AIM: To contribute to the knowledge and understanding of the active ingredients and mechanisms of change in Motivational Interviewing (MI), to enable MI-counsellors to optimise their MI-strategies in daily practice.
METHOD: The body of this dissertation are two multiple case studies, one in 14 patients with schizophrenia receiving MI for medication adherence; another in 24 patients with a coronary artery disease receiving MI for smoking cessation.
FINDINGS: We found that the active ingredients of MI consist of combinations of clinician factors and patient factors, mostly built up during longer interactions. ‘Arguing oneself into change’ was the most frequently observed mechanism of change.
DISCUSSION AND CONCLUSION: Active ingredients in MI consist off combinations of factors contributed by the clinician and factors contributed by the patient. These factors can be employed in a person-centred MI-strategy to trigger a mechanism of change in the patient.
This dissertation adds to the understanding of MI since it provides an explanation of how MI may work. It offers a general idea how counsellors can effectively execute MI. This ‘how-possibly’ explanation may be a building block in the development of a ‘how-actually’ explanation of the interactions leading to the active ingredients and mechanisms of change in MI.

Zie https://tijdschriftverpleegkunde-nl.hr.idm.oclc.org/artikelen/2020/december/editie-4/motiverende-gespreksvoering-actieve-ingredienten-en-verandermechanismen voor een uitgebreide samenvatting van het proefschrift.