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Previous reviews suggest there is minimal evidence for an association between duration of untreated psychosis (DUP) and neurocognition. This is based on tallied findings of studies with small samples and neurocognition viewed as a single construct. We aimed to conduct a systematic review and meta-analysis examining the association between DUP and individual neurocognitive domains and tests in first-episode psychosis (FEP).
MOOSE and PRISMA guidelines were followed. Forty-three studies involving 4647 FEP patients were included. For studies providing correlations between DUP and neurocognition, 12 separate meta-analyses were performed based on neurocognitive domains/indices. The influence of demographic/clinical variables was tested using weighted linear meta-regression analyses.
The relationship between DUP and most neurocognitive domains/indices was not significant. Longer DUP was associated with a larger cognitive deterioration index, i.e. current minus premorbid intellectual functioning (N = 4; mean ES −0.213, 95% confidence interval (CI) (−0.344 to −0.074), p = 0.003). Findings were homogeneous, with no evidence of publication bias or significant influence from moderators. For studies providing mean and standard deviations for neurocognitive measures and DUP, 20 meta-regressions were performed on individual neurocognitive tests. One significant finding emerged showing that longer DUP was associated with fewer Wisconsin Card Sorting Test-perseverative errors (mean ES −0.031, 95% CI (−0.048 to −0.013), p < 0.001). Exploratory meta-regressions in studies with mean DUP <360 days showed longer DUP was significantly associated with poorer performance on Trail Making Test A and B and higher Full-Scale IQ.
There may not be a generalised association between DUP and neurocognition, however, specific cognitive functions may be associated with longer DUP or delayed help-seeking.
Cognitive deficits are predictors of functional outcome in patients with psychosis. While conventional antipsychotics are relatively effective on positive symptoms, their impact on negative and cognitive symptoms is limited. Recent studies have established a link between oxidative stress and neurocognitive deficits in psychosis. N-acetylcysteine (NAC), a glutathione precursor with glutamatergic properties, has shown efficacy on negative symptoms and functioning in patients with schizophrenia and bipolar disorder, respectively. However, there are few evidence-based approaches for managing cognitive impairment in psychosis. The present study aims to examine the cognitive effects of adjunctive NAC treatment in a pooled subgroup of participants with psychosis who completed neuropsychological assessment in two trials of both schizophrenia and bipolar disorder.
A sample of 58 participants were randomized in a double fashion to receive 2 g/day of NAC (n = 27) or placebo (n = 31) for 24 weeks. Attention, working memory and executive function domains were assessed. Differences between cognitive performance at baseline and end point were examined using Wilcoxon's test. The Mann–Whitney test was used to examine the differences between the NAC and placebo groups at the end point.
Participants treated with NAC had significantly higher working memory performance at week 24 compared with placebo (U = 98.5, p = 0.027).
NAC may have an impact on cognitive performance in psychosis, as a significant improvement in working memory was observed in the NAC-treated group compared with placebo; however, these preliminary data require replication. Glutamatergic compounds such as NAC may constitute a step towards the development of useful therapies for cognitive impairment in psychosis.
The longitudinal neuropsychological study of first-episode early-onset psychosis (EOP) patients, whose brain maturation is still in progress at the time of illness onset, provides a unique opportunity to compare their cognitive development with that of healthy subjects, in search of specific patterns resulting from the interaction between neurodevelopmental processes and the presence of psychotic disorders.
Seventy-five first-episode EOP patients (schizophrenia n = 35; bipolar disorder n = 17; other forms of psychosis n = 23) with a mean age of 15.53 years were assessed with a neuropsychological battery that included measures of attention, working memory, memory and executive functions within 6 months following the onset of the first psychotic symptom (baseline) and 2 years later. Psychotic symptoms were assessed at both times with the Positive and Negative Symptom Scale (PANSS). Seventy-nine healthy subjects matched for age and education served as controls.
EOP patients showed significant cognitive impairment at both baseline and the 2-year follow-up, with no significant differences between diagnostic groups at either time. Both healthy controls and EOP patients improved in all cognitive measures, except for patient working memory. Improvement in patient attention lost significance after controlling for psychotic symptom reduction. No significant time/diagnosis interaction was found among patients (p > 0.405).
Cognitive impairment in EOP is already present at the first episode, and cognitive development seems to be arrested early in EOP patients compared to their healthy peers, at least for some cognitive functions. These and previous similar results support the neurodevelopmental hypothesis of psychosis.
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