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Dr Hughes raises an important point that we also address in discussing limitations of the study. We did not take meta-analyses into consideration that had combined studies with inactive treatments and treatment as usual (TAU) as control interventions. We based this decision primarily on methodological reasons. TAU varies widely across patients and settings and can include antidepressant or behavioral treatments. Therefore, equating TAU with placebo treatment or waiting list seemed problematic for us.
Nevertheless, Dr. Hughes’ point is well taken. TAU is an important reference standard, particularly in pragmatic studies because it reflects real-world conditions. In a meta-analysis, however, TAU is difficult to handle especially when the components of TAU across individual trials are not well documented. Using TAU in a meta-analysis often comes down to combining apples and oranges without being able to tell which treatments are the apples and which are the oranges.
Dr. Hughes also argues that patients on waiting lists cannot be prevented from getting some form of treatment. We agree but view this as a general issue of contamination that is almost impossible to control, particularly in pragmatic studies. The fact that, in our study, patients on active treatments had substantially larger treatment effects than those on waiting lists makes us think that contamination issues probably did not have much impact.
This fascinating paper has a serious flaw; the exclusion of all studies with treatment-as-usual (TAU) comparison conditions. The authors justify this decision by stating that TAU is not standardized and cannot be considered an inactive condition. However, the difference between TAU and two included control conditions (wait-list and no care) may be predominantly semantic. Patients randomized to no care or wait-list cannot be forbidden from continuing to participate in the healthcare system and may receive exactly the treatments that they would usually receive if they were not enrolled in a clinical trial; that is, treatment as usual. No care and wait-list may not be any more standardized than TAU. Furthermore, TAU is what happens in the real world. Given the state of the mental health infrastructure in many countries, behavioural treatments are often compared against TAU to see if they are beneficial compared to what the patient would receive otherwise.