Relating C-reactive Protein to Psychopathology after Cardiac Surgery and Intensive Care Unit Admission: A Mendelian Randomization Study

Abstract

Patients admitted to an intensive care unit (ICU) are subjected to a high burden of stress, rendering them prone to develop stress-related psychopathology. Dysregulation of inflammation and, more specifically, upregulation of inflammatory markers such as C-reactive protein (CRP) is potentially key in development of post-ICU psychopathology.\n\nTo investigate the effects of state-independent CRP on symptoms of post-traumatic stress disorder (PTSD) and depression after ICU admission, we analysed the three leading single nucleotide polymorphisms (SNPs) of loci most strongly associated with blood CRP levels (i.e. rs2794520, rs4420638, and rs1183910) in an ICU survivor cohort. Genetic association was estimated by linear and logistical regression models of individual SNPs and genetic risk score (GRS) profiling. Mendelian Randomization (MR) was used to investigate potential causal relationships.\n\nSingle-SNP analyses were non-significant for both quantitative and binary trait analyses after correction for multiple testing. In addition, GRS results were non-significant and explained little variance in psychopathology. Moreover, MR analysis did not reveal any causality and MR-Egger regression showed no evidence of pleiotropic effects (p-pleiotropy >0.05). Furthermore, estimation of causality between these loci and other psychiatric disorders was similarly non-significant.\n\nIn conclusion, by applying a range of statistical models we demonstrate that the strongest plasma CRP-influencing genetic loci are not associated with post-ICU PTSD and depressive symptoms. Our findings add to an expanding body of literature on the absence of associations between trait CRP and neuropsychiatric phenotypes.