The limited resources available for health make it important that money is spent in the best interests of patients. If money is spent on inefficient treatments there is less available for good care, so routine methods should have had their value proved in randomised controlled trials. This ideal is hard to attain. Randomised controlled trials cost time and money and only a minority of medical treatments have been evaluated in this way. To draw firm conclusions several randomised controlled trials in varying circumstances are usually needed and, for chronic conditions, follow up is essential to show that gains last. Finally, treatments which work in randomised controlled trials must be shown to be helpful in audit of routine care.

Given our imperfect knowledge, which are efficient psychotherapies and which not? Which have been well evaluated, for which problems in which circumstances, at what cost, and who can deliver them? Such questions can be answered firmly for some clinical problems, with less confidence for others, and hardly at all for many. Most successful psychotherapies are brief (five to 15 sessions) and focused.