title: Linear and non-linear associations of symptom dimensions and cognitive function in first-onset psychosis.
abstract: BACKGROUND
  Associations between symptom dimensions and cognition have been mainly studied in non-affective psychosis. The present study investigated whether previously reported associations between cognition and four symptom dimensions (reality distortion, negative symptoms, disorganisation and depression) in non-affective psychosis generalise to a wider spectrum of psychoses. It also extended the research focus to mania, a less studied symptom dimension.
  
  
  METHODS
  Linear and non-linear (quadratic, curvilinear or inverted-U-shaped) associations between cognition and the above five symptom dimensions were examined in a population-based cohort of 166 patients with first-onset psychosis using regression analyses.
  
  
  RESULTS
  Negative symptoms showed statistically significant linear associations with IQ and processing speed, and a significant curvilinear association with verbal memory/learning. Significant quadratic associations emerged between mania and processing speed and mania and executive function. The contributions of mania and negative symptoms to processing speed were independent of each other. The findings did not differ between affective and non-affective psychoses, and survived correction for multiple testing.
  
  
  CONCLUSIONS
  Mania and negative symptoms are associated with distinct patterns of cerebral dysfunction in first-onset psychosis. A novel finding is that mania relates to cognitive performance by a complex response function (inverted-U-shaped relationship). The associations of negative symptoms with cognition include both linear and quadratic elements, suggesting that this dimension is not a unitary concept. These findings cut across affective and non-affective psychoses, suggesting that different diagnostic entities within the psychosis spectrum lie on a neurobiological continuum.
authors: NIHR Biomedical Research Centre for Mental Health, South London and Maudsley NHS Foundation Trust and Institute of Psychiatry, King's College London, De Crespigny Park, London SE5 8AF, UK. eugenia.kravariti@kcl.ac.uk
authors: Eugenia
authors: E
authors: Kravariti
authors: Manuela
authors: M
authors: Russo
authors: Evangelos
authors: E
authors: Vassos
authors: Kevin
authors: K
authors: Morgan
authors: Paul
authors: P
authors: Fearon
authors: Jolanta W
authors: JW
authors: Zanelli
authors: Arsime
authors: A
authors: Demjaha
authors: Julia M
authors: JM
authors: Lappin
authors: Elias
authors: E
authors: Tsakanikos
authors: Paola
authors: P
authors: Dazzan
authors: Craig
authors: C
authors: Morgan
authors: Gillian A
authors: GA
authors: Doody
authors: Glynn
authors: G
authors: Harrison
authors: Peter B
authors: PB
authors: Jones
authors: Robin M
authors: RM
authors: Murray
authors: Abraham
authors: A
authors: Reichenberg
mesh_terms: D000293:Adolescent; D000328:Adult; D001244:Association; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology*; D015331:Cohort Studies; D018672:Community Health Planning; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D017711:Nonlinear Dynamics; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000150:complications* / Q000523:psychology*; D012737:Sex Factors; D055815:Young Adult