the mechanism of action". Until recently, ethical and operational issues had prevented robust randomized controlled trials from being conducted comparing 12-step programs directly to other approaches. Others, including addiction researcher Nicole Lee, have expressed concerns about the nature of many published AA studies, given that many are conducted by the "fellowship" itself. More recent studies employing randomized and blinded trials have shown 12-step programs provide similar benefit compared to motivational enhancement therapy (MET) and cognitive behavioral therapy (CBT), and were more effective in producing continuous abstinence and remission compared to these approaches. Cochrane 2020 review A 2020 Cochrane review concluded that "compared to other well-established treatments, clinical linkage using well-articulated Twelve-Step Facilitation (TSF) manualized interventions intended to increase Alcoholics Anonymous (AA) participation" are more effective than other established treatments, such as motivational enhancement therapy (MET) and cognitive-behavioral therapy (CBT), as measured by abstinence rates. Manualized TSF probably achieves additional desirable outcomes—such as fewer drinks per drinking day and less severe alcohol-related problems—at equivalent rates as other treatments, although evidence for such a conclusion comes from low to moderate certainty evidence "so should be regarded with caution". In response to a concern expressed by another addiction researcher that "those more strongly committed to total abstinence after receiving AA/TSF were likely to experience more protracted 'slips' if they did for any reason drink", the Cochrane review authors stated that subjects who did not achieve abstinence did not have worse drinking outcomes overall. Older studies A 2006 study by Rudolf H. Moos and Bernice S. Moos saw a 67% success rate 16 years later for the 24.9% of alcoholics who ended up, on their own, undergoing a lot of AA treatment. The study's results may be skewed by self-selection bias. Project MATCH was a 1990s 8-year, multi-site, $27-million investigation that studied which types of alcoholics respond best to which forms of treatment. Brandsma 1980 showed that Alcoholics Anonymous is more effective than no treatment whatsoever. Membership retention In 2001–2002, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) conducted the National Epidemiological Survey on Alcoholism and Related Conditions (NESARC). Similarly structured to the NLAES, the survey conducted in-person interviews with 43,093 individuals. Respondents were asked if they had ever attended a twelve-step meeting for an alcohol problem in their lifetime (the question was not AA-specific). 1441 (3.4%) of respondents answered the question affirmatively. Answers were further broken down into three categories: disengaged, those