As well as seeking to demonstrate that person-centred therapies are effective, research effort has gone into establishing that they are at least as effective as other approaches to psychotherapy. In this regard special attention has been given to how PCTs compare with CBT but this isn’t the exclusive focus of comparative studies. One important finding from comparative studies of person-centred therapy and other approaches is that, when ‘researcher allegiance’ is accounted for, Elliott et al. (2004a) show that an apparent difference between the efficacy of person-centred therapy and other approaches disappears. In terms of outcome, they are equally effective. This is true of studies across the psychotherapy research literature. One of the most recent of these is the study by Stiles et  al. (2006) using CORE-OM (Clinical Outcomes in Routine Evaluation – Outcome Measure) and data from 1,309  ‘patients’ in which outcome data for cognitive behavioural therapy, person-centred therapy and psychodynamic therapy was compared. This showed that clients receiving each therapy markedly improved and that there was no real difference between the approaches.