Centre for Youth Mental Health - Research Publications
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ItemNo Preview AvailableIntelligence trajectories in individuals at ultra-high risk for psychosis: An 8-year longitudinal analysis(ELSEVIER, 2022-10)Cognitive impairment is a well-documented predictor of transition to a full-threshold psychotic disorder amongst individuals at ultra-high risk (UHR) for psychosis. However, less is known about whether change in cognitive functioning differs between those who do and do not transition. Studies to date have not examined trajectories in intelligence constructs (e.g., acquired knowledge and fluid intelligence), which have demonstrated marked impairments in individuals with schizophrenia. This study aimed to examine intelligence trajectories using longitudinal data spanning an average of eight years, where some participants completed assessments over three time-points. Participants (N = 139) at UHR for psychosis completed the Wechsler Abbreviated Scale of Intelligence (WASI) at each follow-up. Linear mixed-effects models mapped changes in WASI Full-Scale IQ (FSIQ) and T-scores on Vocabulary, Similarities, Block Design, and Matrix Reasoning subtests. The sample showed stable and improving trajectories for FSIQ and all subtests. There were no significant differences in trajectories between those who did and did not transition to psychosis and between individuals with good and poor functional outcomes. However, although not significant, the trajectories of the acquired knowledge subtests diverged between transitioned and non-transitioned individuals (β = -0.12, 95 % CI [-0.29, 0.05] for Vocabulary and β = -0.14, 95 % CI [-0.33, 0.05] for Similarities). Overall, there was no evidence for long-term deterioration in intelligence trajectories in this UHR sample. Future studies with a larger sample of transitioned participants may be needed to explore potential differences in intelligence trajectories between UHR transition groups and other non-psychosis outcomes.
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ItemTwelve-Month Cognitive Trajectories in Individuals at Ultra-High Risk for Psychosis: A Latent Class Analysis(Oxford University Press (OUP), 2022-01-01)Abstract Understanding longitudinal cognitive performance in individuals at ultra-high risk for psychosis (UHR) is important for informing theoretical models and treatment. A vital step in this endeavor is to determine whether there are UHR subgroups that have similar patterns of cognitive change over time. The aims were to: i) identify latent class trajectories of cognitive performance over 12-months in UHR individuals, ii) identify baseline demographic and clinical predictors of the resulting classes, and iii) determine whether trajectory classes were associated with transition to psychosis or functional outcomes. Cognition was assessed using the Brief Assessment of Cognition in Schizophrenia (BACS) at baseline, 6- and 12-months (N = 288). Using Growth Mixture Modeling, a single unimpaired improving trajectory class was observed for motor function, speed of processing, verbal fluency, and BACS composite. A two-class solution was observed for executive function and working memory, showing one unimpaired and a second impaired class. A three-class solution was found for verbal learning and memory: unimpaired, mildly impaired, and initially extremely impaired, but improved (“caught up”) to the level of the mildly impaired. IQ, omega-3 index, and premorbid adjustment were associated with class membership, whereas clinical variables (symptoms, substance use), including transition to psychosis, were not. Working memory and verbal learning and memory trajectory class membership was associated with functioning outcomes. These findings suggest there is no short-term progressive cognitive decline in help-seeking UHR individuals, including those who transition to psychosis. Screening of cognitive performance may be useful for identifying UHR individuals who may benefit from targeted cognitive interventions.
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ItemNo Preview AvailableImpaired olfactory ability associated with larger left hippocampus and rectus volumes at earliest stages of schizophrenia: A sign of neuroinflammation?(ELSEVIER IRELAND LTD, 2020-07)Impaired olfactory identification has been reported as a first sign of schizophrenia during the earliest stages of illness, including before illness onset. The aim of this study was to examine the relationship between volumes of these regions (amygdala, hippocampus, gyrus rectus and orbitofrontal cortex) and olfactory ability in three groups of participants: healthy control participants (Ctls), patients with first-episode schizophrenia (FE-Scz) and chronic schizophrenia patients (Scz). Exploratory analyses were performed in a sample of individuals at ultra-high risk (UHR) for psychosis in a co-submission paper (Masaoka et al., 2020). The relationship to brain structural measures was not apparent prior to psychosis onset, but was only evident following illness onset, with a different pattern of relationships apparent across illness stages (FE-Scz vs Scz). Path analysis found that lower olfactory ability was related to larger volumes of the left hippocampus and gyrus rectus in the FE-Scz group. We speculate that larger hippocampus and rectus in early schizophrenia are indicative of swelling, potentially caused by an active neurochemical or immunological process, such as inflammation or neurotoxicity, which is associated with impaired olfactory ability. The volumetric decreases in the chronic stage of Scz may be due to degeneration resulting from an active immune process and its resolution.
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ItemNeurocognitive predictors of transition to psychosis: medium- to long-term findings from a sample at ultra-high risk for psychosis(CAMBRIDGE UNIV PRESS, 2013-11)BACKGROUND: Individuals at ultra-high risk (UHR) for psychosis show reduced neurocognitive performance across domains but it is unclear which reductions are associated with transition to frank psychosis. The aim of this study was to investigate differences in baseline neurocognitive performance between UHR participants with (UHR-P) and without transition to psychosis (UHR-NP) and a healthy control (HC) group and examine neurocognitive predictors of transition over the medium to long term. METHOD: A sample of 325 UHR participants recruited consecutively from the Personal Assessment and Crisis Evaluation (PACE) Clinic in Melbourne and 66 HCs completed a neurocognitive assessment at baseline. The UHR group was followed up between 2.39 and 14.86 (median = 6.45) years later. Cox regression was used to investigate candidate neurocognitive predictors of psychosis onset. RESULTS: The UHR group performed more poorly than the HC group across a range of neurocognitive domains but only performance on digit symbol coding and picture completion differed between the groups. The risk of transition was only significantly associated with poorer performance on visual reproduction [hazard ratio (HR) 0.919, 95% confidence interval (CI) 0.876-0.965, p = 0.001] and matrix reasoning (HR 0.938, 95% CI 0.883-0.996, p = 0.037). These remained significant even after controlling for psychopathology at baseline. CONCLUSIONS: This study is the longest follow-up of an UHR sample to date. UHR status was associated with poorer neurocognitive performance compared to HCs on some tasks. Cognition at identification as UHR was not a strong predictor of risk for transition to psychosis. The results suggests the need to include more experimental paradigms that isolate discrete cognitive processes to better understand neurocognition at this early stage of illness.
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ItemNo Preview AvailablePhenylthiocarbamide (PTC) perception in ultra-high risk for psychosis participants who develop schizophrenia: Testing the evidence for an endophenotypic marker(ELSEVIER IRELAND LTD, 2012-08-30)Reports suggesting that schizophrenia participants are more likely to be phenylthiocarbamide (PTC) non-tasters when compared to controls have recently been controversial. If supported, a genetic-based phenotypic variation in PTC taster status is implicated, suggesting a greater illness risk for those participants with recessive alleles for the TAS2R38 receptor. Should PTC insensitivity be a schizophrenia endophenotype, then it would be expected in follow-up of ultra high-risk for psychosis participants who later develop schizophrenia (UHR-S). UHR-S was hypothesised to show reduced PTC sensitivity compared to those who were previously at risk, but did not transition (UHR-NP). PTC perception was assessed in 219 UHR participants at long-term follow-up, of whom 53 had transitioned to psychosis (UHR-P) during the follow-up period. Fifteen of the 219 participants were diagnosed with schizophrenia. Seventy-eight had a family history of psychotic disorder. No differences in PTC taster status were found in UHR participants based upon transition to psychosis status, schizophrenia diagnosis, or family history of schizophrenia. This report indicates that schizophrenia development among UHR participants is not associated with PTC tasting deficits and fails to support previous findings that inability to detect the bitter taste of PTC is a schizophrenia endophenotype.