After Depression
Yongling Lu, 15th Oct 2023
Translated by Yongling Lu, 19th Oct 2023
The news of a celebrity's death due to depression is something we are all familiar with, but how does this illness affect our brains? Today, let's explore what happens to your brain after experiencing depression.
1. Gray Matter Changes
Gray matter is a type of neural tissue and an essential component of the central nervous system. It plays a crucial role in the deep processing of information and contains the cell bodies of most brain neurons. Areas of the brain involved in gray matter include muscle control, sensory perception such as vision and hearing, memory, emotions, speech, decision-making, and self-control.
However, studies have shown significant decreases in gray matter volume in certain brain regions due to depression, such as the left and right dorsolateral prefrontal cortex (a region of the brain's temporal lobe associated with auditory language processing) and the right insula (which is involved in sensory processing and emotional responses like moral emotions and empathy, such as disgust, pride, shame, guilt, etc.).
This is because depression leads to a severe decrease in serotonin levels and a significant increase in cortisol levels associated with stress. These cortisol levels can impede the growth of brain cells to some extent. Fortunately, the changes in gray matter volume caused by depression are not irreversible, as treatment can lead to improvements in gray matter volume in the brain.
2. Brain Inflammation
In the book "The Inflamed Brain," the author mentions a study where scientists used brain imaging techniques such as functional magnetic resonance imaging (fMRI) to observe that the regions responsible for emotions, such as the amygdala and cingulate cortex, showed stronger activity in depressed individuals when they saw a sad facial expression compared to healthy individuals. In addition to structural differences, there are also differences in neural signaling. Researchers found that the neurotransmitter serotonin, which is involved in depression, is lower in the brains of individuals with depression compared to healthy individuals.
To gain a more comprehensive understanding of the impact of inflammation on the brain, scientists observed changes in neurons within the brain. They injected a dose of bacterial toxin into the bloodstream of rats, causing them to enter a state of acute inflammatory shock. The inflamed rats became less active, had reduced appetite, and disrupted sleep. It appears as though these rats developed symptoms similar to depression.
From a physiological perspective, the bacterial toxin triggered an inflammatory response in the rats, activating macrophages in their bodies to release cytokines. These cytokines circulate in the bloodstream, transmitting inflammatory signals to other macrophages in the body. When activated in the brain, macrophages not only eliminate inflammation but also cause collateral damage to innocent bystander neurons and surrounding tissues. Neurons in the brain are more prone to cell death or atrophy, and neurotransmitters associated with depression, such as serotonin, are likely to be disrupted or interrupted. These disruptions ultimately contribute to the manifestation of depression.
3. Cognitive Function
Depressed individuals also experience cognitive-related issues. Cognitive function encompasses memory, learning, decision-making, thinking, comprehension, orientation, executive function, and the ability to process information. Depressed individuals may have impairments in memory, attention, and decision-making abilities.
In an article from the University of Cambridge titled "Cognitive impairment in depression: Are our treatments missing an important target?", the author states, “Sufficient cognitive functioning is imperative for the majority of everyday activities, from remembering to pick up the weekly food shop to meeting important deadlines in work. Consequently, impairment in these processes can have a significant impact on quality of life. Deficits in memory and concentration have been linked to unemployment and poorer work performance.” Professor Barbara Sahakian from the University of Cambridge believes that 'Depressed patients with poorer cognition have both poorer outcomes and more frequent relapse. Therefore, if we are to improve outcomes for our patients, we need to successfully treat their cognitive problems, which are not effectively treated by antidepressant drugs.' However, current treatments for depression, both medication and psychological therapy, primarily focus on mood regulation. Due to the lack of research on cognition, it is currently unclear whether these treatments have any impact on cognition... In summary, we advocate considering cognitive function problems as a treatment target for depression. Focusing more on cognitive function in treatment trials will help us understand its role in the course of depression and aid patients in achieving better recovery."