Two therapists of the same tradition may work quite differently, while two therapists in different "camps" may behave more similarly than either they or their colleagues realize. Only in the past 2 decades has it become common practice for psychotherapy researchers to employ a treatment manual and adherence measures. In an adherence check, blind raters verify that the treatment being administered is identifiable as the treatment that the investigator wishes to study (usually by checking for some practices that are specific to the treatment and therefore must be present and some practices that are specific to other treatments and therefore must not be observed).
Ablon and Jones19 showed that interpersonal psychotherapy (IPT) and CBT conducted as part of the landmark NIMH Treatment of Depression Collaborative Research Program both adhered more to an ideal prototype of CBT than to a prototype of IPT. Adherence to the CBT prototype in this study and adherence to a psychodynamic prototype in a separate study20 predicted positive outcome more than assignment to either of the treatments. Thus, there is a great deal more to studying a psychotherapy than identifying it as belonging to one type or another. Current research looks at these "process-outcome" effects as well as the competence of therapists, rather than only their adherence.21 At an even finer grain, some researchers have begun to study the relationship of specific therapeutic interventions to change, a process requiring the painstaking coding of interventions and patients' responses.22 Both approaches will be necessary to sort out the thorny question of how treatments and interventions do and do not differ meaningfully from one another.
Specification of outcome lies at the heart of a century-old debate about the goals of psychotherapy. When studying short-term, symptom-focused therapies, such as CBT and IPT, it has been natural for researchers to use self-report and symptom measures to measure outcome. However, these scales can do a poor job of capturing the more abstract and changing goals of open-ended, exploratory treatments. Clinicians and patients often engage in psychotherapy with less certainty about their goals and a greater focus on identifying what it is the patient wants to do differently, whether this involves a relationship, a career move, or a sense of self. To satisfy both perspectives, outcome studies are moving toward acquiring several types of outcome data. The Shedler-Westen Assessment Procedure (SWAP-200) captures normal and pathological elements of personality along continuous scales based on in-depth clinical interviews and has shown promise in quantifying change in response to long-term psychotherapy.23-25 More such measures are needed.
How does it work?
The Holy Grail of psychotherapy is not only to match patient, treatment, and outcome but also to describe the mechanisms at work and thus explain why particular treatments are indicated for certain patients in pursuit of certain goals. This will require a basic science of interpersonal dynamics and how they shape change in symptoms and character. Fortunately, such a science is beginning to develop through the maturation of cognitive and social psychology and their fusion with cognitive neuroscience.26
Hastened by the application of functional neuroimaging, particularly functional MRI, investigators are studying the neurobiological bases of normal and psychopathological functioning. Neurobiological data promise to outline some of the mechanisms that are difficult to study through self-report and behavior (for example, including the interaction of cognition and emotion and the role of unconscious processes)27,28 and to add empirical and quantitative rigor to the measurement of psychological phenomena. Already, more than 20 studies have used functional neuroimaging to identify ways in which the brain changes in response to psychotherapy, and the number is growing. What we learn about changes in top-down, cortical processing (so far, linked more with psychotherapy) and bottom-up, subcortical processing (so far, linked more with medication) will have a profound impact on how we assign treatments.
Finally, the long-promised genomics revolution is now upon us. In 2007, the completion of the HapMap Project and introduction of gene chips that collect information from 500,000 single nucleotide polymorphisms (SNPs) quickly (on the order of hours) and cheaply (on the order of $1000 per sample) represent a sea change in the capacity of genomic research.29,30 Using samples as small as 1000 subjects, it is possible to search the entire genome for genetic determinants of psychological traits and disorders. This technology has led to an explosion in what we know about genetic determinants in nonpsychiatric illness and a new appreciation for the complexity of the relationship among gene, environment, and pa-thology. Application to psychiatry will improve our nosology (with links to etiology and pathophysiology) and ultimately aid in assigning patients to more effective treatments.
The potential for advances in the science of psychotherapy is exciting. We envision a future in which psychotherapeutic treatments are assigned with a specificity now more common in physical medicine. We can hope for a day when genetic and neuroimaging tools along with psychosocial assessments allow us to identify the precursors and risk factors for psychopathology and prescribe prophylactic treatments, including psychotherapy, before a full disorder develops. Along the way, current categories of psychopathology, psychotherapeutic modalities, and intervention strategies may be replaced by a more empirically based system. Most important, patients will get better care and the mental health profession will have new opportunities to ease the burden of psychiatric illness.