Association of Serum Interleukin 6 and C-Reactive Protein in Childhood With Depression and Psychosis in Young Adult Life

Longitudinal studies have linked the systemic inflammatory markers interleukin 6 (IL-6) and C-reactive protein (CRP) with the risk of developing heart disease and diabetes mellitus, which are common comorbidities for depression and psychosis. Recent meta-analyses of cross-sectional studies have reported increased serum levels of these inflammatory markers in depression, first-episode psychosis, and acute psychotic relapse; however, the direction of the association has been unclear.

To test the hypothesis that higher serum levels of IL-6 and CRP in childhood would increase future risks for depression and psychosis. DESIGN, SETTING, AND PARTICIPANTS: The Avon Longitudinal Study of Parents and Children (ALSPAC)is a prospective general population birth cohort study based in Avon County, England. We have studied a subsample of approximately 4500 individuals from the cohort with data on childhood IL-6 and CRP levels and later psychiatric assessments. MEASUREMENT OF EXPOSURE: Levels of IL-6 and CRP were measured in nonfasting blood samples obtained in participants at age 9 years. MAIN OUTCOMES AND MEASURES: Participants were assessed at age 18 years. Depression was measured using the Clinical Interview Schedule-Revised (CIS-R) and Mood and Feelings Questionnaire (MFQ), thus allowing internal replication; psychotic experiences (PEs) and psychotic disorder were measured by a semistructured interview.