title: Perinatal depression and omega-3 fatty acids: a Mendelian randomisation study.
abstract: BACKGROUND
  There have been numerous studies investigating the association between omega-3 fatty acids (FAs) and depression, with mixed findings. We propose an approach which is largely free from issues such as confounding or reverse causality, to investigate this relationship using observational data from a pregnancy cohort.
  
  
  METHODS
  The Avon Longitudinal Study of Parents and Children (ALSPAC) cohort collected information on FA levels from antenatal blood samples and depressive symptoms at several time points during pregnancy and the postnatal period. Conventional epidemiological analyses were used in addition to a Mendelian randomisation (MR) approach to investigate the association between levels of two omega-3 FAs (docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)) and perinatal onset depression, antenatal depression (AND) and postnatal depression (PND).
  
  
  RESULTS
  Weak evidence of a positive association with both EPA (OR=1.07; 95% CI: 0.99-1.15) and DHA (OR=1.08; 95% CI: 0.98-1.19) with perinatal onset depression was found using a multivariable logistic regression adjusting for social class and maternal age. However, the strength of association was found to attenuate when using an MR analysis to investigate DHA.
  
  
  CONCLUSIONS
  Pleiotropy is a potential limitation in MR analyses; we assume that the genetic variants included in the instrumental variable are associated only with our trait of interest (FAs) and thus cannot influence the outcome via any other pathway.
  
  
  CONCLUSIONS
  We found weak evidence of a positive association between omega-3 FAs and perinatal onset depression. However, without confirmation from the MR analysis, we are unable to draw conclusions regarding causality.
authors.affiliation: MRC Integrative Epidemiology Unit, School of Social and Community Medicine, University of Bristol, Barley House Oakfield Grove, Bristol BS8 2BN, UK; Centre for Academic Mental Health, School of Social and Community Medicine University of Bristol, Barley House Oakfield Grove, Bristol BS8 2BN, UK. Electronic address: Hannah.Sallis@bristol.ac.uk.
authors.forename: Hannah
authors.initials: H
authors.lastname: Sallis
authors.affiliation: Centre for Child and Adolescent Health, School of Social and Community Medicine, University of Bristol, Barley House Oakfield Grove, Bristol BS8 2BN, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Steer
authors.affiliation: MRC Integrative Epidemiology Unit, School of Social and Community Medicine, University of Bristol, Barley House Oakfield Grove, Bristol BS8 2BN, UK.
authors.forename: Lavinia
authors.initials: L
authors.lastname: Paternoster
authors.affiliation: MRC Integrative Epidemiology Unit, School of Social and Community Medicine, University of Bristol, Barley House Oakfield Grove, Bristol BS8 2BN, UK.
authors.forename: George
authors.initials: G
authors.lastname: Davey Smith
authors.affiliation: Centre for Academic Mental Health, School of Social and Community Medicine University of Bristol, Barley House Oakfield Grove, Bristol BS8 2BN, UK.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Evans
mesh_terms: D000328:Adult; D000483:Alleles; D016022:Case-Control Studies; D019052:Depression, Postpartum / Q000097:blood / Q000453:epidemiology; D003866:Depressive Disorder / Q000097:blood / Q000453:epidemiology* / Q000235:genetics; D004281:Docosahexaenoic Acids / Q000097:blood* / Q000235:genetics; D015118:Eicosapentaenoic Acid / Q000097:blood* / Q000235:genetics; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D057182:Mendelian Randomization Analysis; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood / Q000453:epidemiology* / Q000235:genetics; D011446:Prospective Studies; D012306:Risk; D055815:Young Adult
chemical_list: D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid
keywords: ALSPAC; Depression; Mendelian randomisation; Omega-3; Perinatal