How Genetics Can Play a Role in Depression

The causes of depression are as confounding to researchers as the doctors and mental health professionals who treat it, and perhaps most of all, the 300 million people in the world who have it.

Genetics may indicate a risk for depression, but do not always determine whether a person will develop this all-too-common mental health disorder. There is no "number one cause" of depression, and even more complex is the relationship between genetics, depression, and other known contributing factors.

If you were told you have a “depression gene,” you might worry you will become depressed. However, having a genetic predisposition to a condition does not always mean you will get it. It simply means you may be more susceptible to it than someone who doesn’t have the same genetic makeup. 

The Role of Genetics In Depression

As far as researchers know, it's the interplay of genes and other factors (such as environment and trauma) that determine whether someone develops depression.

Some studies have indicated that someone with a first-degree relative diagnosed with depression (a parent, sibling, or child) could be three times more likely to be diagnosed with depression in their lifetime compared to the general population.

However, it’s important to note that while studies have suggested a clear link within families, these findings don’t account for those who develop depression without a family history.  

Studies have suggested there is a heritable component to depression. Some research has also indicated that women may be more susceptible to the genetic influences associated with depression than men. 

Understanding Genetic Variations

Heredity is a complex interplay of many factors, not just individual genes. When studying depression or other health conditions, researchers often look for changes in genes called variants. These changes are classified according to the effect (if any) they have on the gene.

Eye color is an example of how variants affect genes. Changes in certain genes that affect melanin production, as well as several other genes, determine what color your eyes are. You inherit a combination of genes, each with their own unique variants, from your parents.

Heritability is a complex process, even for a seemingly simple trait like eye color. For conditions like depression, research has not yet determined the full implications of genetic variations.

Demystifying the "Depression Gene"

Having a genetic variant can make it more likely—but not definitive—that you will develop a condition associated with that variant. 

If a gene associated with a specific condition is altered, it may be more (or less) likely to contribute to the development of that condition. A benign genetic variant is less likely to influence the condition than a pathogenic variant.

In some cases, researchers identify a genetic variant but don’t know what (if any) effect it has. These variants are referred to as having "unknown significance."

Several large genome-wide studies have proposed potential genetic connections to major depressive disorder. In 2017, researchers identified two new genetic variants associated with depression. 

A 2018 study published in the journal Nature Genetics identified several genetic variants that appeared to be associated with symptoms of depression and, in some cases, physical differences in the brain.  

Scientists believe it's more likely that all the different genes and genetic variants each make a small contribution to a person's overall risk. Research has indicated that genes may be passed down in different ways (modes of inheritance), which is another factor that could affect someone's genetic predisposition to depression.

Can Genetics Affect Mental Health Treatment?

Depression can be treated with medication, psychotherapy, and other interventions like cognitive behavioral therapy (CBT). Some people may be prescribed a combination of treatments.

Your genes may influence how well a specific treatment works for you. For example, research has indicated that certain genes might affect how well your body absorbs, uses, and excretes alcohol and drugs, including antidepressant medications.

Several genes are known to influence drug metabolism, but the results from these studies are primarily of interest to doctors and researchers.

Furthermore, doctors and scientists don't fully know how useful this information may be for consumers. Talk to your doctor before using your genomic health information to make decisions about your health care, including your depression treatment.

Genetics factors aside, if you've been diagnosed with depression and are trying to decide on a treatment, keep in mind that the process can take time. You may need to try more than one type of therapy before finding the right fit. You might even need to adjust or change your treatment plan over time.  

Before starting a medication for depression, tell your health care provider about any medications, vitamins, or herbal remedies you already take. These products can interact with antidepressants and affect how well they work or even cause serious side effects.  

As you try different approaches, stay in touch with your doctor and your mental health care team. Be sure to let them know if you experience any side effects.  

Does Heritability of Depression Affect Children?

People with depression might be concerned they will pass on the condition to their children. While there could be a heritable component to depression, genetics is not the only determinant. Other factors contribute to risk, while some can be protective.  

A child who has a parent with depression may have a genetic predisposition but will not necessarily become depressed. Other factors, including environmental factors or “triggers,” are also involved.  

On the other hand, a child who does not have a family member with depression and is not genetically predisposed to the condition may become depressed if they are exposed to a triggering event such as experiencing a trauma. 

Non-Genetic Causes of Depression 

Genetics is one of several potential causes of depression. Knowing the possible causes can help you better understand depression, but remember that depression can also develop in the absence of a clear cause and be difficult to pinpoint. Other known factors that contribute to all forms of depression and other mental health conditions include:

• Brain chemistry: People with depression sometimes have lower levels of neurotransmitters (brain chemicals that affect mood and well-being). The neurotransmitters they have might be inefficient or function poorly.  
• Changes in brain structure: The brains of people with depression may be physically and structurally different from the brains of people who are not depressed.  
• Hormones: Conditions like pregnancy, thyroid disorders, and menopause can affect hormone levels. Low or high levels of hormones may trigger symptoms of depression, particularly in someone who is genetically susceptible.  
• Extreme stress: Situational depression, or adjustment disorder with depressed mood, may develop in someone who is in a highly stressful situation or experiences trauma.  

A Word From Verywell

Having a genetic predisposition to depression can exacerbate these factors and may influence when someone becomes depressed as well as how long symptoms may last. However, it’s important to remember that depression can develop in anyone—even someone who isn’t genetically predisposed and isn't susceptible to known risk factors.  

Identifying the signs of depression and being able to recognize them in yourself and others is crucial to ensuring the condition doesn’t go untreated.