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Prevalence of low-grade inflammation in depression: a systematic review and meta-analysis of CRP levels.

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Osimo, Emanuele Felice  ORCID logo
Baxter, Luke James 
Lewis, Glyn 
Jones, Peter B 
Khandaker, Golam M 


BACKGROUND: Peripheral low-grade inflammation in depression is increasingly seen as a therapeutic target. We aimed to establish the prevalence of low-grade inflammation in depression, using different C-reactive protein (CRP) levels, through a systematic literature review and meta-analysis. METHODS: We searched the PubMed database from its inception to July 2018, and selected studies that assessed depression using a validated tool/scale, and allowed the calculation of the proportion of patients with low-grade inflammation (CRP >3 mg/L) or elevated CRP (>1 mg/L). RESULTS: After quality assessment, 37 studies comprising 13 541 depressed patients and 155 728 controls were included. Based on the meta-analysis of 30 studies, the prevalence of low-grade inflammation (CRP >3 mg/L) in depression was 27% (95% CI 21-34%); this prevalence was not associated with sample source (inpatient, outpatient or population-based), antidepressant treatment, participant age, BMI or ethnicity. Based on the meta-analysis of 17 studies of depression and matched healthy controls, the odds ratio for low-grade inflammation in depression was 1.46 (95% CI 1.22-1.75). The prevalence of elevated CRP (>1 mg/L) in depression was 58% (95% CI 47-69%), and the meta-analytic odds ratio for elevated CRP in depression compared with controls was 1.47 (95% CI 1.18-1.82). CONCLUSIONS: About a quarter of patients with depression show evidence of low-grade inflammation, and over half of patients show mildly elevated CRP levels. There are significant differences in the prevalence of low-grade inflammation between patients and matched healthy controls. These findings suggest that inflammation could be relevant to a large number of patients with depression.



C-reactive protein, CRP, depression, immunopsychiatry, inflammation, low-grade inflammation, meta-analysis, mood, prevalence, review, Antidepressive Agents, C-Reactive Protein, Depressive Disorder, Humans, Inflammation, Odds Ratio, Prevalence

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Psychol Med

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Cambridge University Press (CUP)


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Cambridge University Hospitals NHS Foundation Trust (CUH) (BRC 2012-2017)
Wellcome Trust (201486/Z/16/Z)
Wellcome Trust (095844/Z/11/Z)
Wellcome Trust (088869/Z/09/Z)
Medical Research Council (MC_PC_17213)
National Institute for Health Research (NIHR) (via Cambridgeshire and Peterborough NHS Foundation Trust (CPFT) (RP PG-0616-20003)
MQ: Transforming Mental Health (MQDS17\40)
Wellcome Trust (201486/Z/16/Z)