Advanced Regression Methods for Single-Case Designs: Studying Propranolol in the Treatment for Agitation Associated With Traumatic Brain Injury Daniel F. Brossart Texas A&M University Jay M. Meythaler Wayne State University Richard I. Parker, James McNamara, and Timothy R. Elliott Texas A&M University Objective: The use of single-case designs in intervention research is discussed. Regression methods for analyzing data from these designs are considered, and an innovative use of logistic regression to analyze data from a double-blind, randomized clinical trial of propranolol for agitation among persons with traumatic brain injury (TBI) is used. Method: Double-blind, randomized clinical trial performed in an outpatient rehabilitation setting. Participants: Nine men and 4 women with TBI. Results: Logistic models indicated that propranolol was not associated with less agitation for most participants (= .135; 90% exact confidence interval was -.03  .135  .29). Four participants displayed a significant response to propanolol. Two participants demonstrated significant improvement, and the other 2 expe- rienced significantly more agitation in the treatment phase. Summary: Advanced regression methods can be used to analyze data from single-case designs to obtain information of clinical and statistical significance from a variety of psychological and medical treatments. Keywords: single-case design, logistic regression, propranolol, brain injury, agitation In a thoughtful commentary, Aeschleman (1991) observed a decreasing interest in single-case research (SCR) designs in the rehabilitation psychology literature: Between 1985 and 1989, Ae- schleman found only 6 out of 402 empirical papers published in Rehabilitation Psychology, Archives of Physical Medicine and Rehabilitation, and Rehabilitation Counseling Bulletin used a sin- gle-subject design (1.5% of the total; Aeschleman, 1991, p. 43). A brief examination of the past 15 years of Rehabilitation Psy- chology reveals one article that offered an innovative way to analyze single-case data (Callahan & Barisa, 2005) and another that was a true single-case study (Pijnenborg, Withaar, Evans, van den Bosch, & Brouwer, 2007). We disagree with Aeschleman’s bleak conclusion that SCR designs “. . . have not made a methodological impact on research in rehabilitation psychology” (Aeschleman, 1991, p. 47). History informs otherwise: Many of the influential research programs in rehabilitation psychology first appeared in the literature in single- case designs. Behavioral approaches— championed in the classic Behavioral Methods in Chronic Pain and Illness (Fordyce, 1976)—were based on earlier single-case studies. The potential of supported employment— arguably one of the few evidence-based practices in rehabilitation psychology with considerable support from many randomized clinical trials (RCTs; Dunn & Elliott, in press)— appeared in a study using a single-case case design published in the Journal of Applied Behavior Analysis (Wehman et al., 1989). And the ground-breaking extensions of Neal Miller’s operant learning models to visceral, reflex, and motor responses were achieved in single-case designs (Brucker & Ince, 1977; Ince, Brucker, & Alba, 1978). Clearly, SCR designs have played a pivotal role in the rehabilitation psychology research base. Unfortunately, SCR and case studies are often misconstrued as one in the same. An uncontrolled case study is a study of a single client, dyad, or group in which observations are made under uncontrolled and unsystematic conditions. The lack of experimen- tal control in such a study may have contributed to an overall suspicion or distrust of results based on a single subject in general. Designs that add more experimental control include systematic, repeated observations of a single client, dyad, or group and are often called intensive single-case designs. For even more experi- mental rigor, one could use a single-case experimental design, which is typically viewed as having greater control than intensive single-case designs. These designs usually have behavioral goals or target behaviors that are the main focus of interest and function as the dependent variable. They also have repeated measurements over time and at least two treatment phases (baseline and treatment). Some have Daniel F. Brossart, Richard I. Parker, James McNamara, and Timothy R. Elliott, Department of Educational Psychology, Texas A&M University; Jay M. Meythaler, Department of Physical Medicine and Rehabilitation, Wayne State University and Rehabilitation Institute of Michigan, Detroit, Michigan. This study was funded in part by National Institute of Disability Re- search and Rehabilitation Grant H 133G000072 awarded to Jay M. Meythaler. Appreciation is expressed to Michael E. Dunn for sharing information and opinions about the history of single-case designs in reha- bilitation psychology research. Graphs of participant data not presented in this article are available upon request from Daniel F. Brossart. Correspondence concerning this study should be addressed to Daniel F. Brossart, Department of Educational Psychology, 4225 TAMU, College Station, TX, 77845. E-mail: brossart@tamu.edu Rehabilitation Psychology 2008, Vol. 53, No. 3, 357–369 Copyright 2008 by the American Psychological Association 0090-5550/08/$12.00 DOI: 10.1037/a0012973 357