CBT Researchers Have Abandoned Independent Blind Assesment – Beware of Findings

I have been looking in vain for the last time CBT researchers assessed outcome on the basis of independent blind assessment, which was a cornerstone of the initial randomised controlled trials of CBT.  Current CBT research is more about academic clinicians marketing their wares. Journals such as Behaviour Research and Therapy and Behavioural and Cognitive Psychotherapy and organisations such as BABCP and BPS are happily complicit in this. The message is give a subject a self-report measure to complete, it is less costly than expensive highly trained independent interviewers blinded to treatment, forget about the demand characteristics of a self-report measure ( a wish to please those who have provided a service) and don’t worry if the measure does not accurately reflect the construct under question. My psychiatric colleagues might be forgiven for saying that at least the trials of antidepressants have usually been double blinded, if since the millennium CBT studies have rarely managed to be single blinded, is it time the CBT-centric era ended? But purveyors of other psychotherapies have even more rarely bought into the importance of independent blind assessment.

The overall impact of inattention to independent blind assessment is that the case for pushing CBT is actually not as powerful as the prime movers in the field would have us believe, this may actually be a relief to struggling practitioners. For example Zhu et al (2014) [Shangai Arch Psychiatry, 26, 319-331 examined 12 randomised controlled trials of CBT for generalised anxiety disorder in which there was supposedly independent blind assessment  but in 6 of the 12 studies the main outcome measure was based on the results of a self-reported scale completed by the client (i.e outcome was not actually assessed by the blinded assessor) and concluded that the quality of the evidence supporting the conclusion that CBT was effective for GAD was poor. A meta-analysis of outcome studies  conducted by Cuijpers (2016) World Psychiatry, 15, 245-258 found that using criteria of the Cochrane risk of bias tool only 17% (24 of 144) rct’s of CBT for anxiety and depressive disorders were of high quality. Cuijper et al concluded that CBT ‘is probably effective in the treatment of MDD, GAD, PAD and SAD; that the effects are large when the control condition is waiting list, but small to moderate when it is care-as-usual or pill placebo; and that, because of the small number of high-quality trials, these effects are still
uncertain and should be considered with caution’. Only half the studies had blind assessors and it is not clear whether they were the determinants of outcome or a client completed self-report measure, the study needs further analysis. My impression is that the weakest of studies are those examining guided self-help, computer assisted CBT, (the step 2 interventions in IAPT) yet these interventions are most commonly offered.

Dr Mike Scott

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