Negative symptoms in schizophrenia: Newly emerging measurements, pathways, and treatments

The Effects of Cognitive Remediation on Negative Symptoms in Schizophrenia-Spectrum Illness: A Meta-analytic Investigation of Efficacy

BACKGROUND AND HYPOTHESIS

The number of clinical efficacy trials of Cognitive Remediation (CR), a behavioral intervention consisting of cognitive task practice and/or strategy training to improve cognitive skills in schizophrenia, has increased substantially over the past 25 years. While recent reviews have highlighted the effects of CR on cognition and function, CR effects on negative symptoms remain understudied. Given the overlap between negative symptoms and cognition, CR effects might be expected.

STUDY DESIGN

Electronic databases were evaluated up to September 2023 using a broad range of search terms. Sixty-nine unique, controlled trials that used negative symptoms as an outcome were meta-analyzed. Data were independently extracted with excellent (>98%) reliability. Random effects models assessed the effects of CR on summary and expressive vs. experiential negative symptoms. Moderator analyses evaluated a broad array of treatment and participant factors.

STUDY RESULTS

The meta-analysis (5319 participants) revealed that CR produced a small effect size improvement on summary negative symptoms (Hedge's g = 0.179). Sample differences in age, duration of illness, symptoms, and antipsychotic dosage did not serve as a barrier to treatment benefit. CR also produced small-to-moderate improvements in alogia (Hedge's g = 0.312) but not experiential negative symptoms. Programs of CR that utilized bridging activities that relate training of cognitive skills to activities of daily living produced greater improvement in negative symptoms (g = 0.281 vs 0.055). Longer CR programs also produce larger effects on negative symptoms.

CONCLUSIONS

CR produces small, consistent reductions in negative symptoms in people with schizophrenia. Variations in CR effects may be linked to different treatment ingredients.

Dynamics of symptom network in patients with first-episode schizophrenia: Insight from the CNFEST project

BACKGROUND

Schizophrenia is a heterogeneous psychotic disorder. Recent theories have emphasized the importance of interactions among psychiatric symptoms in understanding the pathological mechanisms of schizophrenia. In the current study, we examined the symptom network in patients with first-episode schizophrenia (FES) at four time points during a six-month follow-up period.

METHODS

In total, 565 patients with FES were recruited from the Chinese First-Episode Schizophrenia Trial (CNFEST) project. Clinical symptoms were measured using the Positive and Negative Syndrome Scale (PANSS) at baseline and follow-up (514 patients at one month, 429 at three months, and 392 at six months). We used a network analysis approach to estimate symptom networks with individual symptoms as nodes and partial correlation coefficients between symptoms as edges. A cross-lagged panel network (CLPN) model was used to identify predictive pathways for clinical symptoms.

RESULTS

We found stable and strongly connected edges in patients across the time points, such as links between delusions and suspiciousness/persecution (P1:P6), and emotional withdrawal and passive/apathetic social withdrawal (N2:N4). Emotional withdrawal (N2), poor rapport (N3), and passive/apathetic social withdrawal (N4) had high centrality estimates across all four time points. CLPN analysis showed that negative symptoms, including emotional withdrawal (N2), poor rapport (N3), and passive/apathetic social withdrawal (N4), and stereotyped thinking (N7) may have predictive effects for negative and general symptoms at follow-ups.

CONCLUSIONS

The symptom network of schizophrenia may be dynamic as treatment progresses. Negative symptoms remain the central and stable symptoms of schizophrenia. Negative symptoms may be potential therapeutic targets that predict other symptoms.

Defects of parvalbumin-positive interneurons are implicated in psychiatric disorders

Psychiatric disorders are a common cause of severe long-term disability and socioeconomic burden worldwide. Although our understanding of these disorders has advanced substantially over the last few years, little has changed the standards of care for these illnesses. Fast-spiking parvalbumin-positive interneurons (PVIs), a subpopulation of gamma-aminobutyric acid (GABA)ergic interneurons, are widely distributed in the hippocampus and have been reported to play an important role in various mental disorders. However, the mechanisms underlying the regulation of the molecular networks relevant to depression and schizophrenia (SCZ) are unknown. Here, we discuss the functions of PVIs in psychiatric disorders, including depression and SCZ. After reviewing several studies, we concluded that dysfunction in PVIs could cause depression-like behavior, as well as cognitive categories in SCZ, which might be mediated in large part by greater synaptic variability. In summary, this scientific review aims to discuss the current knowledge regarding the function of PVIs in depression and SCZ. Moreover, we highlight the importance of neurogenesis and synaptic plasticity in the pathogenesis of depression and SCZ, which seem to be mediated by PVIs activity. These findings provide a better understanding of the role of PVIs in psychiatric disorders.

Use of video-recordings of site-based interviews for quality assurance in a study of subjects with schizophrenia and persistent negative symptoms

Site-independent ratings derived from audio-digital recordings of site-based interviews are often used for quality assurance monitoring to affirm ratings reliability in CNS clinical trials. The present study of subjects with schizophrenia and persistent negative symptoms used video instead of audio recordings of site-based interviews and thereby facilitated visual observation of the subject by the remote rater. "Paired" site-independent scores of the Positive and Negative Syndrome Scale (PANSS) and Brief Negative Symptom Scale (BNSS) were obtained from video-recordings of site-based interviews. The intraclass correlation between site-based and paired site-independent ratings was r = 0.839 for the total PANSS scores (n = 1006) and r = 0.871 for the total BNSS scores (n = 892); <5 % of paired scores deviated outside the acceptable confidence intervals. Ratings "outliers" were identified and remediated. We examined the pattern of paired scoring deviations for the BNSS, total PANSS, PANSS symptom subscales, and the Marder negative symptom factor. Each metric revealed a bidirectional pattern of scoring deviations such that mean site-based ratings were higher than site-independent ratings when symptom severity was high but lower than site-independent ratings when symptom severity was low. The pattern of bidirectional paired scoring deviations observed in this analysis has previously been noted in paired ratings analyses of subjects experiencing an acute exacerbation of psychosis in schizophrenia and major depressive disorder as well. The bidirectional pattern may reflect inherent differences between live ratings and remotely scored recorded ratings. This analysis affirms the utility of video-recordings of site-based ratings for surveillance in trials with subjects with schizophrenia and persistent negative symptoms.

Inhibition of striatal indirect pathway during second postnatal week leads to long-lasting deficits in motivated behavior

Schizophrenia is a neuropsychiatric disorder with postulated neurodevelopmental etiology. Genetic and imaging studies have shown enhanced dopamine and D2 receptor occupancy in the striatum of patients with schizophrenia. However, whether alterations in postnatal striatal dopamine can lead to long-lasting changes in brain function and behavior is still unclear. Here, we approximated striatal D2R hyperfunction in mice via designer receptor-mediated activation of inhibitory Gi-protein signaling during a defined postnatal time window. We found that Gi-mediated inhibition of the indirect pathway (IP) during postnatal days 8-15 led to long-lasting decreases in locomotor activity and motivated behavior measured in the adult animal. In vivo photometry further showed that the motivational deficit was associated with an attenuated adaptation of outcome-evoked dopamine levels to changes in effort requirements. These data establish a sensitive time window of D2R-regulated striatal development with long-lasting impacts on neuronal function and behavior.

Efficacy of KarXT on negative symptoms in acute schizophrenia: A post hoc analysis of pooled data from 3 trials

BACKGROUND

Currently approved antipsychotics do not adequately treat negative symptoms (NS), which are a major determinant of functional disability in schizophrenia. KarXT, an M1 /M4 preferring muscarinic receptor agonist, has shown efficacy as a broad-spectrum monotherapy for the treatment of schizophrenia in participants with acute psychosis. Post hoc analyses evaluated the possibility that NS improve independently of positive symptoms with KarXT in a subgroup of participants with moderate-to-severe NS and no predominance of positive symptoms.

METHODS

Data were pooled from the three pivotal trials of KarXT monotherapy in people with schizophrenia with an acute exacerbation of psychosis. All 3 studies used similar 5-week randomized, double-blind, placebo-controlled designs (modified intention-to-treat sample N = 640). PANSS criteria proposed in the literature identified a subset of study participants (n = 64) with prominent NS.

RESULTS

KarXT was significantly better than placebo on PANSS Marder Negative Factor Scores in the full sample (p < .001; Cohen's d = 0.42) and more so in the prominent NS subgroup (p < .001; Cohen's d = 1.18). Further, the KarXT effect in the NS subgroup remained significant after accounting for changes in positive symptoms, depression/anxiety, disorganization, and hostility.

CONCLUSIONS

Participants with prominent NS revealed greater improvement of NS following KarXT therapy than the full sample that persisted after accounting for positive and other symptoms. While these findings must be interpreted with caution, they are consistent with the possibility that NS improvements associated with KarXT are not secondary to improvements in other symptom domains and support further investigation in larger, stable outpatient studies.

Cognitive Function in Patients with Psychotic and Affective Disorders: Effects of Combining Pharmacotherapy with Cognitive Remediation

Background: Cognitive impairment is a relevant problem in psychiatry and can be well assessed with a cross-diagnostic test such as the Screen for Cognitive Impairment in Psychiatry (SCIP). The aim of our pilot study is to assess cognitive impairment in acute psychiatric inpatients diagnosed with psychotic disorders, bipolar disorder and depression using the German version of the SCIP (SCIP-G). We also investigate whether cognitive dysfunction improves over the course of the inpatient treatment, where patients are offered a combination of pharmacological treatment and cognitive remediation. Methods: A total of 143 adult inpatients were included in the study. Cognitive testing was performed using two different forms of the SCIP-G. All patients received state-of-the-art pharmacotherapy and cognitive remediation using the COGPACK® software package version 6.06. Results: Based on the ICD-10 Criteria for Research, 54 patients were given an F2 diagnosis (schizophrenia and schizotypal and delusional disorders). Thirty-nine patients met the criteria for bipolar disorder (F30 and F31) and fifty for depression (F32 and F33). At baseline, a significant difference was observed between the SCIP total scores of the F2 and F32/33 patients (p < 0.001) and between the F2 and F30/31 groups (p = 0.022). At the second measurement time point, the SCIP total score showed significant improvement in all three groups (p < 0.001), and there was no statistically significant interaction between SCIP total score and diagnostic groups (p = 0.860). Conclusions: Cognitive dysfunction is present in psychiatric disorders and can be easily assessed during an inpatient hospital stay. In our sample, patients with a psychotic disorder were more cognitively impaired at baseline than patients with an affective disorder. Inpatient treatment, consisting of pharmacotherapy and cognitive remediation, improved cognitive deficits. Patients with psychotic disorders, bipolar disorder and depression showed similar improvements in cognitive performance.

16S rRNA gene sequencing reveals altered gut microbiota in young adults with schizophrenia and prominent negative symptoms

BACKGROUND

Gut dysbiosis has been established as a characteristic of schizophrenia (SCH). However, the signatures regarding SCH patients with prominent negative symptoms (SCH-N) in young adults have been poorly elucidated.

METHODS

Stool samples were obtained from 30 young adults with SCH-N, 32 SCH patients with prominent positive symptoms (SCH-P) along with 36 healthy controls (HCs). Microbial diversity and composition were analyzed by 16S rRNA gene sequencing. Meanwhile, psychiatric symptoms were assessed by the positive and negative syndrome scale (PANSS).

RESULTS

There is a significant difference in β-diversity but not α-diversity indexes among the three groups. Moreover, we found a higher abundance of Fusobacteria and Proteobacteria phyla and a lower abundance of Firmicutes phyla in SCH-N when compared with HC. Besides, we identified a diagnostic potential panel comprising six genera (Coprococcus, Monoglobus, Prevotellaceae_NK3B31_group, Escherichia-Shigella, Dorea, and Butyricicoccus) that can distinguish SCH-N from HC (area under the curve = 0.939). However, the difference in microbial composition between the SCH-N and SCH-P is much less than that between SCH-N and the HC, and SCH-N and SCH-P cannot be effectively distinguished by gut microbiota.

CONCLUSION

The composition of gut microbiota was changed in the patients with SCH-N, which may help in further understanding of pathogenesis in young adults with SCH-N.

The Association of Redox Regulatory Drug Target Genes with Psychiatric Disorders: A Mendelian Randomization Study

Redox regulatory drug (RRD) targets may be considered potential novel drug targets of psychosis due to the fact that the brain is highly susceptible to oxidative stress imbalance. The aim of the present study is to identify potential associations between RRD targets' perturbation and the risk of psychoses; to achieve this, Mendelian randomization analyses were conducted. The expression quantitative trait loci (eQTL) and protein QTL data were used to derive the genetic instrumental variables. We obtained the latest summary data of genome-wide association studies on seven psychoses as outcomes, including schizophrenia (SCZ), bipolar disorder (BD), major depressive disorder (MDD), attention-deficit/hyperactivity disorder, autism, obsessive-compulsive disorder and anorexia nervosa. In total, 95 unique targets were included in the eQTL panel, and 48 targets in the pQTL one. Genetic variations in the vitamin C target (OGFOD2, OR = 0.784, p = 2.14 × 10-7) and melatonin target (RORB, OR = 1.263, p = 8.80 × 10-9) were significantly related to the risk of SCZ. Genetic variation in the vitamin E (PRKCB, OR = 0.248, p = 1.24 × 10-5) target was related to an increased risk of BD. Genetic variation in the vitamin C target (P4HTM: cerebellum, OR = 1.071, p = 4.64 × 10-7; cerebellar hemisphere, OR = 1.092, p = 1.98 × 10-6) was related to an increased risk of MDD. Cognitive function mediated the effects on causal associations. In conclusion, this study provides supportive evidence for a causal association between RRD targets and risk of SCZ, BD or MDD, which were partially mediated by cognition.

Association between elevated serum matrix metalloproteinase-2 and tumor necrosis factor-α, and clinical symptoms in male patients with treatment-resistant and chronic medicated schizophrenia

BACKGROUND

Inflammation has an important role in the pathogenesis of schizophrenia. The aim of this study was to investigate the levels of tumor necrosis factor (TNF) and matrix metalloproteinase-2 (MMP-2) in male patients with treatment-resistant schizophrenia (TRS) and chronic medicated schizophrenia (CMS), and the relationship with psychopathology.

METHODS

The study enrolled 31 TRS and 49 cm male patients, and 53 healthy controls. Serum MMP-2 and TNF-α levels were measured by the Luminex liquid suspension chip detection method. Positive and Negative Syndrome Scale (PANSS) scores were used to evaluate symptom severity and Repeatable Battery for the Assessment of Neuropsychological Status was used to assess cognitive function.

RESULTS

Serum TNF-α and MMP-2 levels differed significantly between TRS, CMS and healthy control patients (F = 4.289, P = 0.016; F = 4.682, P = 0.011, respectively). Bonferroni correction demonstrated that serum TNF-α levels were significantly elevated in CMS patients (P = 0.022) and MMP-2 levels were significantly higher in TRS patients (P = 0.014) compared to healthy controls. In TRS patients, TNF-α was negatively correlated with age (r=-0.435, P = 0.015) and age of onset (r=-0.409, P = 0.022). In CMS patients, MMP-2 and TNF-α were negatively correlated with PANSS negative and total scores, and TNF-α was negatively correlated with PANSS general psychopathology scores (all P < 0.05). MMP-2 levels were positively correlated with TNF-α levels (P < 0.05), but not with cognitive function (P > 0.05).

CONCLUSION

The results indicate the involvement of inflammation in the etiology of TRS and CMS. Further studies are warranted.

Decline in Working Memory in Stable Schizophrenia May Be Related to Attentional Impairment: Mediating Effects of Negative Symptoms, a Cross-Sectional Study

Background

Schizophrenia (SCZ) is a severe mental illness, Cognitive deficits and negative symptoms (NS) are prevalent in individuals with SCZ and are crucial indicators of functional recovery. It is well known that cognitive symptoms and negative symptoms are interrelated and that negative symptoms can affect the ability to take cognitive tests. However, the specific relationship between attention, working memory (WM), and NS in stable SCZ remains unclear. This study aims to explore these associations and provide valuable insights for the subsequent treatment of SCZ.

Methods

We conducted a comprehensive assessment of 145 patients with stable SCZ using the Chinese Brief Neurocognitive Suite of Tests (C-BCT) and the Positive and Negative Symptom Scale (PANSS).

Results

Patients with abnormal cognition exhibited significantly higher PANSS total scores, cognitive symptom scores, and NS than those with normal cognition (P<0.05). Pearson's correlation analysis revealed significant positive correlations between digital breadth(DB) and continuous operation(CO) (r=0.389, P<0.001), as well as a significant negative correlation between DB and NS (r=-0.291, P<0.001). Moreover, CO showed a negative correlation with NS (r=-0.173, P<0.05). However, no significant correlations were found between the digital breadth-anterograde score and CO or NS (r=0.148, P>0.05; r=-0.068, P>0.05). Notably, NS were identified as a mediator in the relationship between attention and WM (effect size=0.024).

Conclusion

Our findings highlight significant associations between WM, attention, and NS in individuals with stable SCZ. Moreover, attention not only directly impacts WM but also indirectly influences it through NS. Addressing cognitive deficits and NS in the treatment of SCZ may lead to improved overall outcomes for affected individuals.

Population Pharmacodynamic Models of Risperidone on PANSS Total Scores and Prolactin Levels in Schizophrenia

Currently, research predominantly focuses on evaluating clinical effects at specific time points while neglecting underlying patterns within the treatment process. This study aims to analyze the dynamic alterations in PANSS total scores and prolactin levels in patients with schizophrenia treated with risperidone, along with the influencing covariates. Using data from an 8-week randomized, double-blind, multicenter clinical trial, a population pharmacodynamic model was established for the PANSS total scores of and prolactin levels in patients treated with risperidone. The base model employed was the Emax model. Covariate selection was conducted using a stepwise forward inclusion and backward elimination approach. A total of 144 patients were included in this analysis, with 807 PANSS total scores and 531 prolactin concentration values. The PANSS total scores of the patients treated with risperidone decreased over time, fitting a proportionally parameterized sigmoid Emax model with covariates including baseline score, course of the disease, gender, plasma calcium ions, and lactate dehydrogenase levels. The increase in prolactin levels conformed to the ordinary Emax model, with covariates encompassing course of the disease, gender, weight, red blood cell count, and triglyceride levels. The impacts of the baseline scores and the course of the disease on the reduction of the PANSS scores, as well as the influence of gender on the elevation of prolactin levels, each exceeded 20%. This study provides valuable quantitative data regarding PANSS total scores and prolactin levels among patients undergoing risperidone treatment across various physiological conditions.