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depression is not just a feeling

Yes, you read that correctly. Depression is NOT just a feeling.

Depression has many causes. And sure, a lot of those are related to internal struggles or external loss. But what is often overlooked is that depression has a biological cause, too.

Depression is more than just feeling sad. We can feel sad about a number of things, like getting a bad grade, missing a cab on a rainy day, when tickets to our favorite event are sold out, when our favorite pet passes away.

What makes feeling sad different from depression?

Depression—clinical depression—is a disorder, which means that it is an abnormal physical and mental condition. It is different from just any kind of sadness, and is usually triggered by a traumatic or stressful life event.

The DSM-5 requires 5 out 9 symptoms of depression to be present nearly every day for at least 2 weeks, causing an impairment in daily functioning.

Imagine it like this: On most days, you feel OK, And on special days, you feel HAPPY. But sometimes, bad things happen, which cause you to feel sad. Sadness lingers, but as soon as circumstances change, you don’t feel sad for long. How about feeling really, really sad—feeling depressed?

It’s like being in a pitch black room, no matter where you turn, you just can’t find the exit. It’s hard to describe, but it’s worse than being sad. You stay there for a long, long time. Depression is not a nice place to be.

So, what exactly causes depression?

There are 3 main biological causes: chemical imbalances, structural abnormalities and genetics

Chemical imbalances: The neurotransmitters


Serotonin is commonly known as the “happy hormone”. It is responsible for our good appetite, restful sleep, memory, and socializing behavior. More importantly, it maintains our good mood. 

In depression, serotonin is depleted. This causes a depressed mood, decreased appetite, disturbed sleep, forgetfulness and difficulty concentrating, social withdrawal and suicidal thoughts


Another neurotransmitter is norepinephrine. It might sound familiar because it functions similarly as ‘epinephrine’ in giving us energy. It boosts our mood and helps control pain. 

Its’ depletion in depression causes us to feel very tired, like we don’t have any energy, even just to get out of bed. It also causes us to feel aches and pains. We may complain about headaches, back pain and stomach aches, even if there’s nothing really wrong there.


A third neurotransmitter is dopamine, or, the “pleasure hormone”. It is responsible for keeping us motivated and seeking reward. 

There is decreased dopamine in depression, causing anhedonia. Anhedonia means that we don’t want to engage in activities that used to make us happy. Aside from a depressed mood, anhedonia is another core symptom of depression.

Structural abnormalities: The brain

These are the abnormalities in our brain’s ‘hardware’.

Brain imaging has recently focused on the hippocampus as an important aspect of depression. The hippocampus is responsible for forming our memories and emotions. Here’s what goes on inside the brains of someone with depression.

Takeaway: There is 25% less gray matter in people suffering from depression than those who don’t. The longer a person stays depressed, the smaller the hippocampus becomes.

There are also sleep abnormalities in depression. There is an increased amount of dreaming, caused by an increased time spent in REM sleep.

Depressed people dream up to 3x as much, have high levels of stress hormones and wake up exhausted in the morning. Depressed people dream too much because they worry too much. Worrying keeps our brain up and running, and these thoughts come out in dreams. Dreaming a lot makes you miss out on restorative sleep, and keeps your brain active throughout the night (instead of resting). These lead to an exhausted brain and body, and many other symptoms of depression.

Neuroendocrine effects

Now, when our brain is stressed—from daily problems, school work, bad relationships, or even from feeling tired, it releases cortisol, the stress hormone. This stress triggers the decrease of neurons in the hippocampus, which contributes to the depressed mood. 

Sometimes, a decrease in our thyroid hormones, caused by a medical illness, can produce symptoms of depression.

Genetics: The serotonin transporter gene

The third biological cause for depression is found in genetics—the serotonin transporter gene.

Genes are made up of DNA. They are the basic physical and structural unit of heredity. An allele is a variation of a gene. Genetic abnormalities make us vulnerable to develop depression. 

The serotonin transporter gene regulates the amount of serotonin taken up by the brain. The differences in this gene affect how strong a stress response can be. Abnormalities lead individuals to be more vulnerable to depression.

Each person has 2 copies of a gene, 1 inherited from each parent. If a person has 1 short and 1 long copy, that person may get depressed over a stressful life event. For persons with 2 short copies, they fare far worse. Having 2 long copies, on the other hand, make a person much less likely to become depressed when faced with similar life stress.


While the exact causes of depression have yet to be pinned down precisely, it is important to remember that…

Fortunately, there are many ways you can seek help.

Medications that increase serotonin have an indirect effect on the growth of brain cells. They promote the release of other chemicals which stimulate neurogenesis—the growth of neurons.

Seeking support by connecting with a friend or a family member can strengthen our feeling of support. 

Therapy with a therapist, psychologist or a psychiatrist can help us identify our issues and work through them. 

Always remember…

You are not alone.

There is HOPE.

Anything is possible.

post script ~
this topic is close to my heart, as it was the first lecture i ever gave to people outside my institution.
i am so grateful for that opportunity, as it opened so many doors for me.
i’ll talk more about those milestones next month. stay tuned!


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