“Chemo brain” is a chemotherapy side effect. It involves cognitive changes such as poor memory and concentration. It may occur during or after treatment.

Knowing about the possible cognitive side effects of chemotherapy can help a person feel more prepared for any changes during or after treatment. A person can also take steps to manage the side effects.

This article explores the cognitive side effects of chemotherapy, their causes, and who might experience them.

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“Chemo brain” is a term that some people use to describe a decrease in mental sharpness due to chemotherapy treatment. It can cause feelings of fuzzy and sluggish thinking, which some people may describe as “chemo fog” or “brain fog.”

Clinicians may use the following medical terms to describe chemo brain:

  • cancer treatment-related cognitive impairment
  • cancer-related cognitive change
  • post-chemotherapy cognitive impairment

According to a 2020 article, out of 15 million cancer survivors in the United States, chemo brain affected around 5 million of them.

Symptoms may begin at the onset of treatment. While they may last for a short time for some people, others may experience symptoms of chemo brain 5–10 years after treatment.

Learn more about chemo brain.

Chemotherapy may cause a range of cognitive impairments. These include:

  • memory lapses
  • problems with concentration and focus
  • trouble remembering details, including names, dates, and significant events
  • difficulty multitasking
  • inability to find the right words to finish a sentence

A person may also experience alterations in the following cognitive abilities:

  • working ability
  • concentration
  • awareness
  • attention
  • visual-verbal memory
  • executive functions, such as decision-making and problem-solving
  • processing speed

Learn more about the side effects of chemotherapy.

The mechanisms underlying chemo brain are still unclear, but experts theorize that it is a combined effect of neuron damage, abnormal repair, and brain remodeling.

A small 2019 study that looked at the brains of children and mice exposed to chemotherapy found a stark reduction in the precursor cells for oligodendrocytes. These are the cells responsible for the myelination of neurons in the brain.

Recent studies have shown that chemotherapy causes toxic effects on cells in the central nervous system (CNS). It induces oxidative stress and cell death, inhibits neuron growth and development, and activates other processes that may be harmful to cells in the brain. These changes alter neuron development and cause problems with learning and memory.

While chemotherapy is the key contributor to cognitive impairment, other factors may also contribute. These include:

Chemo brain affects up to 75% of people during treatment. It persists for several months after chemotherapy treatment in 35% of patients.

What side effects a person may get from chemotherapy and how bad they are varies significantly from person to person.

Learn more about how long chemo brain lasts.

Certain factors may increase a person’s risk of developing chemo brain:

  • other drugs that are part of cancer treatment, including steroids
  • other conditions, such as high blood pressure or diabetes
  • having an infection
  • experiencing depression or anxiety
  • older age, including being postmenopausal
  • surgery and the use of anesthesia for surgery
  • hormone treatments or changes in hormones
  • nutritional deficiencies
  • ingesting substances that may change one’s mental state, such as alcohol

It is best for a person to contact their doctor if they have concerns about the risks of cognitive side effects.

A person’s doctor may recommend cognitive rehabilitation as part of their rehabilitation program for cancer. This includes:

  • finding ways to take in new information and perform tasks
  • repeatedly performing activities that may become harder over time
  • using tools such as diaries to help with organization

Physical activities such as walking or gardening may help improve brain function. Meditation may also help a person improve focus.

Other things that may help a person manage cognitive side effects of chemotherapy include:

  • aiming to do more demanding tasks when they feel their energy levels are the highest
  • keeping a detailed planner or reminders to help with organization and sticking to a routine
  • performing activities that exercise the brain, such as word puzzles
  • keeping items such as keys in one place so it is easier to find them
  • aiming to focus on one task at a time rather than multitasking
  • getting enough sleep and rest
  • consuming a diet rich in vegetables
  • avoiding alcohol and other substances that can affect mental state
  • asking family or friends for help

See more tips for coping with chemo fog.

Here are some frequently asked questions about cognitive changes during chemotherapy.

Can chemo cause dementia-like symptoms?

Chemo can cause cognitive side effects such as memory problems and difficulty concentrating. These are similar to some symptoms of dementia.

How long does chemo affect your brain?

Many chemo side effects may go away after treatment. However, some people may experience cognitive symptoms for months or years afterward.

Is confusion a side effect of cancer treatment?

Confusion is a cognitive impairment that might occur due to chemotherapy treatment for cancer.

“Chemo brain” refers to cognitive symptoms that may occur as a result of chemotherapy treatment. It may be short term or last for months or years after the treatment.

It may affect anyone receiving chemo, but taking other medications, having coexisting conditions, and experiencing certain other factors may increase a person’s risk of cognitive changes.

A doctor can help a person find ways to manage cognitive changes. Staying active, consuming a nutritious diet rich in vegetables, using memory aids, and keeping the brain active may help.