P Allen

Publications (3)13.06 Total impact

• Source

  Available from: Stefan Borgwardt

  Article: Neuroimaging predictors of transition to psychosis--a systematic review and meta-analysis.

  R Smieskova, P Fusar-Poli, P Allen, K Bendfeldt, R D Stieglitz, J Drewe, E W Radue, P K McGuire, A Riecher-Rössler, S J Borgwardt
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  ABSTRACT: In early stage psychosis research the identification of neurobiological correlates of vulnerability to schizophrenia is an important hurdle. We systematically reviewed the neuroimaging publications on high-risk subjects with subsequent transition to psychosis (HR-T) and conducted a meta-analysis calculating the effect size Cohen's d. Out of 30 identified studies 25 met the inclusion criteria. Structural (s)MRI studies showed small to medium effect sizes of decreased prefrontal, cingulate, insular and cerebellar gray matter volume in HR-T compared to high-risk subjects without transition (HR-NT). Meta-analysis revealed relatively larger whole brain volumes in HR-T compared to HR-NT subjects (mean Cohen's d 0.36, 95% CI 0.27-0. 46). Compared to HR-NT, HR-T subjects showed in functional imaging studies reduced brain activation in prefrontal cortex, reduced neuronal density, and increased membrane turnover in frontal and cingulate cortex with medium to large effect sizes. Despite methodological differences between studies, structural and neurochemical abnormalities in prefrontal, anterior cingulate, medial temporal and cerebellar cortex might be predictive for development of psychosis within HR subjects.
  Neuroscience & Biobehavioral Reviews 02/2010; 34(8):1207-22. · 8.65 Impact Factor
• Source

  Available from: Stefan Borgwardt

  Article: The effects of antipsychotics on the brain: what have we learnt from structural imaging of schizophrenia?--a systematic review.

  R Smieskova, P Fusar-Poli, P Allen, K Bendfeldt, R D Stieglitz, J Drewe, E W Radue, P K McGuire, A Riecher-Rössler, S J Borgwardt
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  ABSTRACT: Despite a large number of neuroimaging studies in schizophrenia reporting subtle brain abnormalities, we do not know to what extent such abnormalities reflect the effects of antipsychotic treatment on brain structure. We therefore systematically reviewed cross-sectional and follow-up structural brain imaging studies of patients with schizophrenia treated with antipsychotics. 30 magnetic resonance imaging (MRI) studies were identified, 24 of them being longitudinal and six cross-sectional structural imaging studies. In patients with schizophrenia treated with antipsychotics, reduced gray matter volume was described, particularly in the frontal and temporal lobes. Structural neuroimaging studies indicate that treatment with typical as well as atypical antipsychotics may affect regional gray matter (GM) volume. In particular, typical antipsychotics led to increased gray matter volume of the basal ganglia, while atypical antipsychotics reversed this effect after switching. Atypical antipsychotics, however, seem to have no effect on basal ganglia structure.
  Current pharmaceutical design 02/2009; 15(22):2535-49. · 4.41 Impact Factor
• Article: Neuroimaging predictors of transition to psychosis—A systematic review and meta-analysis

  R. Smieskova, P. Fusar-Poli, P. Allen, K. Bendfeldt, R.D. Stieglitz, J. Drewe, E.W. Radue, P.K. McGuire, A. Riecher-Rössler, S.J. Borgwardt
  [show abstract] [hide abstract]
  ABSTRACT: ObjectivesIn early stage psychosis research the identification of neurobiological correlates of vulnerability to schizophrenia is an important hurdle.MethodsWe systematically reviewed the neuroimaging publications on high-risk subjects with subsequent transition to psychosis (HR-T) and conducted a meta-analysis calculating the effect size Cohen's d.ResultsOut of 30 identified studies 25 met the inclusion criteria. Structural (s)MRI studies showed small to medium effect sizes of decreased prefrontal, cingulate, insular and cerebellar gray matter volume in HR-T compared to high-risk subjects without transition (HR-NT). Meta-analysis revealed relatively larger whole brain volumes in HR-T compared to HR-NT subjects (mean Cohen's d 0.36, 95% CI 0.27–0. 46). Compared to HR-NT, HR-T subjects showed in functional imaging studies reduced brain activation in prefrontal cortex, reduced neuronal density, and increased membrane turnover in frontal and cingulate cortex with medium to large effect sizes.ConclusionsDespite methodological differences between studies, structural and neurochemical abnormalities in prefrontal, anterior cingulate, medial temporal and cerebellar cortex might be predictive for development of psychosis within HR subjects.
  Neuroscience & Biobehavioral Reviews.