If you have a family history of a particular mental disorder there is a chance you have some of the genes associated with it. However this doesn’t mean that you will definitely develop that disorder, you just have a genetic predisposition to it. The genetic component to mental disorders is complex and intermixed with a variety of environmental factors which contribute to the development of a disorder. Written by Placement student Emma Bishop and PhD student Rosa Cheesman.
“Having a relative with a mental disorder doesn’t mean that you will definitely develop it, but that you are likely to have some genetic predisposition to it.”
It is true that mental illnesses have a genetic element, but perhaps not to the extent that people believe. For depression there is around 40% chance that you will have the disorder if you have a genetically identical twin that does, and 20% for a non identical twin. The fact that the chance isn’t 100% for identical twins shows the importance of the environment, on the probability of developing a disorder. Therefore, having a relative with a mental disorder doesn’t mean that you will definitely develop it, but that you are likely to have some genetic predisposition to it.
What do we mean by ‘genetic predisposition’? Research has found that there is not one single gene ‘for’ any mental disorder, it is a combination of many genetic variants. You can read our past blog for more on this. It is the combination of genetics and the environment which increases someone’s risk for developing a mental disorder (Uher & Zwicker, 2017). One popular way of thinking about risk is the diathesis-stress model. This model proposes that, when someone has a heightened vulnerability, certain factors, such as divorce or financial problems, can act as triggers for the disorder developing. A genetic predisposition in combination with stressful situations can lead to a mental illness developing.
“It is the combination of genetics and the environment which increases someone’s risk for developing a mental disorder.”
The Jam Jar analogy highlights this theory very well. In the first image, we see that both environmental factors (orange triangles) and genetic influences (yellow circles) affect mental illness. In the second image you can see how this might develop. Genetic influences are there from the start, but as we travel through life and experience more environmental stress our mental health can deteriorate. This is shown by the risks in the final jar approaching the top, reflecting higher likelihood of a mental health problem developing. In the final image, we can see that by increasing protective factors (adding rings to the jar), we can improve mental health by reducing difficult symptoms.
Image source: http://www.aboutgeneticcounselors.com/FAQs-Resources/Blog/ArtMID/511/ArticleID/75/How-to-Protect-Your-Mental-Health-When-Genetics-Make-You-Vulnerable
There are a range of environmental factors which can act as catalysts for a mental illness developing. The most widely researched are stressful life events, child abuse and chronic illness. Whilst these factors can’t be prevented in all circumstances, there are protective factors which can help to reduce their effects. Think of the extra ‘rings’ in the Jam Jar analogy. The World Health Organisation’s (WHO) list of protective factors include social support and social participation, higher self esteem, stress management skills and exercise. Some forms of treatment work by helping increase some of these protective factors. For example cognitive behavior therapy (CBT) for anxiety and depression works by teaching people how to think about life in more helpful ways and how to reduce behaviors that can worsen mental health problems.
It is important to remember that, just because there is a family history of mental illness, it doesn’t mean that developing the disorder is a certainty. In fact, it is common for people without any family history of depression to develop the disorder and for those with a family history to show no signs of it. (NIH, 2019). There is no way to know for sure whether someone and their children will suffer with depression or anxiety, which is why research such as The GLAD Study, working to uncover the causes, is so important.