Chemo brain plagues many people with cancer.
In a 3-part series, we examine this "mental fog."

Highlights For a thumbnail summary of chemo brain symptoms, click here. Chemo brain is very real. If you experience any of its symptoms, alert your health care team.

Many cancer survivors have worried about, joked about, and been frustrated by the mental cloudiness they experience during and after chemotherapy. This side effect has come to be called “chemo brain.”

Until recently, evidence of this condition was largely anecdotal, but fortunately, the condition has been getting increased attention from both doctors and researchers. As a result, anyone experiencing chemo brain can feel more comfortable addressing the issue with his or her doctor. There is no longer any reason for patients to feel that they are “going crazy” or that “it is all in their heads.” On the contrary, chemo brain is very real.

In this first in a series of three articles, we will look at what chemo brain is and what is thought to be the cause.

What is chemo brain?

According to patients who complain of it and to scientists who research it, chemo brain is a cognitive dysfunction or impairment. "The impact on the individual really depends to a large extent on what kind of demands they have at work or in life in general," says Tim Ahles, PhD.

Here are just a few examples of what patients call chemo brain:

• Memory lapses: forgetting things they usually have no trouble recalling
• Trouble concentrating: finding they can't focus on the task at hand and their minds wander
• Trouble remembering: difficulties remembering small details like names and dates
• Inability to multi-task: difficulty doing more than one thing at a time, like answering the phone while cooking, without losing track of what they were doing
• Taking longer to finish tasks because of slower thinking and processing
• Trouble remembering common words: difficulty finishing sentences because they can't find the right words
• Inability to learn new skills

Not everyone experiences chemo brain.

This is one of the big mysteries about the condition. Not everyone who has had chemotherapy gets chemo brain, and for many of those who do have the condition, it comes on quickly and lasts only briefly. Some people have reported long-term mental changes, but in most cases the problems improve over time. The changes patients notice may be very subtle, and the people around them may not notice any differences at all.

On the other side of the coin, some people report having chemo brain symptoms even before they start chemotherapy. Others report having the symptoms even though they have not even had chemotherapy. Still others notice the problem when they are getting hormone treatments. So the term "chemo brain" may not be completely accurate, but it is the term that most people currently use.

What causes chemo brain?

Unfortunately, the cause of chemo brain is not known – at least not entirely. What is known is that chemo brain can be a byproduct of other chemotherapy side effects such as anemia, fatigue, and depression. In other words, all of these side effects have the potential for causing the symptoms of chemo brain. The good news is that anemia, fatigue, depression, and such are treatable, and treatment may help relieve chemo brain.

What is not known is how to treat those patients whose chemo brain isn't caused by one of the above factors. It’s believed that as many as 25%-30% of patients, both men and women, fall into this category.

Recent research has suggested that chemicals produced by the body in response to cancer (cytokines) may be partly responsible for changes in brain function. There are also other possible factors such as surgical anesthesia, hormone treatment, and medicines that are used to control symptoms.

The specific cause of chemo brain is not known, there is no way to predict who will or will not get it, and at this time there is no way to prevent it. However, researchers are making progress and new studies have yielded more and more insights. In our next issue, we’ll look at some of the progress that’s been made.

A word of caution

It’s important to remember that over time most people fully recover from the effects of chemotherapy, usually a year or two after the end of therapy. Because of this and because chemo brain is usually mild, you should not change your plans for chemotherapy treatment just to try to prevent chemo brain.