Using 'if-then' planning in independently delivered and self-help interventions to promote physical and mental health

The first part of this thesis consists of a systematic literature review of the effectiveness of independently delivered interventions incorporating implementation intentions on health outcomes. The second part is a research study examining the effectiveness of a self-help intervention aiming to improve social confidence for people with visible skin conditions in a randomised controlled trial. In the literature review, ten studies examining the effectiveness of independently delivered interventions incorporating implementation intentions on physical or mental health outcomes were systematically reviewed and critically appraised. Effectiveness was measured by extracting data from the studies and undertaking a meta-analysis. The results showed that independently delivered interventions incorporating implementation intentions had a small, but reliable, overall effect (g+ = 0.16). In the research study, 326 participants with a variety of visible skin conditions were randomised to either (i) self-help enhanced with implementation intentions, (ii) standard self-help without implementation intentions or (iii) a wait-list control condition. The results showed that participants exhibited clinically significant levels of social anxiety, ‘mild’ symptoms of generalised anxiety and ‘moderate’ symptoms of depression. There was no evidence that the standard or enhanced self-help interventions reduced fear of negative evaluation, symptoms of anxiety or symptoms of depression in comparison to the wait-list control condition.