• Introduction
  • Filtering – An Explanation for Families
  • Stress Response
  • Outcomes
  • Management


‘Flooding’ is the term most typically used by people living with the outcomes of a brain injury to describe feelings of sensory overload.

It can be difficult for family and friends to understand and to adjust to this effect a brain injury has on their loved one, not only because many people have no visible scars and look the same as before, but because it isn’t something people usually experience.

Even when there are visible scars and injury, difficulties with understanding can persist.

The closest experience people without brain injuries might use to understand is to imagine how you would feel when you are under-the-weather, stressed, too much is going on, you have a headache, you haven’t eaten, and are at a concert with fireworks going off being pushed around by the crowd. The feelings of irritability and wanting to escape you might have are watered-down versions of flooding. 

In the acute and early stages, sometimes for more prolonged periods, flooding doesn’t go away. The only way you can shut the feelings down is to lay in a quiet, darkened room. 

Flooding post brain injury can create unimaginable confusion and profound anxiety. In some instances, an overload of the senses can lead to a panic attack. The fight or flight response can lead to symptoms such as sweating, a racing or palpitating heart, clammy hands, and irritability or anger.

Many people will isolate themselves and begin to avoid activities outside of the home. Try to bear in mind that brain injury causes the reactions to over-stimulation, and the behavioural responses are neither attention-seeking or deliberate. The flooding response will not just go away; it takes time for the brain to relearn how to filter and to adjust. Some people struggle in diminishing degrees for the rest of their lives.

Filtering – an explanation for families

In a healthy person the brain filters information. It uses attention skills to prioritise what is most important and necessary, and screens out background peripheral stimuli.

The world around us continually floods us with more information than we can process comfortably or handle psychologically so when the brain fails to filter excess data, we become mentally, physically, and emotionally overwhelmed.  The more there is going on, the harder it is for people living with a brain injury to cope.

When the filters no longer work properly, due to slowed processing or missing data/memories, the brain no longer screens background noise, sights, sensations, smells, movement, and so on.

For example, people may become sensitive to how their clothes feel on their skin or to the weight of the bed covers. They may be unable to close out background noises such as the humming of a fridge or freezer. It can become impossible to focus on what you are doing or want to do, such as holding a conversation or trying to navigate a route to a planned destination.

When the filters are damaged or impaired, everything comes at once. People describe feeling bombarded and as though environmental and external information is incoming too fast and all at once. It doesn’t stop here though, individuals are also trying to manage their internal stimuli at the same time.

Slowed processing means that incoming information cannot be sorted fast enough, and memory impairment means that the brain no longer knows what to do with incoming sensations and information. It has no experience to match it to and is unaware of what is safe, what is dangerous or harmful, and what is needed, so everything smashes against the brain like a rogue wave hitting a ship.

When information floods the brain, people can find it hard to maintain their focus and attention. It can be impossible to make choices or to prioritise, so people struggle with knowing what to do first and being able to filter out what to ignore.

Stress response

Sensory overload causes a distinct stress response throughout the body increasing inflammation, and creating a vicious circle wherein the brain will find it even harder to process the outside world because of the effects on the internal environment. This loop can slow recovery without people realising why.

When the overload is intense and prolonged, it may cause the brain to shut down temporarily. You might struggle to equate these ‘switch off’s’ with sensory overload, and the circle perpetuates, sometimes for many years.

Although the shut down is often fleeting, it is obvious and will either create feelings of curiosity or fear. The brain is protecting itself, and preventing further psychological damage and stress. When you regain some semblance of functionality after a ‘switch-off,’ it is best to reduce the input signals as quickly as possible and retreat to somewhere there is less noise/less going on.

You might feel entirely ‘phased out,’ and it can take several hours or even days, to feel recovered.

Overpowering fatigue and increased cognitive impairment are common effects and may lead to frustration, which again worsens the inflammatory response. The more inflammation, the harder the brain has to work, and the worse flooding will become.

Feeling incapacitated and aggravated by the reaction to overload will cause you to take longer to recover. It is better to accept that some situations may need to be better managed and to learn to avoid triggers or conditions that are known to be stressful. Over time you can learn to expose yourself to more stimuli gradually. 

One way to do this is to spend time each day trying to recognise what is coming in through your senses. Acknowledge each one, and then try and think about whether or not it is something you need to be aware of or not. By focussing you attention on your environment in small doses you can help your brain relearn what is dangerous, what is always safe, and what might lay in the middle.


It is much more difficult for the brain to heal and rewire or make new neuronal connections, when it is overloaded or has shut-down. 

The feeling of ‘switch off’ that can happen at times of intense flooding can develop into hours or days of feeling as though the cognitive light has dimmed. This shut-down allows the body the time it needs to recover from the stress response, and it is better to rest and relax while this healing takes place. Pushing yourself will only make things worse.

Known as sensory hypersensitivity, the addition of increased sensitivity to light or noise can exacerbate the flooding response meaning that even small increments in environmental activity can be stressful or may lead to increased headaches and other symptoms.

We know the inflammatory response to stress can cause a chain reaction. Part of this is oxidative stress, which causes an increase in free radicals. Naturopathic doctors have linked oxidative stress with increased noise sensitivity, making it even more vital to eat lots of brightly coloured fruits rich in antioxidants.

Experiences of being intensely overwhelmed can be used to structure coping strategies to suit yourself.

What works for one person may not work for another because every person and every brain injury is unique.

For example, if you know that you can’t deal with background noise, ask for a quiet corner is a restaurant and make your booking at non-peak times. The same with travel and avoiding rush hour traffic and people. You might limit the time you spend at functions or arrive early on or later when there are likely to be fewer people. Strategies like these don’t make issues with sensory overload go away, but they can help you to avoid the experiences of flooding.

N.B. People don’t over-react; they are genuinely debilitated and need support.


Managing flooding can also help you to manage stress in better ways and improve the brain environment for recovery. 

Stress also has far-reaching detrimental effects on the body and immune system. Adverse pressure must be avoided whenever possible as chronic inflammation can be the precursor to illness and disease.

Brain injury does necessitate change, and the sooner you adapt to these, the healthier you will be. Our general health has an impact on enhancing rewiring and improving neuronal structure. It is essential to start the management of the effects of brain injury as early on as possible.

Many people will visit their general practitioner when they notice problems aren’t going away or are getting worse. Often the symptoms of flooding are managed in isolation from each other and the overall brain injury, and people are prescribed medications to help them to cope.

While some people do better, many people living with brain injury report adverse effects to drugs and notice they can impact on the quality of life and exacerbate other symptoms.

For some people ‘talking therapies’ work well as this helps them break down their issues into more recognisable problems. Writing things down and sorting thoughts into a pros and cons list can help people be more able to qualify priorities and to make decisions about what they can cope with inside and outside of the home.

Slowing life down and paying attention to what you want from your lifestyle can bring unexpected rewards. Managing these changes can be harder for some people, especially those with ‘type A’ personalities.

There are many other ways to combat sensory overload, such as reducing stress and addressing inflammation by using techniques like:

  • mindfulness and meditation
  • eating for nutrition/avoidance of inflammatory foods
  • support of the gut microbiome
  • using supplements
  • other therapies and treatments
  • life needs – exercise, daylight and activities such as tai chi or yoga

Many people know what helps them to relax and work on ways of being disciplined about putting time aside for themselves to maybe unwind in a hot bath or take a walk in the fresh air. Other people use earplugs or headphones to help them block out background noise.