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Written by:Jill E. Daino, LCSW-R

Published On: April 7, 2022

Medically reviewed by: Reshawna Chapple, PhD, LCSW

Reviewed On: April 7, 2022

Updated On: July 5, 2023


According to the World Health Organization (WHO), more than 280 million people live with depression globally. There are various possible causes of depression, and often the mood disorder results from a combination of factors.

Continue reading to learn more about what can cause depression. Research has discovered a lot about the causes and triggers of depression. Understanding this treatable mental health condition can help you become better able to navigate depression symptoms and live a happier life.

What Research Says About What Triggers Depression

Scientists have long searched for answers to the question: what is depression caused by. They’ve discovered that people who are depressed have brain differences relative to non-depressed people.

Hippocampus link: A small area of the brain called the hippocampus is very important for memory storage. It’s also a storage center for serotonin receptors. Serotonin is a brain chemical called a neurotransmitter that allows for communication across brain cells. Serotonin levels are associated with both mood and sleep regulation.

Some studies have associated a smaller hippocampus with depression, and one theory suggests this might be because less mass of the hippocampus would accommodate fewer serotonin receptors.

Yet the question remains, is the smaller hippocampus the cause, or the effect, of depression? Scientists don’t quite know why people with depression may have a smaller hippocampus. Though more research still needs to be done, there definitely does appear to be a link between the two.

Serotonin levels: Still, it’s widely accepted that low levels of serotonin can be a contributor to a depressed mood. Selective serotonin reuptake inhibitors (SSRIs) and norepinephrine reuptake inhibitors (SNRIs) used as depression treatment are effective because they increase the levels of serotonin in the brain. Recent research is now looking at the connection between emotional processing and serotonin. This research will better our understanding of how to treat depression as well as manage it.

Cortisol: Other research suggests a link between depression and excessive production of a stress hormone called cortisol. It’s possible that overexposure to cortisol has a shrinking effect on the hippocampus, which might contribute to depression as described above.

There are numerous other regions of the brain to consider as well. There’s no doubt that depression is a complex mental health disorder, so it might be unlikely that any single brain structure would be fully responsible. It’s more likely that various areas of the brain are affected by different stimuli in different ways, all contributing to depression in some people.

“While depression can sometimes be linked to an “obvious” trigger, it’s important to remember that depression can be more subtle at times. It doesn’t have to be one significant event that causes depression. If you’re experiencing depressive symptoms, it’s important to take them seriously and know that you can get support.”

Licensed Clinical Social Worker (LCSW-R), BC-TMH Jill Daino

8 Most Common Causes of Depression

What is depression caused by? Let’s take a closer look at some of the common factors that may contribute to the development of severe or mild depression. One or more of these triggers can cause depression.

Most people are affected by a combination of factors. It’s important to note that exposure to any of the following will not cause depression symptoms in everyone. Only some people will ever develop depression, even when exposure to known causes is equivalent.

High-stress events

It’s possible to slip into severe or mild depression after a highly stressful event like the loss of a loved one, a painful divorce, or the unexpected loss of fortune. If you’ve recently experienced a traumatic or difficult situation that you’re finding hard to deal with, make sure you communicate with your family and loved ones. Give yourself time to wrap your mind around what happened. Be open and honest about your feelings.

Personality type

Some people are just more prone to depressive traits, like poor self-esteem or being excessively self-critical. You may be experiencing the symptoms of depression because of your genetic makeup, negative experiences you had during childhood, or a combination of both. This type of depression is likely to occur in young adults. Teen depression and lack of self-esteem has been resulting from social media.

Family history of depression

If you grew up around family members who had a depressed mood, it could have affected your formative years, ultimately making you more inclined to exhibit depressive symptoms.

Researchers from Temple University note that having a family history of clinical depression (major depressive disorder, or MDD) can be a risk factor for experiencing depressive episodes yourself.

Becoming a mother

Women experience dramatic hormonal and physical changes during and after pregnancy. Sometimes, hormonal fluctuations, combined with the new responsibilities of motherhood, can prove overwhelming, possibly causing postpartum depression or an anxiety disorder.

Being lonely

For many people, it can be very difficult to not have social support. Being in a low mood such as feelings of isolation and loneliness that result from lack of contact with family and friends can make you more prone to developing depression.

Drinking and using illicit substances

Some people attempt to numb or navigate their feelings by drinking alcohol and using illicit drugs. While this may offer some short-term symptom relief, this method of self-treatment will almost always lead to negative results like substance abuse. Nobody has ever successfully defeated depression using drugs or alcohol as a treatment option.

Research from the University of Otago suggests there’s a link between major depressive disorder and substance abuse. The study further claims that with increased alcohol usage, there is an increased risk of depression.

An existing medical condition

Various medical and physical health conditions can contribute to depression. Many people notice feelings of depression after receiving a serious health diagnosis from a healthcare provider. Cardiovascular disease, cancer, diabetes, or any other major or life-threatening health condition could be devastating enough to spark mild to severe depression.

Cranial injury

A serious head injury can trigger emotional problems, mood swings, and depression. Head trauma can disrupt various brain regions, any of which may contribute to depression and a low mood.

Understanding More About Depression

Learning about what can cause depression and how to recognize its symptoms is powerful. It can serve as a tool that allows you to find a treatment option for this mental health condition.

Of course, if you are having more severe depression or if you feel unable to manage it on your own any longer, it’s time to get help. It can be very beneficial to get the support of a licensed mental health professional or your healthcare provider. They can help you understand what the causes of depression might be and then help you come up with depression treatment.

“Reaching out for help can feel daunting when you’re depressed. It’s important to remember that there is treatment for depression, and you don’t have to struggle alone. Getting support from a licensed mental health professional to manage your depression and talk about what you’re experiencing can make a big difference.”

Licensed Clinical Social Worker (LCSW-R), BC-TMH Jill Daino

Talk therapy (also known as psychotherapy) is more accessible, convenient, and affordable than ever before. Online therapy platforms like Talkspace offer custom-matched licensed therapists who can help you overcome your depression, so you can return to living your life. You don’t have to live with depression. You can find a way to manage your symptoms and get back to living your life. 

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Jill E. Daino, LCSW-R

Jill E. Daino, LCSW-R, BC-TMH, is a clinical social worker with over 25 years of experience as a therapist, clinical supervisor, and program director. She works to support quality clinical care at Talkspace. Her work as a clinician and trainer focuses on the mental health impact of body image concerns and eating disorders across the lifespan.

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