ABSTRACT
The prospect of examining a biological substrate of the psychological processes occurring during psychological treatments is fascinating, but needs further evaluation in terms of reliability and validity. The section on identifying and analyzing change includes several new developments in examining longitudinal data over the course of treatment. These developments include multilevel modeling of growth, time-series analysis, and growth mixture modeling. Meta-analysis, which has existed in psychotherapy research for at least 30 years, has advanced as a methodology, and has also advanced the field in integrating findings across studies. In fact, confirmation of the positive effects of psychotherapy, and thus the inclusion of psychotherapy as an important part of the health system, would not have been possible without the contributions of meta-analysis. The framework of multi-trait multi-method models and generalizability theory will help improve the validity and reliability of the assessments in general, as well as for coding procedures used in process and outcome research.
