Psychotherapy for patients with complex disorders and chronic symptoms - The need for a new research paradigm

Background A clear distinction has been made between efficacy and effective ness in relation to the methods of evaluation of new psychological treatmen ts in psychiatry. Efficacy trials target patients with relatively pure cond itions. who may not be representative of the patients who are usually refer red for psychological treatment in a clinical setting. Few studies have exp lored the benefits of psychotherapy in patients with complex disorders and enduring symptoms. Aims To explore the rationale for the distinction between efficacy and effe ctiveness, particularly in relation to outcome studies of patients with com plex and enduring disorders. Method A narrative review with examples drawn from the literature, and an i llustration of a recent naturalistic outcome study which combines features of both efficacy and effectiveness. Results Studies of patients with complex and mixed disorders can be designe d so that they retain internal validity, but also have external validity an d are relevant to clinical practice. Conclusion Studies which evaluate psychological interventions should be car ried out in populations of patients clinically representative of those who are likely to receive the intervention, should it be shown to be of benefit . Declaration of interest None.