Changes in thinking and memory

Changes in thinking and memory

Some people diagnosed with cancer notice changes in the way they think and remember information. This is called cancer-related cognitive impairment, but people may also refer to it as “cancer fog” or “chemo brain”.

Read on to learn more about how to manage your day-to-day tasks and improve thinking and memory.

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What is cancer-related cognitive impairment?

Every day, your brain controls your thoughts, emotions and behaviour. The natural ageing process affects how the brain works (known as cognition or cognitive function). However, people with cancer often report a noticeable or sudden decline in cognitive function.


How can thinking and memory be affected?

Cognitive problems can occur before, during or after cancer treatment. Some people notice small or subtle changes, but for others the effects are more obvious. These may include:

  • a feeling of mental “fogginess” or sluggishness
  • difficulty concentrating or focusing
  • memory changes (forgetting names, dates, words and things you would usually recall)
  • difficulty finding words during conversations
  • finding it hard to do more than one thing at a time (multi-tasking)
  • difficulty processing information, including following directions, problem-solving or learning new skills being unusually disorganised
  • feeling unable to keep up with conversations
  • tiredness or fatigue.

What causes cognitive changes?

The exact causes of thinking and memory changes are unknown. So far, studies show the causes may include:

  • cancer treatments
  • treatment side effects, such as trouble sleeping, fatigue, pain, low blood counts and hormone changes
  • medicines given for surgery or to manage side effects of treatment, including anaesthetic, steroids, painkillers and anti-nausea drugs
  • your emotions, such as feelings of depression or anxiety
  • inflammation caused by the cancer, and the way it impacts brain processes
  • in some cases, the physical presence of a tumour in the brain, which can affect mental function.

Who is affected?

Although thinking and memory changes do not affect everyone with cancer, research shows it is relatively common. According to one study, it can affect up to three in four people during treatment, about one in three people before treatment and one in three after treatment.


How long does it last?

Thinking and memory problems are usually temporary and get better with time. Most people say they notice improvements within the first year after finishing treatment. Other people experience longer- term effects. Learning how to manage cognitive problems may reduce the impact on your daily life.


Effect on your emotional well-being

Dealing with cancer-related cognitive impairment can be challenging. You may not feel like yourself, which can affect your relationships with family, friends and colleagues.

Changes in your thinking or memory can have a big impact on your ability to manage at home, while working or studying, or during social activities. This may make you feel upset, scared or frustrated.

You might feel you have to put in extra mental effort and energy to do tasks. Try to be gentle with yourself and allow time to recover.


Speak with your health care team if you are concerned about your ability to think clearly, concentrate and remember things.

This information was last reviewed in June 2018
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