Is Depression Genetic or Hereditary?

Is depression genetic? That is one of the most elusive questions about this complex illness. Many people want to know what causes depression because when we identify a cause, we can target it and block it so we can stop depression long before it starts. Researchers are discovering that, to a limited extent, depression can sometimes be genetic or hereditary.

Currently, there is no definitive answer about the degree to which depression is genetic. This isn’t for lack of research. There are two types of ongoing studies: Genome-Wide Association Studies (GWAS) and Gene-Environment Interaction studies (GxE). Over 2,000 GWAS studies alone have been undertaken to uncover the genetics behind major depressive disorder. Countless others have attempted to locate a depression gene and solve the mystery of the cause of depression. To date, the exact nature of the genetic link and genes involved hasn’t been identified.

This doesn’t mean, however, that all these studies have been fruitless. Scientists are learning quite a lot about depression and genetics.

No Depression Gene but Still Genetic Vulnerability

One thing is becoming increasingly clear: It’s unlikely that a depression gene exists. The mental health world was hopeful, as having a single gene (or even a handful of them, which was also studied) would make it easy to test people for depression and could lead to medications for effective treatment, too.

All hope isn’t lost. While the existence of a single depression gene is doubtful, researchers have made great strides in understanding the connection between genetics and depression. It’s known with certainty that numerous genes are involved in depression. Scientists are striving to understand how they work in combination to trigger major depressive disorder.

While there are still many questions, it is becoming increasingly clear that having certain genes makes someone genetically vulnerable to developing depression. Possibly, the more genes linked to depression someone has, the more susceptible they are to the illness.

Depression is Heritable

There is an obvious genetic link to depression. If someone has a first-degree relative (a parent, sibling, or child) with depression, their chances of also developing depression are two to three times greater than someone without a close family member with depression.

Does this mean that depression is hereditary? Not exactly. This illness isn’t passed directly from parents to child the way that certain diseases (such as some cancers or Parkinson’s disease) or even eye color is. Instead, depression is heritable. Heritability refers to the percentage of the total cause of a disorder that is attributed to genetics.

Through twin studies, researchers have determined that the heritability of depression is approximately 40-50 percent (likely higher for severe depression). This means that depression comes from a combination of genetic and environmental factors.

Genetics or Epigenetics?

Yes, depression has a genetic component. But as we’ve seen, a specific depression gene probably doesn’t exist. People can have a genetic vulnerability because the illness is heritable, and they can be susceptible to environmental factors, too. Do these two very different causative factors work together?

It seems that genes and the environment do indeed partner up to cause depression. The study of the interaction and how it affects people is known as epigenetics. Epigenetics investigates how factors external to someone can switch genes on and off to influence depression.

An important implication of this is that someone might be genetically vulnerable to depression, but environmental factors (still under investigation) affect whether the genes are turned on, causing depression, or remain off, causing the person to be depression-free.

Major depressive disorder is partially genetic. Heritability, though, isn’t a guarantee that you will develop this illness.  You might have a parent, sibling, or child with depression but not develop it yourself. Also, you might not have depression in your family at all yet live with major depression.

The answer to the question, “Is depression genetic?” is vague. Depression can be genetic, but there are so many complex facets that the specifics are still largely unknown.

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