Backround: A growing number of studies point to a high mental health burden among children and adolescents during the COVID-19 pandemic, particularly concerning anxiety. However, the study quality and effect direction are heterogeneous in the existing primary studies with a lacking overview for the European continent. Therefore, this systematic review aims to critically synthesise the evidence regarding the impact of the COVID-19 pandemic on anxiety among children and adolescents in Europe compared to a pre-pandemic baseline.

Methods: A systematic literature search will be performed in six databases (MEDLINE, EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials, Web of Science, and WHO COVID-19 database) with a peer reviewed search strategy according to the evidence-based checklist Peer Review of Electronic Search Strategies (PRESS). Inclusion criteria are children and adolescents ≤ 19 years living in Europe and data report during the COVID-19 pandemic with an appropriate pre-pandemic baseline. Primary outcomes are general anxiety symptoms and clinically relevant anxiety rates. Risk of bias will be assessed using the ‘Risk of Bias in Non-randomised Studies of Exposure’ (ROBINS-E). Data extraction will systematically include information on study design, population characteristics, COVID-19 determinants, pre-pandemic baseline, diagnostic instruments and outcome. The certainty of evidence for each outcome will be evaluated by using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach adapted to the use of non-randomised studies. All process steps will be performed independently by two reviewers; any discrepancies will be discussed and, if necessary, resolved by a third author. Also, subgroup analysis, sensitivity analysis, publication bias analysis, and meta-regression analysis, if applicable, will be performed. The systematic review was registered in the Prospective Register of Systematic Reviews (PROSPERO) and the protocol was prepared in accordance to the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) statement.

Discussion: This systematic review will address the lack of a critical and comprehensive summary of findings on the COVID-19 pandemic impact on anxiety among children and adolescents in Europe. In addition, it aims to identify pandemic-policy differences, such as the effect of school-closures, and identify particularly vulnerable risk groups.