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Lesson 3.2 Causes of Depression-Neurology, Biology and Genes

Welcome to the third class in our “Depression Essentials” series. In our first lesson, we learned about the prevalence and general background of depression. In our second lesson, we learned about the symptoms of depression. Now, today we will jump into the next lesson of CandleX Classroom series, the causes of depression.

What are the causes of depression?

One often asks why depression happens. Is it a real sickness? Does depression only happen to people with weak will power? Can I get it from my family? What’s happening when someone is depressed? What do you mean that your brain get sick some times?

Well, mental illness is an outcome of a complex malfunction of the brain. Science has made significant progress in understanding the causes, but there’s no single answer. We now know that, mental health is related to genes, biology, neurology and psychology.

  • Neurological Changes

But why do these symptoms happen when someone experiences depression? What is going on inside that brain that causes it? As it turns out, depression affects the connection between the cells in your brain, called neurons.


So what that means, is depression can cause a decrease or increase in these connections and increase or decrease in cell growth in three areas of the brain: the hippocampus, the amygdala, and the thalamus.

The picture above shows you where the Hippocampus is. The hippocampus is in charge of your mood and your memories. Depression causes decrease in cell growth here.

The amygdala is associated with emotions, such as anger, fear, and pleasure. When you are remembering past experiences, your hippocampus brings back the memory, and the amygdala brings back how you were feeling when you experienced a memory.

The thalamus receives most sensory information and sends it to the cerebral cortex. Think of the thalamus like the secretary that sorts out your emotions and sends the information to the rest of the brain. Depression can cause too much cell activity here.

  • Biological Changes

Depression has biological explanations, and can be triggered by environmental factors, like stress. When depression is triggered by stress, it affects the hippocampus. That’s why treatment that uses the molecule serotonin can be helpful for people with depression!

Serotonin is a chemical molecule (neurotransmitter) made in the brain that sends messages between brain cells that affects things such as mood, also known as the happy chemical because when you are feeling good, there is serotonin being released. More importantly, serotonin helps to trigger a process called neurogenesis, which pretty much means that it helps your brain cells make new connections, as seen in this picture below.

Our brain has SO many neurotransmitters that help us function, and serotonin is not the only neurotransmitter that can be affected when someone has depression. Some other important neurotransmitters include dopamine, norepinephrine, and GABA. When our neurotransmitters are out of balance, they can change the signals between our neurons, and can make them either too strong of a message or too weak of a message. We focused mainly on serotonin here, but for more avid learners, we will release a more detailed explanation of neurotransmitters in the future!

  • Genetic

Is depression genetics relevant? Yes. When looking at genetics, studies have found that changes in certain spots of your genes can make you more vulnerable to depression. According to the National Institute of Health, the serotonin transporter gene can have a long version or a short version. Having the short version makes people more vulnerable to depression, because the shorter gene will cause the cells to produce less serotonin. [5] This can explain why depression can possibly run in the family, since you get a copy of the gene from each parent.

There is psychological factor that plays a big role in mental health. Stress, trauma, anxiety also contributes to depression. There are much more factors involved than we explored today. So we are going to expand on these later in this column one by one.

By now, we hope that you would stop thinking that depression is a sign of weakness. We all get sick sometimes, some people are more prone to breast cancer or a heart disease, and others might be prone to depression. It’s tied to the genes, and the environment. Next time you see someone with depression, be kind and caring like you would be to a patient with cancer. After all, depression already takes away their ability to love and care for themselves, your love and care for them can help them to recover.

Reduce the stigma, don’t take part in the stigma!

Stay tuned for our next CandleX Classroom lesson, where we learn what to do when someone is depressed, and how to seek support. Class dismissed!


  1. ASAP Science (2014, August 19) The Science of Depression


  3. Medscape


  5. Short Serotonin Transporter Gene Increases Risk of Depression NIH Study

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