There may be more than one factor responsible for "chemo brain" -- the term used for memory and attention impairments often experienced after undergoing chemotherapy for cancer, according to a small new study.

Researchers from the University of Missouri found that women who had breast cancer surgery but had not yet undergone chemotherapy also experienced similar memory problems.

And importantly, the women who were most likely to experience these problems were also the ones who were more stressed or didn't cope with their stress in a direct way, researchers found. Their research is published in the Journal for Clinical Psychology in Medical Settings.

"It appeared that passive coping strategies, such as denial, disengagement and helplessness, contributed to this relationship." Stephanie Reid-Arndt, chair of the Health psychology Department at the University of Missouri, said in a statement. "This suggests lacking proactive ways to deal with stress can contribute to patients' experience of cognitive difficulties."

The study included 36 women who had undergone breast cancer surgery, but hadn't gone through any chemotherapy or hormone-replacement therapy. Researchers found that 27 percent of them had evidence of verbal fluency deficits, and 14 percent of them had some sort of memory impairment.

How much stress the women reported having was correlated with these impairments, according to the study.

The researchers suggested that women can cope with stress by acknowledging their feelings.

"Teaching patients proactive ways to deal with stress can help them improve their quality of life as well as maintain their cognitive function," Reid-Arndt said in the statement.

A recent study in the journal Cancer also showed that small memory problems plague cancer survivors regardless of whether they underwent chemo or not, Reuters reported.

"It's a very, very subtle thing. We're not talking about patients becoming delirious, demented, amnesic," Barbara Collins, a neuropsychologist at Ottawa Hospital who wasn't involved in the new study, told Reuters. "We're talking about a group of people that are saying, 'I'm pretty much still able to function, but I find it harder ... it doesn't come as easily, and I can't do as many things at the same time.'"

Last year, Health.com reported on a study published in the journal Archives of Neurology, which showed that women who have survived breast cancer actually show changes to their prefrontal-executive function in brain scans. That region of the brain is involved in concentration, information gathering and analysis and impulse control. What's more, researchers found that these changes were more evident in those who've undergone chemotherapy.

"I have patients tell me, 'I'm just working harder and I'm slower at what I do, and I have to check my work and I still find errors, even when I'm working methodically,'" Robert Ferguson, a clinical psychologist at Eastern Maine Medical Center, told Health.com. "This data is consistent with that anecdotal report."

Also on HuffPost: