Childhood inflammatory markers and intelligence as predictors of subsequent persistent depressive symptoms: A longitudinal cohort study

G. M. Khandaker*, J. Stochl, S. Zammit, Ian M Goodyer, G. Lewis, P. B. Jones

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

17 Citations (Scopus)
224 Downloads (Pure)

Abstract

Background
To identify developmental sub-groups of depressive symptoms during the second decade of life, a critical period of brain development, using data from a prospective birth cohort. To test whether childhood intelligence and inflammatory markers are associated with subsequent persistent depressive symptoms.

Methods

IQ, a proxy for neurodevelopment, was measured at age 8 years. Interleukin 6 (IL-6) and C-reactive protein, typical inflammatory markers, were measured at age 9 years. Depressive symptoms were measured six times between 10 and 19 years using the short mood and feelings questionnaire (SMFQ), which were coded as binary variable and then used in latent class analysis to identify developmental sub-groups of depressive symptoms.

Results
Longitudinal SMFQ data from 9156 participants yielded three distinct population sub-groups of depressive symptoms: no symptoms (81.2%); adolescent-onset symptoms (13.2%); persistent symptoms (5.6%). Lower IQ and higher IL-6 levels in childhood were independently associated with subsequent persistent depressive symptoms in a linear, dose–response fashion, but not with adolescent-onset symptoms. Compared with the group with no symptoms the adjusted odds ratio for persistent depressive symptoms per s.d. increase in IQ was 0.80 (95% CI, 0.68–0.95); that for IL-6 was 1.20 (95% CI, 1.03–1.39). Evidence for an association with IL-6 remained after controlling for initial severity of depressive symptoms at 10 years. There was no evidence that IL-6 moderated or mediated the IQ-persistent depressive symptom relationship.

Conclusions
The results indicate potentially important roles for two distinct biological processes, neurodevelopment and inflammation, in the aetiology of persistent depressive symptoms in young people.
Original languageEnglish
Pages (from-to)1514-1522
Number of pages9
JournalPsychological Medicine
Volume48
Issue number9
Early online date15 Nov 2017
DOIs
Publication statusPublished - 1 Jul 2018

Keywords

  • CRP
  • depression
  • depressive symptoms
  • IL-6
  • immunopsychiatry
  • inflammation
  • intelligence
  • IQ
  • latent class analysis
  • longitudinal study
  • neurodevelopment

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