"Chemo brain" is a term used to describe problems with thinking, concentrating and remembering that cancer patients undergoing chemotherapy experience. 

However, a new study revealed that cancer patients may actually start feeling this cognitive fog even before treatment is initiated, leading researchers to suggest that "chemo brain" may have more to do with the stress and fatigue caused by the disease rather than the result of chemotherapy.

The new study found that pre-treatment mental fog and fatigue were associated with cognitive problems, previously believed to be caused by treatment.

Researchers presenting their study at the San Antonio Breast Cancer Symposium on Dec. 7 found that more women with breast cancer scored lower on cognitive function tests before getting chemotherapy compared to women without the disease.

Furthermore, researchers found that women who received radiation treatment rather than chemotherapy also scored lower on memory and thinking tests before therapy.

"It's hard not to believe that chemotherapy could damage the brain, but we found evidence of the problems occurring in many women even before the therapy had begun," said lead author Bernadine Cimprich, associate professor emerita at the University of Michigan School of Nursing, according to HealthDay.

Researchers stress that they aren't saying that chemo brain doesn't exist. However, they say the latest findings show that there are other factors that may make women vulnerable to it and may compound the impact.

Researchers say more needs to be done to help decrease stress and fatigue in cancer patients to help their memory and cognitive function.

"There is a need for increased clinical awareness that cognitive problems can begin before any treatment and might get worse over time," Cimprich told Businessweek. "'Chemo brain may not be the right label for cancer-related cognitive dysfunction. That then opens an opportunity for various interventions that were not there before.''

She explains that stress can lead to fatigue and cancer may cause inflammation and affect a person's mental function.

The latest study consisted of 29 women who underwent chemotherapy, 37 women who underwent radiation therapy and 32 healthy women. All the women performed a working memory task while researchers monitored their brain activity using magnetic resonance imaging before therapy and one month after.

Researchers found that women in the chemotherapy group scored the worst on the cognitive test before treatment and one month after therapy. While women in the radiation therapy group scored just as low on the test as women in the chemotherapy group before getting treatment, they performed just as well as the women without breast cancer on the test one month later.