Depression affects how people think, feel and behave. Some experience mild depression just once or occasionally, while others have severe depression throughout their lives.
This more intense form of depression is called major depressive disorder (MDD).
"Major Depressive Disorder, arises in roughly three to five percent of all males and eight to 10 percent in females," reported Medical Daily.
Many studies have shown there is a change in brain activity when someone is depressed. But what else happens to your brain when you’re depressed?
When it comes to depression, the brain’s hippocampus, prefrontal cortex and amygdala are involved.
Located near the brain’s center, the hippocampus regulates the hormone cortisol. Cortisol is released during physical and mental stress and depression.
Complications occur when extreme amounts of cortisol end up in the brain after such stress.
These high cortisol levels are thought to be part of the problem.
Researchers believe that they’re the lead in changing the brain’s physical structure and chemical activities, which can prompt the onset of MDD.
Cortisol levels are normally highest in the morning and decrease at night. People with MDD have cortisol levels that are always elevated, wrote HealthLine.com.
It’s this long-term exposure to elevated cortisol levels that may slow new neuron production and cause the neurons of the hippocampus to to reduce in size. Simply stated, the brain shrinks.
A global meta-analysis compared 8,927 people’s hippocampuses. Of those studied 1,728 had major depression. The rest had mild depression or were healthy.
Researchers found that the more depressive occurrences someone had, the more their hippocampus decreased in size. Basically, the longer someone was depressed, the more it was found that their brains shrank.
The prefrontal cortex, located in the front of the brain, regulates emotions, makes decisions and forms memories. If there is an excess of cortisol, the prefrontal cortex has also been found to shrink.
The amygdala enables emotional responses. 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.