Retina as a potential biomarker in schizophrenia spectrum disorders: a systematic review and meta-analysis of optical coherence tomography and electroretinography.

INTRODUCTION: Abnormal findings on optical coherence tomography (OCT) and electroretinography (ERG) have been reported in participants with schizophrenia spectrum disorders (SSDs). This study aims to reveal the pooled standard mean difference (SMD) in retinal parameters on OCT and ERG among participants with SSDs and healthy controls and their association with demographic characteristics, clinical symptoms, smoking, diabetes mellitus, and hypertension. METHODS: Using PubMed, Scopus, Web of Science, and PSYNDEX, we searched the literature from inception to March 31, 2023, using specific search terms. This study was registered with PROSPERO (CRD4202235795) and conducted according to PRISMA 2020. RESULTS: We included 65 studies in the systematic review and 44 in the meta-analysis. Participants with SSDs showed thinning of the peripapillary retinal nerve fiber layer (pRNFL), macular ganglion cell layer- inner plexiform cell layer, and retinal thickness in all other segments of the macula. A meta-analysis of studies that excluded SSD participants with diabetes and hypertension showed no change in results, except for pRNFL inferior and nasal thickness. Furthermore, a significant difference was found in the pooled SMD of pRNFL temporal thickness between the left and right eyes. Meta-regression analysis revealed an association between retinal thinning and duration of illness, positive and negative symptoms. In OCT angiography, no differences were found in the foveal avascular zone and superficial layer foveal vessel density between SSD participants and controls. In flash ERG, the meta-analysis showed reduced amplitude of both a- and b-waves under photopic and scotopic conditions in SSD participants. Furthermore, the latency of photopic a-wave was significantly shorter in SSD participants in comparison with HCs. DISCUSSION: Considering the prior report of retinal thinning in unaffected first-degree relatives and the results of the meta-analysis, the findings suggest that retinal changes in SSDs have both trait and state aspects. Future longitudinal multimodal retinal imaging studies are needed to clarify the pathophysiological mechanisms of these changes and to clarify their utility in individual patient monitoring efforts.

Polydipsia and autistic traits in patients with schizophrenia spectrum disorders.

Introduction: Polydipsia, prevalent in 6%-20% of patients with schizophrenia, results in seclusion and prolonged hospitalization. It is also observed in autistic individuals, with previous studies reporting that autism accounted for 20% of all hospitalized patients with polydipsia. The current study investigated the association between polydipsia and autistic traits in patients with schizophrenia spectrum disorders (SSDs) based on the hypothesis that higher autistic traits would be observed in schizophrenic patients with polydipsia. Methods: In the first study (study A), the autism-spectrum quotient [(AQ); Japanese version] scores of long-stay inpatients with and without polydipsia were compared. Furthermore, the association between polydipsia and autistic traits was also examined in short-stay inpatients and outpatients with SSDs (study B). Results: Study A showed that patients with polydipsia scored significantly higher on the three AQ subscales (attention switching; communication; and imagination) compared to those without. Study B also showed that patients with polydipsia had significantly higher AQ scores overall and for several subscales compared to those without polydipsia. Binary logistic regression analysis of the combined sample showed that male gender and higher autistic traits were significant predictors of polydipsia. Discussion: The study highlights the importance of focusing on such traits to understand the pathogenesis of polydipsia in SSD patients.

Retinal layers and associated clinical factors in schizophrenia spectrum disorders: a systematic review and meta-analysis.

INTRODUCTION: The retina shares structural and functional similarities with the brain. Furthermore, structural changes in the retina have been observed in patients with schizophrenia spectrum disorders (SSDs). This systematic review and meta-analysis investigated retinal abnormalities and their association with clinical factors for SSD. METHODS: Studies related to retinal layers in SSD patients were retrieved from PubMed, Scopus, Web of Science, Cochrane Controlled Register of Trials, International Clinical Trials Registry Platform, and PSYNDEX databases from inception to March 31, 2021. We screened and assessed the eligibility of the identified studies. EZR ver.1.54 and the metafor package in R were used for the meta-analysis and a random-effects or fixed-effects model was used to report standardized mean differences (SMDs). RESULTS: Twenty-three studies (2079 eyes of patients and 1571 eyes of controls) were included in the systematic review and meta-analysis. The average peripapillary retinal nerve fiber layer (pRNFL) thickness, average macular thickness (MT), and macular ganglion cell layer-inner plexiform layer (GCL-IPL) thickness were significantly lower in patients than in controls (n = 14, 6, and 3, respectively; SMD = -0.33, -0.49, and -0.43, respectively). Patients also had significantly reduced macular volume (MV) compared to controls (n = 7; SMD = -0.53). The optic cup volume (OCV) was significantly larger in patients than in controls (n = 3; SMD = 0.28). The meta-regression analysis indicated an association between several clinical factors, such as duration of illness and the effect size of the pRNFL, macular GCL-IPL, MT, and MV. CONCLUSION: Thinning of the pRNFL, macular GCL-IPL, MT, and MV and enlargement of the OCV in SSD were observed. Retinal abnormalities may be applicable as state/trait markers in SSDs. The accumulated evidence was mainly cross-sectional and requires verification by longitudinal studies to characterize the relationship between OCT findings and clinical factors.

Mediating effects of self-stigma and depression on the association between autistic symptoms and recovery in patients with schizophrenia-spectrum disorders: a cross-sectional study.

BACKGROUND: Several studies have indicated that self-stigma is associated with depressive symptoms and could be a barrier to recovery in patients with schizophrenia-spectrum disorders. More recently, an association between autistic symptoms and self-stigma was found in schizophrenia-spectrum patients. This study aimed to investigate the association between self-stigma, autistic and depressive symptoms, and recovery in patients with schizophrenia. METHODS: In total, 105 participants were evaluated using the Autism Spectrum Quotient, the Internalized Stigma of Mental Illness Scale, the Quick Inventory of Depressive Symptomatology, and the Recovery Assessment Scale to investigate autistic symptoms, self-stigma, depressive symptoms, and recovery, respectively. The relationship between self-stigma, autistic symptoms, depressive symptoms, and recovery was assessed using structural equation modeling analysis. RESULTS: Impaired attention switching, one symptom of autism, was found to positively affect stereotype endorsement, which negatively influenced recovery through depressive symptoms. Moreover, problems with communication skills negatively affected recovery through depressive symptoms. Concerning self-stigma, stereotype endorsement and perceived discrimination had a negative effect on recovery through depressive symptoms, whereas stigma resistance had a direct negative effect on recovery. CONCLUSIONS: This study may provide meaningful insight into the psychological structure of recovery and could inform effective interventions for patients with schizophrenia-spectrum disorders. This was a cross-sectionally designed study; therefore, further longitudinal studies are needed to identify the causal relationships between self-stigma, autistic and depressive symptoms, and recovery.