Western medicine’s great strides are largely due to understanding etiology (the biological basis of disease), defining a nosology (a system of categorizing diseases), and testing treatments aimed at these nosological entities, not at individual patients. Take 100 healthy volunteers, swab their throats with Streptococcus, and perhaps 88 will soon develop strep throat. Both our knowledge of bacterial infections (etiology) as well as repeated empirical observation of similar cases leads us to conclude that Streptococcus causes a recognizable condition called strep throat (nosology). Once patients are diagnosed with strep throat — once their conditions become exemplars of this disease category — experiments can be done to show which treatments relieve the condition. Western medicine is the accretion of such knowledge.
Hypotheses about disease categories, and about treatments aimed at these categories, can be tested using randomized controlled trials (RCTs), our most powerful statistical method to assess the effect of independent variables. As in the rest of medicine, evidence supporting the efficacy of psychopharmacology, as well as manualized psychotherapies such as CBT, depends on sorting patients into nosological categories such as “major depression,” applying different treatments to comparison groups, and finding statistically significant group mean differences. In psychology such a research approach is called nomothetic; the goal is to identify general laws of behavior.
However, another kind of knowledge is important too. Why didn’t the other 12 subjects get strep throat? Is it the same reason for all 12, or is the answer different for each of them? Looking at what makes people unique, as opposed to members of a category, is called idiographic research in psychology. This is the nature of psychodynamic theory and treatment, and why it resists the usual RCT approach to research. Patients who present for such treatment rarely fit neatly into a category such as “depressed.” They vaguely say their lives aren’t working well for them, or that their relationships are unsatisfying in a particular way. They lack meaning and purpose in life. They get a “funny feeling” when dealing with competition. Their boss triggers authority issues. They can’t trust their spouse’s fidelity. And on and on. Such complaints are not exemplars of a nosological category. We may not know what causes schizophrenia or bipolar disorder — we have no etiological understanding of any psychiatric disorder, one reason they are called “disorders” and not “diseases” — but at least these labels reflect a coherent nosology. Not so with the presenting complaints of most psychotherapy patients.
Psychodynamic therapists and psychoanalysts find little of value in the nomothetic approach. DSM-IV and similar nosology sheds no light on the particular patient in the office, with his unique history, dreams, fears, hopes, etc. The psychoanalytic/dynamic perspective is to understand the uniqueness of that specific patient, and to promote unique helpful changes that may have no relevance to any other patient seen in the practice.
This is not to discount the importance of the nomothetic approach where it applies. If a patient’s condition is exemplary of a nosological category, it should be treated that way. Doing so allows us to use powerful research tools to separate bias and wishful thinking from real treatment effects. If a patient presents with major depression, bipolar disorder, or schizophrenia, nomothetic research can and should guide treatment. In such cases, psychodynamic therapy must stand or fall on the same RCT basis as other treatments. The evidence base for manualized psychotherapies such as CBT, IPT, and a few others is stronger than for dynamic psychotherapy. If someone is seeking relief of major depression, pure and simple, I am happy to refer them to a CBT therapist, and have done so on a number of occasions. It would be nice to be able to claim strong evidence for the efficacy of prescription antidepressants as well, but unfortunately this is less clear.
CBT and other manualized therapies for specific conditions are much easier to study than dynamic therapy for ill-defined complaints. So it’s really no surprise there are more such studies. Idiographic research methods, e.g., pre and post measures in single-case designs, have been used to study dynamic psychotherapy, both whether it works and how. But nomothetic researchers consider this “weak science”: There are no control groups — no groups at all, actually.
The bottom line is that dynamic psychotherapy has different goals than CBT or medication. It doesn’t aim to treat a nosological category such as major depression. Since it isn’t based on a nomothetic treatment model, RCTs are the wrong assessment tools to use. Idiographic research methods may be statistically weaker than their nomothetic counterparts, but they are the best that this domain of inquiry allows. (Seligman argues that naturalistic surveys have their place too.) Dynamic psychotherapy is based on a rich theoretical foundation that has been scrutinized and refined for the past century. But ultimately it comes down to the individual and the unique mix of discomforting feelings and troubling thoughts that led him or her to reach out for help.