Predictors of entering a long-term drug treatment study of panic disorder.

Three hundred thirty-three consecutive individuals with panic and agoraphobic-like symptoms were evaluated as part of the screening for entry in a long-term imipramine treatment study of panic disorder with agoraphobia. The present report compares three subgroups of potential subjects--those who entered the study (n = 139, 41.7%), those who were rejected from participation based on exclusion criteria (n = 161, 48.3%), and those who qualified to enter but refused participation (n = 33, 10.0%)-in order to characterize pretreatment attrition and address two specific questions: What variables other than inclusion and exclusion criteria predict the likelihood of entering the trial?, and What variables significantly predict the likelihood of refusal to participate? Logistic regression analysis revealed that the likelihood of entering the trial was influenced significantly and independently by a number of variables that included extroversion, anxiety, and work satisfaction and performance measures. The refused and rejected groups differed significantly on a number of variables that were not a priori exclusionary criteria, such as a history of substance abuse other than alcohol and current use of alcohol to decrease anxiety, but none of these variables emerged as independent, significant predictors of refusing behavior as a separate category of nonparticipation. Findings suggest the presence of factors common to both the rejected and the refused groups that significantly influence pretreatment attrition and caution that categorizing pretreatment attrition into refused and rejected categories may not always be clear cut. Research and clinical implications are briefly discussed.