In my last post, I wrote about the use of placebos in clinical practice -- or more accurately, about giving medical treatments based on psychological comfort, not physiological effect. However, the area where placebos are most used and accepted is human research, not clinical practice. Psychiatric research in particular introduces some interesting conceptual issues regarding the use of placebos. To decide whether any new medication actually helps patients, the "randomized, double-blind, placebo controlled study" is the gold standard. In this type of experiment, research subjects who all have the same disease (or are all equally healthy) are randomly assigned to take either the new medication or a placebo: an identical twin of the medication lacking any of its active ingredients. The subjects do not know whether they are in the medication arm or the placebo arm of the study -- they are "blind" to this fact. Their doctor, or whomever rates their outcomes in the experiment, does not know either; this makes the experiment "double-blind." If the only difference between the two arms of the study is the presence of the active ingredients, then any outcome differences, on average, between the groups can be attributed to those ingredients.
The reason such experiments are double-blind, and the reason for the placebo in the first place, is to separate the medication's physiological effects from any rating bias or placebo effects. Outcome ratings can be distorted by raters' expectations; people often see what they want to see. Placebo effects are psychological factors in the subjects that improve rated outcome. These include wanting to please the experimenter by getting better, hope that the medication will work, improvement due to feeling attended to and cared for, etc. A "controlled" experiment carefully dissects away rating biases and placebo effects, so that only physiological effects count.
There is great value in knowing that an antibiotic and a sugar pill lead to different medical outcomes. Patients can feel attended to and cared for -- they can feel "better" -- and still die of infection. Disease has a life of its own, apart from subjective experience. Western medicine prides itself on its scientific foundation, and rightly so. We don't want merely to feel better, we want to be better.
However, the situation is less clear with many psychiatric disorders. Depression and anxiety, for example, do not appear to have lives of their own, apart from the patient's subjective experience. If the patient feels better, he or she is better. Thus, the rationale for placebo controlled studies in this area bears further reflection. Why does it matter if mood or anxiety improvement from a medication is physiological, or "merely" a placebo effect?
One answer is that we hope to further our scientific/medical understanding of such disorders, and placebo controlled studies help us do that. Another is that drug makers and the FDA justify the value of pharmaceuticals by virtue of their active ingredients, not the psychological features surrounding their use. Yet another is that placebo effects are idiosyncratic and vary across the population, and we strive for more predictability. Nevertheless, as discussed in my previous post, for a given patient it ultimately doesn't matter why a treatment works, as long as it really does. (For a more technical discussion, see this British Journal of Psychiatry editorial.)
Another fascinating conceptual problem is whether and how to include placebo controls in psychotherapy research. Psychotherapy, like depression and anxiety medication, treats distress that is inseparable from subjective experience. Thus the importance of differentiating "active ingredient" and "placebo" effects is unclear at best. In addition, the treatment itself consists of the very psychological influences a placebo controlled study aims to remove.
By analogy with medication studies, psychotherapy researchers have tried to isolate the "active ingredients" in therapy, and to fashion studies with a treatment arm and a placebo arm differing only by the presence of those ingredients. So far, no active ingredient has been identified as essential (although the overall efficacy of psychotherapy is not seriously in question, see here and here). What if there are none -- what if psychotherapy is all "placebo effect?"
This sounds like psychotherapy is quackery, much like the headline "Half of Doctors Routinely Prescribe Placebos" sounds like quackery exposed (see my previous post). But if psychotherapy is compared not to medication but to other human relationships, the "active ingredient" idea seems out of place. The helpfulness and support of a parent, teacher, spouse, sports coach, or minister cannot be reduced to any specific ingredient. Growth or self-improvement gained from such relationships comes organically and emergently, not as a result of a discrete intervention. This does not make the value of such relationships, or the benefits gained, any less real.
Placebos are essential for careful medical research, yet carry overtones of fakery and worthlessness. When the placebo concept is applied in an overly broad fashion, its negative connotation can tarnish highly beneficial human interactions that are neither fake nor worthless.
