Randomized study
schizophrenia
Participants were randomly assigned (2:1) to receive antipsychotics plus metformin or antipsychotics alone using a computer-based random number generator. Because the treating clinicians were not blinded to the groups, we established an independent cognitive performance evaluator who was blinded to the treatment. See Patients in the metformin group received 500 mg of metformin (Lilinghengtai, Beijing, China) three times daily as an add-on treatment for 24 weeks. The initial metformin dose was 500 mg orally in the evening for the first two days, then 1000 mg daily on day three, then 1500 mg daily on day five and thereafter. Patients who could not tolerate the maximum dose of metformin were maintained at their highest tolerated dose. The dose of metformin was chosen based on the safety and efficacy findings of a prior study of Chinese patients with chronic schizophrenia [