Life and stress can feel like a package deal but some people are more susceptible to stress than others. The same crisis can cause some to grow and others to break and become sick with illnesses such as depression.

Researchers have shed the light on why.

The answer lies in our genes. The response to stress is determined by a complex interaction between versions of the depression gene and the environment.

The research, published in the Journal of Neuroscience, has found that stressful life events interact with certain genes to change the size of the hippocampus, the part of the brain that processes emotions and transfers new information into long-term memories. An effectively functioning hippocampus is critical for learning.

What does stress do to the brain?

The hippocampus is particularly sensitive to stress because of the damaging effects of cortisol, the stress hormone.

When the body is subject to stress, cortisol attacks the neurons and the hippocampus shrinks in size. This is commonly seen in people with depression and is the reason for some of the physical symptoms.

The effect of cortisol is to force attention onto the emotions being experienced, while at the same time compromising the capacity to take in new information.

The duration of stress can be almost as damaging as the degree of stress.

What about positive stress?

On the other hand, positive stress, such as that which is experienced in exciting social situations, can cause the hippocampus to increase in size.

It’s our genes that decide whether the same stressful event causes the hippocampus to shrink or enlarge, and therefore whether the stress is good or bad for our brain.

The greater the number of risk genes somebody has, the more likely it is that stressful life events will shrink the hippocampus.

If there are only a small number or none of the risk genes present, the same stressful event can have a positive effect on the anatomy of the brain.

The research. What they did.

Researchers collected information from healthy participants about any stressful life events they’d been through, such as deaths of loved ones, divorce, unemployment, financial losses, relocations, serious illnesses or accidents.

Genetic analyses were also carried out, as well as scans of the subjects’ hippocampi.

What They Found.

As explained by lead researcher, Lukas Pezawas, ‘People with the three gene versions believed to encourage depression had a smaller hippocampus than those with fewer or none of these gene versions, even though they had the same number of stressful life events.’

On the other hand, people with one or none of the risk genes had an enlarged hippocampus when compared with people who had been through similar life events but had more of the risk genes.

Other Effects of Stress on the Brain 

As well as changing the size of the hippocampus, stress has also been found to have the following effects on the brain:

• The fight or flight response becomes activated. When this happens, the part of the brain responsible for automatic reactive responses takes charge, sidelining a more thoughtful, considered response.
• Increased cortisol can result in diminished short-term memory function.
• The hippocampus also plays a role in immune system function so when its efficiency is compromised, so too is the immune system. This is why illness often strikes when you’re stressed.

Nature/nurture is a topic that has fuelled lively debate. In the case of the neurological effects of stress, it would seem both make it off the bench.

‘These results are important for understanding neurobiological processes in stress-associated illnesses such as depression or post-traumatic stress disorder … It is ultimately our genes that determine whether stress makes us psychologically unwell or whether it encourages our mental health.’ – Lukas Pezawas, lead researcher.

Genes don’t mean destiny though, and the environment and our response to stressful situations have an enormous influence on the final outcome. Awareness of a susceptibility to fall quicker and harder to the ravages of stress makes it all the more important to take deliberate measures to keep stress levels under control as much as possible.

Mindfulness: A Heroic Defence Against Stress

Mindfulness is exceptional in its capacity to control stress and the effectiveness of this ancient practice is seeing it take its place in the mainstream. Everybody can do it. Everybody can make time for it. Here’s how it works …

As little as one minute a day of concentrated stillness can have a huge effect, but the more you can do, the more the effect will carry through. 15 minutes three times a week will have a profound effect on mental health. 

Mindfulness is all about experiencing what’s happening in the moment rather than being strapped by the past (rumination – going over and over the details – which can lead to depression) or worrying about the future (which can lead to anxiety). To practice basic mindfulness:

• breathe in for five seconds,
• hold for five seconds,
• breathe out for five seconds. 
• while you do this, focus on your sensory experience. What are you experiencing right now?What do you feel against your skin? What smells can you notice? Sounds? Temperature? What’s happening beneath your skin? Bodily sensations? Can you hear your breathing? Feel your heartbeat? 
• let other thoughts come and go but the idea is not to hang on to them for too long. Stay as much as you can in the present moment.

Mindfulness can take a bit of practice, especially if your mind is used to racing around on its own. The more you practice, the easier it will become.

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