Breast cancer patients who have undergone chemotherapy often claim to suffer from “chemofog” as a result of the treatment. They report difficulties with memory and in thinking clearly. But chemofog may be a myth. Two recent studies of breast cancer patients being treated with chemotherapy did not find any evidence of chemotherapy-related impairments in cognitive function. The results were reported this week in Chicago at the annual meeting of the American Academy of Neurology. One of the studies, conducted in Australia, compared 30 cancer patients with 30 similar women who did not have cancer. Both groups took tests to measure their cognitive function and their feelings of depression and anxiety. For the cancer patients, the tests were done before each cycle of chemotherapy and 28 days after the last cycle. The researchers found that the cancer patients scored lower on cognitive performance and learning ability even before chemotherapy had begun. Of the 3 patients who did develop cognitive impairment over the course of chemotherapy, none of them seemed to be aware of it, as they did not subjectively report cognitive difficulties, depression, or anxiety that matched their test results. The other study was done in Michigan and involved 58 patients. These patients had a new diagnosis of breast cancer, a benign diagnosis, or had completed chemotherapy at least 1 year prior to the study. The newly diagnosed patients, who had not had any chemotherapy, scored lower on memory tests than the 1-year survivors. The researchers attribute the memory problems some patients experience to stress related to the diagnosis of breast cancer, not to any treatments.