What Is Chemo Brain and Why Does It Happen?

Most people agree that undergoing chemotherapy isn’t a fun experience, but everyone experiences the treatment and side effects differently. One potential side effect that is mentioned a lot is so-called “chemo brain.”

While chemo brain isn’t a medical term, it’s often used to describe mental fogginess during or after chemotherapy treatment. Unfortunately, it’s also really common in people who have undergone chemotherapy.

Below, doctors break down what’s behind chemo brain, while cancer patients who have been through chemotherapy explain what this feels like. And, because taking action is always important, an occupational therapist who treats patients with chemo brain explains the best things you can do to move forward if you’re dealing with this yourself.

Experts Featured in This Article:

Wael Harb, MD, is a hematologist and medical oncologist at MemorialCare Cancer Institute at Orange Coast and Saddleback Medical Centers in Orange County, CA.

Heather Jim, PhD, is co-leader of the Health Outcomes and Behavior Program at Moffitt Cancer Center.

Krysten Chadwick is an occupational therapist at The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute Oncology Rehabilitation.

What Is Chemo Brain?

Chemo brain is a phenomenon where people with cancer notice that they can’t think as clearly as they used to, according to the American Cancer Society (ACS). That can include having trouble remembering things, finishing tasks, or learning something new.

“This is sometimes experienced by cancer patients during treatment and especially after chemotherapy,” says Wael Harb, MD, a medical oncologist at MemorialCare Cancer Institute at Orange Coast and Saddleback Medical Centers in Orange County, CA. “We don’t really understand the exact mechanism but we think it’s related to the cancer itself.”

But while this is called “chemo brain,” it’s not specific to the treatment. “Patients who do not receive chemotherapy may also experience short- or longer-term cognitive impairment,” says Heather Jim, PhD, co-leader of the Health Outcomes and Behavior Program at Moffitt Cancer Center.

What Causes Chemo Brain?

There are a few potential things that may be behind chemo brain, Dr. Jim says. That can include inflammation, accelerated cellular aging, or the cancer treatments themselves, she says.

“Why some patients develop cognitive impairment after cancer, and others do not, is not clear, however,” Dr. Jim says.

Stress, anxiety, or depression; trouble sleeping; not getting the right nutrients in your diet; or being weak or frail can also contribute to chemo brain, according to the ACS.

What Does Chemo Brain Feel Like?

Julia Park Tracey, a breast cancer survivor and author of “Silence: A Novel,” says that her experience with chemo brain was “challenging, to say the least.”

“I couldn’t remember simple words, although I knew what I meant,” she says. “I got lost coming home. I forgot people’s names. I didn’t trust myself to edit any work. I couldn’t remember the word for ‘tears,’ so I called it ‘eye saliva.’ I was spacey and forgetful, and not capable of deep thought.”

Kommah McDowell, a breast cancer survivor and author of “Silver Lining: Cancer Was the Best Worst Thing That Ever Happened to Me,” says that she thought the “memory gaps” she was experiencing were just due to forgetfulness. But eventually she realized the blocks in memory weren’t just affecting the present, but her memory of the past, too. “That’s the reality of chemo brain: It affects both my short-term and long-term memory. I could be in the middle of a conversation — or even a sentence — and suddenly, whatever I was trying to say is completely gone, often never to return.”

Signs and Symptoms of Chemo Brain

These are the most common signs and symptoms of chemo brain, according to the ACS:

“These symptoms may be worse when patients are tired, stressed, or trying to multitask,” Dr. Jim says.

How to Combat and Manage Chemo Brain

Every patient’s experience with chemo brain is different and, with that, there are various options to try to combat it, according to Krysten Chadwick, an occupational therapist at The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute Oncology Rehabilitation.

“Your brain is kind of like a muscle and it needs to be worked out or managed to get better,” she says. Creating lists or calendar reminders are a “great first step,” Chadwick says. Beyond that, doing cognitive training or brain games can help target the elasticity of the brain, she says.

Tracey says she found it helpful to work around her chemo brain symptoms. “I tried to do anything that needed real attention first thing in the day, not later when I was tired,” she says. “And I simply did not even try on days one to two of weekly chemo. Days three through six were better for thinking.”

Tracey says she also gave herself permission not to think. “I watched bland TV. I didn’t read much, just watched mysteries on TV. Easy on the brain meant less stress, better healing,” she says.

McDowell says she’s learned the value of taking notes. “Just as important is being surrounded by people I trust — people who know how to gently remind me of things I forget, and who can laugh with me about the things I can and can’t recall,” she says. “Laughter, for me, has been an incredible balm. I’ve had to infuse humor into these little ‘blips’ in time, or else those moments would be filled with tears, which was often the case during the first five years of my journey.”

Ultimately, Chadwick says it’s important to advocate for yourself and to speak up if you’re struggling with chemo brain. “It is something that can get better, especially with help,” she says. “It doesn’t need to be something that you’re stuck with forever.”

Korin Miller is a writer specializing in general wellness, health, and lifestyle trends. Her work has appeared in Women’s Health, Self, Health, Forbes, and more.