Canadian Cancer Society logo
You are here: 

Cognitive changes and chemotherapy

Some chemotherapy drugs can affect the way the brain functions, so a small number of people will notice problems with memory and concentration. Sometimes this is called “chemo-brain” or “mental fatigue.”


It is unknown exactly how chemotherapy affects the brain, so it is not clear if chemotherapy directly causes these problems. Other factors may also play a role in cognitive changes, such as:

  • dose of chemotherapy drugs (larger doses cause more severe effects)
  • antinausea drugs (may affect concentration)
  • anxiety
  • depression
  • changes in routine
  • poor nutrition


Changes in memory and concentration can be very subtle and mild. Some people:

  • have trouble with short-term memory, such as not remembering where they put things, what they were talking about or phone numbers
  • cannot do simple arithmetic problems
  • are easily distracted
  • tire easily when doing things that need mental energy

These effects can go away after chemotherapy is finished or may last up to a year after treatment is over. Sometimes these effects occur long after treatment is finished.

Prevention and management

The healthcare team can suggest ways to help improve concentration and manage changes in memory. Mild cognitive problems tend to respond well to rehabilitation efforts, such as cognitive retraining techniques and exercises.

To cope with changes to memory and concentration, you can try the following:

  • Plan activities that require concentration for the times of the day when you are most rested.
  • Make lists to help keep track of things, such as appointments or when to take medicines.
  • Ask a family member or friend to help you remember by listening, taking notes and asking questions at appointments.


Dr Christopher Phenix Dr Christopher Phenix developed a new tool to watch aggressive cancers.

Learn more

Volunteers provide comfort and kindness

Illustration of volunteers

Thousands of Canadian Cancer Society volunteers work in regional cancer centres, lodges and community hospitals to support people receiving treatment.

Learn more