Overview

Chemo brain is a common term people with cancer use to describe trouble with thinking and memory that can happen during and after cancer treatment. Chemo brain also can be called chemo fog, cancer-related cognitive impairment or cognitive dysfunction.

Chemo brain is a widely used term because this condition was first reported in people having chemotherapy treatments. But experts don't fully know the causes of these concentration and memory changes. There's likely more than one cause.

No matter the cause, chemo brain can be a tough side effect of cancer and its treatment. Researchers are working to understand the memory changes that people with cancer have.

Symptoms

Chemo brain signs and symptoms include changes in memory and thinking.

Symptoms of chemo brain linked to memory may include:

  • Trouble recalling what you've said to others.
  • Trouble recalling what you've seen, such as images or lists of words.
  • Trouble recalling what's happened recently, called short-term memory issues.

Symptoms of chemo brain linked to thinking may include:

  • Trouble finding the right words.
  • Trouble learning new skills.
  • Trouble doing more than one thing at a time.
  • Mental fog.
  • Short attention span.
  • Taking longer than usual to do routine tasks.

When to see a doctor

If you have trouble with memory or thinking, make an appointment with your healthcare professional. Keep a journal of your symptoms to help your healthcare professional know how your memory issues affect your life.

Causes

There are many causes of changes in memory and thinking in people with cancer. These chemo brain symptoms can be caused by the cancer, treatment for the cancer, complications of cancer treatment and other things.

Cancer-related causes may include:

Cancer

  • The stress of a cancer diagnosis, which can cause worry and distress. These can add to issues with memory and thinking.
  • Chemicals some cancers make that affect memory.
  • Cancers that begin in the brain or spread to the brain may cause changes in thinking.

Cancer treatments

  • Bone marrow transplant, also called stem cell transplant.
  • Chemotherapy.
  • Hormone therapy.
  • Immunotherapy.
  • Radiation therapy.
  • Surgery.
  • Targeted therapy.

Complications of cancer treatment

  • Low levels of healthy red blood cells or hemoglobin needed to carry oxygen to the body's tissues, called anemia.
  • Weakness and tiredness.
  • Infection.
  • Menopause or other hormonal changes caused by cancer treatment.
  • Sleep issues.
  • Pain due to cancer treatments.

Other causes

  • Some people may be more likely to get chemo brain based on genetic makeup.
  • Medicines for other cancer-related symptoms, such as pain medicines.
  • Other medical conditions, such as diabetes, thyroid conditions, depression, anxiety and not getting enough nutrients.

Risk factors

Factors that may increase the risk of chemo brain and memory changes in people with cancer include:

  • Brain cancer.
  • Cancer that spreads to the brain.
  • Higher doses of chemotherapy or radiation.
  • Radiation therapy to the brain.
  • Younger age at time of cancer diagnosis and treatment.
  • Older age.

Complications

Some people with chemo brain have thinking and memory changes that affect their ability to work. Most people with cancer can return to work at least part-time. But some may find that tasks now take extra focus or time. Others may not be able to return to work.

If you have trouble focusing on what you need to do for your job, tell your healthcare professional. Your healthcare professional may send you to a specialist who can help, such as an occupational therapist. This person can help find ways to make it easier to do your job.

Rarely, people with chemo brain can't work. Ask your healthcare team to refer you to a social worker. This person may help you find programs that support people who can't work because of a health condition.

March 06, 2025

Living with chemo brain?

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  4. Survivorship. National Comprehensive Cancer Network. https://www.nccn.org/guidelines/guidelinesdetail?category=3&id=1466. Accessed Aug. 29, 2024.
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  6. Distress management. National Comprehensive Cancer Network. https://www.nccn.org/guidelines/guidelinesdetail?category=3&id=1431. Accessed Aug. 29, 2024.
  7. Klaver KM, et al. Cancer-related cognitive problems at work: Experiences of survivors and professionals. Journal of Cancer Survivorship. 2020; doi:10.1007/s11764-019-00830-5.

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