More Americans are surviving cancer, but cancer treatments often take a toll on brain health. Chemo brain refers to a wide range of cognitive impairments affecting many cancer survivors for months or even decades. The neurological deficits may be minimal and short-term or drastic and permanent, decreasing or increasing over time. Studies suggest 75% of cancer survivors experience chemo brain during or after cancer treatment, and it lingers more than a few months for approximately 35%. Chemo brain is the topic of groundbreaking research currently underway.


Reports about chemo brain first appeared in the 1990s; the complaints came from people who had received high-dose chemotherapy. Women were among the first to speak out about cognitive problems and coined the term "chemo brain." Oncologists were initially skeptical about this phenomenon because they did not believe that chemotherapy treatments for non-central nervous system cancers could affect the brain. Now, studies indicate some chemotherapy medications do cross the blood-brain barrier. Thus, these drugs may be toxic to the brain or trigger inflammation. Surgery, radiation, and hormonal therapy appear to produce physiological reactions that potentially affect the brain as well.

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Studies suggest chemo brain symptoms may develop before cancer treatment commences, and therapies may exacerbate the condition. Research published in Neuroscience found that tumor-fighting cytokines can cause inflammation in the brain and nervous system, affecting cognitive processing. A cancer diagnosis often leads to stress and depression, which can cloud the mind as well. Neuro-oncologists at the University of California, Irvine discovered chemotherapy kills brain stem cells that would have developed into neurons that create and store memories. These combined factors lead to shrinking in areas of the brain responsible for memory and learning. Anxiety, sleep problems, and oxidative stress can also contribute to the onset or progression of chemo brain in people with cancer. Clinical studies show that high anxiety and depression before cancer treatment correlates to low cognitive functioning.

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Gut-Brain Axis

A 2018 study published in Frontiers in Behavioral Neuroscience hypothesizes that neurological and psychological problems following chemotherapy are largely due to dysregulation of the gut-brain axis. Multiple pathways connect the gut and brain bidirectionally in both health and disease. The study’s authors posit that chemotherapy-induced toxicity primarily impacts the digestive tract and the central nervous system. Social and psychological factors affect digestive function and perceptions and behaviors regarding illness and pain. In turn, visceral discomfort influences behavior, mood, and nerve pathways. The study particularly examines evidence linking microbiota imbalance, intestinal permeability, and nerve damage with chemotherapy-induced neuroimmunological changes.

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Chemo brain symptoms may subside after cancer treatments end. However, some people experience cognitive challenges for months after treatment, before returning to normal. Unfortunately, other individuals do not fully recover from chemo brain. Symptoms include

  • Confusion
  • Concentration difficulties
  • Word recall difficulties
  • Lack of mental clarity
  • Decreased attention span
  • Requiring more time to finish routine tasks
  • Difficulty with visual or verbal memory

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Chemo Brain vs. Depression

Like chemo brain, depression can produce difficulties with short-term memory, focus, and multitasking. Both conditions may find their cause in similar factors such as gut microbiome imbalance, systemic inflammation, and sleep issues. However, depression also causes loss of motivation, irritability, and sadness. According to the Dana-Farber Cancer Institute, these symptoms do not normally accompany chemo brain.

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Risk Factors

Some individuals seem to be more susceptible to chemo brain and are more drastically affected by it. Conditions or medications that suppress the immune system may make a person more vulnerable to neurological complications with cancer treatment. Factors that may increase the occurrence of chemo brain include

  • Cancer of the brain
  • Cancer that spreads to the brain
  • High doses of chemotherapy or radiation
  • Young age at cancer diagnosis and treatment
  • Menopause
  • Aging
  • Genetic alterations

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Treatment: Exercise

Physical and cognitive exercises can help lower stress and increase alertness. Researchers report that physical exercise may be more effective than mental exercise in helping people with chemo brain. Working out creates positive stress or eustress within the body, prompting the release of feel-good hormones. Meditation practices, computerized training, and games or puzzles help sharpen mental acuity.

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Treatment: Cognitive Behavioral Therapy

Cognitive behavioral therapy involves learning how the brain functions and the best ways to learn new information and implement new behaviors. CBT teaches individuals tools to enhance organization and memory. The authors of a small 2016 study published in Cancer noted marked gains after researchers taught a type of CBT called Memory and Attention Adaptation Training to breast cancer survivors via videoconference technology.

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Researchers have been studying drugs as treatments for cognitive dysfunction in people with cancer. They tested erythropoietin-stimulating medications and psychostimulants with mixed results. In a 2012 study published in PloS One, an antidepressant appeared to protect against neurological damage from cytostatic drugs. A 2018 study discusses a drug that may reverse chemo brain symptoms. In animal studies, researchers administered medication that deactivated the brain’s microglia immune cells. This facilitated the function of astrocytes, cells that help neurons work properly. Consequently, the drug appeared to alleviate many cognitive disorders associated with chemo brain.

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Foods rich in healthy fats and anti-inflammatory nutrients may enhance brain health. DHA, a type of omega-3 fatty acid, is the brain’s most abundant fatty acid, and EPA has important anti-inflammatory properties. Increasing consumption of dietary sources of omega-3 fats such as cold-water fish, flax seeds, dark leafy greens, and fish oil supplements can help combat oxidative stress and inflammation in the brain and throughout the body. Refined sugars increase inflammation in the body. An article by the Breast Cancer Research and Treatment journal reported that sugar comprised over 30% of the daily caloric intake of some chemotherapy patients, although the World Health Organization advises that no more than 10% of daily calories should come from added sugars. Animal studies show that sugar may increase inflammation and halt new nerve growth in the hippocampus, an area of the brain responsible for discrimination memory.

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