Why do some people experience anxiety more intensely than others?

WE ALL know that person, the one who, when faced with what looks like an overwhelming problem, shrugs their shoulders, comes up with a solution and moves on without so much as a furrowed brow.

To someone with even a fleeting relationship with anxiety, it can seem staggering how others go through life with such aplomb. Why are some protected, while others are more prone to experiencing it? Like most aspects of our behaviour, genetics play a part, as do environmental pressures and lifestyle choices. Thankfully, a better understanding of how they interact is helping us find new ways to minimise the problem.

Let’s start with your genes. Studies show that about 30 per cent of the variation of generalised anxiety disorder in the general population is attributable to genetics. This isn’t due to a particular gene, but rather to a host of interacting genetic factors.

For some people, it may be genes associated with the hormone serotonin, which passes messages around the brain. One study in marmosets found a causal relationship between the animals’ perceived level of anxiety and genes responsible for the proteins that mop up serotonin in a brain region called the amygdala, which deals with fear-related memories. When serotonin was blocked from being taken up by cells in the amygdala, the animals’ anxiety seemingly decreased.

This suggests that some people might have a genetic predisposition to absorb too much serotonin into their cells in this region. As a result, less serotonin passes between neurons, disrupting the messages that help us monitor and process threats, which then leads to anxiety. Drugs that block serotonin uptake, called SSRIs, are often the first medication offered to treat generalised anxiety disorder.

The spotlight has also turned to genes associated with a protein called brain-derived neurotrophic factor (BDNF), which helps neurons grow. Casey Guillot at the University of North Texas and his colleagues have found links between variants of BDNF genes and an individual’s vulnerability to anxiety. BDNF is intimately involved in how our brain matures, and altered levels are thought to affect how fear circuits in the hippocampus, prefrontal cortex and amygdala develop during early adolescence. Putting it all together, “it’s reasonable to speculate that variations in BDNF genes have effects on brain signalling that result in greater vulnerability to anxiety”, says Guillot.

We can’t place all the blame on our genes, though. While some of us have a genetic susceptibility to anxiety, environmental factors can help or hinder its expression. For instance, a study of more than 41,000 people found that stressful events such as loneliness amplified the effects of a genetic susceptibility to anxiety.

Your gut microbiome may play a role, too. Last year, Mary Butler at University College Cork, Ireland, and her colleagues compared the gut bacteria of 31 people with social anxiety disorder – which is a fear around social situations – and 18 people without it. They found several differences between the groups. For example, those with social anxiety disorder had more of the species Anaeromassilibacillus sp An250, while those without the condition had more Parasutterella excrementihominis.

Butler says that “attempts are under way” to work out how these interact with the body and brain, which could lead to treatments. There is reason to be hopeful. For instance, research has shown how manipulating gut microbes can help with drug-resistant depression (see “Five scientific ways to help reduce feelings of anxiety”).

There is another way your diet could affect your anxiety levels. One meta-analysis found a correlation between caffeine intake and elevated risk of anxiety, especially when people had more than 400 milligrams of it, or around five regular cups of coffee, a day. The reason isn’t clear, but it may be because high volumes of caffeine increase heart rate, which could trigger anxiety via “interoception”. It has been shown that people who are overly aware of internal sensations, like their heartbeat, may be at higher risk of experiencing anxiety (see “The new evidence that explains what anxiety really is”). The positive news is that interoception can be modified: when people are taught ways to better interpret physiological sensations, they are able to decrease their anxiety.

So, while you can’t change your genes, if you have been dealt a genetic predisposition towards anxiety, and want to overcome it, switching to decaf and developing a more accurate perception of bodily sensations may not be a bad place to start.