C3 and neurodevelopmental disorder: Patients with neurodevelopmental disorders (n = 7) had significantly raised plasma levels of C3bc with median value of 16 CAU/mL (IQR 12–17 CAU/mL) compared to patients without psychiatric disorders (n = 21, p = 0.019) where the corresponding values were 9.4 CAU/mL (IQR 7.4–12 CAU/mL), as well as to patients with learning difficulties (n = 10, p = 0.036) where the corresponding values were 8.0 CAU/mL (IQR 5.4–13 CAU/mL), patients with delayed development (n = 9, p = 0.030) were the corresponding values were 8.8 CAU/mL (IQR 5.8–14 CAU/mL) and healthy individuals (p = 0.002).