For this reason, the neurobioavailability of iron and the ability of the brain to capture iron from the blood are important for maintaining adequate levels of BDNF and neurotransmitters involved in emotional processes, including depression [142]. The hypothesis that dysfunctions in the glutamatergic system may be associated with the appearance of depression is currently under intensive investigation and is not yet fully confirmed. The gene discussed is BDNF; the disease is depressive disorder.