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Background and Aims It has been proposed that more use should be made of Bayes factors in hypothesis testing in addiction research. Bayes factors are the ratios of the likelihood of a specified hypothesis (e.g. an intervention effect within a given range) to another hypothesis (e.g. no effect). They are particularly important for differentiating lack of strong evidence for an effect and evidence for lack of an effect. This paper reviewed randomized trials reported in Addiction between January and June 2013 to assess how far Bayes factors might improve the interpretation of the data. Methods Seventy-five effect sizes and their standard errors were extracted from 12 trials. Seventy-three per cent ( n = 55) of these were non-significant (i.e. P > 0.05). For each non-significant finding a Bayes factor was calculated using a population effect derived from previous research. In sensitivity analyses, a further two Bayes factors were calculated assuming clinically meaningful and plausible ranges around this population effect. Results Twenty per cent ( n = 11) of the non-significant Bayes factors were < ⅓ and 3.6% ( n = 2) were > 3. The other 76.4% ( n = 42) of Bayes factors were between ⅓ and 3. Of these, 26 were in the direction of there being an effect (Bayes factor > 1 and < 3); 12 tended to favour the hypothesis of no effect (Bayes factor < 1 and > ⅓); and for four there was no evidence either way (Bayes factor = 1). In sensitivity analyses, 13.3% of Bayes Factors were < ⅓ ( n = 20), 62.7% ( n = 94) were between ⅓ and 3 and 24.0% ( n = 36) were > 3, showing good concordance with the main results. Conclusions Use of Bayes factors when analysing data from randomized trials of interventions in addiction research can provide important information that would lead to more precise conclusions than are obtained typically using currently prevailing methods. [ABSTRACT FROM AUTHOR]

Aims This study examines the preliminary outcomes of an intervention targeting service providers in methadone maintenance therapy ( MMT) clinics in China. The intervention effects on both service providers and clients are reported. Design The MMT CARE intervention pilot was developed and implemented collaboratively with local health educators. After three group intervention sessions, trained providers in intervention clinics delivered two individual motivational interviewing sessions with their clients. Settings Six clinics in Sichuan, China, were randomized to either the MMT CARE intervention condition or a standard care condition. Participants A total of 41 providers and 179 clients were sampled from the six clinics. Measurements At baseline and three-, six-, and nine-month assessments, providers completed self-administrated paper/pencil questionnaires regarding provider-client interaction, MMT knowledge, perceived job-related stigma and clinic support. Clients completed a face-to-face survey about their concurrent drug use and drug avoidance self-efficacy. Mixed-effects regression models with clinic-level random effect were used to assess the intervention effects. Findings Significant intervention effects for providers were found in improved MMT knowledge, provider-client interaction and perceived clinic support. For clients, better improvements in drug avoidance self-efficacy and reduced concurrent drug use were observed for the intervention compared with the standard care group. Conclusions The MMT CARE intervention targeting providers in methadone maintenance clinics can improve providers' treatment knowledge and their interaction with clients. The intervention can also reduce clients' drug-using behavior through motivational interviewing sessions conducted by trained providers. [ABSTRACT FROM AUTHOR]