How Does Genetics Relate to Mental Illness?

It's a common misconception that we're born with the genes we're born with, and that's that, end of story. Except that's only the beginning of the story, and that's what the field of epigenetics is starting to explore. It has the potential to revolutionize our understanding of why people get sick.

When we consider the idea of nature versus nurture, we often think of it as two very separate things. We're born with what we're born with, and that's the end of that. Except it's actually far more complicated than that.

There has been a genetic element identified in mental illness, with heredity playing a larger or smaller role depending on the illness. Schizophrenia has a particularly significant genetic component. Twin studies are a useful way of learning about this. Identical twins come from a single ovum and single sperm, so they share the exact same DNA, whereas fraternal twins come from two separate ovum and sperm pairs, which means they do not share the same set of genes. However, unlike other sets of siblings, fraternal twins experience the same in utero conditions just as identical twins do. If identical twins have higher concordance rates (i.e. both twins sharing a disorder) compared to fraternal twins, that's a good indicator that genes are playing a role.

Still, how do we explain why some identical twins don't share the same illness? There has to be something going on aside from just the basic DNA material itself; otherwise, all identical twins would have 100 percent concordance rates. Well, one factor is the role of epigenetics. This has revolutionized our understanding of how DNA functions in the body.

While we can't change the genes we're born with, what our cells do with those genes is changeable. Environmental factors, including trauma and even in utero conditions, affect whether or not and how often various code segments get read to produce proteins. This is epigenetics.

Genes are chunks of DNA found on our chromosomes that code for amino acids, which form proteins that carry out various functions within the cell. Cells are constantly making the things they need by accessing the DNA code in order to assemble these proteins. All cells in our body share the same DNA, but their function is determined based on which parts of the DNA they are transcribing to make proteins.

DNA is normally wrapped up in a double helix configuration, but for the cell's version of a bar code scanner to read the DNA code, the double helix has to temporarily open up so the code is accessible. This opening up process is influenced by a few different factors, including histone proteins and a process by which one-carbon methyl groups attach to the DNA. Changes in the nature of these histones and the extent of DNA methylation will influence whether or not the cell's bar code scanner proteins are able to get access to each section of DNA. This will result in changes in the overall functioning of the cell.

Epigenetic changes, such as changes that occur as a result of environmental trauma can actually be passed from generation to generation, giving a whole new meaning to the concept of intergenerational trauma. These sorts of epigenetic changes have been associated with an increased risk of developing addictions. Epigenetic inheritance has also been linked to depression and anxiety.

This is a field of scientific study that may be able to shed more light on the question of nature versus nurture. It is becoming increasingly clear that the external environment interacts closely with our predetermined genome. A better understanding of this could allow for the development of interventions that specifically target some of these root causes. Who knows, it may even become possible to prevent mental illness before it even develops. And maybe, just maybe, this will even start to come about within our lifetime.