April 7th is the World Health Organization’s annual “World Health Day” to commemorate the anniversary of the organization’s founding. It’s also an opportunity for the WHO to kick off a year-long campaign bringing awareness and education to specific health issues. The theme of 2017 is depression, and the campaign aims to increase awareness and conversations about depression using the hashtag #letstalk.
Given that there are genetic links to depression, we at Helix wanted to take this opportunity to talk about what the scientific and health community knows–and doesn’t know–about the role that DNA plays in depression. So let’s talk DNA, and how your genetics work in this pervasive illness affecting over 15 million Americans.
“Depression is an illness characterized by persistent sadness and a loss of interest in activities that you normally enjoy, accompanied by an inability to carry out daily activities for at least two weeks.” The World Health Organization
A refresher on how DNA works
If you want to understand the links between DNA and depression, it’s helpful to have a good understanding of how DNA can play a role in your health, and the health of your family. If you haven’t brushed up on your science in a while, here’s a helpful reminder of what DNA is.
- DNA stands for deoxyribonucleic acid. It is the genetic information that every parent passes on to their biological children. DNA plays a role in physical features (height, and eye color), in disease (multiple sclerosis, cancer, or depression), and even behavioral traits (risk-taking).
- A gene is a set of instructions, kind of like a recipe, to build proteins in your body. These proteins then play a role in the way your body functions every day — like how you digest your breakfast, why your heart rate goes up when you run up the stairs and how your brain sends signals.
- A variant is a different version of a gene. You might have a blue eyes variant or a brown eyes variant. Variants can be related to physical traits like height or complex conditions like cancer and depression.
- Inheritance is the passing down of genetic material from parents to their biological children. Traits that have been inherited have a genetic component. Something like feeling depressed may not be directly inherited, but there are genes related to brain chemistry and how your neurons communicate can be inherited from your parents. Though you may never become depressed, you may have gene variants that predispose you towards it.
There is no “Depression Gene”
While DNA is not always a contributing factor to depression — in fact the WHO cites several contributing factors, from grief to work-life-balance — there are scientifically-proven, genetic links between DNA and depression. In fact, there are several genes linked to depression, however, none of them on their own has any direct causal effect. Simply put, just because you have a variant linked with depression does not mean you will develop it in your lifetime. It appears that there is a combination of genes that, when put together, can be linked to depression. Recent estimates suggest that an individual’s unique combination of variants may account for up to 50% of their risk for genetics.
Understanding the inherited risk of depression
Scientists have studied the genetics of depression by studying families. These studies have shown that depression is more common in those who have blood-related family members that are also affected. Does this mean that if your mother or father has experienced depression, that you could inherit it as well? The short answer is no. No one simply inherits depression from their parents. External factors, like sharing the same household, also contribute to the risk of developing depression.
Predicting depression with genetics
Despite knowing that depression is influenced by DNA, researchers have yet to find genes that can predict whether someone will develop depression. Gene variants are therefore associated with depression but they aren’t predictive of it. You may have the variants that have been linked with depression, but you might never develop it yourself. Why is that? Because depression results from a multitude of factors and circumstances, both biological and environmental. The amount of stress you’re under, the family life you grew up in, and traumatic or tragic events can also trigger the onset of depression. And, your unique genetic variants may also increase that risk.
You can think of it like a game of Jenga. Each risk factor is like taking more and more tiles out of the tower. Are you under a lot of stress? Take two tiles out. Did a tragic event just occur in your life? Take 3 tiles out. Do you have genetic risk factors? Take a tile out for each variant you have. Hopefully you can see that having more genetic risk factors increases the chance the jenga tower falls over, but it isn’t a guarantee.
Most of the genetic studies about depression are designed to find genetic differences between people with depression and people without depression. The results of these types of studies show us variants that are more common in people with depression. However, few studies have actually tried to determine if these variants are predictive of depression.
In order to determine whether gene variants associated with depression can actually predict whether you will develop it, we need to look at many more people who all have their DNA information. A successful study on depression will require much larger collections of human DNA samples than in other diseases. In order to get if statistically significant signals, more than 100,000 people would be needed for the study. With this large group, we could try to predict, based on what we know, who might develop depression. Then, we would need to follow them over time and see if the people we thought would develop depression actually did. If we also record different life events, lifestyle, and environmental factors, we would be able to be able to learn how different genetic variants interact with non-genetic causes.
While today, we don’t have the research or the data to predict who will or who won’t get depression based on their personal genetics, there are new discoveries coming out more and more frequently, so it may be possible in the future. This is made possible with the cost of genetic sequencing decreasing, and the rise of consumer sequencing options (like Helix). More people are learning about how their DNA and their lifestyle come together to give a personal perspective on their health risks, like depression. We believe that the more you can learn about your personal genetic makeup, the better informed you are to make the right choices for yourself and your family.
Talking about depression is important
What we know definitively is that depression can affect anyone, and that regardless of why, or how, or who you are, it’s important to talk to someone about it. If you or anyone you know is concerned about depression, visit these sites of our reputable partners to learn more:
Mount Sinai Hospital