Cognitive problems

Cognitive function refers to your thinking abilities. This includes communication, reasoning, perception, judgment, learning, attention, memory, organization and problem solving. Problems with cognitive function may be called cognitive impairment or cognitive dysfunction.

Cognitive problems can affect your emotional well-being and overall quality of life. You may have difficulty at school, at work or in your daily activities. Cognitive problems may also interfere with your ability to understand or make decisions and decrease your independence.

Cancer or its treatment can affect cognitive function. Cognitive problems can develop during or immediately after treatment. They can also develop years later.


People with cancer can have cognitive problems for many different reasons. These problems may be caused by more than one factor.


Certain cancers, including a brain tumour or another cancer that has spread (metastasized) to the brain, can cause cognitive problems.

Cancer treatment

The type, dose and length of cancer treatment can affect cognitive function.

Radiation therapy to the head and neck or total body irradiation (TBI) can damage brain cells. A high dose of radiation, radiation to a large area of the brain, or chemotherapy at the same time as radiation increases the risk of cognitive problems. Cognitive problems usually show up 1 to 2 years or longer after radiation therapy to the head.

Chemotherapy may cause problems with attention, memory or problem solving. This is sometimes called chemo brain or chemo fog. High doses of chemotherapy and chemotherapy given for a long time are more likely to cause cognitive problems.

Surgery to take a biopsy or remove a tumour from the brain can damage areas of the brain and cause cognitive problems. Sometimes removing the tumour can improve cognitive function.

Other cancer treatments, such as hormonal therapy and immunotherapy, may cause cognitive problems.


Medicines that can cause cognitive problems include:

  • drugs used to suppress the immune system
  • antibiotics
  • corticosteroids
  • pain relievers
  • antidepressants
  • anti-anxiety medicines
  • heart medicine
  • medicine to help you sleep
  • medicines used to manage medical problems and symptoms related to cancer or its treatment

Other factors

Other factors that can cause cognitive problems include:

  • infections, especially of the brain and spinal cord or those that cause a high fever
  • other diseases or conditions, such as diabetes and high blood pressure
  • not getting enough vitamins and minerals, such as iron, vitamin B and folic acid
  • stress, anxiety or depression
  • older age


Cognitive problems can be mild and may lessen or go away in the days or months following treatment. Sometimes cognitive problems are more serious and may take longer to improve, not improve at all or become worse over time.

Cognitive changes are different for everyone. They may cause difficulty with:

  • language skills, including expressing yourself in words, remembering words or naming objects, understanding words or conversations, and writing
  • math
  • memory, including problems remembering names, dates and appointments
  • learning new things
  • performing different tasks at once (multi-tasking) or switching between tasks
  • focusing attention, concentrating or organizing thoughts
  • judgment and reasoning
  • fine motor skills, such as buttoning clothes or using cutlery
  • thinking quickly

Cognitive changes can also include changes in your behaviour or emotions, including:

  • disorientation
  • mood swings
  • inappropriate anger or crying
  • irrational behaviour
  • confusion

If symptoms get worse or don’t go away, report them to the doctor or healthcare team without waiting for your next scheduled appointment.

Cognitive problems in children

Children aged 5 and younger who have had cancer treatment often have long-term cognitive problems. The problems can happen months or years after treatment is over.

Treatments that are more likely to cause cognitive problems are:

  • radiation therapy to the head, neck or spine
  • total body irradiation
  • chemotherapy that is given into the spine or brain

Cognitive problems that children may have include:

  • lowered intelligence
  • learning disabilities
  • lowered attention span
  • delayed social, emotional and behavioural development
  • lowered success in reading, math and language skills
  • lowered ability to understand language or express themselves
  • lessened memory skills

Early intervention seems to be helpful. Be aware of possible cognitive problems and talk to your child’s doctor right away if you notice a problem.

Find out more about learning problems and speech-language problems in children.


The early signs of cognitive problems may be subtle and easy to miss. Some of the changes associated with cognitive problems can also be confused with or made worse by depression or fatigue.

Family members are often the first people to notice a change in a loved one’s cognitive function or personality. You can ask a family member or caregiver to keep track of changes in your thinking, communication and memory. If you or someone else notices changes in your cognitive function, tell your doctor. Your doctor may do a simple evaluation or refer you to a specialist for a more thorough assessment.

To assess cognitive function, your doctor may:

  • do a physical exam
  • talk to you about any cognitive changes you’ve noticed
  • do cognitive testing to check your awareness of surroundings, judgment and reasoning, math and language skills, and memory

Your doctor may order a CT scan or an MRI of the head to check for tumours, damage to the brain caused by radiation therapy or changes in the brain.

Find out more about tests and procedures, including physical exams, CT scans and MRIs.

Managing cognitive problems

Cognitive rehabilitation means teaching or re-teaching thinking, reasoning or memory skills. These skills may not return to the way they were before cancer or its treatment, but cognitive rehabilitation can help improve your confidence and quality of life.

If cognitive problems are caused by a condition, such as anemia or an infection, they will usually go away after the condition or cancer is treated. Cognitive problems caused by medicine should also go away after you stop taking it.

Cognitive problems caused by cancer or its treatment may go away after treatment is finished, continue for a long time or become permanent. Managing long-term and permanent cognitive problems may include medicines, therapy and counselling.

Medicines that may help with cognitive problems include:

  • stimulants to improve concentration and memory
  • antidepressants, if cognitive problems are due to or made worse by depression
  • medicine to make you less drowsy if you are taking opioids, such as morphine, for pain

Cognitive training and cognitive rehabilitation may be given to help you improve cognitive skills and cope with cognitive problems.

Occupational therapy and vocational rehabilitation may help you with everyday tasks and job-related abilities.

Counselling and support during cognitive rehabilitation can help you adjust the rehabilitation as your needs change over time. The counsellor can give support to both you and your family.

Cognitive problems in children may be managed with:

  • occupational therapy
  • speech therapy
  • behavioural therapy and social skills training
  • cognitive rehabilitation
  • medicines for attention deficit hyperactivity disorder (ADHD)
  • in-school specialized programs in math and reading

Talk to the healthcare team about what help is needed to manage cognitive problems.

Coping strategies

Many people with cognitive problems feel frustrated, defensive and embarrassed about their reduced abilities. Some people aren’t aware that they have cognitive problems. It is also common for caregivers to feel frustrated and helpless. Everyone copes with cognitive problems differently, and it’s not always possible to make a full recovery.

The following strategies may help you cope with thinking, memory and attention problems.

Use different tools to help you remember

Keep a record of your symptoms. This record might help you figure out when you become more distracted. It can also show you if your memory is worse when you are tired or hungry or at other times. Knowing when your cognitive function is at its best or worst can help you plan your day so that you do more difficult tasks when you feel the best.

Use a paper or electronic calendar or daily organizer to record appointments, activities, notes and important dates. Set alarms on your smartphone or tablet as reminders. You can also use a note-making app. Keep the calendar or organizer with you so that you can look at it throughout the day. Make a habit of checking it first thing in the morning, around noon and then again in the evening. This will help you keep track of tasks that need to be done that day and reschedule tasks that can be done another day. Try to do just one task at a time.

Take care of yourself

Physical activity, such as walking, swimming or gardening, can help make you mentally alert. It is also important to get plenty of rest and try to reduce your stress. Yoga or meditation can help you relax and think clearer.

Exercise your brain. Try different activities, such as doing jigsaw or crossword puzzles, painting, playing a musical instrument or learning a new hobby. Wordplay, such as rhyming, can also help you remember things.

Talk to your family and friends about how you feel and how changes to your cognitive function affect you. They can better support you if they understand how you feel. They may also have some suggestions about how they can help.

Talk to your employer about getting support if you have problems at work, such as managing your workload or meeting deadlines.


All people who are treated for cancer need regular follow-up. The healthcare team will develop a follow-up plan based on the type of cancer, how it was treated and your needs.

Make sure you tell your doctor all the treatments you received. If you are at risk for cognitive problems, your doctor will ask you about your symptoms and how you are coping. You may have a physical exam and cognitive testing.

Ask your healthcare team questions at your appointments. You can also take a friend or family member with you to take notes so that you can read what was said after the appointment.

Expert review and references

  • American Society of Clinical Oncology. Attention, Thinking, or Memory Problems. 2016:
  • Brown PD, Schagen SB, Wefel JS . Neurocognitive effects. DeVita VT Jr, Lawrence TS, Rosenberg SA. Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2015: 144: 2068 - 2073.
  • Camp-Sorrell D . Chemotherapy toxicities and management. Yarbro CH, Wujcki D, Holmes Gobel B, (eds.). Cancer Nursing: Principles and Practice. 8th ed. Burlington, MA: Jones and Bartlett Learning; 2018: 16: 497 - 554.
  • Cohen MZ, White L . Cancer-related distress. Yarbro CH, Wujcki D, Holmes Gobel B, (eds.). Cancer Nursing: Principles and Practice. 8th ed. Burlington, MA: Jones and Bartlett Learning; 2018: 24: 759 - 779.
  • Dest VM . Radiation therapy: toxicities and management. Yarbro CH, Wujcki D, Holmes Gobel B, (eds.). Cancer Nursing: Principles and Practice. 8th ed. Burlington, MA: Jones and Bartlett Learning; 2018: 13: 333 - 374.
  • Landier w, Armenian SH, Meadows AT, Bhatia S . Late effects of childhood cancer and its treatment. Pizzo PA & Poplack DG (eds.). Principles and Practice of Pediatric Oncology. 7th ed. Philadelphia: Wolters Kluwer; 2016: 48: 1173 - 1196.
  • National Cancer Institute. Late Effects of Treatment for Childhood Cancer (PDQ®) Health Professional Version. 2018:
  • National Cancer Institute. Cognitive Impairment in Adults with Non-Central Nervous System Cancers (PDQ®) Health Professional Version. 2018:

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

We do our best to make sure that the information we provide is accurate and reliable but cannot guarantee that it is error-free or complete.

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