Schizophrenia and CRP meta-analysed again

"Our study provides evidence that higher CRP [C-reactive protein] levels are associated with increased risk of SZ [schizophrenia], especially for young adult patients less than 30 years."

So said the results of the 'updated' meta-analysis by Zhichao Wang and colleagues [1] (open-access available here) surveying the peer-reviewed literature on this topic "from inception to November 1, 2016." The 'updated' bit to their discussion refers to the fact that this is not the first time that CRP - a molecule associated with inflammation or inflammatory processes - and schizophrenia have received the meta-analysis treatment (see here for example).

So, "18 studies representing 1963 patients with SZ and 3683 non-SZ controls" were identified and as per the opening sentence to this post, "blood CRP levels were moderately increased in people with SZ... irrespective of study region, sample size of included studies, patient mean age, age of SZ onset and patient body mass index."

The authors do mention the idea that elevated levels of CRP in cases of schizophrenia fits in with the idea that immune function might be doing so much more than just fighting off infection and the like (see here). Indeed, they talk about: "The rationale that plasma CRP levels were increased significantly in studies with participants’age less than 30 years probably lies in that in the early stages of SZ, a particularly large number of inflammatory substances will be secreted, such as blood CRP and interleukin-10, which are very likely to be related to the development of SZ" with the requirement for further investigations. They also talk about how "high peripheral levels of CRP could increase the permeability of the blood–brain barrier through the adjustment of the function of tight junctions, which contributed to the increase in some pro-inflammatory cytokines, such as CRP to enter the central nervous system." This is an idea that has found favour in other quarters too [2].

Armed with such data, one might envisage that further studies on the possibility of controlling CRP and other related compounds (see here) *could* represent one route to eventually treating at least some types of schizophrenia...

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[1] Wang Z. et al. Association between C-reactive protein and risk of schizophrenia: An updated meta-analysis. Oncotarget. 2017 May 18.

[2] Najjar S. et al. Neurovascular Unit Dysfunction and Blood-Brain Barrier Hyperpermeability Contribute to Schizophrenia Neurobiology: A Theoretical Integration of Clinical and Experimental Evidence. Front Psychiatry. 2017 May 23;8:83.

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