Clinical trials of cognitive behavioural psychotherapy (CBT) for depression are often of poor quality – and are no better than trials of the rival psychodynamic school.
So says a new American Journal of Psychiatry paper that could prove controversial.
CBT is widely perceived as having a better evidence base than other therapies. The “creation myth” of CBT (at least as I was taught it) is that it was invented by a psychoanalyst who got annoyed at the unscientific nature of psychodynamic i.e. Freudian-influenced therapy. CBT has always looked on clinical trials more favorably than the dynamic school.
However, the authors of this meta-analysis found that while there are certainly lots of published CBT trials for depression, they’re actually no better quality than the psychodynamic trials.
“Surprisingly” (their word), they found no difference between the CBT for depression trials, and the psychodynamic trials, on a rating score of trial methodology.
Trials got better over time, but the two groups improved equally (see above). The mean score was 25.5 for CBT and 25.1 for dynamic, on a scale that goes from 0 to 48. Anything over 24 points is deemed acceptable but this is clearly an arbitrary cut-off.
The RCTP-QRS scale is relatively new and it was developed by the people who wrote this paper (albeit with the input of other experts.) There’s 24 items and each gets a score from 0 (bad) to 2 (good). Items are things like “Adaquate sample size”, “Patients randomly assigned to group”, etc.
Worryingly, better CBT trials tended to find smaller benefits of CBT over the comparison treatment. The overall results showed that while CBT was clearly better than doing nothing, it was pretty much the same as antidepressants, and other psychotherapies, in adults with depression:
The article follows one from the same group, Gerber et al, who reviewed the evidence for psychodynamic therapy in more detail. And last year, another team reported evidence of publication bias in psychotherapy trials. In this study, the authors report possible publication bias, but they don’t go into detail.
Overall this is interesting stuff, and a reminder that while CBT has the most evidence of any psychotherapy, this is not the same thing as saying that it has the best evidence…