TUESDAY, April 15 (HealthDay News) -- The stress of being diagnosed with breast cancer -- not the chemotherapy treatment to combat it -- may be responsible for patient complaints about problems with memory and concentration, two new studies suggest.

"This is an important issue, particularly as survival rates for breast cancer improve," study author Dr. David G. Darby, chief medical officer of CogState Ltd., the Australian company that developed the cognitive tests used in the studies, said in a prepared statement. "People could be making decisions about whether or not to have chemotherapy based on stories they've heard about 'chemofog' or 'chemobrain.' Hopefully, this information will help people make informed decisions."

The studies were to be presented April 15 at the American Academy of Neurology annual meeting, in Chicago.

In the first study, cognitive tests were given to 30 women with breast cancer before each cycle of chemotherapy and also to 30 healthy women. The breast cancer patients had slight problems in attention and learning skills before chemotherapy even started. After treatments, they showed a minor slowing in thinking speed. Three women, or 10 percent, did develop cognitive problems during chemotherapy.

"We also found that the women who reported that they had problems with memory, concentration and other cognitive skills were not actually the ones who developed problems as determined by the tests," Darby said.

The second study tested the cognitive abilities of three groups of women -- pre-treatment breast cancer patients, recent post-benign biopsy patients and breast cancer survivors who were one year past completed treatment. They were also evaluated for anxiety, depression, their overall quality of life and the amount of social support they had.

The recently diagnosed women and those who recently had benign biopsies scored about the same on tests of working memory and spatial learning. However, both groups were slower and less accurate than the breast cancer survivors. In addition, memory and learning scores for the breast cancer patients did not dip significantly during the initial stages of treatment, the study found.

The recently diagnosed women who had better overall quality of life also had better scores on the cognitive tests.

"These results suggest that cognitive difficulties experienced by women with a new breast cancer diagnosis may be related to stress as a result of the diagnosis and other quality-of-life factors, and not simply due to the effects of chemotherapy or radiation," study author Michael J. Boivin, of Michigan State University, said in a prepared statement.

More information

The U.S. National Cancer Institute has more about breast cancer.