The basis of any mental illness is a violation of the structure, activity of various areas of the brain, an imbalance of mediators or neurotransmitters . There are no functional mental illnesses. Therefore, the treatment of depression should be directed to the focus and area of the brain damage.
Activation of the right hemisphere of the brain leads to depression, and decreased activity of this hemisphere leads to mania. Reducing the activity of the medial orbitofrontal reward cortex affects the connection between the temporal lobes. As a result, depression develops. The increased activity of the lateral orbitofrontal cortex leads to a disruption in communication with the hippocampus, which increases depression.
In depression, abnormalities of the cortico-pallidary thalamic chain of brain neurons and changes in the size of the globus pallidus were found.
It has been proven that right-sided striatal atrophy leads to drug-resistant depression (R. Shah et al., 2002)
Studies on the genesis of depression indicate dysfunction of neurotransmitters and neural networks in the limbic, cortical, and subcortical areas of the brain. This is why depression develops in neurological and somatic diseases. There is a connection between depression and heart vascular disease, tumors, and HIV infection.
In the study of the brain using diffusion tensors (DTI), a violation of the integrity of the white matter of the brain in various areas was found in the main depressive disorder. This was especially true for the zones of the right frontal lobe, left frontal lobe, occipital lobe and fusiform gyrus. Voxel analysis of the diffusion tensor in patients with major depressive disorder showed partial anisotropy of the white matter connecting the prefrontal cortex of the frontal, temporal, and occipital lobes with the amygdala and hippocampus. Thus, changes in the structure of the white and gray matter of the brain can lead to depression.