = .08) between the SCH and HC groups. Amphetamine administration significantly decreased BPND in all striatal regions across all subjects in both groups. No differences were observed in [11C]NPA ΔBPND (repeated-measures analysis of variance, F1,26 = 1.9, p = .18) between HCs and subjects with SCH. Amphetamine significantly increased positive symptoms in subjects with SCH (19.5 ± 5.3 vs. 23.7 ± 4.1, paired t test, p < .0001); however, no correlations were noted with [11C]NPA BPND or ΔBPND.

CONCLUSIONS

This study provides in vivo indication of a role for postsynaptic factors in amphetamine-induced psychosis in SCH.

Nigral Stress-Induced Dopamine Release in Clinical High Risk and Antipsychotic-Naïve Schizophrenia

Background

Striatal dopamine (DA) synthesis capacity and release are elevated in schizophrenia (SCZ) and its putative prodrome, the clinical high risk (CHR) state. Striatal DA function results from the activity of midbrain DA neurons projecting mainly from the substantia nigra (SN). Elevated stress-induced DA release in SCZ and CHR was observed in the striatum; however, whether it is also elevated in the SN is unclear. The current study aims to determine whether nigral DA release in response to a validated stress task is altered in CHR and in antipsychotic-naïve SCZ. Further, we explore how DA release in the SN and striatum might be related.

Methods

24 CHR subjects, 9 antipsychotic-naïve SCZ and 25 healthy volunteers (HV) underwent 2 positron emission tomography (PET) scans using the DA D2/3 agonist radiotracer, [11C]-(+)-PHNO, which allows simultaneous investigations of DA in the SN and striatum. Psychosocial stress-induced DA release was estimated as the percentage differences in BPND (%[11C]-(+)-PHNO displacement) between stress and sensory-motor control sessions.

Results

We observed a significant diagnostic group by session interaction, such that SCZ exhibited greater stress-induced [11C]-(+)-PHNO % displacement (25.90% ± 32.2%; mean ± SD), as compared to HVs (-10.94% ± 27.1%). Displacement in CHRs (-1.13% ± 32.2%) did not differ significantly from either HV or SCZ.

Conclusion

Our findings suggest that elevated nigral DA responsiveness to stress is observed in antipsychotic-naïve SCZ.

Acquisition of nicotine self-administration in amphetamine and phencyclidine models of schizophrenia: A role for stress?

Nicotine use and dependence is very high in patients with schizophrenia. One possible reason is that altered dopamine or glutamate activity in schizophrenia enhances the reinforcing effectiveness of nicotine. We used animal models to test the hypothesis that a hyperdopaminergic state (induced by repeated intermittent injections of amphetamine) or altered glutamate function (subchronic injection of phencyclidine, PCP) facilitates spontaneous acquisition of nicotine self-administration in rats. In Experiment 1 animals in an amphetamine-induced sensitized state (AISS) did not differ from saline-injected controls in their acquisition and maintenance of nicotine self-administration. This effect was replicated in experiment 2, but it was also found that AISS rats and saline-injected controls showed higher rates of nicotine self-administration compared to uninjected controls. This difference was maintained across several fixed ratio and progressive ratio schedules of reinforcement. In Experiment 3 PCP treated rats and their saline-injected controls did not differ in nicotine self-administration. However, both groups showed consistently increased responding for nicotine on FR and PR schedules compared to an uninjected control group. Injection-stress appeared to influence the outcomes of these experiments in two ways. Firstly, injection stress potentially masked the impact of the AISS and PCP treatment on nicotine self-administration. Secondly, injection stress itself may have been sufficient to induce plastic changes in dopamine and glutamate systems, and these changes enhanced the acquisition and maintenance of nicotine self-administration. Further investigation is needed into the role of stress in the development of nicotine use and dependence, in the aetiology of schizophrenia and in their co-morbidity.

Perceived social stress and symptom severity among help-seeking adolescents with versus without clinical high-risk for psychosis

Research suggests that social stress exposure influences illness presentation and course among youth at clinical high-risk (CHR) for psychosis, though less is known about the extent to which self-reported perceptions of social stress relate to the severity of positive symptoms. Importantly, despite the notion that youth at CHR are especially susceptible to elevations in positive symptoms under conditions of stress, no study has examined this presumption relative to other psychiatric groups. Extending previous work demonstrating that perceived social stress was higher in a CHR group than in a clinical group of non-CHR, help-seeking controls, the current study aimed to: (1) examine whether perceived social stress is related to the severity of attenuated positive symptoms in the full sample (N=110); and (2) determine whether CHR status moderates the stress-symptom relation. Exploratory analyses examined relations of perceived social stress to negative, disorganized, and general symptoms. Greater perceptions of social stress were associated with more severe positive symptoms in the entire sample; however, although positive symptoms and perceived social stress were higher in the CHR group, the strength of this relation was statistically indistinguishable across groups. No differential effect of perceived social stress was observed for any symptom domain. Results provide some support for the diathesis-stress model of psychosis, while also suggesting that social stress and symptomatology are related independent of clinical vulnerability to psychosis. Future research would benefit from longitudinal studies of stress-symptom relations across CHR and help-seeking control groups.

Reliving, Replaying Lived Experiences Through Auditory Verbal Hallucinations: Implications on Theories and Management

Objective: This study aims to understand the impact of negative life experience (NLE) in auditory hallucinations (AHs) and explain the heterogeneity in phenomenology of auditory verbal hallucinations (AVHs). Method: In depth interviews were conducted with 21 individuals (7 males and 14 females) experiencing AHs and accessing mental health treatment services at a not-for-profit organization. Maximum variation purposive sampling technique was used to select the sample to ensure variegation is accounted for and was collected until saturation of themes data was obtained. Results: Various different forms and functions of hallucinations are obtained with an evident pattern that links voices back to the NLE of the individual. Implications for therapeutic methods focusing on distress arising from said NLE is emphasized. Conclusions: The results obtained from this study implicate NLEs as a contributing factor in the development and maintenance of hallucinations. Sociocultural factors act as a catalyst with psychological factors creating distress and contributing to the voice-hearing experience. Treatment strategies must thus focus on content of voices and past experiences of the individual to promote recovery. A model toward conceptualization of the diversity in phenomenology is put forth.

Cognitive Function and Monoamine Neurotransmission in Schizophrenia: Evidence From Positron Emission Tomography Studies

Positron emission tomography (PET) is a non-invasive imaging technique used to assess various brain functions, including cerebral blood flow, glucose metabolism, and neurotransmission, in the living human brain. In particular, neurotransmission mediated by the monoamine neurotransmitters dopamine, serotonin, and norepinephrine, has been extensively examined using PET probes, which specifically bind to the monoamine receptors and transporters. This useful tool has revealed the pathophysiology of various psychiatric disorders, including schizophrenia, and the mechanisms of action of psychotropic drugs. Because monoamines are implicated in various cognitive processes such as memory and executive functions, some PET studies have directly investigated the associations between monoamine neurotransmission and cognitive functions in healthy individuals and patients with psychiatric disorders. In this mini review, I discuss the findings of PET studies that investigated monoamine neurotransmission under resting conditions, specifically focusing on cognitive functions in patients with schizophrenia. With regard to the dopaminergic system, some studies have examined the association of dopamine D1 and D2/D3 receptors, dopamine transporters, and dopamine synthesis capacity with various cognitive functions in schizophrenia. With regard to the serotonergic system, 5-HT1A and 5-HT2A receptors have been studied in the context of cognitive functions in schizophrenia. Although relatively few PET studies have examined cognitive functions in patients with psychiatric disorders, these approaches can provide useful information on enhancing cognitive functions by administering drugs that modulate monoamine transmission. Moreover, another paradigm of techniques such as those exploring the release of neurotransmitters and further development of radiotracers for novel targets are warranted.

Towards an Integrated View of Early Molecular Changes Underlying Vulnerability to Social Stress in Psychosis

Psychotic disorders are heterogeneous and complex, involving many putative causal factors interacting along the course of disease development. Many of the factors implicated in the pathogenesis of psychosis also appear to be involved in disease onset and subsequent neuroprogression. Herein, we highlight the pertinent literature implicating inflammation and oxidative stress in the pathogenesis of psychosis, and the potential contribution of N-methyl-D-aspartate receptors (NMDARs). We also emphasize the role of peripubertal social stress in psychosis, and the ways in which hippocampal dysfunction can mediate dysregulation of the hypothalamic-pituitary-adrenal axis and cortisol release. Finally, we propose a model wherein inflammation and oxidative stress act as a first hit, producing altered parvalbumin interneuron development, NMDAR hypofunction, microglial priming, and sensitivity to a second hit of peripubertal social stress. With a greater understanding of how these factors interact, it may be possible to detect, prevent, and treat psychosis more effectively.

Treatment outcomes in schizophrenia: qualitative study of the views of family carers

BACKGROUND

Schizophrenia is a complex, heterogeneous disorder, with highly variable treatment outcomes, and relatively little is known about what is important to patients. The aim of the study was to understand treatment outcomes informal carers perceive to be important to people with schizophrenia.

METHOD

Qualitative interview study with 34 individuals and 8 couples who care for a person with schizophrenia/schizoaffective disorder. Interviews were transcribed verbatim and analysed by a thematic framework based approach.

RESULTS

Carers described well-recognised outcomes of importance, alongside more novel outcomes relating to: Safety (of the patient/others); insight (e.g. into non-reality of psychotic phenomena); respite from fear, distress or pain; socially acceptable behaviour; getting out of the house; attainment of life milestones; changes in personality and/or temperament; reduction of vulnerability to stress; and several aspects of physical health.

CONCLUSIONS

These findings have the potential to inform the development of patient- or carer- focused outcome measures that take into account the full range of domains that carers feel are important for patients.

Prefrontal Cortex Dysfunction Increases Susceptibility to Schizophrenia-Like Changes Induced by Adolescent Stress Exposure

Stress during adolescence is a risk factor for schizophrenia, and medial prefrontal cortex (mPFC) dysfunction is proposed to interfere with stress control, increasing the susceptibility to stress. We evaluated the impact of different stressful events during adolescence (restraint stress [RS], footshock [FS], or the combination of FS and RS) on behaviors correlated with schizophrenia in rats as adults. At adulthood, animals were tested for anxiety responses (elevated plus-maze), cognitive function (novel-object recognition test) and dopamine (DA) system responsivity (locomotor response to amphetamine and DA neuron activity in the ventral tegmental area (VTA) using in vivo electrophysiology). All adolescent stressors impaired weight gain and induced anxiety-like responses in adults. FS and FS + RS also disrupted cognitive function. Interestingly, only the combination of FS and RS induced a DA hyper-responsivity as indicated by augmented locomotor response to amphetamine and increased number of spontaneously active DA neurons which was confined to the lateral VTA. Additionally, prelimbic (pl) mPFC lesions triggered a DA hyper-responsivity in animals exposed to FS alone during adolescence. Our results are consistent with previous studies showing long-lasting changes induced by stressful events during adolescence. The impact on DA system activity, however, seems to depend on intense multiple stressors. Our data also suggest that plPFC dysfunction increases the vulnerability to stress in terms of changes in the DA system. Hence, stress during adolescence could be a precipitating factor for the transition to schizophrenia, and stress control at this vulnerable period may circumvent these changes to prevent the emergence of psychosis.

Dopamine, cognitive biases and assessment of certainty: A neurocognitive model of delusions

This paper examines the evidence that delusions can be explained within the framework of a neurocognitive model of how the brain assesses certainty. Here, 'certainty' refers to both low-level interpretations of one's environment and high-level (conscious) appraisals of one's beliefs and experiences. A model is proposed explaining how the brain systems responsible for assigning certainty might dysfunction, contributing to the cause and maintenance of delusional beliefs. It is suggested that delusions arise through a combination of perturbed striatal dopamine and aberrant salience as well as cognitive biases such as the tendency to jump to conclusions (JTC) and hypersalience of evidence-hypothesis matches. The role of emotion, stress, trauma and sociocultural factors in forming and modifying delusions is also considered. Understanding the mechanisms involved in forming and maintaining delusions has important clinical implications, as interventions that improve cognitive flexibility (e.g. cognitive remediation therapy and mindfulness training) could potentially attenuate neurocognitive processes.

Elevated Striatal Dopamine Function in Immigrants and Their Children: A Risk Mechanism for Psychosis

Migration is a major risk factor for schizophrenia but the neurochemical processes involved are unknown. One candidate mechanism is through elevations in striatal dopamine synthesis and release. The objective of this research was to determine whether striatal dopamine function is elevated in immigrants compared to nonimmigrants and the relationship with psychosis. Two complementary case-control studies of in vivo dopamine function (stress-induced dopamine release and dopamine synthesis capacity) in immigrants compared to nonimmigrants were performed in Canada and the United Kingdom. The Canadian dopamine release study included 25 immigrant and 31 nonmigrant Canadians. These groups included 23 clinical high risk (CHR) subjects, 9 antipsychotic naïve patients with schizophrenia, and 24 healthy volunteers. The UK dopamine synthesis study included 32 immigrants and 44 nonimmigrant British. These groups included 50 CHR subjects and 26 healthy volunteers. Both striatal stress-induced dopamine release and dopamine synthesis capacity were significantly elevated in immigrants compared to nonimmigrants, independent of clinical status. These data provide the first evidence that the effect of migration on the risk of developing psychosis may be mediated by an elevation in brain dopamine function.

Presynaptic Dopamine Capacity in Patients with Treatment-Resistant Schizophrenia Taking Clozapine: An [18F]DOPA PET Study

Some patients with schizophrenia show poor response to first-line antipsychotic treatments and this is termed treatment-resistant schizophrenia. The differential response to first-line antipsychotic drugs may reflect a different underlying neurobiology. Indeed, a previous study found dopamine synthesis capacity was significantly lower in patients with treatment-resistant schizophrenia. However, in this study, the treatment-resistant patients were highly symptomatic, whereas the responsive patients showed no or minimal symptoms. The study could not distinguish whether this was a trait effect or reflected the difference in symptom levels. Thus, we aimed to test whether dopaminergic function is altered in patients with a history of treatment resistance to first-line drugs relative to treatment responders when both groups are matched for symptom severity levels by recruiting treatment-resistant patients currently showed low symptom severity with the clozapine treatment. Healthy controls (n=12), patients treated with clozapine (n=12) who had not responded to first-line antipsychotics, and patients who had responded to first-line antipsychotics (n=12) were recruited. Participants were matched for age and sex and symptomatic severity level in patient groups. Participants' dopamine synthesis capacity was measured by using [¹⁸F]DOPA PET. We found that patients treated with clozapine show lower dopamine synthesis capacity than patients who have responded to first-line treatment (Cohen's d=0.9191 (whole striatum), 0.7781 (associative striatum), 1.0344 (limbic striatum), and 1.0189 (sensorimotor striatum) in line with the hypothesis that the dopaminergic function is linked to treatment response. This suggests that a different neurobiology may underlie treatment-resistant schizophrenia and that dopamine synthesis capacity may be a useful biomarker to predict treatment responsiveness.

Dopamine, fronto-striato-thalamic circuits and risk for psychosis

A series of parallel, integrated circuits link distinct regions of prefrontal cortex with specific nuclei of the striatum and thalamus. Dysfunction of these fronto-striato-thalamic systems is thought to play a major role in the pathogenesis of psychosis. In this review, we examine evidence from human and animal investigations that dysfunction of a specific dorsal fronto-striato-thalamic circuit, linking the dorsolateral prefrontal cortex, dorsal (associative) striatum, and mediodorsal nucleus of the thalamus, is apparent across different stages of psychosis, including prior to the onset of a first episode, suggesting that it represents a candidate risk biomarker. We consider how abnormalities at distinct points in the circuit may give rise to the pattern of findings seen in patient populations, and how these changes relate to disruptions in dopamine, glutamate and GABA signaling.

The impact of Disrupted-in-Schizophrenia 1 (DISC1) on the dopaminergic system: a systematic review

Disrupted-in-Schizophrenia 1 (DISC1) is a gene known as a risk factor for mental illnesses possibly associated with dopamine impairments. DISC1 is a scaffold protein interacting with proteins involved in the dopamine system. Here we summarise the impact of DISC1 disruption on the dopamine system in animal models, considering its effects on presynaptic dopaminergic function (tyrosine hydroxylase levels, dopamine transporter levels, dopamine levels at baseline and after amphetamine administration) and postsynaptic dopaminergic function (dopamine D1 and D2 receptor levels, dopamine receptor-binding potential and locomotor activity after amphetamine administration). Our findings show that many but not all DISC1 models display (1) increased locomotion after amphetamine administration, (2) increased dopamine levels after amphetamine administration in the nucleus accumbens, and (3) inconsistent basal dopamine levels, dopamine receptor levels and binding potentials. There is also limited evidence for decreased tyrosine hydroxylase levels in the frontal cortex and increased dopamine transporter levels in the striatum but not nucleus accumbens, but these conclusions warrant further replication. The main dopaminergic findings are seen across different DISC1 models, providing convergent evidence that DISC1 has a role in regulating dopaminergic function. These results implicate dopaminergic dysregulation as a mechanism underlying the increased rate of schizophrenia seen in DISC1 variant carriers, and provide insights into how DISC1, and potentially DISC1-interacting proteins such as AKT and GSK-3, could be used as novel therapeutic targets for schizophrenia.

An Integrative Perspective on the Role of Dopamine in Schizophrenia

We propose that schizophrenia involves a combination of decreased phasic dopamine responses for relevant stimuli and increased spontaneous phasic dopamine release. Using insights from computational reinforcement-learning models and basic-science studies of the dopamine system, we show that each of these two disturbances contributes to a specific symptom domain and explains a large set of experimental findings associated with that domain. Reduced phasic responses for relevant stimuli help to explain negative symptoms and provide a unified explanation for the following experimental findings in schizophrenia, most of which have been shown to correlate with negative symptoms: reduced learning from rewards; blunted activation of the ventral striatum, midbrain, and other limbic regions for rewards and positive prediction errors; blunted activation of the ventral striatum during reward anticipation; blunted autonomic responding for relevant stimuli; blunted neural activation for aversive outcomes and aversive prediction errors; reduced willingness to expend effort for rewards; and psychomotor slowing. Increased spontaneous phasic dopamine release helps to explain positive symptoms and provides a unified explanation for the following experimental findings in schizophrenia, most of which have been shown to correlate with positive symptoms: aberrant learning for neutral cues (assessed with behavioral and autonomic responses), and aberrant, increased activation of the ventral striatum, midbrain, and other limbic regions for neutral cues, neutral outcomes, and neutral prediction errors. Taken together, then, these two disturbances explain many findings in schizophrenia. We review evidence supporting their co-occurrence and consider their differential implications for the treatment of positive and negative symptoms.

Oestrogens, prolactin, hypothalamic-pituitary-gonadal axis, and schizophrenic psychoses

Interest is growing in the potential effect of gonadal hormones, prolactin, and the hypothalamic-pituitary-gonadal axis in schizophrenic psychoses. Many studies from clinical, epidemiological, and fundamental research have confirmed that oestradiol, the main component of oestrogens, can have protective effects in schizophrenic psychoses. Furthermore, many patients with schizophrenic psychoses-even in the untreated prodromal stages-have hyperprolactinaemia and gonadal dysfunction, with oestrogen deficiency in women and testosterone deficiency in men. The understanding of the pathogenetic mechanisms underlying these findings could contribute to a better understanding of the aetiopathogenesis of schizophrenic psychoses and improve therapeutic approaches. In this Series paper, we aim to review methodologically sound studies in this area, propose a theory to explain these findings in the context of psychosis, and suggest therapeutic strategies and implications for further research.

Pathway-Specific Dopamine Abnormalities in Schizophrenia

In light of the clinical evidence implicating dopamine in schizophrenia and the prominent hypotheses put forth regarding alterations in dopaminergic transmission in this disease, molecular imaging has been used to examine multiple aspects of the dopaminergic system. We review the imaging methods used and compare the findings across the different molecular targets. Findings have converged to suggest early dysregulation in the striatum, especially in the rostral caudate, manifesting as excess synthesis and release. Recent data showed deficit extending to most cortical regions and even to other extrastriatal subcortical regions not previously considered to be "hypodopaminergic" in schizophrenia. These findings yield a new topography for the dopaminergic dysregulation in schizophrenia. We discuss the dopaminergic innervation within the individual projection fields to provide a topographical map of this dual dysregulation and explore potential cellular and circuit-based mechanisms for brain region-dependent alterations in dopaminergic parameters. This refined knowledge is essential to better guide translational studies and efforts in early drug development.

The Role of Genes, Stress, and Dopamine in the Development of Schizophrenia

The dopamine hypothesis is the longest standing pathoetiologic theory of schizophrenia. Because it was initially based on indirect evidence and findings in patients with established schizophrenia, it was unclear what role dopamine played in the onset of the disorder. However, recent studies in people at risk of schizophrenia have found elevated striatal dopamine synthesis capacity and increased dopamine release to stress. Furthermore, striatal dopamine changes have been linked to altered cortical function during cognitive tasks, in line with preclinical evidence that a circuit involving cortical projections to the striatum and midbrain may underlie the striatal dopamine changes. Other studies have shown that a number of environmental risk factors for schizophrenia, such as social isolation and childhood trauma, also affect presynaptic dopaminergic function. Advances in preclinical work and genetics have begun to unravel the molecular architecture linking dopamine, psychosis, and psychosocial stress. Included among the many genes associated with risk of schizophrenia are the gene encoding the dopamine D2 receptor and those involved in the upstream regulation of dopaminergic synthesis, through glutamatergic and gamma-aminobutyric acidergic pathways. A number of these pathways are also linked to the stress response. We review these new lines of evidence and present a model of how genes and environmental factors may sensitize the dopamine system so that it is vulnerable to acute stress, leading to progressive dysregulation and the onset of psychosis. Finally, we consider the implications for rational drug development, in particular regionally selective dopaminergic modulation, and the potential of genetic factors to stratify patients.

Stress Sensitivity and Psychotic Experiences in 39 Low- and Middle-Income Countries

Stress has a central role in most theories of psychosis etiology, but the relation between stress and psychosis has rarely been examined in large population-level data sets, particularly in low- and middle-income countries. We used data from 39 countries in the World Health Survey (n = 176 934) to test the hypothesis that stress sensitivity would be associated with psychotic experiences, using logistic regression analyses. Respondents in low-income countries reported higher stress sensitivity (P < .001) and prevalence of psychotic experiences (P < .001), compared to individuals in middle-income countries. Greater stress sensitivity was associated with increased odds for psychotic experiences, even when adjusted for co-occurring anxiety and depressive symptoms: adjusted odds ratio (95% CI) = 1.17 (1.15-1.19) per unit increase in stress sensitivity (range 2-10). This association was consistent and significant across nearly every country studied, and translated into a difference in psychotic experience prevalence ranging from 6.4% among those with the lowest levels of stress sensitivity up to 22.2% among those with the highest levels. These findings highlight the generalizability of the association between psychosis and stress sensitivity in the largest and most globally representative community-level sample to date, and support the targeting of stress sensitivity as a potential component of individual- and population-level interventions for psychosis.

Adversity in childhood linked to elevated striatal dopamine function in adulthood

Childhood adversity increases the risk of psychosis in adulthood. Theoretical and animal models suggest that this effect may be mediated by increased striatal dopamine neurotransmission. The primary objective of this study was to examine the relationship between adversity in childhood and striatal dopamine function in early adulthood. Secondary objectives were to compare exposure to childhood adversity and striatal dopamine function in young people at ultra high risk (UHR) of psychosis and healthy volunteers. Sixty-seven young adults, comprising 47 individuals at UHR for psychosis and 20 healthy volunteers were recruited from the same geographic area and were matched for age, gender and substance use. Presynaptic dopamine function in the associative striatum was assessed using 18F-DOPA positron emission tomography. Childhood adversity was assessed using the Childhood Experience of Care and Abuse questionnaire. Within the sample as a whole, both severe physical or sexual abuse (T63=2.92; P=0.005), and unstable family arrangements (T57=2.80; P=0.007) in childhood were associated with elevated dopamine function in the associative striatum in adulthood. Comparison of the UHR and volunteer subgroups revealed similar incidence of childhood adverse experiences, and there was no significant group difference in dopamine function. This study provides evidence that childhood adversity is linked to elevated striatal dopamine function in adulthood.

Hypothalamic-pituitary-adrenal axis measures and cognitive abilities in early psychosis: Are there sex differences?

INTRODUCTION

Measures of hypothalamic-pituitary-adrenal (HPA) axis activity such as increased diurnal cortisol levels or a blunted cortisol awakening response (CAR) have been associated with cognitive impairments in people with psychotic disorders. We aimed to explore whether there are sex differences in the relationship between HPA axis measures and cognition in early psychosis (EP).

METHODS

60 EP outpatients and 50 healthy subjects (HS) were assessed with the MATRICS Consensus Cognitive Battery. Saliva cortisol levels were determined at the neuropsychological assessment and on another day at 6 sampling times: awakening; 30' and 60' post-awakening; and 10:00h, 23:00h and 10:00h the day after the administration of 0.25mg of dexamethasone, which occurred at 23:00h. Three HPA axis measures were calculated: CAR, cortisol diurnal slope and cortisol suppression ratio of the dexamethasone suppression test (DST). Multiple linear regression analyses were conducted to explore the relationship between HPA axis measures and cognitive tasks while adjusting for covariates (education level, smoking, cannabis use, and cortisol levels at the cognitive assessment). Interactions between female sex, EP diagnosis and HPA axis measures were examined.

RESULTS

An increased CAR was associated with a poorer cognitive performance in EP women in processing speed and verbal memory. In contrast, a more flattened diurnal cortisol slope was associated with poorer functioning in the spatial working memory of EP women. DST suppression ratio was associated with better visual memory, without sex differences.

CONCLUSIONS

Our study suggests that there are sex differences in the relationship between HPA axis measures and cognitive abilities in EP.

Sex differences in morning cortisol in youth at ultra-high-risk for psychosis

Research suggests abnormalities in hypothalamic-pituitary-adrenal (HPA) axis function play an important role in the pathophysiology of psychosis. However, there is limited research on the biological stress system in young people at ultra high risk (UHR) for psychosis. Morning cortisol levels are particularly relevant to study in this context, as these markers reflect HPA regulation. This is the first examination of sex differences in morning cortisol levels in UHR individuals. Twenty-eight UHR and 22 matched healthy control participants were assessed in respect to symptoms and had home-based collection of salivary cortisol over three time points in the morning. It was predicted that the UHR participants would exhibit lower morning cortisol levels and lower cortisol would be associated with greater symptomatology (i.e. higher positive, negative, and depressive symptoms). Additionally, sex differences in morning cortisol levels were explored based on recent evidence suggesting that sex differences may play an important role in the exacerbation of psychosis. While there were no group differences in morning salivary cortisol secretion, there was a sex by time interaction among UHR individuals, such that only UHR males exhibited flat cortisol levels across two hours after awakening, whereas UHR females had a pattern of cortisol secretion similar to healthy controls, even among medication-free individuals (F=6.34, p=0.004). Cortisol AUC (area under the curve) across the three time points had a trend association (medium effect size; r=0.34, p=0.08) with depressive, but not positive or negative, symptom severity. These results stress the importance of considering sex differences in the psychosis-risk period, as they improve understanding of pathogenic processes.

Making Sense of: Sensitization in Schizophrenia

Sensitization is defined as a process whereby repeated intermittent exposure to a given stimulus results in an enhanced response at subsequent exposures. Next to robust findings of an increased dopamine synthesis capacity in schizophrenia, empirical data and neuroimaging studies support the notion that the mesolimbic dopamine system of patients with schizophrenia is more reactive compared with healthy controls. These studies led to the conceptualization of schizophrenia as a state of endogenous sensitization, as stronger behavioral response and increased dopamine release after amphetamine administration or exposure to stress have been observed in patients with schizophrenia. These findings have also been integrated into the neurodevelopmental model of the disorder, which assumes that vulnerable neuronal circuits undergo progressive changes during puberty and young adulthood that lead to manifest psychosis. Rodent and human studies have made an attempt to identify the exact mechanisms of sensitization of the dopaminergic system and its association with psychosis. Doing so, several epigenetic and molecular alterations associated with dopamine release, neuroplasticity, and cellular energy metabolism have been discovered. Future research aims at targeting these key proteins associated with sensitization in schizophrenia to enhance the knowledge of the pathophysiology of the illness and pave the way for an improved treatment or even prevention of this severe psychiatric disorder.

Corticolimbic dysfunction during facial and prosodic emotional recognition in first-episode psychosis patients and individuals at ultra-high risk

Emotional processing dysfunction is widely reported in patients with chronic schizophrenia and first-episode psychosis (FEP), and has been linked to functional abnormalities of corticolimbic regions. However, corticolimbic dysfunction is less studied in people at ultra-high risk for psychosis (UHR), particularly during processing prosodic voices. We examined corticolimbic response during an emotion recognition task in 18 UHR participants and compared them with 18 FEP patients and 21 healthy controls (HC). Emotional recognition accuracy and corticolimbic response were measured during functional magnetic resonance imaging (fMRI) using emotional dynamic facial and prosodic voice stimuli. Relative to HC, both UHR and FEP groups showed impaired overall emotion recognition accuracy. Whilst during face trials, both UHR and FEP groups did not show significant differences in brain activation relative to HC, during voice trials, FEP patients showed reduced activation across corticolimbic networks including the amygdala. UHR participants showed a trend for increased response in the caudate nucleus during the processing of emotionally valenced prosodic voices relative to HC. The results indicate that corticolimbic dysfunction seen in FEP patients is also present, albeit to a lesser extent, in an UHR cohort, and may represent a neural substrate for emotional processing difficulties prior to the onset of florid psychosis.

Consensus paper of the WFSBP Task Force on Biological Markers: Criteria for biomarkers and endophenotypes of schizophrenia part II: Cognition, neuroimaging and genetics

OBJECTIVES

Schizophrenia is a group of severe psychiatric disorders with high heritability but only low odds ratios of risk genes. Despite progress in the identification of pathophysiological processes, valid biomarkers of the disease are still lacking.

METHODS

This comprehensive review summarises recent efforts to identify genetic underpinnings, clinical and cognitive endophenotypes and symptom dimensions of schizophrenia and presents findings from neuroimaging studies with structural, functional and spectroscopy magnetic resonance imaging and positron emission tomography. The potential of findings to be biomarkers of schizophrenia is discussed.

RESULTS

Recent findings have not resulted in clear biomarkers for schizophrenia. However, we identified several biomarkers that are potential candidates for future research. Among them, copy number variations and links between genetic polymorphisms derived from genome-wide analysis studies, clinical or cognitive phenotypes, multimodal neuroimaging findings including positron emission tomography and magnetic resonance imaging, and the application of multivariate pattern analyses are promising.

CONCLUSIONS

Future studies should address the effects of treatment and stage of the disease more precisely and apply combinations of biomarker candidates. Although biomarkers for schizophrenia await validation, knowledge on candidate genomic and neuroimaging biomarkers is growing rapidly and research on this topic has the potential to identify psychiatric endophenotypes and in the future increase insight on individual treatment response in schizophrenia.

Redox dysregulation, neuroinflammation, and NMDA receptor hypofunction: A "central hub" in schizophrenia pathophysiology?

Accumulating evidence points to altered GABAergic parvalbumin-expressing interneurons and impaired myelin/axonal integrity in schizophrenia. Both findings could be due to abnormal neurodevelopmental trajectories, affecting local neuronal networks and long-range synchrony and leading to cognitive deficits. In this review, we present data from animal models demonstrating that redox dysregulation, neuroinflammation and/or NMDAR hypofunction (as observed in patients) impairs the normal development of both parvalbumin interneurons and oligodendrocytes. These observations suggest that a dysregulation of the redox, neuroimmune, and glutamatergic systems due to genetic and early-life environmental risk factors could contribute to the anomalies of parvalbumin interneurons and white matter in schizophrenia, ultimately impacting cognition, social competence, and affective behavior via abnormal function of micro- and macrocircuits. Moreover, we propose that the redox, neuroimmune, and glutamatergic systems form a "central hub" where an imbalance within any of these "hub" systems leads to similar anomalies of parvalbumin interneurons and oligodendrocytes due to the tight and reciprocal interactions that exist among these systems. A combination of vulnerabilities for a dysregulation within more than one of these systems may be particularly deleterious. For these reasons, molecules, such as N-acetylcysteine, that possess antioxidant and anti-inflammatory properties and can also regulate glutamatergic transmission are promising tools for prevention in ultra-high risk patients or for early intervention therapy during the first stages of the disease.

Sex differences in the effect of childhood trauma on the clinical expression of early psychosis

Childhood trauma, a risk factor of psychosis, is associated the clinical expression of the illness (greater severity of psychotic symptoms; poorer cognitive performance). We aimed to explore whether there are sex differences in this relationship. We studied 79 individuals with a psychotic disorder (PD) with <3years of illness and 59 healthy subjects (HS). All participants were administered the MATRICS Cognitive Consensus Cognitive Battery (MCCB) to assess cognition. Depressive, positive and negative psychotic symptoms, and global functioning were also assessed. History of childhood trauma was assessed using the Childhood Trauma Questionnaire (CTQ). Patients reported a greater history of childhood trauma on all CTQ domains (emotional, physical and sexual abuse, and physical and emotional neglect). A poorer cognitive performance was also observed in PD when compared to HS. No sex differences were found in the CTQ scores. In the relationship between childhood trauma and psychopathological symptoms, significant correlations were found between CTQ scores and positive and negative psychotic symptoms, depressive symptoms and poorer functionality, but only in women. Childhood trauma was associated with poorer social cognition in both men and women. Of all CTQ dimensions, emotional neglect and physical neglect were more clearly associated with a more severe psychopathological and cognitive profile. Our results suggest that childhood trauma, particularly emotional and physical neglect, is associated with the clinical expression of psychosis and that there are sex differences in this relationship.

HPA-axis function and grey matter volume reductions: imaging the diathesis-stress model in individuals at ultra-high risk of psychosis

The onset of psychosis is thought to involve interactions between environmental stressors and the brain, with cortisol as a putative mediator. We examined the relationship between the cortisol stress response and brain structure in subjects at ultra-high risk (UHR) for psychosis. Waking salivary cortisol was measured in 22 individuals at UHR for psychosis and 17 healthy controls. Grey matter volume was assessed using magnetic resonance imaging at 3 T. The relationship between the stress response and grey matter volume was investigated using voxel-based analyses. Our predictions of the topography of cortisol action as a structural brain modulator were informed by measures of brain glucocorticoid and mineralcorticoid receptor distribution obtained from the multimodal neuroanatomical and genetic Allen Brain Atlas. Across all subjects, reduced responsivity of the hypothalamus-pituitary-adrenal (HPA) axis was correlated with smaller grey matter volumes in the frontal, parietal and temporal cortex and in the hippocampus. This relationship was particularly marked in the UHR subjects in the right prefrontal, left parahippocampal/fusiform and parietal cortices. The subgroup that subsequently developed psychosis showed a significant blunting of HPA stress response, observed at trend level also in the whole UHR sample. Altered responses to stress in people at high risk of psychosis are related to reductions in grey matter volume in areas implicated in the vulnerability to psychotic disorders. These areas may represent the neural components of a stress vulnerability model.

Diurnal cortisol variation and cortisol response to an MRI stressor in schizophrenia and bipolar disorder

Markers of HPA axis function, including diurnal cortisol rhythm and cortisol responses to stress or pharmacological manipulation, are increasingly reported as disrupted in schizophrenia (SZ) and bipolar disorder (BD). However, there has been no direct comparison of cortisol responses to stress in SZ and BD in the same study, and associations between cortisol dysfunction and illness characteristics remain unclear. In this study we used spline embedded linear mixed models to examine cortisol levels of SZ and BD participants at waking, during the first 45min after waking (representing the cortisol awakening response; CAR), during the period of rapid cortisol decline post the awakening response, and in reaction to a stressor (MRI scan), relative to healthy controls (HC). Contrary to expectations, neither SZ nor BD showed differences in waking cortisol levels, CAR, or immediate post-CAR decline compared to HC; however, waking cortisol levels were greater in BD relative to SZ. In response to the MRI stressor, the SZ group showed a significant absence of the expected increase in cortisol responsivity to stress, which was seen in both the BD and HC groups. Clinical factors affecting the CAR differed between SZ and BD. In SZ, higher antipsychotic medication dosage was associated with a steeper incline of the CAR, while greater positive symptom severity was associated with a more blunted CAR, and greater levels of anxiety were associated with the blunted cortisol response to stress. In BD, longer illness duration was associated with a steeper incline in CAR and lower levels of waking cortisol. These results suggest that cortisol responses may normalize with medication (in SZ) and longer illness duration (in BD), in line with findings of aberrant cortisol levels in the early stages of psychotic disorders.

Early-Life Stress Affects Stress-Related Prefrontal Dopamine Activity in Healthy Adults, but Not in Individuals with Psychotic Disorder

Early life stress may have a lasting impact on the developmental programming of the dopamine (DA) system implicated in psychosis. Early adversity could promote resilience by calibrating the prefrontal stress-regulatory dopaminergic neurotransmission to improve the individual's fit with the predicted stressful environment. Aberrant reactivity to such match between proximal and distal environments may, however, enhance psychosis disease risk. We explored the combined effects of childhood adversity and adult stress by exposing 12 unmedicated individuals with a diagnosis of non-affective psychotic disorder (NAPD) and 12 healthy controls (HC) to psychosocial stress during an [18F]fallypride positron emission tomography. Childhood trauma divided into early (ages 0-11 years) and late (12-18 years) was assessed retrospectively using a questionnaire. A significant group x childhood trauma interaction on the spatial extent of stress-related [18F]fallypride displacement was observed in the mPFC for early (b = -8.45, t(1,23) = -3.35, p = .004) and late childhood trauma (b = -7.86, t(1,23) = -2.48, p = .023). In healthy individuals, the spatial extent of mPFC DA activity under acute psychosocial stress was positively associated with the severity of early (b = 7.23, t(11) = 3.06, p = .016) as well as late childhood trauma (b = -7.86, t(1,23) = -2.48, p = .023). Additionally, a trend-level main effect of early childhood trauma on subjective stress response emerged within this group (b = -.7, t(11) = -2, p = .07), where higher early trauma correlated with lower subjective stress response to the task. In the NAPD group, childhood trauma was not associated with the spatial extent of the tracer displacement in mPFC (b = -1.22, t(11) = -0.67), nor was there a main effect of trauma on the subjective perception of stress within this group (b = .004, t(11) = .01, p = .99). These findings reveal a potential mechanism of neuroadaptation of prefrontal DA transmission to early life stress and suggest its role in resilience and vulnerability to psychosis.

Altering the course of schizophrenia: progress and perspectives

Despite a lack of recent progress in the treatment of schizophrenia, our understanding of its genetic and environmental causes has considerably improved, and their relationship to aberrant patterns of neurodevelopment has become clearer. This raises the possibility that 'disease-modifying' strategies could alter the course to - and of - this debilitating disorder, rather than simply alleviating symptoms. A promising window for course-altering intervention is around the time of the first episode of psychosis, especially in young people at risk of transition to schizophrenia. Indeed, studies performed in both individuals at risk of developing schizophrenia and rodent models for schizophrenia suggest that pre-diagnostic pharmacotherapy and psychosocial or cognitive-behavioural interventions can delay or moderate the emergence of psychosis. Of particular interest are 'hybrid' strategies that both relieve presenting symptoms and reduce the risk of transition to schizophrenia or another psychiatric disorder. This Review aims to provide a broad-based consideration of the challenges and opportunities inherent in efforts to alter the course of schizophrenia.

Progress and Future Directions in Research on the Psychosis Prodrome: A Review for Clinicians

LEARNING OBJECTIVES

After participating in this activity, learners should be better able to:

ABSTRACT

The psychosis prodrome, or period of clinical and functional decline leading up to acute psychosis, offers a unique opportunity for identifying mechanisms of psychosis onset and for testing early-intervention strategies. We summarize major findings and emerging directions in prodromal research and provide recommendations for clinicians working with individuals suspected to be at high risk for psychosis. The past two decades of research have led to three major advances. First, tools and criteria have been developed that can reliably identify imminent risk for a psychotic disorder. Second, longitudinal clinical and psychobiological data from large multisite studies are strengthening individual risk assessment and offering insights into potential mechanisms of illness onset. Third, psychosocial and pharmacological interventions are demonstrating promise for delaying or preventing the onset of psychosis in help-seeking, high-risk individuals. The dynamic psychobiological processes implicated in both risk and onset of psychosis, including altered gene expression, cognitive dysfunction, inflammation, gray and white matter brain changes, and vulnerability-stress interactions suggest a wide range of potential treatment targets and strategies. The expansion of resources devoted to early intervention and prodromal research worldwide raises hope for investigating them. Future directions include identifying psychosis-specific risk and resilience factors in children, adolescents, and non-help-seeking community samples, improving study designs to test hypothesized mechanisms of change, and intervening with strategies that, in order to improve functional outcomes, better engage youth, address their environmental contexts, and focus on evidence-based neurodevelopmental targets. Prospective research on putatively prodromal samples has the potential to substantially reshape our understanding of mental illness and our efforts to combat it.

Cardiometabolic risk factors in young people at ultra-high risk for psychosis: A systematic review and meta-analysis

BACKGROUND

The physical health of people with schizophrenia is poor, and associated with increased morbidity and mortality. Unhealthy lifestyles and side-effects of antipsychotic medication contribute to cardiometabolic dysfunction. Yet it is unclear when this unhealthy profile starts. We aimed to see if people at ultra-high risk for psychosis (UHR) have increased rates of cardiometabolic risk factors.

METHOD

An electronic search of MEDLINE, PsycINFO, Embase and the Cochrane Central Register of Controlled Trials was conducted on 1st May 2015 using terms associated with the ultra-high risk state and health. Eligible studies were peer-reviewed English language research articles with populations that met at-risk diagnostic criteria and reported cardiometabolic risk factors. A meta-analysis was conducted on smoking data, the cardiometabolic risk factor that yielded the most studies.

RESULTS

Forty-seven eligible studies were identified. UHR samples had low levels of physical activity, and high rates of smoking and alcohol abuse compared with controls. No differences were found for body mass index. An overall pooled rate of smoking for UHR participants was 33% (95% CI=0.24-0.42) and significantly more UHR individuals smoked compared with controls with a pooled odds ratio of 2.3 (P<0.05; 95% CI=-1.48-3.48).

CONCLUSIONS

UHR samples display cardiometabolic risk factors which are largely modifiable. The UHR phase is an important opportunity for early intervention services to improve physical health.

Social Stress and Psychosis Risk: Common Neurochemical Substrates?

Environmental risk factors have been implicated in the etiology of psychotic disorders, with growing evidence showing the adverse effects of migration, social marginalization, urbanicity, childhood trauma, social defeat, and other adverse experiences on mental health in vulnerable populations. Collectively, social stress may be one mechanism that could link these environmental risk factors. The exact mechanism(s) by which social stress can affect brain function, and in particular the molecular targets involved in psychosis (such as the dopaminergic (DA) system), is (are) not fully understood. In this review, we will discuss the interplay between social environmental risk factors and molecular changes in the human brain; in particular, we will highlight the impact of social stress on three specific neurochemical systems: DA, neuroinflammation/immune, and endocannabinoid (eCB) signaling. We have chosen the latter two molecular pathways based on emerging evidence linking schizophrenia to altered neuroinflammatory processes and cannabis use. We further identify key developmental periods in which social stress interacts with these pathways, suggesting window(s) of opportunities for novel interventions. Taken together, we suggest that they may have a key role in the pathogenesis and disease progression, possibly provide novel treatment options for schizophrenia, and perhaps even prevent it.

Dopamine cross-sensitization between psychostimulant drugs and stress in healthy male volunteers

Dysregulation of the stress response system is a potential etiological factor in the development of and relapse to multiple neuropsychiatric disorders. Previously we reported that repeated intermittent d-amphetamine administration can lead to progressively greater dopamine release, thereby providing evidence of drug-induced neurochemical sensitization. Here, we test the hypothesis that repeated exposure to d-amphetamine increases dopaminergic responses to stress; that is, produces cross-sensitization. Using positron emission tomography, we measured in 17 healthy male volunteers (mean ± s.d. = 22.1 ± 3.4 years) [(11)C]raclopride binding responses to a validated psychosocial stress task before and 2 weeks after a regimen of repeated d-amphetamine (3 × 0.3 mg kg(-1), by mouth; n = 8) or placebo (3 × lactose, by mouth; n = 9). Mood and physiological measurements were recorded throughout each session. Before the d-amphetamine regimen, exposure to the stress task increased behavioral and physiological indices of stress (anxiety, heart rate, cortisol, all P ⩽ 0.05). Following the d-amphetamine regimen, the stress-induced cortisol responses were augmented (P < 0.04), and voxel-based analyses showed larger stress-induced decreases in [(11)C]raclopride non-displaceable binding potential across the striatum. In the placebo group, re-exposure to stress led to smaller clusters of decreased [(11)C]raclopride binding, primarily in the sensorimotor striatum (P < 0.05). Together, this study provides evidence for drug × stress cross-sensitization; moreover, random exposure to stimulants and/or stress cumulatively, while enhancing dopamine release in striatal areas, may contribute to a lowered set point for psychopathologies in which altered dopamine neurotransmission is invoked.

Salivary cortisol in early psychosis: New findings and meta-analysis

BACKGROUND

Schizophrenia is a multifactorial disorder and environmental risk factors for it might contribute to hypothalamo-pituitary-adrenal axis (HPA) dysregulation. While increased cortisol levels have been reported in schizophrenia, as well as in early psychosis (compared to healthy controls), a crucial unresolved issue is whether elevated cortisol levels could be related to the distress of an emerging illness, rather than being specific to psychosis. Here, we report new findings from the first French cohort of young help-seekers (ICAAR) including ultra-high risk subjects (UHR), first-episode of psychosis (FEP) and non at-risk help seekers controls (HSC), followed by a meta-analysis of all available reports on salivary basal cortisol levels in early psychosis (UHR and FEP).

METHODS

In the ICAAR study, 169 individuals (15-30 years old) had their basal cortisol levels sampled and they were categorized (at baseline) as either UHR, FEP, or HSC using the criteria of the Comprehensive Assessment of At-Risk Mental States (CAARMS). The three groups were compared at baseline, and the UHR and HSC individuals were also included in a one-year longitudinal follow-up. UHRs who converted to psychosis at the follow up (UHR-P) were compared to non-converters (UHR-NP). We also performed a meta-analysis from case-control studies with basal salivary measures of cortisol, drawing from a systematic bibliographic search using the keywords 'cortisol', 'glucocorticoid', 'HPA' with 'UHR', 'CHR', 'at-risk mental state', 'schizotypal ', 'prodromal schizophrenia', 'first-episode psychosis', 'first episode schizophrenia', 'newly diagnosed schizophrenia', 'recent onset schizophrenia' [in Medline, Web of Knowledge (WOS), EBSCO], followed by a systematic screening of the resulting articles.

RESULTS

Basal cortisol levels were not significantly different between UHR, FEP, and HSC controls in the ICAAR cohort. Interestingly, initial cortisol levels were correlated with positive symptoms at the one year follow-up in the ICAAR cohort. The meta-analysis revealed a significant elevation of the salivary basal cortisol levels in UHR individuals compared to controls (8 studies--1060 individuals), but not between FEP and controls (6 studies--441 individuals). Indirect comparison of salivary basal cortisol levels between UHR and FEP did not yield significant differences. Finally, no differences were detected between the baseline cortisol of UHR-P and UHR-NP (4 studies--301 individuals).

CONCLUSION

The meta-analysis (including new data) indicates that basal cortisol levels were increased in UHR compared to controls, but FEP levels were not different from UHR or controls. Many confounding factors could decrease the effect size in FEP especially medication intake. Taken together with our new results (which made use of help-seeker controls, and not merely healthy controls), the findings indicate that basal cortisol levels may not be a reliable biomarker for early psychosis. Further studies are needed to clarify the precise role of the HPA axis in psychotic conversion.

Baseline putamen volume as a predictor of positive symptom reduction in patients at clinical high risk for psychosis: A preliminary study

OBJECTIVES

Illness course in individuals at clinical high risk (CHR) status for psychosis is heterogeneous, which limits effective treatment for all CHR subgroups. Baseline predictors of positive symptom trajectory in the CHR group will reduce such limitations. We singled out the putamen, thought to be involved in the generation of the key schizophrenia symptoms early in the course of disease, as a potential predictor of positive symptom trajectory in CHR patients.

METHOD

We recruited 45 CHR patients and 29 age- and gender-matched healthy controls (HC). The CHR group was divided into patients with positive symptom reduction (CHR-R) and patients without positive symptom reduction (CHR-NR) at 6 months. Comparisons were made between the baseline putamen volumes of CHR-R, CHR-NR and HC groups. The relationship between baseline putamen volumes and clinical measures was investigated.

RESULTS

Left putamen volumes of CHR-R patients were significantly smaller than those of HCs (p=0.002) and of CHR-NR patients (p=0.024). CHR-R patients had significantly reduced leftward laterality compared to HCs (p=0.007). In the CHR-R group, bilateral putamen volumes were correlated with positive symptom severity at baseline (r=-0.552, p=0.001) and at 6 months (r=-0.360, p=0.043), and predicted positive symptom score change in 6 months at a trend level (p=0.092).

CONCLUSION

Smaller left putamen volumes in CHR-R patients, and the correlation between positive symptom severity and putamen volumes suggest that putamen volume is a possible risk-stratifier and predictor of clinical course in the CHR population.

Pituitary volume and clinical trajectory in young relatives at risk for schizophrenia

BACKGROUND

Stress and vulnerability likely interact to play a major role in psychosis. While much has been written about the neural diathesis-stress model in psychosis and its clinical risk states, little is known about HPA axis biomarkers in non-help-seeking individuals at familial high risk (FHR). We sought to prospectively measure pituitary volume (PV) in adolescents and young adults at FHR for schizophrenia and to follow their emerging sub-clinical psychotic symptoms and clinical trajectories.

METHOD

Forty healthy controls and 38 relatives of patients with schizophrenia or schizoaffective disorder were identified in Pittsburgh, USA. PV was derived from baseline 1.5 T magnetic resonance imaging. Chapman's schizotypy scales were acquired at baseline, and structured clinical interviews for DSM-IV-TR Axis I diagnoses were attempted annually for up to 3 years.

RESULTS

Seven individuals converted to psychosis. PV did not differ between FHR and control groups overall. Within the FHR group, PV was positively correlated with Chapman's positive schizotypy (Magical Ideation and Perceptual Aberration) scores, and there was a significant group × PV interaction with schizotypy. PV was significantly higher in FHR subjects carrying any baseline Axis I diagnosis (p = 0.004), and higher still in individuals who went on to convert to psychosis (p = 0.0007).

CONCLUSIONS

Increased PV is a correlate of early positive schizotypy, and may predict trait vulnerability to subsequent psychosis in FHR relatives. These preliminary findings support a model of stress-vulnerability and HPA axis activation in the early phases of psychosis.

Premorbid multivariate prediction of adult psychosis-spectrum disorder: A high-risk prospective investigation

Premorbid prediction of psychosis-spectrum disorders has implications for both understanding etiology and clinical identification. The current study used a longitudinal high-risk for psychosis design that included children of parents with schizophrenia as well as two groups of controls (children whose parents had no mental illness, and children with at least one parent with a non-psychotic psychiatric diagnosis). Premorbid neurological factors and an indication of social function, as measured when participants were 10-13years of age, were combined to predict psychosis-spectrum disorders in adulthood. Through a combination of childhood predictors, the model correctly classified 82% (27 of 33) of the participants who eventually developed a psychosis-spectrum outcome in adulthood. With replication, multivariate premorbid prediction, including genetic risk, social, and neurological variables, could potentially be a useful complementary approach to identifying individuals at risk for developing psychosis-spectrum disorders.

Aberrant Salience Is Related to Reduced Reinforcement Learning Signals and Elevated Dopamine Synthesis Capacity in Healthy Adults

The striatum is known to play a key role in reinforcement learning, specifically in the encoding of teaching signals such as reward prediction errors (RPEs). It has been proposed that aberrant salience attribution is associated with impaired coding of RPE and heightened dopamine turnover in the striatum, and might be linked to the development of psychotic symptoms. However, the relationship of aberrant salience attribution, RPE coding, and dopamine synthesis capacity has not been directly investigated. Here we assessed the association between a behavioral measure of aberrant salience attribution, the salience attribution test, to neural correlates of RPEs measured via functional magnetic resonance imaging while healthy participants (n = 58) performed an instrumental learning task. A subset of participants (n = 27) also underwent positron emission tomography with the radiotracer [(18)F]fluoro-l-DOPA to quantify striatal presynaptic dopamine synthesis capacity. Individual variability in aberrant salience measures related negatively to ventral striatal and prefrontal RPE signals and in an exploratory analysis was found to be positively associated with ventral striatal presynaptic dopamine levels. These data provide the first evidence for a specific link between the constructs of aberrant salience attribution, reduced RPE processing, and potentially increased presynaptic dopamine function.

Bridging the gap between research into biological and psychosocial models of psychosis

Summary

Paul Bebbington’s recent Special Article provides an excellent synthesis of recent advances in psychosocial research on psychosis. However, we doubt that a model based solely on social epidemiology and cognitive theory can totally describe psychosis, and to be fair, Bebbington does not suggest that it does. A complete model must also incorporate what we have learned from non-social epidemiology, neuroscience, and genetics. Evidence indicates that both the social risk factors that interest Bebbington and biological risk factors, such as abuse of stimulants and cannabis, can provoke psychotic symptoms by dysregulating striatal dopamine. The role of neurodevelopmental deviance also needs to be considered in the etiology of schizophrenia-like psychosis. Moreover, the striking advances in our understanding of the genetic architecture of psychosis open an exciting door into studies examining gene-environment correlation and gene-environment interaction. In short, Bebbington demonstrates the value of cognitive and social researchers talking to each other, but the occasional chat with the more biologically inclined could produce a more comprehensive model.

 

 

The dopaminergic response to acute stress in health and psychopathology: A systematic review

Previous work in animals has shown that dopamine (DA) in cortex and striatum plays an essential role in stress processing. For the first time, we systematically reviewed the in vivo evidence for DAergic stress processing in health and psychopathology in humans. All studies included (n studies=25, n observations=324) utilized DA D2/3 positron emission tomography and measured DAergic activity during an acute stress challenge. The evidence in healthy volunteers (HV) suggests that physiological, but not psychological, stress consistently increases striatal DA release. Instead, increased medial prefrontal cortex (mPFC) DAergic activity in HV was observed during psychological stress. Across brain regions, stress-related DAergic activity was correlated with the physiological and psychological intensity of the stressor. The magnitude of stress-induced DA release was dependent on rearing conditions, personality traits and genetic variations in several SNPs. In psychopathology, preliminary evidence was found for stress-related dorsal striatal DAergic hyperactivity in psychosis spectrum and a blunted response in chronic cannabis use and pain-related disorders, but results were inconsistent. Physiological stress-induced DAergic activity in striatum in HV may reflect somatosensory properties of the stressor and readiness for active fight-or-flight behavior. DAergic activity in HV in the ventral striatum and mPFC may be more related to expectations about the stressor and threat evaluation, respectively. Future studies with increased sample size in HV and psychopathology assessing the functional relevance of stress-induced DAergic activity, the association between cortical and subcortical DAergic activity and the direct comparison of different stressors are necessary to conclusively elucidate the role of the DA system in the stress response.

Altered mesocorticolimbic functional connectivity in psychotic disorder: an analysis of proxy genetic and environmental effects

BACKGROUND

Altered dopaminergic neurotransmission in the mesocorticolimbic (MCL) system may mediate psychotic symptoms. In addition, pharmacological dopaminergic manipulation may coincide with altered functional connectivity (fc) 'in rest'. We set out to test whether MCL-fc is conditional on (familial risk for) psychotic disorder and/or interactions with environmental exposures.

METHOD

Resting-state functional magnetic resonance imaging data were obtained from 63 patients with psychotic disorder, 73 non-psychotic siblings of patients with psychotic disorder and 59 healthy controls. With the nucleus accumbens (NAcc) as seed region, fc within the MCL system was estimated. Regression analyses adjusting for a priori hypothesized confounders were used to assess group differences in MCL connectivity as well as gene (group) × environmental exposure interactions (G × E) (i.e., to cannabis, developmental trauma and urbanicity).

RESULTS

Compared with controls, patients and siblings had decreased fc between the right NAcc seed and the right orbitofrontal cortex (OFC) as well as the left middle cingulate cortex (MCC). Siblings showed decreased connectivity between the NAcc seed and lentiform nucleus compared with patients and controls. In addition, patients had decreased left NAcc connectivity compared with siblings in the left middle frontal gyrus. There was no evidence for a significant interaction between group and the three environmental exposures in the model of MCL-fc.

CONCLUSIONS

Reduced NAcc-OFC/MCC connectivity was seen in patients and siblings, suggesting that altered OFC connectivity and MCC connectivity are vulnerability markers for psychotic disorder. Differential exposure to environmental risk factors did not make an impact on the association between familial risk and MCL connectivity.

Hypofunction of prefrontal cortex NMDA receptors does not change stress-induced release of dopamine and noradrenaline in amygdala but disrupts aversive memory

RATIONALE

A dysfunction of prefrontal cortex has been associated with the exacerbated response to stress observed in schizophrenic patients and high-risk individuals to develop psychosis. The hypofunction of NMDA glutamatergic receptors induced by NMDA antagonists produces cortico-limbic hyperactivity, and this is used as an experimental model to resemble behavioural abnormalities observed in schizophrenia.

OBJECTIVES

The aim of the present study was to investigate whether injections of NMDA antagonists into the medial prefrontal cortex of the rat change (1) the increases of dopamine, noradrenaline and corticosterone concentrations produced by acute stress in amygdala, and (2) the acquisition of aversive memory related to a stressful event.

METHODS

Male Wistar rats were implanted with guide cannulae to perform microdialysis and bilateral microinjections (0.5 μl/side) of the NMDA antagonist 3-[(R)-2-carboxypiperazin-4-yl]-propyl-1-phophonic acid (CPP) (25 and 100 ng). Prefrontal injections were performed 60 min before restraint stress in microdialysis experiments, or training (footshock; 0.6 mA, 2 s) in inhibitory avoidance test. Retention latency was evaluated 24 h after training as an index of aversive memory.

RESULTS

Acute stress increased amygdala dialysate concentrations of dopamine (160% of baseline), noradrenaline (145% of baseline) and corticosterone (170% of baseline). Prefrontal injections of CPP did not change the increases of dopamine, noradrenaline or corticosterone produced by stress. In contrast, CPP significantly reduced the retention latency in the inhibitory avoidance test.

CONCLUSIONS

These results suggest that the hypofunction of prefrontal NMDA receptors does not change the sensitivity to acute stress of dopamine and noradrenaline projections to amygdala but impairs the acquisition of aversive memory.