Is ‘chemo brain’ real?

chemo brain chemotherapy

‘Chemo brain’ and cognitive decline after cancer – is it real?

Cancer and its treatments cause a variety of side effects, some of which people recover from quickly, while others last long after treatment is over. After chemotherapy, around 70% of cancer survivors report difficulties with memory and concentration – this is colloquially known as “chemo brain”.

But while many cancer survivors report problems with memory or concentration, few studies have found a relationship between the results of formal cognitive testing and self-reported symptoms. In fact, formal cognitive assessments of survivors often show their performance is still within the normal range.

This doesn’t mean that cognitive symptoms should be ignored. If you think something is wrong, you can undergo a formal assessment by a neuropsychologist (a psychologist who specialises in the brain), which usually involves standardised clinical neuropsychological tests – pencil-and-paper or computer-based tests that measure memory, language and perception.

Intellectual performance

Studies that evaluate cancer patients over time (longitudinal studies) have shown that about 20% to 30% have cognitive problems, whereas we would expect about 10% impairment in healthy people.

Earlier research suggested anywhere between 15% to 50% of adults with early stage cancers may have cognitive impairment after chemotherapy. But much of the research has been limited to women with a breast cancer diagnosis. And the early studies tested people once after chemotherapy, so they cannot tell us how people’s cognitive function was before chemotherapy.

Despite some variability in research results, there seems to be a group of people who experience cognitive impairment during or after cancer treatment, which may be worse after high-dose chemotherapy. And for some people it may last five to ten years or more.

While the cognitive deficit is usually mild (such as difficulty finding the right word or forgetting people’s names), it can impact people’s daily activities and may be more pronounced in specific situations such as those requiring multitasking.

What’s to blame – cancer or chemo?

Studies testing people after a cancer diagnosis show that around 30% of people with breast or colorectal (bowel) cancer will have cognitive impairment, before any chemotherapy. So simply attributing the cognitive decline on chemotherapy is not accurate, as the cancer could, in fact, be to blame.

Cognitive impairment has also been shown in some women diagnosed with breast cancer who did not undergo chemotherapy but were treated with hormonal therapies such as tamoxifen, anastrozole and letrozole.

Even before chemotherapy, some people with cancer experience problems with memory, language and judgement. Image from

The underlying causes of cognitive impairment in cancer survivors are unknown. But a number of proposed mechanisms are being investigated. These include the toxic effects from chemotherapy and/or the cancer on the brain, changes in hormonal levels, clotting or inflammation in the brain, and genetic predispositions.

Some genetic factors known to increase the risk of Alzheimer’s disease have also been implicated in causing cognitive decline after chemotherapy. But most of these studies are small and there are some conflicting results.

Multiple other genes are being investigated, including ones that influence the metabolic breakdown of dopamine, DNA repair, regulation of inflammation in the brain and the blood-brain barrier designed to protect our brain from toxic insults.

Changes in oestrogen levels due to early abrupt menopause in women treated with some chemotherapy agents were also implicated, but larger studies have not shown a strong association.

Most work evaluating the mechanisms of cognitive impairment has been done with animal models. These suggest that in rodents at least some chemotherapy agents may decrease the generation of new neurons in the hippocampal area of the brain, cause damage to white matter or small blood vessels in the brain, or interfere with the hypothalamic-pituitary axis (the hormone glands).

Future treatments

No interventions have yet proven to prevent cognitive impairment from occurring in people with cancer or to treat it once it has occurred. But our team is running a number of studies to evaluate different types of interventions.

Two of these studies are evaluating approaches to cognitive rehabilitation (retraining the brain) for those experiencing ongoing cognitive symptoms six months to five years after chemotherapy for early stage cancer: one is via a 15-week computer-based training program that can be done at home; the other is six weeks of face-to-face retraining and learning sessions.

No therapies have been shown to prevent cognitive decline in people with cancer but the research is underway. Flickr/Judy **

The third study is evaluating whether a standardised extract of the herb gingko biloba can help to prevent or decrease cognitive impairment with chemotherapy.

To test these interventions we include a control group of people in each study who don’t receive the intervention – this shows us how much improvement occurs naturally with time.

It’s hoped that these studies, as well as work we are doing in animal models, will tell us what causes cognitive problems in people with cancer, and then enable us to develop more targeted strategies for preventing or minimising cognitive impairment in cancer survivors.

The Conversation

This article was originally published in The Conversation by Janette Vardy, University of Sydney and Haryana M Dhillon , University of Sydney

Janette Vardy receives funding from the NHMRC, Cancer Australia, Cancer Council NSW and the American Society of Clinical Oncology, USA. She is affiliated with The University of Sydney and Concord Cancer Centre, Concord Hospital, Sydney. Haryana M Dhillon receives funding from NHMRC. Cancer Australia and Cancer Council NSW.

This article was originally published on The Conversation. Read the original article.

Chemo image:

Share the love


  1. Sarah and Janette and commentators on The Conversation site, you are discussing the inappropriate concept of the origin as well as the treatment(s) of cancers. First there are all the various cancers diagnosable because there are a miriad of different functioning tissues in the body.
    The human and animal bodies have good reason to cause structural damage (tumor start, progression and life termination) in these tissues. The following is a rarely understood concept of how disease starts (and I am keeping it way too brief!) The cause (one of them!) of disorders (disease) we are all subject to are found in the start of body cells dying. Cells have a limited time to exist and do their jobs. Once completed they “prefer” to die a natural (apoptosis) death. Not given that chance the natural message to accomplish that gets confused and they will start to grow uncontrolably. Another cause of dying cells is that they become damaged due to trauma. This can be a physical as well as a mental trauma. The German New Medicine concept is great at understanding the latter. Either way cells of the affected area(s) die and spill their contents into the blood stream. This intra-cellular (the nuclei’s especially!) content is VERY TOXIC and when found in the blood it is then called self- or auto-antigens. The body, given a healthy bone marrow, will make auto-antibodies to them. A long story beyond that is that when something goes wrong physiologically and these antibodies are NOT created or removed, they will stop the normal repair of the damaged area(s) and no relief of any sort is found. There is also the potential chance that a distant area will become damaged as well (and in a special way I need to mention via a longer presentation) When an irritation as such is created it is possible that a protective response is created and cells try to protects themselves with a cocoon-like enveloppe and voila, a cancer may start to grow. I will be happy to present both writers with my full article ready for publicaiton by either. Give me a nod.
    I am Dr. Pieter Dahler, DDS, MD, ND (hon Profeswsor), Ph.D, In Colorado, USA

    • Sarah McKay on May 26, 2014 at 7:24 am

      Send the paper this way Pieter! Love to read it. Sarah

  2. Health care & checkup on December 22, 2017 at 12:51 pm

    I think this is one of the most significant information for me. And i’m glad reading your article. Thank for sharing!

Leave a Comment

download my free checklist


9 Daily Habits of Highly Healthy Brains

Learn how to use neuroscience in your everyday life.