Study Finds Scientific Basis for Chemo Brain

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Many women who get chemotherapy to treat breast cancer say they have problems remembering, thinking, and concentrating during and after treatment. These problems are commonly called “chemo brain” or “chemo fog” – doctors call these issues “cognitive impairment” or “cognitive problems.”

Some women may have trouble with:

  • learning new tasks
  • remembering names
  • paying attention and concentrating
  • finding the right words
  • multitasking
  • organizing thoughts
  • remembering where things are (keys, glasses, etc.)

A study found a link between chemo brain and lower neuropsychological test scores. Neuropsychological tests assess a person’s ability to think, talk, and make decisions, as well as the person’s behavioral and motor skills. Professional Advisory Board member Patricia Ganz, M.D., director of cancer prevention and control research at the University of California–Los Angeles Jonsson Comprehensive Cancer Center, led the study.

The study was published online on April 18, 2013 in the Journal of the National Cancer Institute. Read the abstract of “Cognitive Complaints After Breast Cancer Treatments: Examining the Relationship With Neuropsychological Test Performance.”

Women who’ve received chemotherapy to treat breast cancer have long complained about chemo brain. Still, doctors haven’t been able to find any physical evidence that allowed them to diagnose the condition, and some question whether chemo brain actually exists. Others think the condition is related to depression and anxiety instead of chemotherapy.

So the researchers wanted to see if women who complained about chemo brain had different scores on neuropsychological tests than women who didn’t complain about chemo brain. To overcome the issue of depression’s influence on chemo brain, the researchers excluded any women who had serious symptoms of depression.

The study looked at 189 women about 1 month after they were done with surgery and other treatments for early-stage breast cancer and before they started hormonal therapy:

  • 66% of the women had lumpectomy
  • more than 50% got chemotherapy
  • 70% planned to take hormonal therapy
  • 75% had radiation therapy

The average age of the women in the study was 52.

The researchers then matched the women in the study by age to a group of health women who hadn’t been diagnosed with breast cancer.

All the women filled out a questionnaire on memory and thinking skills and took a neuropsychological test given by the researchers.

Women who had been diagnosed with breast cancer were more likely to have more severe complaints about memory and problem-solving compared to women who hadn’t been diagnosed:

  • 23.3% of women diagnosed with breast cancer had memory complaints
  • 19% of women diagnosed with breast cancer had problem-solving and reasoning complaints

Women who had both memory and problem-solving complaints were more likely to have had both chemotherapy and radiation.

When the researchers then looked at the women’s neuropsychological test scores, they found that women diagnosed with breast cancer who reported even subtle changes in memory and thinking had detectable differences in their test scores compared to women who hadn’t been diagnosed with breast cancer. Lower neuropsychological test scores were linked to:

  • more severe complaints about memory and thinking
  • having both chemotherapy and radiation treatment
  • symptoms related to depression

"In the past, many researchers said that we can't rely on patients' self-reported complaints or that they are just depressed, because previous studies could not find this association between neuropsychological testing and cognitive complaints," Dr. Ganz said. "In this study, we were able to look at specific components of the cognitive complaints and found they were associated with relevant neuropsychological function test abnormalities."

The results reported here are part of an ongoing study that is looking at if and how hormonal therapy contributes to chemo brain. By gathering results on chemo brain before the women started hormonal therapy, the researchers will be able to see if the women’s thinking and memory problems change after they start hormonal therapy.

The good news is that most women who have memory and thinking problems during breast cancer treatment recover and are able to remember and think clearly after treatment is done. Still, a small number of women continue to have problems for a year or more after treatment ends.

If you’ve been diagnosed with breast cancer and are having thinking and memory problems, there are things you can do to help yourself. You might want to check out the transcript of’s Ask-the-Expert Online Conference on Managing Chemo Brain to read about other women’s experiences and questions, as well as the answers from medical experts. You’ll find tips on:

  • managing memory challenges
  • keeping your mind alert
  • getting more and better quality sleep
  • staying safe when you’re not so alert

Stay tuned to Research News for the latest information on chemo brain and its causes.

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