Auto immune disorders and severe infections are risk factors for schizophrenia. Patients with schizophrenia on average have elevated inflammatory markers. CRP is a commonly measured inflammatory marker, levels are usually below 3 mg/l, but can be up to 10mg/l. Association with CRP and schizophrenia has been reported in case control studies in the past.
Marie Kim Wium-Andersen and team from Denmark report the results of a large prospective study looking at the CRP levels and later diagnosis if schizophrenia.
CPR was measured in two large independent general population cohorts. ( 78810 subjects). They were followed for up to 20 years .Hospitalisation data was collected from national patient registry.
CRP levels were grouped in to 4 quartiles. Hazard ratios for schizophrenia for individuals in the first quartile were 1.7 (95% CI: 0.3– 8.9) for second quartile, 2.1 (0.4–10) for third quartile, and 11 (2.8–40) for fourth quartile individuals. Ie patients with higher CRP had considerable higher chance of having schizophrenia.
Mean CRP levels were 63% higher for individuals with schizophrenia compared to those without.CRP were associated with a 6- to 11-fold increased risk of late- or very-late-onset schizophrenia, the relationship remained when adjusted for various factors.
A study by Benros ME et al 2011 (with 3.6 million individuals) have previously shown that auto immune disorders or severe infections ( where CRP is elevated) increase risk of schizophrenia. CRP might disrupt BBB and increase the permeability for pro inflammatory cytokines and/or autoantibodies.
Limitations: All participants were above age 20 at inclusion, and thus cohort is selective ( late onset schizophrenia only). Severity of disorder was not studied. Cannot exclude that elevated CRP levels per se may be causally associated with schizophrenia.
Summary of the article:
Wium-Andersen MK, Ørsted DD, Nordestgaard BG. Schizophr Bull. 2014 ;40(5):1117-27