GDNF and schizophrenia: GSK-3 dysfunction has been linked to the pathophysiology of mood disorders, schizophrenia, Alzheimer's disease and metabolic conditions like diabetes.23 Lithium also increases the levels of brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF) and vascular endothelial growth factor (VEGF).24 In addition, lithium has been shown to increase levels of the antiapoptotic protein B-cell lymphoma 2 (Bcl-2), preventing the activation of proapoptotic caspases and modulating the excitotoxicity caused by the NMDA receptor.24