How does Depression Affect the Brain?

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depression-84404_640What is Depression?

Depression can be defined as feelings of severe despondency, dejection, and inadequacy. However, depression is a multi-faceted mental health condition. That is, there are many different types of depressive disorders. The most common ‘type’ of depression is known as major depressive disorder. Depression is more than just a low mood, it is a serious mental health condition that affects an individuals physical and mental well-being. Furthermore, depression is the leading cause of disability worldwide. In a single year, approximately one million Australian adults and 14.8 million American adults will experience depression. This amounts to 6.7% of the American population.

What Symptoms Are Associated with Depression?

For depression to be diagnosed by a clinician, symptoms must be present for two weeks or more. Behavioural symptoms include: loss of pleasure, lack of interest in hobbies, remaining at home, not completing important school/work tasks, withdrawing from family and friends, inability to concentrate for extended periods of time, and using alcohol and/or drugs to help ease symptoms. Emotional symptoms include: feeling overwhelmed, irritable, unhappy, disappointed, sad, and frustrated. Physical symptoms include: constantly feeling tired/run down, constant headaches and muscle pains, stomach issues, insomnia/hypersomnia, and changes in appetite/weight.
For those experiencing depression, negative automatic thoughts cloud their thoughts daily. These thoughts can include ‘I’m a failure,’ ‘Nothing good every happens to me,’ ‘Life is not worth living,’ or, ‘I’m worthless.’ When these thoughts occur frequently and intensely, many people suffering from depression feel as though their only choice is to end their lives. In fact, in Australia alone, over 90% of completed suicides within the past year have been done by people who had been suffering from clinical depression. This alone highlights the hopelessness that is felt by people with depression.
However, some of the aforementioned symptoms appear to be quite general, and if an individual is experiencing depression, specific symptoms are often easier to understand and relate to. These could include:
• Things seeming ‘off’
• Not feeling hopeful or happy at anything, even big milestones
• Crying for no apparent reason/for an insignificant reason
• Feeling as though you are moving in slow motion
• Finding it difficult to maintain a ‘normal’ conversation
• Having difficulty making simple decisions
• Feeling ‘out of love’ with a spouse or partner
• Becoming forgetful
• You have recurring thoughts of death or suicidal ideations
• You feel as though you are suffocating.
• Your senses seem dulled
• Feelings of anxiety

Depression and the Brain

Research has indicated that there are three key areas in the human brain that play a role in depression. These are the hippocampus, the amygdala, and the prefrontal cortex. Many current researchers believe that it is high cortisol levels that result in the changing structure and chemical activity in these regions of the brain. Typically, cortisol is higher in the morning and decreases at night. In people with depression however, cortisol levels are constantly high.


The hippocampus is an area of the brain located in the brains centre. It is responsible for regulating the production of cortisol. Cortisol is a hormone that is released by the body during periods of physical and/or mental stress. This includes times of depression. While cortisol is not necessarily harmful in small amounts, problems occur when excessive amounts of cortisol are sent to the brain, resulting in a chemical imbalance. In a typical, health brain, neurons (brain cells) are produced within the hippocampus throughout a human life. However, in people with depression, long term exposure to increased cortisol levels can slow the production of neurons, and even cause neurons in the hippocampus to shrink in size. Consequently, this can result in memory problems. Furthermore, in a study of approximately 8,930 individuals, MRI data was used to conclude that those experiencing recurring episodes of depression, also had a smaller hippocampus. Those who were experiencing their first episode of depression showed evidence of hippocampus shrinkage, suggesting that it is repetitive episodes of depression that causes shrinking.

Prefrontal Cortex

The prefrontal cortex is an area located at the very front of the brain. It is responsible for emotional regulation, decision making, and creating memories. Like the hippocampus, when an individual is depressed and cortisol levels increase, the prefrontal cortex also appears to shrink. Furthermore, although depression involves an overall reduction in brain activity, the prefrontal cortex is more affected than other areas of the brain, with the severity of depression correlating with the extent of decline in activity. Decline in activity in the prefrontal cortex consequently results in poor decision making, memory concerns, and an impaired ability to regulate emotion.


The amygdala is the part of the brain that creates emotional responses such as fear or pleasure. When people experience depression, increased cortisol levels cause the amygdala to enlarge and become more active. An enlarged and hyperactive amygdala, together with abnormal brain functioning in other regions of the brain, can result in sleep disturbances and distorted activity patterns. Furthermore, it can also cause the body to release irregular amounts of hormones and chemicals, thus leading to further complications.

Author: emily habelrih

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