Article: PDF OnlyOlfson Mark MD MPHJournal of Psychiatric Practice®: January 1999 - p 20-24 Buy Abstract Efficacy and effectiveness research differ in their goals and methods. Both types of studies are important and their findings can make complementary contributions to the clinical decision-making process. The author first reviews the different characteristics of the two types of research, such as eligibility criteria, average length of study, outcomes assessed, and other features. Three types of effectiveness research are then described in detail: experimental effectiveness research, quality of care research, and observational effectiveness research. These descriptions are illustrated with examples of the types of clinical findings such studies can produce. © 1999 by Lippincott Williams & Wilkins, Inc.