Life After Cancer

Dealing with ‘Chemobrain’

Posted by Dr Jane Clark on 02 July 2021

This article is adapted by Dr Jane Clark from an article originally written by Jane and Dr Peter Harvey. See our introduction for a background on this series of articles.

A number of people report that their brain doesn’t seem to work as well during chemotherapy – a phenomenon that may last well beyond the duration of the treatment for some. Researchers have termed this cancer-related cognitive impairment.


There are so many things going on in your life, so many changes, so many unpredictable events that it probably seems quite natural that you feel a bit muddle-headed. However, once things begin to settle a little as the treatment ends, you may find that there are some residual problems which cause you concern, these can include:

  • feeling that your memory is not working as well as you remember
  • finding it more difficult to concentrate or think clearly
  • feeling that it is more difficult to find the right words when talking
  • finding it more difficult to plan or put thoughts into action

“I remember literally forgetting the simplest of words in the middle of a conversation. But I think I found it really hard to make decisions, to work out how and when to do things. Trying to keep on top of things at home, children, school, food shopping. It all just felt overwhelming. I leant on my husband a lot to keep everything going at home.

Whilst there is little doubt that many people experience a loss of mental sharpness, just why this should be, is not an easy question to answer. Many factors can affect how we think and act – as well as how we assess and judge our own performance.


The stress and worry of the diagnosis, for example, can send you into a state of extreme worry which can have profound effects on your thought processes as well as being a powerful distractor. This distraction can mean that you pay less attention to things, which will affect your memory as things do not get properly registered.

You are also in a situation which may be quite unfamiliar to you, having to grasp a huge amount of new and complex information and which may be difficult to understand. In some cases, the cancer itself may have had subtle effects on other bodily systems which may affect cognitive processes.


Alongside chemotherapy that may cause changes in your cognition, research has suggested that hormone therapy may also play a role in causing cognitive problems. In addition, fatigue and menopausal sympyoms are also a contributing factor in changes in cognition.

If you are finding the problem worse on returning to work, it may be a symptom of simply being out of practice – many of us experience a problem settling back into work, even after a short holiday – and your break has been neither short nor a holiday. Many of us also experience a loss of clear thinking if we have a relatively minor illness – so if that happens after a dose of the ‘flu, think what could happen after a much more significant disruption to your health.


The problem can be amplified by our awareness of it. You may be – quite understandably – fearful that your memory is not as good as it was and may fear that not only will it not get better but may actually get worse. In turn, this may lead to you to feel that you will never be able to function normally again. So, you are not only monitoring each ‘failure’ and becoming very aware of these (and will probably take less notice of any ‘successes’) but your worry and anxiety will also make your performance less effective, so you get caught in a self-defeating loop.

All-in-all, therefore, there are many possible explanations for the cognitive decline that you may be experiencing, and the effects of chemo may be just one of them. There is scientific evidence on this problem, but like the phenomenon itself is does not give a clear or straightforward answer.


One problem is that it is actually quite difficult to measure accurately, easily and quickly what are quite complicated functions. There are also important individual differences – we all have different strengths in our cognitive system and our performance itself can vary over time (for example, you may be better in the morning whereas your partner may be better in the evening). So, any formal testing has to take account of these factors as well as all the many disease and treatment differences that might influence test performance.

What does seem to be emerging is that for some people there are quite small, but measurable, effects on memory and some other cognitive functions some of which are detectable for a number of months post-chemotherapy. The evidence so far does not suggest that these effects are major or serious. That does not mean that they are not frustrating or debilitating to live with every day. The research also suggests that the cognitive changes improve as the time from chemotherapy increases (but if you are still taking hormone therapies then you may not notice these improvements).

Most of the studies have been done with women treated for breast cancer and most have not looked at time periods longer than two years after the treatment has finished so we are still a long way from having a clear idea of just what is going on. Some research has suggested that post-menopausal women may experience greater cognitive impairment after treatment with chemotherapy and/or hormone therapy. But again, this needs further investigation.


So, is there anything that you can do about this? The short answer is yes. Perhaps the most important first step is (as with many other issues we have discussed here) not to be cross or annoyed with yourself and think that if only you tried a bit harder, it would all come good. These effects are real and there are quite logical and understandable reasons for why they might be occurring as we have seen.

It is also important to look at the time since your treatment finished. What you have experienced in the first few weeks post-treatment will be very different from what you experience twelve months later.


It is also very important (and much easier said than done) not to worry overmuch about this – worry will make things worse rather than better. You do need to ask yourself some questions, however. Have you actually forgotten anything very important (an appointment, a birthday or anniversary, for example)? Are you able to function on an everyday level reasonably effectively?

Remind yourself that before your diagnosis and treatment you forgot things, mislaid your glasses or car keys – many of us have lapses of memory and concentration in everyday life irrespective of whether we have been treated for cancer or not.

For a few weeks you may have to make lists or keep a diary – which is quite normal and may just give you the confidence you need to trust your own thought processes.

If you are really worried that you are not functioning as well as you used to or you feel that your mental processes are getting worse than you should discuss this with your specialist. It is important to bring some evidence of what you experience in some detail so they are able to decide whether to refer you on to a clinical neuropsychologist who would be able to assess your cognitive function in greater detail.

Dr Jane Clark, Consultant Clinical Psychologist

Next 12: Regaining Trust in Yourself

The information and content provided in this page is intended for information and educational purposes only and is not intended to substitute for professional medical advice.

June 2021


Claire diagnosed in 2016
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