Selecting an optimal instrument to identify active ingredients of the motivational interviewing-process

Motivational Interviewing (MI) can effectively stimulate motivation for health behavior change, but the active ingredients of MI are not well known. To help clinicians further stimulate motivation, they need to know the active ingredients of MI. A psychometrically sound instrument is required to identify those ingredients. The purpose of this study is to describe and evaluate the capability of existing instruments to reliably measure one or more potential active ingredients in the MI process between clients and MI-therapists.