Mental Health Literacy (MHL) is important for improving mental health and reducing inequities in treatment. The Mental Health Literacy Scale (MHLS) is a valid and reliable assessment tool for MHL. This systematic review will examine and compare the measurement properties of the MHLS in different languages, enabling academics, clinicians and policymakers to make informed judgements regarding its use in assessments.

The review will adhere to the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology for systematic reviews of patient-reported outcome measures and the Joanna Briggs Institute (JBI) Manual for Evidence Synthesis and will be presented following the Preferred Reporting Items for Systematic reviews and Meta-Analysis 2020 checklist. The review will be conducted in four stages, including an initial search confined to PubMed, a search of electronic scientific databases PsycINFO, CINAHL, Scopus, MEDLINE, Embase (Elsevier), PubMed (NLM) and ERIC, an examination of the reference lists of all papers to locate relevant publications and finally contacting the MHLS original author to identify validation studies that the searches will not retrieve. These phases will assist us in locating studies that evaluate the measurement properties of MHLS across various populations, demographics and contexts. The search will focus on articles published in English between May 2015 and December 2023. The methodological quality of the studies will be evaluated using the COSMIN Risk of Bias checklist, and a comprehensive qualitative and quantitative data synthesis will be performed.

Ethics approval is not required. The publication will be in peer-reviewed journals and presented at national and international conferences.

CRD42023430924.