A common method of research practice is the use of double-blind experimentation. This occurs when item identification is concealed in order to gauge an unbiased opinion, as in the case of a taste test. However, in psychology, assessing the progress of treatment cannot be done under double-blind conditions because the treating therapist and the patient are aware of the approach and issue being treated. Therefore, single-blind evaluations are made with the use of independent evaluators (IEs). These individuals are most often other therapists or students who rate the treatment progress by gauging symptom change and behavioral transformation. But does this unique method of assessment limit the measurement of psychological treatments? To answer this question, Adam B. Lewin of the Department of Pediatrics and Psychiatry at the University of South Florida’s College of Medicine recently conducted a study that compared IE’s ratings to those of therapists, clients, and parents using the Clinician’s Global Impressions (CGI) scale.
The participants were 71 children with obsessive compulsive disorder (OCD). They received 14 weeks of treatment, and evaluations were taken at four different points throughout. Lewin discovered that the IEs and the therapists provided similar ratings, even though the IEs had limited information and were not privy to in-session improvements. Additionally, the children and parents had similar ratings, but tended to rate the improvements more aggressively than the therapists and IEs. These findings are important for future research because they show that therapists’ ratings are in line with those of blind raters (IEs) and do not appear to be biased. This can be helpful in situations when blind evaluators are not available. Although the sample was relatively young, and the therapists were highly trained in OCD practices, the findings of this study have important implications for treatment measurement and future research efforts. “Our data suggest that blindness may not be essential for making accurate improvement ratings, provided that raters are well trained and efforts are made to minimize bias,” Lewin said.
Lewin, A. B., Peris, T. S., De Nadai, A. S., McCracken, J. T., Piacentini, J. (2012). Agreement between therapists, parents, patients, and independent evaluators on clinical improvement in pediatric obsessive-compulsive disorder. Journal of Consulting and Clinical Psychology. Advance online publication. doi: 10.1037/a0029991
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