Negative Symptoms in Schizophrenia: Where We have been and Where We are Heading

Ferroptosis in schizophrenia: Mechanisms and therapeutic potentials (Review)

Schizophrenia, a complex psychiatric disorder, presents with multifaceted symptoms and important challenges in treatment, primarily due to its pathophysiological complexity, which involves oxidative stress and aberrant iron metabolism. Recent insights into ferroptosis, a unique form of iron‑dependent cell death characterized by lipid peroxidation and antioxidant system failures, open new avenues for understanding the neurobiological foundation of schizophrenia. The present review explores the interplay between ferroptosis and schizophrenia, emphasizing the potential contributions of disrupted iron homeostasis and oxidative mechanisms to the pathology and progression of this disease. The emerging evidence linking ferroptosis with the oxidative stress observed in schizophrenia provides a compelling narrative for re‑evaluating current therapeutic strategies and exploring novel interventions targeting these molecular pathways, such as the glutathione peroxidase 4 pathway and the ferroptosis suppressor protein 1 pathway. By integrating recent advances in ferroptosis research, the current review highlights innovative therapeutic potentials, including N‑acetylcysteine, selenium, omega‑3 fatty acids and iron chelation therapy, which could address the limitations of existing treatments and improve clinical outcomes for individuals with schizophrenia.

Aberrant brain functional connectivity mediates the effects of negative symptoms on cognitive function in schizophrenia: A structural equation model

BACKGROUND

Schizophrenia is a severe psychiatric disorder, characterized by positive symptoms, negative symptoms, and cognitive deficits. Elucidating the mechanism of negative symptom and cognitive deficits could contribute to the treatment and prognosis of schizophrenia. We hypothesized that abnormal functional connectivity would be involved in the indirect effects of negative symptoms on cognitive function.

METHODS

A total of 150 schizophrenia male patients and 108 healthy controls matched for age, education and gender were enrolled in the study. The scores of Brief Negative Symptom Scale were divided into two factors: motivation and pleasure deficits (MAP) and diminished expression (EXP). Subsequently, a series of classic neurocognitive tests were used to evaluate cognitive functions. Resting-state fMRI data was collected from all participants. The Anatomical Automatic Labeling template was employed to establish regions of interest, thereby constructing the functional connectivity network across the entire brain. Eventually, scores of patients' negative symptoms scale, cognitive function, and strengths of abnormal functional connectivity were incorporated into a structural equation model to explore the interactions among variables.

RESULTS

MAP exhibited a distinctly and significantly negative impact on cognitive function. The functional connectivity between the left insula and left precuneus, along with that between the left precuneus and right angular gyrus, collectively served as intermediaries, contributing to the indirect effects of MAP and EXP on cognitive function.

CONCLUSIONS

Our findings demonstrated the moderating role of aberrant brain functional connectivity between negative symptoms and cognitive function, providing clues about the neural correlates of negative symptoms and cognitive deficits in schizophrenia.

Exploring the latent cognitive structure in schizophrenia: implications for antipsychotic treatment responses

BACKGROUND

Individuals diagnosed with schizophrenia present diverse degrees and types of cognitive impairment, leading to variations in responses to antipsychotic treatments. Understanding the underlying cognitive structures is crucial for assessing this heterogeneity. Utilizing latent profile analysis (LPA) enables the delineation of latent categories of cognitive function. Integrating this approach with a dimensional perspective allows for the exploration of the relationship between cognitive function and treatment response.

METHODS

This study examined 647 patients from two distinct cohorts. Utilizing LPA within the discovery cohort (n = 333) and the replication cohort (n = 314), latent subtypes were identified categorically. The stability of cognitive structures was evaluated employing Latent Transition Analysis (LTA). The relationship between cognitive function and treatment response were investigated by comparing Positive and Negative Syndrome Scale (PANSS) reduction rates across diverse cognitive subtypes. Furthermore, dimensional insights were gained through correlation analyses between cognitive tests and PANSS reduction rates.

RESULTS

In terms of categorical, individuals diagnosed with schizophrenia can be categorized into three distinct subtypes: those 'without cognitive deficit', those 'with mild-moderate cognitive 'eficit', and those 'with moderate-severe cognitive deficit'. There are significant differences in PANSS reduction rates among patients belonging to these subtypes following antipsychotic treatment (p < 0.05). Furthermore, from a dimensional perspective, processing speed at baseline is positively correlated with PANSS score reduction rates at week 8/week 10 (p < 0.01).

CONCLUSIONS

Our findings have unveiled the latent subtypes of cognitive function in schizophrenia, illuminating the association between cognitive function and responses to antipsychotic treatment from both categorical and dimensional perspectives.

Impact of Negative Symptoms on Functioning and Quality of Life in First Psychotic Episodes of Schizophrenia

Negative symptoms are not considered a unitary construct encompassing two different domains, diminished expression, and avolition-apathy. The aim of this study was to explore the relationships between each domain and psychosocial functioning and quality of life in people with a first psychotic episode of schizophrenia. In total, 61 outpatients were assessed with the Clinical Assessment Interview for Negative Symptoms (CAINS), The Functioning Assesment Short Test (FAST) and The Quality of Life Scale (QLS). The mean global score for CAINS was 21.5 (SD: 15.6), with a CAINS Avolition-Apathy (MAP) score of 17.0 (SD: 11.8), and CAINS Diminished Expression (EXP) score of 4.5 (SD: 5.0). The mean FAST score was 31.9 (SD: 18.9), and 41.1 (SD: 17.9) for QLS. Linear regression analysis revealed a significant (F(4,53) = 15.65, p < 0.001) relationship between MAP and EXP CAINS’ score and FAST score. CAINS-MAP was more predictive of FAST scores (β = 0.44, p = 0.001) than CAINS-EXP (β = 0.37, p = 0.007). Linear regression analysis for QLS revealed a significant model (F(4,56) = 29.29, p < 0.001). The standardized regression weight for the CAINS-MAP was around three times greater (β = −0.63, p < 0.001) than for CAINS-EXP (β = −0.24, p = 0.024). The two different domains are associated differently with functionality and quality of life.

Factor structure and internal consistency of the Clinical Assessment Interview for Negative Symptoms (CAINS) on a sample of persons with psychotic disorders in Bosnia and Herzegovina

The assessment of negative symptoms is crucial for development of adequate therapeutic interventions. This is a challenging task due to complex clinical presentation and lack of reliable and valid instruments. This study examined the psychometric characteristics of the Clinical Assessment Interview for Negative Symptoms (CAINS). The sample consisted of 81 persons with schizophrenia or schizoaffective disorder recruited from two health institutions in the Sarajevo Canton: the Clinical Center of the University of Sarajevo and the Psychiatric Hospital of the Sarajevo Canton. The 13 CAINS items grouped into four factors (expression, motivation and satisfaction in the recreational domain, motivation and satisfaction with social relationships, motivation and satisfaction with job and education). The four-factor solution accounted for 87.83% of the variance of manifest items. The reliabilities of extracted factors were as follows: for motivation and satisfaction with social relationships α = 0.897, for motivation and satisfaction with job and education α = 0.961, for Motivation and satisfaction in the recreation domain α = 0.981, and for expression α = 0.938. The highest correlation between factors was found between Motivation and satisfaction with recreation and Motivation and satisfaction with social relationships. On the other hand, the lowest correlation was found between motivation and satisfaction with social relations and motivation and satisfaction with job and education. In conclusion, the study showed that the latent structure of CAINS is adequate, clearly interpretable, and consisted of four factors. The measure can be used for assessment of the negative symptoms in outpatients with psychosis in Bosnia and Herzegovina.

Clinical outcomes of paliperidone long-acting injection in patients with schizophrenia: a 1-year retrospective cohort study

BACKGROUND

Schizophrenia is a severe psychiatric disorder. Poor medical adherence increases relapse rate. Long-acting injection of antipsychotic agent is developed for improving medical adherence. In this study, we examined the effect of paliperidone long-acting injection (PLAI) treatment in patients with schizophrenia in a real-world setting.

METHODS

In this retrospective cohort study, 467 patients with schizophrenia were enrolled, treated with risperidone PLAI or oral antipsychotics, and followed for 1 year. Concomitant medication, namely anticonvulsants, antidepressants, anxiolytics, sedatives or hypnotics, anticholinergics, and beta-blockers, were administered. Patients were classified into 2 groups: the LAI group (patients received LAI for treatment) and the NLAI group (patients taking only oral antipsychotics). The incidence of hospitalization, the length of hospitalization, and the incidence of emergency room visits were assessed.

RESULTS

The LAI group had a higher incidence of psychiatric acute ward admission (NLAI group = 4.8%; LAI = 30.3%) and emergency room visits (NLAI group = 7.3%; LAI group = 36.0%) before enrolment. During the one-year follow-up, the incidence of acute ward admission and emergency room visit did not differ in the NLAI group (P = .586 and .241) compared with before enrolment, whereas both incidences were significantly decreased in the LAI group (P < .0001 in both of them).

CONCLUSIONS

PLAI reduces the incidence of admission and emergency room visits.

Cannabidiol Displays Proteomic Similarities to Antipsychotics in Cuprizone-Exposed Human Oligodendrocytic Cell Line MO3.13

Cannabidiol, a compound of Cannabis sativa, has been proposed as an alternative treatment of schizophrenia. Preclinical and clinical data have suggested that cannabidiol shares more similarity with atypical antipsychotics than typical, both of which are customarily used to manage schizophrenia symptoms. While oligodendrocytes are known to be relevant targets of antipsychotics, the biochemical knowledge in this regard is still limited. Here we evaluated the molecular pathways modulated by cannabidiol compared to the antipsychotics clozapine (atypical) and haloperidol (typical), additionally evaluating the effects of benztropine, a muscarinic receptor antagonist that displays a protective effect in oligodendrocytes and myelination. For this purpose, we employed nano-chromatography coupled with mass spectrometry to investigate the proteomic response to these drugs both in healthy oligodendrocytic cells and in a cuprizone-based toxicity model, using the human oligodendrocyte precursor cell line MO3.13. Cannabidiol shares similarities of biochemical pathways with clozapine and benztropine, in agreement with other studies that indicated an atypical antipsychotic profile. All drugs tested affected metabolic and gene expression pathways and cannabidiol, benztropine, and clozapine modulated cell proliferation and apoptosis when administered after cuprizone-induced toxicity. These general pathways are associated with cuprizone-induced cytotoxicity in MO3.13 cells, indicating a possible proteomic approach when acting against the toxic effects of cuprizone. In conclusion, although modeling oligodendrocytic cytotoxicity with cuprizone does not represent the entirety of the pathophysiology of oligodendrocyte impairments, these results provide insight into the mechanisms associated with the effects of cannabidiol and antipsychotics against cuprizone toxicity, offering new directions of study for myelin-related processes and deficits.

Assessing negative symptoms in schizophrenia: Validity of the clinical assessment interview for negative symptoms in Singapore

This study aimed to examine the validity of the Clinical Assessment Interview for Negative Symptoms (CAINS) in Singapore. 274 participants with schizophrenia were assessed on the CAINS, Scale for the Assessment of Negative Symptoms (SANS), Positive and Negative Syndrome Scale (PANSS), Calgary Depression Scale for Schizophrenia (CDSS), Social and Occupational Functioning Assessment Scale (SOFAS) and the Simpson-Angus Extrapyramidal Side Effects Scale (SES). Factor analyses were conducted and Cronbach's coefficient alpha was calculated. Spearman's correlation coefficient was used to assess correlations. The 2-factor model of the CAINS failed to fit our data. Exploratory factor analysis of a randomly selected split-half of the sample yielded four factors: motivation-pleasure (MAP) social, MAP vocational, MAP recreational and expression (EXP), accounting for 73.94% of the total variance. Confirmatory factor analysis on the remaining sample supported this factor structure. Cronbach's alpha for the CAINS was 0.770. Significant correlations were observed between the CAINS total and the SANS total and PANSS negative subscale scores. Good divergent validity was shown by insignificant correlations with PANSS positive subscale score and CDSS total score. The MAP social and recreational factor scores had moderate correlations with the SANS anhedonia-asociality subscale scores, whereas the MAP vocational factor had the highest correlation with the avolition-apathy subscale of the SANS. EXP factor score correlated strongly with the SANS affective flattening and alogia subscales scores. In conclusion, the CAINS has good psychometric properties and can be used by clinicians to assess negative symptoms in individuals with schizophrenia in the local population.

Thinking dispositions and cognitive reflection performance in schizotypy

Schizotypy refers to the continuum of normal variability of psychosis-like characteristics and experiences, often classified as positive schizotypy (‘unusual experiences’; UE) and negative schizotypy (‘introvertive anhedonia’; IA). Here, we investigated the link between schizotypy and cognitive processing style and performance. A particular focus was on whether schizotypy is associated more with Type 1 (automatic/heuristic) than Type 2 (reflective/effortful) processes, as may be expected from findings of impaired top-down control in schizophrenia. A large sample (n = 1,512) completed online measures pertaining to schizotypy (Oxford-Liverpool Inventory for Feelings and Experiences; O-LIFE), thinking style (Rational Experiential Inventory-10, Actively Open-Minded Thinking Scale), and reasoning performance (Cognitive Reflection Test). Higher positive (UE) and negative (IA) schizotypy were associated with more pronounced Type 1 processing, i.e. greater self-reported Faith in Intuition (FI), lower Need for Cognition (NFC), lower Actively Open-Minded Thinking (AOT), and lower cognitive reflection test (CRT) scores. Canonical correlation analysis confirmed a significant association between UE and increased FI, lower AOT and lower CRT performance, accounting for 12.38% of the shared variance between schizotypy and thinking dispositions. IA was more highly associated with reduced NFC. These findings suggest that schizotypy may be associated with similar thinking dispositions to those reported in psychosis, with different patterns of associations for positive and negative schizotypy. This result informs research on reasoning processes in psychosis and has clinical implications, including potential treatment targets and refinements for cognitive therapies.

Long-term course of negative symptom subdomains and relationship with outcome in patients with a psychotic disorder

BACKGROUND

The longitudinal course of the negative symptoms subdomains social amotivation (SA) and expressive deficits (ED) remains largely unknown. We investigated i) the longitudinal course of SA and ED subdomain scores, ii) whether subgroups based on the course of SA and ED subdomain scores could be identified, iii) whether baseline SA and ED subdomain scores were related to functioning and quality of life six years later and iv) the longitudinal relationship between subgroups and outcomes.

METHODS

Measurements at baseline, three and six years from 1067 patients participating in the Genetic Risk and Outcome of Psychosis (GROUP) project were used. We applied mixed models analysis, regression analysis and trajectory analyses.

RESULTS

SA and ED subdomain scores decreased over time. Within both subdomains, four subgroups were identified: for both SA and ED a steady low course (±60%), increased (±15%) and decreased course (±15%). Within SA only, a higher level decreased course (±6%) and within ED only, a course with relatively stable high ED scores (±6%) was found. Lower symptom levels at baseline were related to better functioning (SA & ED) and quality of life (SA) at six years. Overall, low SA and low ED subgroups showed better outcomes than the other subgroups.

CONCLUSION

In many patients the course of negative symptoms is unstable and related to the course of outcome. Patients who do show steady low negative symptom levels (60%) may complicate the interpretation of treatment evaluation studies, as they may average out possible effects in subgroups with fluctuating symptom levels.

Serum BDNF Is Positively Associated With Negative Symptoms in Older Adults With Schizophrenia

OBJECTIVES

Older adults with chronic schizophrenia are at greater risk for functional disability and poorer health outcomes than those without serious mental illness. These individuals comprise 1-2% of the elderly population in the United States and are projected to number approximately 15 million by 2030. The symptoms of schizophrenia can be disabling for individuals, significantly reducing quality of life. Often, the negative symptoms (NS) are the most resistant to treatment and are considered a marker of illness severity, though they are challenging to measure objectively. Biomarkers can serve as objective indicators of health status. Brain-derived neurotrophic factor (BDNF) is a potential biomarker for schizophrenia and may serve as an important indicator of illness severity.

METHODS

A cross-sectional study with 30 older adults with chronic schizophrenia. Participants were assessed on serum levels of BDNF and psychiatric symptoms (Positive and Negative Syndrome Scale). Pearson's bivariate correlations (two-tailed) and linear regression models were used.

RESULTS

A significant positive association ( p < .05) was found between higher serum levels of BDNF and greater severity for the NS items of passive, apathetic, social withdrawal, and emotional withdrawal. In multivariate analyses, the association remained significant.

CONCLUSIONS

Although the association between BDNF and NS was not in the expected direction, the data corroborate findings from previous work in patients with schizophrenia. It is possible that higher serum levels of BDNF reflect compensatory neuronal mechanisms resulting from neurodevelopmental dysfunction.

[Psychopathological aspects of negative symptoms in schizophrenia]

During the past ten years, research on schizophrenia has witnessed a clear emphasis on studies based on negative symptoms. This interest can be explained in terms of diagnosis, specific treatment, functional prognosis and outcome issues. However, main current approaches consider negative symptoms from an operationalist view, which implies objective and atheoretical descriptions of clinical criteria, observed from a third person perspective. And the understanding of negative symptoms in schizophrenia, still a crucial issue of mental health, remains only partial. From a different perspective, psychopathology - and notably psychiatric phenomenology -, can provide a conceptual and clinical framework, taking into account subjective experience (first person perspective), based on a global understanding of the clinical situation lived by patients with schizophrenia. In the present review, we give a brief survey on the historical aspects of the description of negative symptoms. Then, we introduce the clinical contributions raised by clinical phenomenology. We principally develop Minkowski's notion of loss of vital contact, and Blankenburg's notion of loss of natural evidence. Then we highlight the current debates which are discussed and explored in contemporary psychopathology. In conclusion, we discuss the possible articulation between objective and subjective approaches, in order to better understand pauci-symptomatic forms of schizophrenia.

[Negative symptoms in schizophrenia: psychotherapeutic approaches]

Although negative symptoms are recognized as a central feature of schizophrenia, their definition as well as phenomenology have long been a vexing issue. During these last years, a major progress has been made with the delineation of two underlying subdomains of negative symptoms: diminished expression and anhedonia-avolition-apathy. As current guidelines are not always in accord on the efficacy of treatments on negative symptoms, it may be tempting to re-interpret the findings of clinical trials by looking at the effects of treatments on these two subdomains. This could concern both psychotropic treatments and psychotherapeutic interventions. Furthermore, neuroimaging as well as emotional response studies have permitted to better understand the mechanism which could be at the root of diminished expression and anhedonia in schizophrenia. On this basis, new psychotherapeutic methods have been devised which, by specifically targeting these two subdomains, are likely to be more efficient on negative symptoms. Further research is warranted to test their efficacy in randomized controlled trials.

Confirmatory Factor Analysis and Differential Relationships of the Two Subdomains of Negative Symptoms in Chronically Ill Psychotic Patients

Research suggests a two factor structure for negative symptoms in patients with psychotic disorders: social amotivation (SA) and expressive deficits (ED). Applying this two-factor structure in clinical settings may provide valuable information with regard to outcomes and to target treatments. We aimed to investigate 1) whether the factor structure is also supported in chronically ill patients with a psychotic disorder and 2) what the relationship is between these factors and functioning (overall functioning and living situation), depressive symptoms and quality of life. 1157 Patients with a psychotic disorder and a duration of illness of 5 years or more were included in the analysis (data selected from the Pharmacotherapy Monitoring Outcome Survey; PHAMOUS). A confirmatory factor analysis was performed using items of the Positive and Negative Syndrome Scale that were previously identified to reflect negative symptoms (N1-4, N6, G5, G7, G13, G16). Subsequently, regression analysis was performed on outcomes. The results confirmed the distinction between SA (N2, N4, G16) and ED (N1, N3, N6, G5, G7, G13) in chronically ill patients. Both factors were related to worse overall functioning as measured with the Health of the Nation Outcome Scales, ED was uniquely associated with residential living status. Higher scores for SA were associated with more depressive symptoms and worse quality of life. Thus, SA is most strongly related to level of social-emotional functioning, while ED are more related to living situation and thereby are indicative of level of everyday functioning. This subdivision may be useful for research purposes and be a valuable additional tool in clinical practice and treatment development.

Reward-dependent modulation of working memory is associated with negative symptoms in schizophrenia

The negative symptoms of schizophrenia have been associated with altered neural activity during both reward processing and cognitive processing. Even though increasing evidence suggests a strong interaction between these two domains, it has not been studied in relation to negative symptoms. To elucidate neural mechanisms of the reward-cognition interaction, we applied a letter variant of the n-back working memory task and varied the financial incentives for performance. In the interaction contrast, we found a significantly activated cluster in the rostral anterior cingulate cortex (ACC), the middle frontal gyrus, and the bilateral superior frontal gyrus. The interaction did not differ significantly between the patient group and a healthy control group, suggesting that patients with schizophrenia are on average able to integrate reward information and utilize this information to maximize cognitive performance. However within the patient group, we found a significant inverse correlation of ACC activity with the factor diminished expression. This finding is consistent with the model that a lack of available cognitive resources leads to diminished expression. We therefore argue that patients with diminished expression have difficulties in recruiting additional cognitive resources (as implemented in the ACC) in response to an anticipated reward. Due to this lack of cognitive resources, less processing capacity is available for effective expression, resulting in diminished expressive behavior.

Neonatal stress-induced affective changes in adolescent Wistar rats: early signs of schizophrenia-like behavior

Psychiatric disorders are multifactorial diseases with etiology that may involve genetic factors, early life environment and stressful life events. The neurodevelopmental hypothesis of schizophrenia is based on a wealth of data on increased vulnerability in individuals exposed to insults during the perinatal period. Maternal deprivation (MD) disinhibits the adrenocortical response to stress in neonatal rats and has been used as an animal model of schizophrenia. To test if long-term affective consequences of early life stress were influenced by maternal presence, we submitted 10-day old rats, either deprived (for 22 h) or not from their dams, to a stress challenge (i.p. saline injection). Corticosterone plasma levels were measured 2 h after the challenge, whereas another subgroup was assessed for behavior in the open field, elevated plus maze (EPM), social investigation and the negative contrast sucrose consumption test in adolescence (postnatal day 45). Maternally deprived rats exhibited increased plasma corticosterone (CORT) levels which were higher in maternally deprived and stress challenged pups. Social investigation was impaired in maternally deprived rats only, while saline injection, independently of MD, was associated with increased anxiety-like behavior in the EPM and an impaired intake decrement in the negative sucrose contrast. In the open field, center exploration was reduced in all maternally-deprived adolescents and in control rats challenged with saline injection. The most striking finding was that exposure to a stressful stimulus per se, regardless of MD, was linked to differential emotional consequences. We therefore propose that besides being a well-known and validated model of schizophrenia in adult rats, the MD paradigm could be extended to model early signs of psychiatric dysfunction, and would particularly be a useful tool to detect early signs that resemble schizophrenia.