Higher schizotypy predicts better metabolic profile in unaffected siblings of patients with schizophrenia

Insulin Resistance, Temperament and Personality Traits Are Associated with Anhedonia in a Transdiagnostic Sample

Anhedonia constitutes a core symptom of major depressive disorder (MDD) mediating the ultimate goal of MDD treatment: functional remission. Anhedonia is also present in other clinical populations, including patients with chronic pain. Recent data links anhedonia to insulin resistance (IR). Some researchers have underlined a different dimension of anhedonia as a temperament/personality trait. The objective of this post-hoc analysis was to explore the links between anhedonia (main outcome) and (1) IR, (2) temperamental, personality, and schizotypy traits (exposures). The study population included patients with MDD, fibromyalgia, and healthy controls. Participants were split into groups: (1) insulin resistant (IR[+] n = 69, HOMA-IR ≥ 2.1) and (2) insulin sensitive (IR[-] n = 69, HOMA-IR < 2.1). Anhedonia was significantly higher in the IR[+] group than the IR[-] group. IR was a predictor of higher anhedonia levels. IR[+] vs. IR[-] participants showed higher levels of anxiety and lower levels of hyperthymic affective temperaments, as well as conscientiousness and emotional stability personality traits. Depressive, irritable, and anxious temperaments, cognitive disorganization, and introvertive anhedonia positively predicted anhedonia, while hyperthymic temperament, conscientiousness, extraversion, and emotional stability traits negatively predicted anhedonia. IR partially mediated the relationship between depressive temperament and anhedonia. In sum, IR, affective temperaments, and personality traits are predictors of anhedonia.

Positive and negative schizotypy personality traits are lower in individuals on ketogenic diet in a non-clinical sample

Schizotypal personality comprises traits such as odd beliefs, perceptual abnormalities, and social difficulties; these traits are distributed throughout the general population. While not meeting the clinical threshold for schizophrenia or schizotypal personality disorder, schizotypal personality traits still provide insights for understanding early clinical risk factors. Ketogenic diet reportedly reduces psychotic symptoms in preclinical and clinical studies. Therefore, we investigated whether ketogenic diet is associated with lower schizotypal traits in the general population. Participants following a ketogenic or other diet were recruited using opportunity sampling. Individuals completed a survey investigating general demographic, socioeconomic, health, diet and lifestyle questions, followed by the Schizotypal Personality Questionnaire - Brief Revised version (SPQ-BR). We found that individuals following a ketogenic diet (n = 118) had lower ideas of reference, magical thinking, suspiciousness, unusual perceptions, constricted affect, social anxiety scores, cognitive (positive) perceptual scores, interpersonal (negative) scores and total SPQ-BR compared to individuals on the other diets (n = 139). Magical thinking, constricted affect, social anxiety, cognitive perceptual, interpersonal scores and total SPQ-BR scores remained significant when we controlled for body mass index (BMI) and age. Disorganised features were not influenced by ketogenic diet. The longer individuals adhered to a ketogenic diet the lower their positive and negative schizotypy traits. These findings highlight that ketogenic diet is associated with lower non-clinical schizotypal personality traits. Our results suggest that ketogenic diet might have potential prophylactic properties for individuals at-risk for psychosis.

Glucose homeostasis in unaffected first-degree relatives of schizophrenia patients: A systematic review and meta-analysis

It has been proposed that type 2 diabetes and schizophrenia-spectrum disorders share overlapping genetic backgrounds. Therefore, we aimed to perform a systematic review and meta-analysis of studies comparing fasting levels of glucose and insulin, the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), glucose levels during the oral glucose tolerance test (OGTT) and the levels of glycated hemoglobin (HbA1c) in unaffected first-degree relatives of patients with schizophrenia and controls. Online searches covered the publication period from database inception until May 8th 2020. Meta-analyses were performed using random-effects models with Hedges' g as the effect size estimate. Out of 2556 records identified, 12 studies representing 672 relatives of schizophrenia patients and 6446 controls were found to be eligible. There were no significant differences in fasting levels of glucose (g = 0.54, 95%CI = -0.26 to 1.35, p = 0.188) and insulin (g = 0.07, 95%CI = -0.14 to 0.29, p = 0.491), HOMA-IR (g = 0.12, 95%CI = -0.19 to 0.43, p = 0.433), and the levels of HbA1c (g = 0.38, 95%CI = -0.02 to 0.77, p = 0.061) between relatives of schizophrenia patients and controls. Two studies demonstrated significantly higher 2-hour glucose levels during OGTT in relatives of patients with schizophrenia (g = 0.90, 95%CI = 0.49 to 1.31, p < 0.001). Our findings do not support the hypothesis that familial liability to psychosis is related to altered fasting parameters of glucose homeostasis. However, this population might show impaired glucose tolerance. More studies are needed to confirm these observations.

Is there an association between cardiorespiratory fitness and stage of illness in psychotic disorders? A systematic review and meta-analysis

BACKGROUND

Clinical staging models describe where an individual exists on a continuum from asymptomatic at-risk states (Stage 0) through to established late-stage disease (Stage 4). We applied this framework to systematically assess evidence for any associations between objectively assessed cardiorespiratory fitness (CRF) and stage of psychosis.

METHOD

Nine electronic databases were searched for relevant publications from inception until October 31, 2019. Pooled effect sizes (Hedges' g and 95% confidence intervals (95% CI)) were estimated for differences in CRF for studies that reported mean oxygen uptake (max, peak, or predicted VO₂ in ml/kg/min).

RESULTS

Thirty-eight studies were eligible. Findings indicated that suboptimal CRF can be present at Stages 0 and 1. Meta-analyses of 22 studies demonstrated that CRF was significantly reduced in individuals classified between Stages 1 and 4 compared with matched or general population controls (g = -0.93; 95% CI -1.14, -0.71). Mean VO₂ was decreased by 28% in Stage 4 compared with Stage 1 (34.1 vs. 24.66 ml/kg/min); the largest effect size for CRF reduction was reported between Stages 2 and 3 (g = -1.16; 95% CI -1.31, -1.03).

CONCLUSIONS

Although not identifying direct causal links between clinical stage and CRF, using this framework may enhance understanding of co-associations between mental and physical health markers across the entire spectrum of psychosis. Limitations include lack of research on CRF in Stages 0 and 1 alongside problems determining stage in some studies. However, impaired CRF is reported in emerging psychosis, supporting calls that early intervention programmes should address both mental and physical wellbeing.

Psychometric liability to psychosis and childhood adversities are associated with shorter telomere length: A study on schizophrenia patients, unaffected siblings, and non-clinical controls

Compared to the general population, individuals diagnosed with Schizophrenia (SCZ) experience a higher frequency and an earlier onset of chronic medical disorders, resulting in a reduction in life expectancy by an average of 15-25 years. Recently, it has been hypothesized that SCZ is a syndrome of accelerated aging. Childhood adversity was also associated with the pathogenesis and course of SCZ. Our hypothesis was that both SCZ patients and their unaffected siblings would have shorter telomere length (TL) compared to of non-clinical controls. Our additional goals were to determine (1) whether shorter TL correlates with intermediate phenotypes of SCZ (i.e. Psychosis-like symptoms and schizotypal traits); and (2) whether childhood adversities have a moderating role in TL shortening among SCZ and their unaffected siblings. To this end, SCZ patients (n = 100), their unaffected siblings (n = 100) and non-clinical controls (n = 100) were enrolled. The main variables were TL, measured by aTL-qPCR; psychotic-like and schizotypal symptoms, assessed by The Community Assessment of Psychic Experience (CAPE) and the Structured Interview for Schizotypy-Revised (SIS-R), respectively; and childhood adversities evaluated by the Childhood Experience of Care and Abuse (CECA)-Interview. Potentially relevant variables also included in the analyses were: Global Assessment of Functioning (GAF) scores, cognitive performance, and socio-demographic features. In contrast to our hypothesis patients had similar TL when compared to the non-clinical controls. Interestingly, unaffected siblings had longer TL compared to both patients and controls (p < 0.001). Independent from group status a negative correlation was observed between TL and psychotic-like symptoms as rated by the CAPE (p < 0.01). Childhood adversities, especially loneliness between ages 0 and 11 were also negatively associated with TL (p < 0.05). Our findings suggest that psychometric liability to psychosis and childhood adversities may be associated with shorter TL. Unaffected siblings had longer TL, suggesting the potential role of resilience on both the TL and the clinical presentation. These findings must be considered preliminary, calling for larger-scale replication efforts.