C4A and schizophrenia: In the present work, levels of different complement components showed different relationships to cortical thickness in the brain depending on whether schizophrenia was present or not: in affected individuals, higher levels of C4, factor B and factor H were associated with thinner primary sensory cortex; in healthy controls, higher levels of C1q, C4 and factor H were associated with thicker left dorsolateral prefrontal cortex.