C-reactive Protein: A Biomarker for Bipolar Disorder

Abstract

Clinically, bipolar disorder (BD) can be difficult to distinguish from unipolar depression (UD). As a result, nearly 40% of individuals with bipolar disorder are initially misdiagnosed as having depression. An incorrect diagnosis of BD not only delays appropriate treatment but can also worsen symptoms if selective serotonin reuptake inhibitors (SSRIs) - also known as antidepressants - are incorrectly prescribed. This is because individuals with BD are more sensitive to SSRIs, which exaggerates the drug’s effects and can trigger manic states and rapid cycling. Since behavioural symptoms alone cannot always distinguish between these disorders, it is imperative that a biological marker be part of the diagnostic process. Fortunately, researchers found that the level of C-reactive protein in blood plasma can be used as a biomarker to distinguish between BD and UD. C-reactive protein is synthesized by the liver and indicates the presence of inflammation in the body. In BD, cytokines secreted by the immune system contribute to neuroinflammation, which signals the liver to release the C-reactive protein (CRP). A clinically relevant biomarker, such as CRP, could decrease the degree to which physicians rely on behavioural symptoms for diagnosis, enabling early and objective diagnosis.