Effectiveness and psychological mechanism of group-based IMPROVE therapy for treatment seeking college students with problematic internet use in China: study protocol for a prospective, single-blind, randomised clinical trial.

INTRODUCTION: Problematic internet use (PIU) is a prevalent and heterogeneous mental health problem among university students, associated with significant psychological distress and functional impairment. Although various psychosocial interventions have demonstrated efficacy, existing randomised controlled trials (RCTs) are frequently limited by small sample sizes, single-component designs and insufficient investigation of underlying psychological mechanisms. This study aims to evaluate the effectiveness and psychological mechanisms of IMPROVE (Identify, Monitor, Plan, Real-world activities, Observe emotion, Vulnerability and Emotion regulation), a manualised, multimodal group-based psychotherapy integrating cognitive-behavioural strategies with motivational elements, mindfulness training and socially interactive exercise for the treatment of PIU among university students. METHODS AND ANALYSIS: This single-blind RCT will recruit 600 university students with moderate-to-severe PIU (Internet Addiction Test (IAT) ≥50) from multiple campuses. Participants will be randomised (1:1) to either an 8-week IMPROVE intervention or an enhanced waitlist control condition. The primary outcome is change in PIU severity (IAT score) from baseline to post-intervention. Secondary outcomes include remission rates, internet-related behaviours, craving, functional impairment, comorbid psychopathology and well-being. Candidate psychological mediators-maladaptive cognitions, self-efficacy, emotion regulation, mind wandering, anhedonia, resilience and perceived stress-will be assessed longitudinally to support formal mediation analyses. Prespecified moderation analyses will examine treatment heterogeneity across PIU subtypes and baseline characteristics. ETHICS AND DISSEMINATION: The study was approved by the Ethics Committee of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine (approval no. 2026-0152). Written informed consent will be obtained from all participants prior to enrolment. Study findings will be disseminated through peer-reviewed publications and conference presentations. TRIAL REGISTRATION NUMBER: NCT07434778 (https://clinicaltrials.gov/study/NCT07434778).