title: Examining Skill Enactment and Knowledge Acquisition in Digital Cognitive Behavioural Therapy for Depression and Anxiety
Creators: name: Jackson, Hayley
Publisher: name: The Australian National University
Year: 2025

description: Substantial evidence supports the effectiveness of digital mental health interventions (DMHIs) in treating and preventing depression and anxiety disorders. Interventions based on cognitive behavioural therapy (CBT) show the most robust evidence. However, challenges remain in effectively engaging users with DMHIs. Most research has relied on usage metrics such as the number of logins or modules accessed to measure engagement. This approach may not fully capture other important processes, such as the application of intervention strategies in daily life (i.e., skill enactment) or the acquisition of knowledge about mental health and strategies to address symptoms (i.e., knowledge acquisition). Accordingly, this thesis aimed to investigate skill enactment (primary aim) and knowledge acquisition (secondary aim) in digital CBT interventions for depression and anxiety. Four studies were conducted that used narrative synthesis, quantitative, and/or qualitative approaches. Study 1 was a systematic review that synthesised the literature on skill enactment and knowledge acquisition in randomised controlled trials (RCTs) of digital CBT interventions for depression and anxiety. Study 2 examined predictors of engagement and explored the relationship between skill enactment and mental health outcomes among adolescents in a cluster-randomised controlled trial (cRCT) of a school-based online depression prevention program. Study 3 employed mixed methods to assess the effects of a video-based intervention on skill enactment, evaluate the impact of skill enactment on mental health outcomes, and explore experiences of skill enactment among university students with mild to moderate psychological distress. Study 4 qualitatively explored experiences of learning and enacting skills among adult users of publicly available digital CBT interventions. Results suggest that digital CBT interventions can enhance skill enactment and knowledge acquisition among adults with elevated symptoms or those who recognise a need for treatment (Studies 1 and 4). While both constructs are likely important for mental health outcomes in these contexts, their significance may vary depending on the specific type or aspect of skill enactment or knowledge, as well as factors such as perceived control, motivation to change, and active coping. In contrast, no significant changes in skill enactment were observed among young adult users of a digital CBT program (Study 3), nor was skill enactment found to influence mental health outcomes among adolescents or young adults (Studies 2 and 3). Key factors influencing skill enactment included perceived learning and knowledge reinforcement, the relevance and usefulness of intervention strategies to the individual user, and barriers such as time constraints and low motivation. The thesis advances understanding of engagement with digital CBT interventions by consolidating evidence on skill enactment and knowledge acquisition, while offering new insights into skill enactment among different groups of young people and user experiences of learning and implementing skills outside trial settings. The thesis findings suggest that personalised content, learning support strategies, and ongoing resources beyond the intervention may help support the acquisition, retention, and use of knowledge and skills. Enhancing skill enactment and knowledge acquisition may be critical for optimising the impact of DMHIs, although further investigation into the mechanisms by which these constructs influence mental health outcomes is warranted.