CBT/GET "success" appears to be very fragile
Something else has been bothering me about the UK CBT/GET studies for years. In most research, a subject drop-out rate of 5% is considered acceptable. I don't recall seeing any of their studies that had a drop-out rate of less than 5%, and my memory may be faulty but I recall one at something like 50%. If, in the interest of fairness, we deduct 5% from their drop-out rate, and then count the remainder as fails, what would happen to their "success" rate, even if you believed their other results? I wonder if there is someone out there with the resources to go back and recalculate the stats for some of their studies - I am fairly sure that many if not most of the CBT/GET studies would be abject failures if we applied this standard.
The following information from systematic reviews may help, keeping in mind that no severely affected patients were included and most trials use Oxford 1991, CDC 1994, or even just a fatigue scale as criteria. I will mostly stick to the issue of dropouts, and to a lesser extent, adverse effects.
Cochrane 2008 (CBT)
Despite all the hyperbole we hear about recoveries and substantial improvements in the majority of patients, the analysis revealed that at post-treatment there was a small effect on reported "fatigue", and for a minority of patients (ie 40% for CBT vs 26% no therapy) a "clinical response", but no significant effect on physical functioning etc, inconclusive evidence for any long term benefits on any measurement (including anxiety and depression), mostly non-CDC criteria studies used to calculate the reported benefits.
"
The mean aggregate reported dropout rate of all 15 studies was 16.4%." Range was 0%-40%, with 6 studies reporting dropout rates of over 20%. Dropout rates and reasons for dropout were broadly similar between groups, and dropout was also defined differently between studies, but on average patients assigned to CBT were significantly more likely to dropout than those assigned to usual care. Adverse effects were poorly reported.
"
At follow-up, 1-7 months after treatment ended, people who had completed their course of CBT continued to have lower fatigue levels, but when including people who had dropped out of treatment, there was no difference between CBT and usual care." This finding, and that of a sub-group analysis ("there was no significant difference between CBT and waiting list control") seem to suggest fragility of the results. Limited evidence also suggests no advantage of CBT over exercise, which undermines the relevance of a targeted cognitive component.
Cochrane 2004 (GET)
Significant improvements to "fatigue" and physical functioning which did not diminish
but became non-significant within several months when compared to the control group. Very limited evidence base. Notes that higher exercise intensity may explain higher dropout rates and poorer outcome. Higher rates of dropout (almost twice as high as control group) but deemed non-significant. Also, "
no evidence that exercise therapy may worsen outcomes on average" (but no data was reported for adverse effects?).
Chambers et al 2006 (CBT/GET etc)
Concludes that CBT and GET may reduce symptoms and improve physical functioning for some patients. Discusses several methodological problems regarding outcome measures, differing CFS criteria, etc. On the issue of dropouts and adverse effects: "
Our review did not find any new evidence of adverse effects (sufficient to cause withdrawal from treatment) associated with GET or CBT. However, reasons for withdrawals were often poorly reported and should be investigated in more detail in future studies." ... "
There is limited evidence about adverse effects associated with behavioural interventions. Withdrawals from treatment in RCTs suggest that there may be an issue but the evidence is often difficult to interpret because of poor reporting."
Malouff et al 2008 (CBT)
Uses a somewhat different evidence base with more optimistic conclusions than Cochrane 2008 (eg higher effect sizes, 50% of patients no longer reporting clinical levels of fatigue after CBT at last followup). Notes that Oxford 1991 criteria has a trend towards significantly higher effect sizes than CDC 1994 criteria." (0.83 [0.40-1.26] vs 0.40 [0.02-0.78]) but is deemed non-significant. Similar dropout rates and range as Cochrane 2008, and mentions that "
dropout with chronic fatigue clients is not unusually high" (compared to psychotherapy for anxiety disorders).
Surprisingly, an earlier (non-CFS) meta-analysis (
Wierzbicki & Pekarik 1993) of 125 studies on psychotherapy dropout in general reports a mean dropout rate of 46.86%. I found this at the
"Criticisms and questions regarding effectiveness" section of the Wikipedia article on Psychotherapy.