When deciding which treatments are of benefit, results from placebo-controlled trials are conventionally preferred above all others, and treatments not supported by such trials are viewed sceptically. In this paper it is argued that while randomised controlled trials are desirable they are not always informative. Other, less robust, research designs can be acceptable when they provide independent evidence that their results are not invalidated by remission, regression to the mean, or placebo effect, particularly if they provide post-treatment follow-up assessments. Even when there are difficulties with a research design one can reasonably conclude that the treatment was responsible for the improvement provided a standard treatment was delivered, patient compliance was good, and a dose-response relationship was identified.