The Virginia Department of Corrections (VADOC) is responsible for about 28,000 inmates and 66,000 probationers and parolees annually. Mental health services are often conducted through therapeutic groups, many of which are manualized and based in cognitive behavioral therapy theory. In the three years, 2017 through 2019, VADOC conducted 172 therapeutic group therapy studies, and the resulting data, in the form of t-test scores, were made available for academic research. This meta-analysis investigated whether cognitive behavioral...