Cancer-related memory and cognition problems

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on April 29, 2022.

Everyone may forget where they put their keys every once in a while, but when you’re a cancer patient, your memory may slip more often. You may find yourself in moments of intense confusion, unable to follow the thread of your thoughts, at a loss to put the pieces together, or having difficulty remembering names, ages, faces or dates.

Memory problems and cognitive deficits—sometimes called “chemo brain”—are likely the result of treatment side effects and the effects of cancer. While experts don’t know exactly what causes common cognitive changes in cancer patients, tackling the issue head-on may help you get back to feeling better faster, and improve your quality of life both during and after cancer treatments.

Possible causes of cognitive changes

The root cause for brain function changes could be a treatment side effect or worsening illness. Possible reasons for memory and cognitive problems include:

  • Cancer that has spread to the brain or the fluid around the brain
  • Cancer treatments such as chemotherapy, radiation, surgery, immunotherapy or a stem cell transplant
  • Drugs that may or may not be taken as part of cancer treatment, such as opioids, steroids, nausea or allergy medicine, appetite stimulants and sleep aids
  • Not enough oxygen getting to the brain
  • Not enough iron in the blood
  • Unbalanced electrolytes or low blood sugar
  • Organ failure
  • Pain, infection or fever

Identifying and addressing some of these issues may help your cognitive symptoms improve.

Risk factors for memory lapses and confused thinking

Chemo brain isn’t limited to cancer patients on chemotherapy—it may happen to anyone with cancer. Mental fogginess may come on quickly and only last a short time for some. But it may be a long-term issue from delayed treatment effects for others.

Certain factors increase the risk for confusion, memory issues and even delirium:

  • The location of the cancer
  • The drugs used for treatment
  • Other illnesses or conditions you have
  • Other symptoms you have
  • Underlying emotional issues, such as depression and anxiety 
  • Older age and a poor score on a health and performance assessment that measures difficulty of doing daily tasks
  • Having had surgery and anesthesia
  • Having an infection
  • Hormone status and treatments
  • Nutritional deficiencies
  • Use of alcohol or other substances


It’s possible to feel a general cloudiness or loss of short-term memory during cancer treatment or a more serious cognitive dysfunction that causes confusion and delirium.

People reporting cognitive declines after cancer treatment cite issues such as:

  • Trouble remembering details or learning new skills
  • Forgetting things they already knew, like common words or familiar objects
  • Inability to focus long enough to finish a task or follow instructions
  • Losing track of tasks in the middle, especially when multitasking
  • Problems with thinking clearly or a decrease in mental sharpness
  • Issues managing money, either losing track of bills or forgetting to pay them
  • Loss of motivation or increased anxiety or depression

11 tips for coping with cognitive issues

If you feel you’ve lost some mental sharpness, below are coping strategies, treatment options and exercises that may help.

  • Tell your friends and family: It’s important to open up to your loved ones in your support network about your struggles with mental fogginess and confusion. If they know you’re struggling, they’ll better understand what you’re going through and help keep you safe when you have a confusion spell.
  • Consider having someone accompany you to appointments: They may be able to update the doctor on your cognitive issues, while also taking note of any instructions or recommendations.
  • Stay in familiar environments: Being in your usual surroundings may help you stay safe if you get confused. Create and stick to a routine. Following the same daily schedule helps keep you on track, as you'll have fewer curveballs to deal with.
  • Keep your cancer care team informed: The earlier you tell your doctors about cognitive issues, the sooner they’re able to step in. Your care team may be able to help pinpoint what’s causing the issue and address it. When you speak with your doctor, ask these specific questions:
    • What underlying issues could be causing my cognitive changes?
    • Are there ways to treat those issues that could help reverse my fogginess?
    • When can I expect these changes to go away?
    • How do I manage my chemo brain in the meantime?
    • How do I decrease symptoms and prevent new ones?
    • Should I see a specialist?
  • Try cognitive rehabilitation: Keeping your mind sharp may take a little work. As part of a general cancer rehabilitation program, you may go through cognitive rehabilitation, which includes:
    • Information on how the brain works
    • New ways to use your brain
    • Tools to keep yourself organized
    • Mental exercises to improve brain function
    • At home, you may try doing crosswords and puzzles, taking online classes or learning a language.
  • Try to stay organized: Having a place for everything and having everything in its place may help keep you from losing things. Use a diary or planner. Try adopting a system to keep your notes, schedule and thoughts in one place. It may be on paper or your phone, but keeping everything together may help you find the information you need.

    You may also use your planner or diary to track memory issues and confused thinking. Note which medicines you’re taking, what time of day you notice symptoms, and the overall situation when you’re feeling foggy. Looking for trends in this information may help you root out the issue and be ready for the next time. Keep notes on what time of day you feel your best and focus on doing your most demanding tasks then.
  • Get physical exercise: Being active helps improve your brain health. Even just getting more movement throughout the day by gardening, walking the dog, or doing chores around the house may help get your brain back on track. Endorphins released during exercise may improve your mood, and the activity may help you feel more alert. Try tai chi or yoga for both their exercise value and stress relief benefits.
  • Meditate: Meditation is a wonderful tool for learning how to focus. It may help reduce stress, but it’s also a practice of awareness for your body, brain and world. Training your brain with meditation may improve your ability to pay attention and focus throughout the day.
  • Boost sleep quality: Sleep is great for helping you stay sharp. When you’re feeling muddied, try taking a nap for an hour or less (too much napping may interfere with sleep quality at night). If you’re having trouble sleeping at night, ask your doctor about treatment options.
  • Treat your body well: Eat good-for-you foods like fruits, veggies and lean sources of protein. Limit or avoid alcohol.
  • Give yourself time: In many cases, your brain and body may simply need more time to heal. If your chemo brain persists long term, inform your doctor and get reviewed by a neuropsychologist or another specialist. Be gentle on yourself—you can’t control how your body reacts to cancer treatment any more than you can control how the cancer reacts.

For the caregiver

When confusion becomes severe, it's considered delirium. Delirium usually comes on suddenly. It’s caused by many of the same mechanisms as confusion.

Memory loss or confusion may hit harder when your loved one is in a new place, maybe on vacation or visiting family. It may also worsen at night—a phenomenon called sundowning.

Signs to monitor include:

  • Loss of speech, exceptionally long pauses or slurred words
  • Changes in behavior and personality
  • Sudden shifts in emotion, including anxiety, depression or other mood changes
  • Confusion about where they are or what they’re doing
  • Need for help with basic hygiene tasks such as bathing and dressing
  • Cloudy or disorganized thoughts

If your loved one experiences any of these signs or symptoms, becomes violent, or tries to hurt themselves or others, contact their care team to explore the underlying cause and treatment options.

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