GDNF and schizophrenia: Serum GDNF levels of first-episode psychosis patients who did not use medication were followed for 8 weeks and measured in the 2nd, 4th, 6th and 8th weeks; GDNF levels, which were initially found to be lower in schizophrenia patients than in healthy controls, increased with the use of antipsychotic drugs (Xiao, Ye et al. 2016).