In people with MDD, the constant exposure to high levels of cortisol enlarges the amygdala and makes it hyperactive.
Take an enlarged and hyperactive amygdala, add the activity in the hippocampus and prefrontal cortex, and you've got problems with sleep and activity patterns.
So what’s really responsible for the brain shrinkage?
The key, according to a Yale University study, has to do with too much of the protein, REDD1, which reduces the fatty material that protects neurons.
Yale scientists bred rats genetically so that they did not produce REDD1. Then they exposed them to extreme stress. The results?
Those rats fought off brain changes linked to depression; thus no brain shrinkage.
The normal rats, who were not genetically altered, had brain shrinkage after exposure to stress.
When another group of rats who were bred to overproduce REDD1 were injected with stress hormones, their REDD1 levels spiked. Then they were given a drug that blocked stress hormone production.
After that, the REDD1production stopped, even though the rats were stressed explained MedicalDaily.com.
When postmortem human brain tissue was studied, researchers discovered similarities in humans.
Depression sufferers had an overabundance of REDD1.
Researchers agree that more studies are needed, but at present, too much cortisol and REDD1 causes shrinkage and alters normal brain activity.
Reviewed May 6, 2106
by Michele Blacksberg RN
Edited by Jody Smith
Cirino, Erica. "The Effects of Depression on the Brain." Healthline. N.p., n.d. Web. 03 May 2016.
Davey, Melissa. "Chronic Depression Shrinks Brain's Memories and Emotions." The Guardian. Guardian News and Media, 2015. Web. 03 May 2016.
Weller, Chris. "Depression Shrinks The Brain, And Now Scientists Know Why." Medical Daily. N.p., 2014. Web. 03 May 2016.