Cognitive deficits among people with schizophrenia and prediabetes or diabetes

Insulin-resistance as a modifiable pathway to cognitive dysfunction in schizophrenia: A systematic review

BACKGROUND

Cognitive deficits are difficult to treat and negatively influence quality of life and functional outcomes of persons with schizophrenia. In the last twenty years, extensive literature demonstrated that persons with diabetes and insulin resistance (IR) also display cognitive deficits. Being type 2 diabetes (T2DM) and IR highly frequent in persons with schizophrenia, it is plausible to hypothesize that these conditions might play a role in determining dyscognition. If that is the case, acting on glucose dysmetabolism may eventually improve cognitive functioning. This review aims at: 1. evaluating the association between IR or T2DM and cognitive dysfunction in schizophrenia; 2. reviewing the evidence that pharmacological treatment of IR or T2DM may improve dyscognition in schizophrenia.

METHODS

Two systematic searches were conducted in PubMed, PsycInfo, and Scopus. We followed the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines.

RESULTS

From the first search we included 17 studies, 8 on the effects of T2DM and 9 on the effects of IR-other prediabetes measures on cognition in persons with schizophrenia. From the second search we included 12 studies investigating the effect on cognition of glucose (4 studies), insulin (2 studies), metformin (2 studies), PPAR-γ agonists (2 studies), GLP-1 agonist (1 study), bromocriptine (1 study).

CONCLUSIONS

T2DM was associated with worse cognitive function in persons with schizophrenia, while IR was less strongly associated with cognitive dysfunction. Evidence regarding the efficacy of glucose-lowering medications on cognition in schizophrenia is inconclusive, yet methodological issues likely contribute to explain conflicting results.

Cancer-related cognitive impairment as a key contributor to psychopathology in cancer survivors: implications for prevention, treatment and supportive care

A significant proportion of cancer survivors will experience some form of mental health compromise across domains including mood, anxiety, psychosis, eating disorders, and substance use. This psychopathology within cancer survivors is related to a range of negative outcomes and can also have a substantial negative impact on quality of life. Along with psychopathology, cognitive impairments are also commonly experienced, resulting in deficits in memory, reasoning, decision-making, speed of processing, and concentration, collectively referred to as cancer-related cognitive impairment (CRCI). Within the non-oncology literature, cognitive deficits are consistently demonstrated to be a key transdiagnostic aetiological feature of psychopathology, functionally contributing to the development and perpetuation of symptoms. Whilst there is an acknowledgement of the role mental health concerns might play in the development of and perception of CRCI, there has been limited acknowledgement and research exploring the potential for CRCI to functionally contribute toward the development of transdiagnostic psychopathology in cancer survivors beyond simply psychosocial distress. Given the theoretical and empirical evidence suggesting cognitive deficits to be an aetiological factor in psychopathology, we provide a rationale for the potential for CRCI to be a factor in the development and perpetuation of transdiagnostic psychopathology in cancer survivors. This potential functional association has significant implications for risk identification, prevention, treatment, and supportive cancer care approaches regarding psychopathology in cancer survivorship. We conclude by providing directions for future research in this area.

Can neurocognitive performance account for dimensional paranoid ideation?

OBJECTIVE

Paranoid ideation underlies numerous psychological disorders and has debilitating effects on daily life. Deficits in neurocognition are highlighted as a contributing factor to paranoid-related disorders, but the impact on the symptom-level experience of paranoid ideation is unclear. This study aimed to employ a dimensional approach to understand the association between neurocognition and the severity and presence of paranoid ideation.

METHODS

400 participants, representative of the general population of the USA, completed an online questionnaire consisting of the Brief Symptom Inventory-53, and demographic and clinical questions. The participants then completed four computerised neurocognitive tasks measuring working memory, shifting, inhibition, and speed of processing.

RESULTS

Speed of processing accounted for unique variance in the severity of paranoid ideation with a small effect size, after controlling for covariates. Working memory, shifting, and inhibition could not uniquely or collectively, account for paranoid ideation. Neurocognitive performance could not distinguish between individuals with and without paranoid ideation experiences.

CONCLUSIONS

This research supports the body of literature that speed of information processing may be a key feature of paranoid ideation. Future research should employ non-linear dynamic methods to better understand the potential interactions between neurocognitive components and how this may relate to paranoid ideation.

The volume of gray matter mediates the relationship between glucolipid metabolism and neurocognition in first-episode, drug-naïve patients with schizophrenia

We aimed to examine the hypotheses that glucolipid metabolism is linked to neurocognition and gray matter volume (GMV) and that GMV mediates the association of glucolipid metabolism with neurocognition in first-episode, drug-naïve (FEDN) patients with schizophrenia. Parameters of glucolipid metabolism, neurocognition, and magnetic resonance imaging were assessed in 63 patients and 31 controls. Compared to controls, patients exhibited higher levels of fasting glucose, triglyceride, and insulin resistance index, lower levels of cholesterol and high-density lipoprotein cholesterol, poorer neurocognitive functions, and decreased GMV in the bilateral insula, left middle occipital gyrus, and left postcentral gyrus. In the patient group, triglyceride levels and the insulin resistance index exhibited a negative correlation with Rapid Visual Information Processing (RVP) mean latency, a measure of attention within the Cambridge Neurocognitive Test Automated Battery (CANTAB), while showing a positive association with GMV in the right insula. The mediation model revealed that triglyceride and insulin resistance index had a significant positive indirect (mediated) influence on RVP mean latency through GMV in the right insula. Glucolipid metabolism was linked to both neurocognitive functions and GMV in FEDN patients with schizophrenia, with the effect pattern differing from that observed in chronic schizophrenia or schizophrenia comorbid with metabolic syndrome. Moreover, glucolipid metabolism might indirectly contribute to neurocognitive deficits through the mediating role of GMV in these patients.