Background and Objectives:
Following a systematic assessment of mental health literacy tools in 2014, O’Conner and Casey developed a comprehensive mental health literacy measure in 2015, which was based on the six attributes endorsed by Jorm et al. in 1997. Since it was first developed, the Mental Health Literacy Scale (MHLS) has found widespread application in mental health literacy research worldwide. This scoping review aims to map the existing MHLS validation research and summarize its validity in different populations.

Methods:
A scoping review was conducted following the guidelines of the Joanna Briggs Institute. A comprehensive literature search was conducted in December 2022 on PubMed, PsycINFO, Embase, CINAHL, Cochrane Library, Scopus, Medline, and ERIC from 2015 to 2022. The review focused on validation studies of O’Conner and Casey MHLS. The study participants and locations were not limited in the search. Reference list search and publication suggestions from MHLS authors were performed as well. Non-English studies and grey literature were excluded.

Results:
The study included 14 articles that have validated the MHLS worldwide. The scale was validated and translated into Chinese, French, Persian, Portuguese, Slovenian, Arabic, Turkish, and Urdu. Seven studies performed Exploratory Factor Analysis, Six performed Confirmatory Factor Analysis (CFA), and one performed Principal Component Analysis. The sample size average was 662 (282-1189), the expert panel average was 9 (4-21), the Cronbach’s alpha average was 0.818 (0.744-0.89), and the Interclass Correlation Coefficient (ICC) average was 0.85 (0.741-0.99). In addition, items 20, 21, and 22 were commonly removed based on the individual article’s CFA results.

Conclusion:
This review provided a compendium of MHLS validation research by systematically searching, selecting, and synthesizing existing publications. It also provided an evidence map for future researchers attempting to utilize the MHLS in their local settings.