Development and validation of the of a State-based Wellbeing Scale to Evaluate the "A Lust for Life Schools Programme"

The increasing prevalence of mental health difficulties in children and adolescents highlights the significant need to promote positive mental health and wellbeing in youth. Schools are uniquely positioned to provide universal interventions that foster resilience, coping skills and wellbeing. However, capturing the effectiveness of such programmes relies on the use of valid, contextually appropriate psychometric scales. The research presented in this thesis is aimed to explore the scales used to measure wellbeing in school-based positive psychology interventions (PPIs), and to develop a psychometrically valid, child-centred scale of state-wellbeing. Accordingly, a systematic review of six systematic reviews and meta-analyses revealed a lack of state-based wellbeing psychometric scales used in school-based wellbeing, mindfulness, and PPI research. The review recommended a list of scales and highlighted the need to align the intervention goal with the evaluation methods. Building on these findings, the empirical research of this thesis involved the development and validation of the Feeling Better Scale (FBS) - a novel, state-based self-report scale designed for use with children aged 8-13 following participation in the A Lust for Life (ALFL) Schools Programme. The FBS was created through a multi-stage, mixed-methods process including focus groups and psychometric assessments. The central findings of the study were that a 23-item, 2-factor version of the FBS best fit the data and demonstrated good internal consistency, construct validity, and responsiveness to change. Collectively, these findings support the development of child-informed, state-sensitive scales for more accurate and meaningful programme evaluations of PPIs and provide a number of implications for practice.