The study, published in Genetics in Medicine, assessed the psychological adjustment to DNA testing for BRCA gene mutations associated with hereditary breast cancer.

In the 215 women in the study, the results were "true negative" in 31, positive in 37 and in 147 -- more than two-thirds of the total -- "inconclusive."

Women with negative results had the lowest rates of worry and cancer-related distress, but the levels of worry and distress in women with inconclusive results were similar to those who tested positive.

Although women in all three groups were less worried than before being tested, the Leiden University Medical Center researchers, led by Sandra van Dijk ,say counselors help women accurately understand the BRCA test -- including the uncertainty associated with inconclusive results.

"Not only must women's expectations before BRCA testing be addressed, but also the issue of how women are planning to come to terms with an inconclusive result," the researchers said in a statement.

"Women who report feeling uncertain or ambivalent about their inconclusive DNA test result report higher levels of worry and distress," and this was "very strongly related" to whether they came to terms with their result and its implications.