A cell phone study funded by the industry group Wireless Technology Research and the National Cancer Institute found no evidence that the devices cause brain cancer among people who used cell phones for an average of less than three years.

The study of 891 people, reported in the Journal of the American Medical Association, did find a slightly increased risk for a rare type of brain cancer, but the researchers said it was not statistically significant. Researchers said that while the study does not answer the question of whether longer-term use is dangerous, overall results should reassure the more than 86 million cell phone users nationwide.