Researchers in Taiwan found a 3.33x greater risk of benign brain tumors in patients who had been prescribed benzodiazepines for at least 2 months. The research drew on data from the National Health Insurance System of Taiwan on 62,186 patients who had been prescribed benzodiazepines matched against 62,050 controls. The study appears in Journal of the Neurological Sciences.
Harnod, T., Lin, C., Sung, F., Kao, C.; An Association between Benzodiazepine Use and Occurrence of Benign Brain Tumors. Journal of the Neurological Sciences. Online November 16, 2013