Rethinking Therapist Drift

One of the strangest ways I have ever been evaluated in my career was while delivering a psychological intervention in a prison. My job was to stand in front of a room of young offenders and facilitate group discussions of their "thinking skills". The prison service has a clear idea of what this should look like, indeed so clear that every session I did was filmed. Auditors could then check that I was sticking to the protocol. 

This remarkable surveillance was an attempt to minimize what is commonly called "therapist drift", the process whereby a therapist ostensibly delivering an evidence-based therapy winds up doing something else instead. Psychotherapies are not easy things to administer, and in the face of diverse people and problems it's easy to see how one might end up straying from the guidelines outlined in therapy delivery manuals. But if you claim to be doing, say CBT when you aren't in fact doing anything of the sort, you might not get the same results.

For the most part, therapist drift is regarded as a bad thing. This makes sense (at least, it's internally consistent). Drift is a problem for people who are trying to research a therapy (because they don't end up testing what they intend to) and it's potentially a problem for people who are trying to deliver a therapy (because rather than delivering something that has been demonstrated to be effective, they do something which is not).

But there is a strand of thought in clinical psychology and psychotherapy that maintains suspicion about the notions of "adherence" and "drift", and of evidence-based therapy altogether. Critics of this stripe view evidence-based-approaches as overly rigid and formulaic, too focused on technique at the expense of relationship. There is some good quality criticism of manualized therapy (here's a good example), but also much exaggeration about manualized therapies making the process "robotic" (as though a set of instructive principles were incompatible with being human). 

Recently I looked into the topic (in a very non-systematic way) to see what research had found about the importance of adherence and drift. Most studies that have been done (and it is surprising how few there are that focus specifically on drift) seem to support the contention that "drifting" can lead to less impressive outcomes. However, one study had an intriguing result.

Examining CBT for panic disorder, researchers (Jonathan Huppert and colleagues) took measures of patient motivation (rated by the therapists) and adherence to the therapy manual (rated by listening to audiotapes of sessions). Perhaps counter-intuitively, the researchers found that among highly motivated patients, the therapist adherence did not have much impact on outcome (look at the graph and you can see the blue line only slopes upward a small amount; this difference was not found to be significant). However, among less motivated patients, adherence was associated with worse outcomes than drift.*

One possible explanation for this (one that Huppert and colleagues themselves suggest) is that patients with low motivation present an extra degree of complexity which cannot be adequately addressed by staying within the set protocol. An experienced therapist will depart from the standard protocol to address in some way the low motivation, before continuing with the planned process. Under this interpretation, the therapists who show the greater adherence with the "low-motivation" patients are paradoxically failing to do something with the low adherence therapists are succeeding at it. Although they are moving beyond the purview of the manual, it seems misguided to call this "drift". This squares with the extended discussion by Drew Westen and colleagues on the more tendentious implications of therapy manuals:

...manualization commits researchers to an assumption that is only appropriate for a limited range of treatments, namely that therapy is something done to a patient—a process in which the therapist applies interventions— rather than a transactional process in which patient and therapist collaborate. (p.639)

And yet still some idea of therapist "drift" seems important. Unless we believe there is no value to specific training for psychologists and psychotherapists, we want to have some reasonably defined sense of what we're up to; some sense of what it looks like to do the job properly. It is any deviation from this that can reasonably be considered drift. In other words: in the space between conforming, robot-like, to a predetermined protocol and doing whatever the hell you want, there lies a knowable range of skills which we ideally would want to adhere to. That set of skills is what constitutes being a good psychologist. This definition extends the realm of evidence based practice some way beyond the parameters of individual evidence based treatments. 

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*Though the authors note: "it is important to keep in mind that even when therapists were rated as less adherent, adherence was still rated as “good” or better, suggesting that therapists did not cease doing CBT for panic, but likely incorporated other strategies into their armamentarium" p.202