C4A and schizophrenia: This lack of consensus, together with a growing evidence base indicating that complement is involved in brain development (Stephan et al., 2012, Stevens et al., 2007), as well as the recent genetic study implicating C4 as a susceptibility locus for schizophrenia (Sekar et al., 2016), has motivated us to explore whether changes in the complement system can be detected in FEP in comparison with healthy controls.