Anxiety disorders, obsessive–compulsive disorder (OCD) and post-traumatic stress disorder (PTSD) are common in children and adolescents and can lead to significant impairment. Cognitive behavioural therapy (CBT) with exposure is the first-line treatment, yet approximately half of treated youth do not achieve full remission. Dysfunctional cognitions—negative automatic thoughts, maladaptive beliefs and distorted interpretations—are considered key targets of CBT, but evidence in youth is mixed and underpowered. This study will examine whether change in dysfunctional cognitions mediates treatment outcome in anxiety, OCD and PTSD symptoms and whether this association varies across individual characteristics.

An individual participant data meta-analysis (IPDMA) of randomised controlled trials of CBT for youth aged 5–18 years with anxiety disorders, OCD or PTSD will be conducted. The search strategy includes the databases APA PsycINFO, MEDLINE and Web of Science Core Collection from inception to 8 September 2025. It is supplemented by screening reference lists, trial registries, grey literature and outreach to relevant research groups. Eligible trials must include at least one validated measure of dysfunctional cognitions administered at minimum pre- and post-treatment, and clinical outcomes assessed at post-treatment and follow-up. The two primary outcomes are (1) child-reported symptom severity and (2) clinician-rated clinical severity. Data will be harmonised for dysfunctional cognition scores, moderators (age, gender, socioeconomic status, comorbidity), and primary outcomes. One-stage Bayesian mixed-effects models will examine whether changes in dysfunctional cognitions predict improvements in primary outcomes and whether these effects are moderated by individual characteristics. Missing data will be addressed using multiple imputation within the Bayesian framework, and study-level heterogeneity will be modelled using random intercepts and slopes.

All datasets will be de-identified and managed under General Data Protection Regulation standards. Each included trial will have ethical approval permitting data sharing and reuse, and the secondary analysis of the shared datasets has been approved by the University of Amsterdam. Findings will be disseminated via a peer-reviewed publication, scientific conferences and open sharing of analysis scripts and harmonisation procedures.

CRD420251139130.

Temporomandibular disorders (TMDs) are a prevalent group of musculoskeletal conditions affecting the temporomandibular joint, associated structures and masticatory muscles. The internet has become a primary source of health information for many patients; however, the readability, reliability, content and quality of online information on TMDs vary widely. A comprehensive synthesis of the characteristics and evaluation methods of such content is currently lacking.

This scoping review will follow the Joanna Briggs Institute methodology and be reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews checklist. Peer-reviewed primary and secondary studies assessing online information on TMDs will be included if they report on readability, reliability, content or quality. Eligible information sources include publicly available websites, videos and social media; discussion forums and printed materials will be excluded. No language, date or geographical restrictions will be applied. A three-step search strategy will be implemented across PubMed, Web of Science, Embase, PsycINFO and CINAHL, followed by citation tracking. Screening will be conducted independently by two reviewers using Rayyan. Data will be extracted with a pilot-tested charting tool and synthesised narratively and descriptively in tabular and graphical formats.

As this study will only use data from publicly available sources, ethical approval is not required. Findings will be disseminated through publication in a peer-reviewed journal, conference presentations and professional networks, with the aim of guiding the development of accessible and reliable digital resources for individuals seeking information on TMDs.

This protocol has been prospectively registered on the Open Science Framework (OSF): https://doi.org/10.17605/OSF.IO/TAH7K.