Int. J. Environ. Res. Public Health 2012, 9 204 Figure 2. Cessation rates with placebo across different addictions (number of participants). Table 3. Influence of variables in NRT trials on cessation rates with placebo. Intervention is as described in each review, and details of the reviews is in Table 1. Numbers of patients 43,108 Percent abstinent with NRT Placebo 17 10 Relative benefit (95% CI) 1.6 (1.5 to 1.7) NNT (95% CI) 16 (14 to 17) 4,480 24,520 18,823 1,283 11,427 3,236 12,348 16,907 7,140 19,120 18,175 986 3,109 887 20 15 20 30 11 14 13 15 27 18 16 17 16 24 9 10 14 19 7 10 8 10 18 11 10 9 8 12 1.9 (1.6 to 2.2) 1.5 (1.4 to 1.6) 9.4 (7.9 to 12) 21 (18 to 25) 1.5 (1.4 to 1.7) 1.6 (1.3 to 1.9) 1.5 (1.3 to 1.7) 1.3 (1.04 to 1.6) 1.6 (1.4 to 1.7) 1.5 (1.4 to 1.6) 1.6 (1.4 to 1.7) 1.4 (1.3 to 1.5) 1.7 (1.5 to 1.8) 1.9 (1.3 to 2.6) 2.0 (1.6 to 2.5) 2.0 (1.5 to 2.7) 17 (14 to 20) 9 (7 to 17) 25 (20 to 34) 25 (16 to 62) 20 (16 to 25) 21 (17 to 26) 11 (9 to 14) 15 (13 to 17) 17 (15 to 20) 13 (8 to 28) 12 (10 to 17) 8 (6 to 14) Variable All trials six months or longer Duration of follow up Six months Twelve months Trial setting Community volunteers Smoking clinic Primary care Hospital recruitment Level and type of support Low level of support High level support for individual High level support for group Type of NRT Gum Patch Inhaler Lozenge or tablet Nasal spray 3.2. Alcohol Information was available from two systematic reviews [25,26] with data on over 4,600 participants (predominantly acamprosate and naltrexone [26]) were used, with cessation rates between three and 12 or 24 months; one review of opioid antagonists had 208 participants in longer-term studies [25]. Both used only properly randomised trials, used various means to assess abstinence, and used placebo, usually with some form of psychosocial intervention.