Sometimes people with cancer worry about, joke about, or become frustrated by what they describe as mental cloudiness or changes they might notice before, during, and after cancer treatment. This cloudiness or mental change is commonly referred to as chemo brain (or chemobrain). Doctors and researchers may call chemo brain many things, such as cancer treatment-related cognitive impairment, cancer-related cognitive change, or post-chemotherapy cognitive impairment. The word "cognitive" refers to the way your brain works to help you communicate, think, learn, solve problems, and remember.
Most define it as a decrease in mental “sharpness” and describe it as being unable to remember certain things and having trouble finishing tasks, concentrating on something, or learning new skills. Even though its exact cause isn’t known, it can happen at any time when you have cancer.
These mental changes can make people unable to perform usual activities like school, work, or social activities. Or it can seem like it takes a lot of mental effort to do them. Many people don't tell their cancer care team about their problems until it affects their everyday life. It's important to get help and support, so be sure to let your cancer care team know if you notice any mental changes, no matter how small.
Here are some examples of what patients with chemo brain may experience:
For most people, these mental changes only last a short time. Others can have long-term or delayed mental changes. How long chemo brain lasts is a major factor in how much it affects a person’s life. When it starts, how long it lasts, and how much trouble it causes may be different for every patient. Usually the changes that patients notice are subtle, and others around them might not even notice any changes at all. Still, the people who are having problems are aware of the differences in their thinking.
Chemo brain is most commonly connected with chemotherapy, but other treatments, such as hormone therapy, radiation, and surgery may be associated with it also. These treatments can cause short-term, long-term, or delayed mental changes or cognitive problems. Beyond the chemo brain symptoms that start during and just after treatment, there are some cases where chemo brain symptoms start and continue after treatment is over. Some people with cancer have very real brain problems even though they haven’t had chemo.
Certain things can increase the risk of developing chemo brain or worsening brain function problems. These include:
Most of these cause short-term problems, and get better as the underlying problem is treated or goes away. Others can lead to long-lasting brain problems unless the cause is treated.
Treatments for chemo brain may include:
Talk to your cancer care team about these treatment suggestions and other options they may recommend to help you cope with any cognitive problems.
There are some things that you can do to help you sharpen your mental abilities and manage chemo brain. Some examples are:
Another thing you can do to better manage chemo brain is tell family, friends, and your cancer care team about it. Finding and getting support is important. Let them know what you’re going through. You may feel relieved once you tell people about the problems you sometimes have with your memory or thinking.
Chemo brain is a side effect you can learn to manage. Even though this might be a change that’s not easy to see, like other changes such as hair loss or skin changes, your family and friends might have noticed some things and may even have some helpful suggestions. For instance, your partner might notice that when you’re rushed, you have more trouble finding things.
Tell your friends and family members what they can do to help. Their support and understanding can help you relax and make it easier for you to focus and process information.
If brain problems cause trouble at work or school, or interfere with your usual activities, talk with your doctor to try and pinpoint what’s causing your brain fog and what can be done about it. This is especially important for people with chemo brain that lasts longer than the treatment period and keeps causing trouble in their daily lives.
It helps a lot if you have a diary or log of the situations you have trouble with. It also helps to let your doctor know some of the things that make the problem worse or better. For instance, are they worse in the morning or evening? Do you have more trouble when you are hungry or tired? Does it help to nap, walk, or have a snack? Your doctor will want to know when the problems started and how they affect your daily life.
You may need to visit a larger hospital or cancer care center to find experts on testing brain function, including chemo brain. Ask if you can get a referral to one of these specialists who can help you learn the scope of your problem and work with you on ways to manage it. You’ll want to find out what your insurance will cover before you start.
These are just some of the questions you may want to ask your doctor:
So far, there is no known way to prevent the cognitive changes that cause chemo brain. This is because the causes are still being studied. For some people, treating their cancer will mean they might have trouble with thinking, memory, planning, and finding the right words. Chemo brain seems to happen more often in people who get high doses of chemo, and is more likely to happen if the brain is also treated with radiation therapy.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
Brown PD, Butts AM, Parsons MW, Cerhan. Neurocognitive effects. In DeVita VT, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 11th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2019:2175-2179.
Brant JM, Stringer LH. Cognitive impairment. In Brown CG, ed. A Guide to Oncology Symptom Management. 2nd ed. Pittsburgh, PA: Oncology Nursing Society; 2015:203-228.
National Cancer Institute (NIH). Cognitive impairment in adults with non-central nervous system cancers (PDQ®)- Patient Version. 2018. Accessed at https://www.cancer.gov/about-cancer/treatment/side-effects/memory/cognitive-impairment-pdq on August 5, 2019.
National Cancer Institute (NIH). Memory or concentration problems and cancer. 2015. Accessed at https://www.cancer.gov/about-cancer/treatment/side-effects/memory on August 5, 2019.
National Comprehensive Cancer Network (NCCN). Survivorship. Version 2.2019. Accessed at https://www.nccn.org/professionals/physician_gls/pdf/survivorship.pdf on August 5, 2019.
Yust-Katz S, Khagi S, Gilbert MR. Neurologic complications. In Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:688-705.
Last Revised: February 1, 2020
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