AI-Supported Therapy for Depression and Anxiety Compared With Standard CBT

This study is a pivotal, randomised, controlled, non-inferiority trial evaluating "Nook," an AI-delivered, neurosymbolic, clinician-supervised digital psychological intervention for depression and anxiety, compared with standard cognitive behavioural therapy (CBT). The trial will recruit 400 participants aged 16-64 years in the UK with moderate depression and/or anxiety symptoms. Participants will be randomised to receive either Nook or therapist-delivered CBT. The primary objective is to determine whether Nook is non-inferior to CBT in reducing depression and anxiety symptoms, measured using the PHQ-9/PHQ-A and GAD-7 scales. Secondary outcomes include quality of life, functional impairment, sleep quality, treatment engagement, participant satisfaction, safety outcomes, and exploratory health economic measures. The intervention incorporates clinician oversight and predefined escalation pathways for suicidality and clinical deterioration. Outcomes will be analysed using longitudinal mixed-effects models under an intention-to-treat framework.