Cognitive Behavioural Therapy (CBT) has many advantages for treating depression. Among them, the fact that it’s easy to standardise, it’s intuitive and it can deliver results relatively quickly (think weeks, not years as some other therapies demand). For many people with depression, it’s also far more acceptable than the prospect of taking mind-altering drugs. But now the bad news: CBT’s efficacy seems to be declining.

That’s the suggestion of a new meta-analysis (pdf) that’s looked at outcome data from 70 studies published between 1977 and 2014 and involving more than 2,426 people diagnosed with depression (uni polar depression, not bipolar). Across studies, 31 per cent of the participants were male; the average age of participants was 41.

To allow comparison over time, Tom Johnsen and Oddgeir Friborg chose to focus only on studies that used the Beck Depression Inventory or the Hamilton Depression Rating Scale – two popular measures that involve the patient or therapist, respectively, providing scores of the patient’s depression. Looking at the effect of CBT on adults’ depression scores using either of these scales (i.e. by comparing scores pre vs. post therapy), the researchers found a linear and steady reduction in the therapy’s apparent efficacy over time. Simply put, CBT doesn’t seem to be helping reduce depression symptoms as much today as it used to when it was first developed in the 1970s.

This main finding held true even when the researchers focused on certain types of study – such as analysing only those that involved a control group. The finding can’t be explained by a general change in people’s ability to recover from depression: there was no comparable decline in change scores among participants in control groups who didn’t receive CBT. Nor is it the case that recent studies, more than older studies, tended to involve depressed patients who also had other mental health problems (in fact the opposite is true).

Changes in therapist competence (e.g. their level of training) also can’t explain the declining trend in CBT efficacy. And to debunk one last potential explanation, the researchers point out that the decline in efficacy was actually steeper for trials involving manualised CBT – so it’s not the case that more modern trials have simply become sloppier in their CBT methods.

So, why is CBT apparently losing it’s power to help people with depression? Johnsen and Friborg can only speculate. One suggestion they have is that CBT is somehow losing its placebo effect over time:

In the initial phase of the cognitive era, CBT was frequently portrayed as the gold standard for the treatment of many disorders. In recent times, however, an increasing number of studies … have not found this method to be superior to other techniques. Coupled with the increasing availability of such information to the public, including the Internet, it is not inconceivable that patients’ hope and faith in the efficacy of CBT has decreased somewhat, in recent decades. Moreover, whether widespread knowledge of the present meta-analysis results might worsen the situation, remains an open question.”

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Johnsen, T., & Friborg, O. (2015). The Effects of Cognitive Behavioral Therapy as an Anti-Depressive Treatment is Falling: A Meta-Analysis. Psychological Bulletin DOI: 10.1037/bul0000015

—further reading—

Is it possible to predict who will benefit from cognitive behavioural therapy (CBT)?

CBT-based self-help books can do more harm than good

What is cognitive behavioural therapy like for a teenager?

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.