BMC Public Health 2005, 5:75 http://www.biomedcentral.com/1471-2458/5/75 participation for more responsive patients." (page 155). The likely selection effect in the current data was illus- trated by the anomalous group participants who dropped out after attending only one treatment session as shown in Figures 1 and 2. Those who received zero treatment had better outcomes than those who received one session of treatment. Few would argue that this shows that treatment was harmful. A more likely explanation for this difference is some sort of self-selection. The higher drinking level of the 1 session dropout participants at baseline suggests that they may have been more dependent on alcohol than those in the 0 session dropout group. The relative higher level of dependence may have put these individuals under more pressure to do something about their drinking, explaining why they did not drop out prior to the first ses- sion. A similar logic could apply to the outcomes of the consistent attendees of the full treatment group. The likely selection effect is also shown in that participants with higher drinking levels at week 1 were more likely to drop out of treatment (Table 3). The decreased drinking in both untreated and treated par- ticipants can be explained by a number of factors. One factor is that part of the effect is not real; many active alco- holics underreport drinking. Collateral informant inter- views and other verification techniques are only partially effective in correcting the data. The Rand study [10], for example, found that 30% of the collateral informants were unable to provide information. Underreporting can make treatment appear more effective than it actually is. Additionally, there are a number of non-treatment effects likely to result in reduced drinking [19,21-23]. In order to enter the trial participants had to first achieve a level of abstinence or reduced intake. If a participant arrives at a site in an intoxicated state immediate action is required by staff, such as admission to a detox unit, or detainment in the waiting room until the breath alcohol level returns to normal. These rules would have applied to each participant in Project MATCH at the time of enrollment and would have contributed to the rapid improvement seen in the week one data. The pre-study screening proce- dures used in clinical trials, both the overt criteria and the subjective criteria, are designed to select participants who are motivated to reduce their drinking. Enrolling in the trial suggests that the alcoholic has crystallized a decision to reduce or abstain from drinking. Once in the trial, the continued monitoring of drinking behavior by staff per- sonnel may have both motivational and therapeutic benefits. For example, in one study with a 2 year follow- up [21], over half the participants indicated they liked the "caring, concern and help" follow-up telephone contact, and in another [24], the telephone interviewers reported that they usually entered in a sympathetic interaction with the study participants. Such positive empathetic contact could be of therapeutic benefit. There are a number of limitations to these analyses. The data from two thirds of the subjects were not used in the illustration of mean drinking levels shown in the figures and in Table 6. However these data were used in Tables 2 though 5, and are presented in more detail in the attached data [see Additional File 1]. The linear relationship shown in Tables 2 and 3, and the means in Tables 4 and 5 indi- cated that no information was left out. Additionally, other analyses of these groups have been previously published, e.g., by the Project MATCH research group [20]. We chose to highlight several specific groups. The logic of selecting the group that received no treatment and the group that received all 12 sessions of treatment was clear – they offered an unambiguous treatment comparison. The data presented here show that the outcomes of the 12 session group were better than the outcomes of participants who received between 2 and 11 sessions, making the 12 ses- sion group a fair comparison. Additionally we identified an anomalous group, the one session rapid dropouts, and used that group in an attempt to interpret the data. The mathematical bases for the anomalous designation, and thus the selection of this group, were presented. Analyses were primarily limited to descriptive and simple inferential statistics. This was done because the findings are likely to be extremely controversial. We have therefore presented results that are easily replicated, and easily understood. Although the results are essentially negative, suggesting that current treatments are not effective, we do not offer suggestions for future directions. We feel we will have made a contribution if the data presented can be accepted as accurate. If they are accepted then implications for future research and treatment will naturally follow. For example, if the patient's motivations, opportunities, beliefs and hopes are the critical issues, how do we measure them? How do we influence them? How do they interact with the treatment environment? It may be that pre-treatment patient characteristics (e.g., level of dependence, social support, etc.) have a large influence on both the number of treatment sessions attended and drinking outcome. However, even if this is true, it would not be evidence of treatment effectiveness. Only if one could show that positive prognostic factors were weighted heavily against the treatment attendees and in favor of the dropouts would these results be open to reinterpretation. The baseline and week one drinking data presented here do not support the likelihood of such a possibility. Additionally, there is no evidence in the literature to support the notion that, for example, Page 9 of 11 (page number not for citation purposes)