title: Association of depression with peripheral leukocyte counts in EPIC-Norfolk--role of sex and cigarette smoking.
abstract: OBJECTIVE
  To investigate the associations among depression, smoking behaviour and enumerative measures of immunity in a population-based cohort study.
  
  
  METHODS
  Participants in the European Prospective Investigation into Cancer and Nutrition in Norfolk, England, aged 40-80 years, were identified through age-sex general practice registers. After exclusions for prevalent conditions, white blood cell (WBC) counts and a measure of depressive episode history were available from 11,367 participants and, after a mean interval of 44 months, from 11,857 at a second health check. The measure of depression was completed between health checks.
  
  
  RESULTS
  Observed associations between leukocyte counts and depression for men were weakened following adjustment for cigarette smoking. There was an incremental elevation in age-smoking adjusted mean WBC count by recency of depression such that there was a 3.1% (P=.03) and 5.6% (P=.0004) difference across depression history subgroups (never, lifetime, current) at the first and second health checks, respectively. No age-smoking adjusted associations were observed for women.
  
  
  CONCLUSIONS
  Following adjustment for age and cigarette smoking, these data provide evidence for an association between major depressive disorder and leukocyte counts for men, but not for women.
authors.affiliation: Strangeways Research Laboratory, Institute of Public Health, University of Cambridge, Worts Causeway, England, UK. paul.surtees@srl.cam.ac.uk
authors.forename: Paul
authors.initials: P
authors.lastname: Surtees
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wainwright
authors.forename: Nicholas
authors.initials: N
authors.lastname: Day
authors.forename: Robert
authors.initials: R
authors.lastname: Luben
authors.forename: Carol
authors.initials: C
authors.lastname: Brayne
authors.forename: Kay-Tee
authors.initials: KT
authors.lastname: Khaw
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D003865:Major Depressive Disorder / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D017678:Sex Distribution; D012907:Smoking / Q000097:blood* / Q000453:epidemiology; D011795:Surveys and Questionnaires