It has also been proven that participation in group therapy, during and following treatment, can help maintain abstinence. A longitudinal study was conducted in 2011 among a U.S. national sample of people who were living in communal-living recovery/transition homes (Oxford Houses) and were also actively involved with Alcoholics Anonymous and Narcotics Anonymous. “Categorical involvement in a set of 12-step activities and averaged summary scores of involvement were examined in relation to abstinence and self-efficacy for abstinence. Participants who were categorically involved in all 12-step activities reported significantly higher levels of abstinence and self-efficacy for abstinence at 1 year compared with those who were less involved” (Majer, 2011). The results suggest that the 12-step program provides individuals with substance use disorders the resources they need for ongoing recovery. In 2013, a longitudinal study, similar to the previous one, was conducted among a U.S. sample of patients who were in the process of leaving treatment for substance use dependencies.