Scientists have now identified the physical locus of depression, greatly expanding scientific understanding of a disorder that affects millions of people of all ages. Researchers did MRI scans of the brains of 900 subjects. The results show feelings of low self-esteem and loss are link to the functioning of the orbitofrontal cortex, the region of the brain that governs sensory integration, decision-making and expectation.
Computational psychiatrist Jianfeng Feng from the University of Warwick in the UK, and Fudan University in China, says:
Our finding, with the combination of big data we collected around the world and our novel methods, enables us to locate the roots of depression, which should open up new avenues for better therapeutic treatments in the near future for this horrible disease.
Feng and his team recruited 909 people in China to participate in MRI brain scans. This group included 421 of the participants who had been diagnosed with major depressive disorder. The other 488 participants did not suffer from depression; they comprised the control group.
The MRI scans indicated depression is linked to the neural activity of two different portions of the orbitofrontal cortex (OFC): the medial OFC and lateral OFC.
The medial OFC becomes active when something good happens. When the medial OFC is activated, we feel happy. Researchers found subjects with depression had weaker neural connections between the medial OFC and the hippocampus, site of the brain’s memory systems. This could mean people with depression have a more difficult time accessing positive memories.
The depressed subjects in the study also exhibited stronger neural connections around the lateral OFC, an area link to processing non-reward outcomes. These connections involved the precuneus (believed to be involved with the sense of self) and the angular gyrus (responsible for memory retrieval and attention).
Researchers concluded the hightened brain activity around the lateral OFC could indicate depressed people more easily relive negative experiences and have a harder time feeling good about themselves.
Interestingly, the neural activity of depressed subjects taking antidepressant medication showed the processing of non-reward outcomes was lower. This indicates antidepressants do have a positive effect on evening out brain functioning.
Physicians report that approximately half of prescriptions do not initially work to relieve depression, and finding the right drug and dosage is a process of trail and error. A better understanding of the physical origins and mechanisms of depression could improve the way we fight the disorder.