EFFECT SIZE AS A MEASURE OF SYMPTOM-SPECIFIC DRUG CHANGE IN CLINICAL-TRIALS

A data-analytic strategy is proposed for identifying the symptom-speci fic effects of each medication in a clinical trial. The within-group e ffect size is a standardized ratio of the pre-post change relative to the stability of change for each treatment group. Advantages of using this descriptive approach are illustrated by examining antidepressant effects of alprazolam, imipramine, and placebo in a clinical trial for patients meeting criteria for both panic disorder and depression. The re was a significant difference between active medication and placebo on the Hamilton Rating Scale for Depression (HAM-D) total, but no diff erence between the antidepressant effects of the active medications de spite their diverse psychopharmacologic properties. Examination of eff ect sizes for each HAM-D item revealed distinct symptom-specific effec ts of each active medication in this study sample. Although these desc riptive findings cannot be used for inferential conclusions, they can be used to guide the design of future trials.