What Are The Causes of Depression

Depression, like most mental illnesses, is a complex disease. Many have tried to narrow down the single cause of depression. Some have said it’s a chemical imbalance that causes depression; others say it’s hereditary, and some argue it’s caused by life circumstances.

But what research so far has found is a lot more complicated. There isn’t just one thing that causes some people, and not others, to have depression. For most people, many different things come together and lead them to be depressed.

Depression is an undiscriminating illness, and it can affect anyone regardless of age, gender, race, or nationality. 10% of people will experience at least one depressive episode in their lifetimes.

There are, however, certain risk factors that make some people more likely to be depressed. Here, we’ll break down the most common causes of depression, along with some additional risk factors.

Genetics

Researchers have identified a genetic component in depression^[1]. In other words, depression tends to run in families. If you have a parent, sibling, or another family member who has depression, then you’re more likely to experience it, as well.

However, this is far from a life sentence for people with depression in their gene pool. You aren’t doomed to a life with depression if you have a family member who has it.

Studies have found that 40 to 50% of the likelihood of becoming depressed is due to genetics. That could mean the other 50% is decided by other factors. It could also mean that for some people, genetics is responsible for 100% of their risk, while for others, it plays a 0% role.

More research is being conducted to find a definitive answer. At this point, all we know is that depression does seem to be inherited, at least for some people 一 and at least to a certain degree.

Some experts report that if you have a parent or sibling with depression, you may be two to three times more likely to also get depression than people who don’t have depressed family members.

There isn’t just one “depression gene” you inherit that will cause you to have depression. Instead, it’s more likely there are a number of different genes that affect things like your resilience, brain chemistry, and stress response, which may make you more likely to get depression.

Brain chemistry

You’ve probably heard that people with depression suffer due to a chemical imbalance in the brain. While the facts are a lot more complicated 一 many things can lead to depression, not only brain chemistry 一 there is at least some truth to this statement.

It’s been found that the brains of people with depression undergo several changes.^[2] Some (not all) people with depression have been found to have a smaller hippocampus, a complex part of the brain that’s responsible for memory, among other things. Other areas of the brain that are affected by depression include the amygdala (the part of the brain associated with emotions) and the thalamus (the part of the brain that transmits sensory information to the rest of the brain, including vision, taste, touch, and balance).

Neurotransmitters, the chemicals that allow the brain’s nerve cells to communicate with each other, may also play a role in depression. When your brain is affected by depression or mania, it may release too much (or too little) of a certain neurotransmitter or reabsorb it too quickly. Some neurotransmitters that are affected by depression include:

• Serotonin (mood, well-being, happiness)
• Norepinephrine (reactions to stress and anxiety)
• Dopamine (reward or pleasure)
• Acetylcholine (motivation, arousal, attention, learning, memory)
• Glutamate (learning, memory)
• Gamma-aminobutyric acid-GABA (natural brain relaxant)

This is why antidepressant medications are thought to be effective 一 by correcting the complex brain circuits that may have gone awry under the influence of depression.

However, the truth is a lot more complicated than saying that a chemical imbalance is what causes depression.^[3] We now know there are many different factors which interact to cause someone to become depressed.

Researchers are still studying the impact of brain chemistry on depression, but we do know that it isn’t the whole story. This may be why antidepressant medications aren’t always effective. Studies show that around half of people with depression don’t find relief through medication.^[4]

Stressful life events

For many people, it’s life 一 and all the suffering that comes along with it 一 which leads them to become depressed. Stressful life events are one of the top risk factors for depression. Around 70% of first depressive episodes are triggered by a stressful event.^[5]

Some people go through one particularly traumatic event that contributes to their depression. Someone who loses their job, for example, could become depressed. Others describe their depression as more of a downward spiral. One stressful event after another could pile up, leading the person to eventually reach their “breaking point.”

Some examples of stressful life events that could cause someone to become depressed include:

• Death of a loved one
• Divorce
• Partner’s infidelity
• Being diagnosed with a chronic or terminal illness
• Partner’s illness
• Job loss or economic hardship
• Assault or abuse
• Loneliness, or being cast out of a social group

Although these events are commonly linked with depression, it’s not so much the event itself that matters 一 but how much stress the event causes for you.

Again, though, the link between depression and stress isn’t cut-and-dried. How severely impacted you are by stressful life events depends on many factors, including genetics, early childhood abuse, your personality or temperament, and your pre-existing levels of chronic stress.

Depending on these factors, some people could become depressed after an event like this. Others might be more resilient, and be able to overcome the effects of the life event without becoming depressed.

Studies show women are particularly vulnerable to the effects of stress, and may be more likely to become depressed after a stressful life event. They’re also more likely to have depression in general.

It’s also important to note that stress and depression have a bidirectional relationship 一 meaning that each affects the other.

Stressful life events can trigger the initial depressive episode, but research shows people with depression are more likely to go through stressful life events, as well. People with depression are prone to behaving in ways that may cause stress to build up, like pushing loved ones away or using substances to try to cope with their symptoms.

This complex relationship can lead people to become trapped in a stress-depression cycle that only gets worse over time.

Personality

People with certain personalities are at higher risk for getting depression than others. Some specific personality traits that have been linked to depression include:

• Perfectionism: People who tend to be perfectionistic and have overly high standards for themselves and others tend to be more likely to become depressed.
• High levels of neuroticism: Neuroticism is the term to describe someone who is more likely to feel negative emotions due to stressful events. In some ways, it’s the opposite of emotional resilience. If you become easily upset by the things happening around you, then you may be more likely to become depressed.
• Negative ways of thinking: People who tend to be more pessimistic about life, and see the glass half empty, are more prone to depression.
• Low self-esteem: Low self-esteem has been linked to depression, although it’s unclear which comes first. Having depression can also lower your self-esteem.

However, it’s important to note, none of the research that studied the relationship between personality traits and depression suggests a causal relationship. In simpler terms, we don’t know these personality traits cause depression. It could be the same third factor causes both these personality traits and a higher risk for depression.

Poverty

It’s not something most people think of when contemplating causes of depression, but it’s been proven that people who live in poverty are also more likely to be depressed.[6]

As with most other causes of depression, it’s unclear what comes first: poverty or depression. But experts say the obvious financial stress that comes along with poverty can lead to someone becoming depressed. People who live in poverty are also less likely to be able to access the necessary treatment to improve their depression symptoms.

On the other hand, having depression or another mental illness may also put someone at higher risk for poverty. If depression is severe, it can interfere with someone’s ability to work and make a living. It may also lead to other life problems, including substance use, that may result in legal issues.

To a large degree, poverty isn’t always a factor individual people with depression can control. People may become locked in a cycle of poverty and mental illness.

Gender and hormones

Women are twice as likely as men to have depression.^[7] This has been linked to several factors^[8], including:

Societal discrimination, including the wage gap

Socioeconomic factors (women are more likely to live in poverty)

• Balancing work and family
• Higher vulnerability to stress
• Hormones and menstrual cycles

Additionally, some women who get pregnant and give birth can become depressed during this time. This is called Major Depression with Peripartum Onset, more commonly known as postpartum depression.^[9]

Depression can come on during pregnancy and after childbirth because of hormonal changes that happen during this time. When you’re pregnant, certain reproductive hormones like estrogen rise. After giving birth, these hormone levels drop sharply, which can cause symptoms of depression.

On top of that, the arrival of a newborn baby, no matter how joyous, is a stressful life event. The lack of sleep and the pressure that can come along with taking care of a newborn may also contribute to someone becoming depressed.

Medications

Some medications that are prescribed for different health conditions can cause symptoms of depression.^[10] These include:

• Anticonvulsants used to treat epileptic seizures
• Barbiturates and benzodiazepines, or central nervous system depressors, used to treat anxiety disorders
• Calcium-channel blockers used to treat high blood pressure, congestive heart failure, or abnormal heart rhythms
• Isotretinoin used for severe acne
• Some birth control methods containing estrogens, including NuvaRing
• Certain beta-blockers, which are used for heart problems like high blood pressure and angina
• Opioids, which are intended for use as pain relievers; however, this class of medication is often abused
• Statins, a type of medication to lower cholesterol
• Corticosteroids, used for inflammation due to a number of different health conditions, including rheumatoid arthritis and Lupus

If you think your medication may be causing your depression symptoms, it’s important to see your doctor. Your provider will weigh the benefits of the medication with any adverse effects. It may be more important to continue your medication, despite the depression symptoms.

Childhood trauma

Research has shown that experiencing trauma in childhood is highly linked to chronic depression as an adult.

In one study, three out of four adults with chronic depression reported going through significant childhood trauma.^[11] Around a third reported multiple incidents of childhood trauma, and these people were also more likely to have more severe symptoms.

For this reason, trauma is considered a separate cause of depression outside of stressful life events. For some people, a stressful event directly precedes a depressive episode. Those who have gone through childhood trauma may already be more vulnerable to getting depression even before becoming an adult.

Drug and alcohol use

People with substance use disorder are much more likely to have depression than the general population. ^[12] And the relationship goes the other way, as well 一 depression makes people twice as likely to battle addiction.

There are several different factors that may explain this relationship.

First, there may be some genetic or biological factors that make certain people more likely to face addiction and get depression. There may be other third factors that lead to both of these conditions as well, such as chronic pain or childhood abuse.

Next, people who already have depression may be more likely to use drugs and alcohol to try to self-medicate their symptoms. Self-medicating in this way isn’t healthy or effective. In fact, using drugs and alcohol only makes depression symptoms worse. However, for people who don’t or can’t access mental health care, it may feel like their only option.

People who already have problems with drug and alcohol addiction may also be more susceptible to depression. Using drugs and alcohol can cause other problems in your life or lead you to make poor or impulsive decisions.

For example, substance use can cause problems at your job or push away your closest relationships. These problems, in turn, can increase your risk for depression.

Using or withdrawing from drugs and alcohol can also cause temporary symptoms of depression. For example, people withdrawing from cocaine often experience anhedonia, a common symptom of depression that makes it difficult for people to feel pleasure.

Chronic illness and pain

Lastly, people with chronic pain or illness are at higher risk of getting depressed. It’s estimated that up to 85% of people with chronic pain also report being depressed.^[13] And the treatment prognosis is poorer for people with both chronic pain and depression (compared with people who just have depression).

Living with chronic pain is exhausting and can severely affect your life. Pain and disability might lead people to lose their jobs, friendships, and romantic partnerships. Chronic pain can also prevent people from exercising and getting enough sleep 一 both things that can heighten the risk for depression.

Chronic pain and depression have been found to share some brain mechanisms. In other words, the same neural mechanisms may cause both.

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[1] https://med.stanford.edu/depressiongenetics/mddandgenes.html
[2] https://www.health.harvard.edu/mind-and-mood/what-causes-depression
[3] https://www.npr.org/sections/health-shots/2012/01/23/145525853/when-it-comes-to-depression-serotonin-isnt-the-whole-story
[4] https://www.ncbi.nlm.nih.gov/books/NBK361016/
[5] https://www.family-institute.org/sites/default/files/pdfs/csi_stroud_stress_depression.pdf
[6] https://www.npr.org/sections/goatsandsoda/2016/10/30/499777541/can-poverty-lead-to-mental-illness
[7] https://www.womenshealth.gov/mental-health/mental-health-conditions/depression
[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478054/
[9] https://www.nimh.nih.gov/health/publications/perinatal-depression
[10] https://www.health.harvard.edu/blog/depression-common-medication-side-effect-2018071614259
[11] https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC4677006/
[12] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851027/
[13] https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC5494581/