Debating the dodo verdict: Does one form of psychotherapy work better than another?

Health and medicine explained.
June 29 2011 12:46 PM

Couch Wars

Does one form of psychotherapy work better than another?

The Dodo. Click image to expand.
Is there a "dodo-bird verdict" effect in psychotherapy?

Soon after Alice descends into Wonderland in Lewis Carroll's novel, she and the Mouse, the Duck, the Eaglet, and the Lory find themselves competing in a race with no clear beginning or end. A half-hour later they ask the organizer of the event, the Dodo, to name a victor. The bird mulls it over and then proclaims, "Everybody has won, and all must have prizes."

For 75 years, the same dictum has been applied to the study of psychotherapy: Alice and the animals are like patients who each choose their own form of treatment and find their own path to happiness. It doesn't matter which style of therapy they get, Freudian or cognitive-behavioral or interpersonal, because in the end, everybody feels better.

We know that therapy works—studies find it's about as useful as antidepressants for treating moderate to severe depression—but curiously, these benefits seem to be realized irrespective of the therapists' theoretical beliefs. This effect—or rather, this appraisal of the field of psychotherapy—is called the dodo-bird verdict. All patients get a prize.


Nonetheless, some researchers argue that the dodo-bird verdict is far from settled. They concede that no established form of treatment has an advantage when it comes to mildly depressed adults, and they agree that in such cases any intervention at all seems to work better than no intervention. But that doesn't mean that all treatments are the same in every case. Cognitive-behavioral therapy, for example, may be particularly well-suited to patients suffering from panic disorder. Exposure-based therapies seem to work best for post-traumatic stress disorder.

The debate has played out in duelling studies over the past 35 years. But the question of whether the dodo really has wings will soon be even more important for Americans. As part of the health care reform act passed last year, psychological treatment will be more accessible to more people, and patients and insurers will demand to know how best to spend their money and time. Should the dodo verdict be overturned?

The notion that no therapy is better than any other originated in the 1930s with psychologist Saul Rosenzweig, then a research associate at the Harvard Psychological Clinic. His ideas on the matter were shaped by an interest in the history of curative techniques, from the kings who applied the healing "royal touch" to the therapeutic spinning chair proposed by Erasmus Darwin and the theories of Sigmund Freud. Rosenzweig thought that all these healers and treatments (which he had memorialized in a peculiar wall-hanging displayed in his office) had a similar way of working on the minds of patients—they used drama and ritual to effectuate a cure. If that approach worked for hundreds or thousands of years of human history, he reasoned, why should contemporary mind-based therapies be any different?

In 1936, Rosenzweig proposed a catchall recipe for treatment—any treatment at all—in a famous paper titled "Some Implicit Common Factors in Diverse Methods of Psychotherapy." The ingredients most frequently cited today include the collaborative bond between the patient and therapist, known as the "therapeutic alliance"; the provision of a believable framework that normalizes the patient's distress; and the buoying hope the patient feels once he has embarked on therapy.

Over the years, Rosenzweig's argument has been bolstered by the research literature. An important paper from 2002 gathered together 17 prior studies of the relative merits of various psychotherapies, mostly for depression. The authors found that the treatments—which included cognitive-behavioral, psychodynamic, and systematic desensitization therapy—showed few differences in terms of outcome, and concluded that the dodo-bird verdict is "alive and well—mostly." The caveat refers to a few data points suggesting that short-term psychodynamic treatment—which focuses on how past experiences affect your present-day life—doesn't work as well as cognitive-behavioral therapy. Similar surveys (here, here, and here) have supported the dodo-bird verdict with fewer qualifications.

Adherents to particular schools of therapy hate the dodo verdict, of course. Most ruffled are the cognitive-behaviorists, who have long taken pride in their rigorously tested, standardized methods. Indeed, there have been many randomized, controlled trials showing that cognitive-behavioral therapy is more effective for anxiety and depression than placebos, and that it compares favorably with antidepressants. These results are not contested. But they don't disprove the dodo-bird verdict, since other forms of therapy might be just as good.

Dodo deniers hold that various psychotherapeutic treatments might happen to produce similar improvements in clinical trials, but that's not because they're doing the same thing. Rather, different mechanisms of action end up moving patients roughly equal distances toward recovery. To support this idea, they point to studies demonstrating that the therapeutic alliance, supposedly one of the key factors common to all therapies, has only a moderate impact on treatment outcome: Even if patients report an extremely strong bond with their therapist, this is not enough to guarantee that they will improve .

The deniers also cite research showing that some forms of treatment seem to work better than others for specific disorders. A pair of studies from the mid-1990s found that patients with panic disorder benefited more from cognitive-behavioral therapy than something called "applied relaxation therapy." (The creator of applied relaxation published his own data suggesting otherwise.) Meanwhile, patients with PTSD may do better when they're asked to confront traumatic memories, rather than learn anxiety-management strategies. (A caveat: More of the patients in the anxiety-management group dropped out of the program, which may have skewed the results.)

Another line of argumentation from dodo opponents is that the survey studies, which are the basis of the dodo-bird verdict, commit various methodological errors. For instance, they lean heavily on particular disorders, such as adult depression and anxiety, and have few or no examples of other types of patients, such as people with psychosis and children. They also tend to focus on familiar treatments, such as cognitive-behavioral therapy and psychodynamic therapy, instead of testing the full range available. As such, they don't give a fair appraisal of how psychotherapies stack up across the board.

On top of all this, the debate has been muddied by the slippery question of therapist ability. Better, more-experienced practitioners achieve better results—that much seems clear. But there have been few studies of how the skills of a given therapist affect the outcome of treatment. Even defining those qualities that make for a better therapist can be complicated. One study looked at data from a major NIH depression trial and concluded that the better therapists weren't the ones who had more experience but those who would rather talk to their patients than prescribe medication and who expected talk-therapy to take a long time.

For now many researchers are sidestepping the dodo debate altogether. Instead of trying to figure out whether one therapy is more effective than another, they're looking for simple ways to make all therapies work better. Certain factors that have little to do with the theoretical foundation of a treatment could make a huge difference. The therapist's ability to form a strong bond with the client, for example, and the manner in which he or she gives instructions to patients, would both affect the outcome of any intervention. Some research has explored patient characteristics and showed that people who tend to balk at requests and are easily provoked respond better to therapists who allow them to take the lead in conversation. This may seem obvious, but it held true irrespective of the therapist's theoretical perspective and again suggests that all treatments could be tweaked to boost their impact.

Patients and insurers might still wonder whether the dodo should be extinct, and if it matters what treatment someone gets. There's at least one study under way, of panic disorder, which hopes to confirm or deny the classic verdict. It is led by University of Pennsylvania and Cornell researchers from both the psychodynamic and cognitive-behavioral schools, and it compares the two treatments in a population of around 200 people who suffer panic attacks. The idea is to have any bias cancel out, while ensuring that patients in both treatment groups receive high-quality care. It's not clear whether the study will save the dodo or finally kill it off. At the very least, we'll know a little more.

Alastair Gee is a San Francisco-based journalist and has written for the Economist, the New York Times, and the Lancet.

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