It's not what you say, but how you say it The effectiveness of message frame-tailoring in online computer-tailored health communication

With this dissertation, I aimed to systematically develop and explore the potential of the novel approach of message frame-tailoring. It was tested whether message frame-tailoring, which refers to adapting the message frame – the HOW of a message – to an individual’s communication preference as reflected in their need for autonomy, in isolation and in addition to conventional content-tailoring, resulted in higher message effectiveness. To reach this aim, I firstly aimed to identify the most autonomy-supportive message frame (i.e., the use of a suggestive language and the provision of choice) suitable for online computer-tailored health interventions in the context of addictive behaviours (i.e., alcohol reduction and smoking cessation). Secondly, I systematically redesigned an existing online computer content-tailored smoking cessation intervention to include message frame-tailoring and subsequently tested it among experts and potential end-users to reach optimal usability. This intervention was subsequently tested for effectiveness in a randomised controlled trial. Findings confirmed the positive effect of content-tailoring on seven-day point prevalence abstinence from smoking at one-month follow-up, as found in previous research. However, message frame-tailoring did not significantly increase smoking abstinence rates, neither alone nor in combination with content-tailoring. It appeared that message frame-tailoring, content-tailoring and their combination significantly predicted perceived relevance of the smoking cessation message, which in turn predicted self-determined motivation to quit smoking. Self-determined motivation, positively affected attitudes towards smoking cessation and self-efficacy beliefs, but only self-efficacy positively predicted smoking abstinence.