Mental health disorders can be devastating for those who have them and their families. They are also incredibly complex, with many genetic and environmental factors contributing to the risk of developing a disorder. In this article, we'll explore both genetics and epigenetics—two significant contributors to risk—as well as how they interact with one another and contribute to mental illness development.
Genes are thought to account for 40-60% of the risk of developing mental health disorders. Genes are inherited from our parents and can be passed down for generations. However, it is essential to note that just because you have a gene does not mean that you will develop a mental health disorder; it simply increases your risk.
For example, if one parent has bipolar disorder (BD) and the other does not have BD but carries the same gene mutation(s), then there is an increased chance that their child will develop BD compared with someone who does not carry any mutations on their X chromosome (50% vs. 25%). If both parents carry this mutation, there is an even greater chance that their offspring will develop BD (75%).
Epigenetics is the study of external modifications to DNA that turn genes on or off and affect how cells read genes. The term "epigenetics" was coined in 1942 by chemist Arthur N. Walpole, but it wasn't until the 1980s that researchers started to explore this phenomenon more deeply.
In recent years, epigenetics has become a popular topic in scientific research because it is thought to be involved in many diseases, including cancer and mental health disorders such as depression, anxiety, and schizophrenia. Researchers are particularly interested in studying epigenetics because it can be changed by external factors like diet and lifestyle choices--and, therefore, may provide us with new ways of preventing disease development or treating existing conditions.
Epigenetics refers to the study of changes in gene expression that are not caused by changes in the DNA sequence. Environmental factors, such as diet and stress, can influence these changes.
One example of an epigenetic mechanism is DNA methylation, which is the addition of a methyl group (CH3) to cytosine nucleotides in the genome. This modification acts as a switch for turning genes off or on without changing their actual sequence. Histone modifications are another type of epigenetic change: chemical groups can be added to histone proteins that make up chromosomes, which affects how tightly packaged DNA is within chromatin structures and, thus, how efficiently it's expressed in terms of transcriptional activity (that is, whether or not your cells manufacture RNA from these genes). Other types include microRNAs (miRNAs) -- small RNAs produced by certain types of cells that regulate gene expression -- as well as DNA damage response pathways.
Genetic mutations are found in those with mental health disorders, including autism spectrum disorder (ASD), schizophrenia, bipolar disorder, Tourette syndrome, OCD, and generalized anxiety disorder (GAD).
A number of studies have identified genetic mutations that increase the risk of developing these conditions. For example:
The immune system is involved in many mental health disorders. In fact, it's been suggested that the immune system may be involved in depression and other mental health disorders.
Mutations in genes that regulate the immune response have been linked to depression. For example, some people with bipolar disorder have a mutation on chromosome 6 that causes a deficiency in an enzyme called tryptophan hydroxylase 2 (TPH2). This enzyme helps make serotonin--a brain chemical that helps regulate mood and sleep cycles--from tryptophan (an amino acid found in food).
The immune system may also play a role in the onset and progression of schizophrenia. Research suggests that some people with this disorder have antibodies against the brain chemical dopamine; these antibodies might be produced by an overactive immune response. The presence of these dopamine-reactive antibodies may lead to inflammation and further damage to neurons, which could explain why schizophrenia symptoms get worse over time.
Epigenetics is the study of how gene expression is regulated by external factors. It's essential for understanding how the environment can affect gene expression and, in turn, our health.
Epigenetic mechanisms may regulate immune response genes and activate them in some people only under certain environmental conditions. For example, mice exposed to stress have been found to have increased methylation of a gene called interleukin-6 (IL6). This causes the production of more IL6 than normal mice who were not stressed--and it leads to anxiety behaviors like freezing or hiding away when exposed to stressful situations again later on in life.
Both genetics and epigenetics contribute to a person's risk of developing a mental health disorder; however, not everyone with mutations in the same gene will develop the same disorder. For example, if you have a mutation in the gene that codes for serotonin (a neurotransmitter), there is no guarantee that you will develop depression or anxiety. In fact, some people who carry this mutation never experience symptoms of these disorders at all!
This fact illustrates how both genetics and epigenetics interact with each other: your genome can be modified by experiences--both good and bad--and these modifications may affect your brain development from childhood through adulthood. These changes are called "epigenetic marks" because they don't involve changes within our DNA sequence itself but rather on top of it (hence "epi-" meaning above). Epigenetic marks can last throughout life if they're not removed--and sometimes even passed down through generations--which means that environmental factors such as stressors during pregnancy could influence an individual's risk for mental illness later on down the road.
In conclusion, both genetics and epigenetics play a role in the development of mental health disorders. However, not everyone with mutations in the same gene will develop the same disorder. This underscores the fact that these are complex diseases with many contributing factors, and we are still learning about them every day. As research continues into these areas, we will learn more about how these factors interact with each other and what role they play in the development of mental health disorders.