title: Amyloid-beta and depression in healthy older adults: a systematic review.
abstract: OBJECTIVE
  Depression has been shown to be a risk factor for Alzheimer's disease (AD), and in older adults may provide a marker for the beginning of the prodromal phase of AD. The purpose of this systematic review is to examine the relationship between amyloid-β (Aβ), a key biomarker of AD, and depression in older adults.
  
  
  METHODS
  The literature search was limited to studies conducted from 2006 to 2014 that were published in English in peer-reviewed journals. Studies were selected if they included a group of older adults who either met established criteria for Major Depressive Disorder or Dysthymia; or were assessed for depressive symptoms on a standardised measure. Studies were also required to include an outcome variable that was a direct measure of Aβ levels in either blood or cerebrospinal fluid (CSF) samples, or via neuroimaging techniques such as positron emission tomography (PET).
  
  
  RESULTS
  Nineteen studies were identified, 15 of which found significant differences in Aβ levels between depressed and non-depressed older adults. However, studies were limited by their cross-sectional design, reliance on blood-based measures of Aβ, and potential sample bias.
  
  
  CONCLUSIONS
  Future investigations should consider prospective longitudinal design using neuroimaging and CSF measures of Aβ.
authors.affiliation: School of Psychology, Deakin University, Geelong, Victoria, Australia Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia karra.harrington@florey.edu.au.
authors.forename: Karra D
authors.initials: KD
authors.lastname: Harrington
authors.affiliation: Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia Department of Neurology, Warren Alpert School of Medicine, Brown University, Providence, RI, USA.
authors.forename: Yen Ying
authors.initials: YY
authors.lastname: Lim
authors.affiliation: School of Psychology, Deakin University, Geelong, Victoria, Australia.
authors.forename: Emma
authors.initials: E
authors.lastname: Gould
authors.affiliation: Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia CogState Ltd., Melbourne, Victoria, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Maruff
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism; D000544:Alzheimer Disease / Q000150:complications* / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001921:Brain / Q000378:metabolism*; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000150:complications* / Q000378:metabolism*; D015577:Geriatric Assessment / Q000706:statistics & numerical data*; D006801:Humans; D059906:Neuroimaging; D049268:Positron-Emission Tomography
chemical_list: D016229:Amyloid beta-Peptides; D015415:Biomarkers
keywords: Alzheimer’s disease; Amyloid-β; Depression