For Mental Health Awareness Week, the BBC is showing a series of films featuring public figures talking about their personal experiences with mental illness. In one of these, Nadiya Hussain (chef, author, and television presenter) talks to me and my twin sister Margie about what twins can tell us about the nature and nurture of anxiety. Anxiety can be very impairing, especially when it’s at a disorder level. Anxiety disorders are common, impacting between 15-30% of people in Europe at some point in their life. Genes (nature) play a key role in explaining why some people are more anxious than others, in how our experiences (nurture) shape us, and even why some people might respond more to certain treatments. Here are 10 headlines from anxiety genetics research to date.
Anxiety is very complex.
Lots of different factors influence why people show different levels of anxiety, and these might differ between us. But this doesn’t mean that we don’t know anything about why people vary in anxiety, or that it’s not worth investing a lot of effort into high-quality research.
Twins provide a neat natural experiment for disentangling how nature and nurture influence anxiety.
By comparing identical and non-identical twins, we can unpick how much genetic versus environmental differences between people can explain differences in their anxiety. Like other pairs of identical twins, my sister and I share 100% of our genes. In contrast, non-identical twins only share 50% on average. Identical and non-identical twin pairs are equally similar in their sharing of a family environment. It follows that, if identical twins are more similarly anxious than non-identical twins, there must be a genetic component to anxiety.
Thanks to twin studies, we know that genetic factors play a substantial role in anxiety.
The amount of genetic influence on anxiety (“heritability”) is 30-60%, depending on the type of anxiety or the age group being studied. This leaves an important role for the environment, which could include aspects of parenting and adverse life events.
There isn’t a single ‘anxiety gene’.
Molecular genetics research (where we study samples of DNA from lots of people) clearly shows that anxiety risk involves many genes. Individually, these genes have quite small effects, but collectively they have a sizeable influence on risk of anxiety. It’s important to note that genes influence risk, rather than determining your experience of anxiety per se.
Genes and environments don’t work in isolation, so we can’t understand one without the other.
For example, highly genetic traits are still influenced by the environment. Also, genetic effects often act through the environment, because our genetic makeup (e.g. inherited anxiety risk factors) can affect what experiences we are drawn to, and how we respond to them.
Genetics could help to predict and prevent anxiety.
Predictive approaches could be improved by combining genetic and environmental risk factors for anxiety. The goals of early prediction and prevention are especially important given that anxiety tends to develop at a strikingly young age — the average age of onset is 11.
Genetic research gives us information on the biology underlying anxiety
Researchers have now identified nearly 50 genetic links to anxiety and depression (which are highly related conditions). These discoveries allow us to look deeper into the mechanisms linking genes, brain and behaviour.
Genetics sheds light on how anxiety gets passed down in families
In other words, do parents and children resemble each other because children learn to be anxious from their parents, or because both generations share the same genetic risks? It’s likely to be a combination of both. One exciting way of working this out is to study the children of twins. This type of approach could lead to a better understanding of when and where is best to intervene to prevent the development of anxiety.
Genetics might help us to understand who will respond best to different types of psychological treatments.
This growing field of study is called ‘therapygenetics’. It’s important because it might help specialists to cater treatments better to individuals.
If you’ve experienced anxiety (and/or depression), and want to help researchers find out more, you can sign up to be part of the GLAD study
GLAD stands for ‘Genetic Links to Anxiety and Depression’. This is the biggest ever study of anxiety and depression. Importantly, this study, which is funded by the National Institute for Health Research (NIHR; who fund NHS relevant research) and is part of the NIHR BioResource, is committed to recruiting a large, diverse group of people, which will help shed light on gene-environment interplay and who will drive forward science in the area by agreeing to be recontacted for future research.
Watch ‘Nadiya: Anxiety And Me’ on Wednesday 15th May at 9pm on BBC One.