Thank you for the opportunity to review your manuscript. This is a systematic review to identify and synthesize evidence on the use of action research methods in mental health nursing care. Overall, I think the article has the potential to make a useful contribution. I have made a few suggestions below which I hope will improve the readers’ understanding of the paper.

INTRODUCTION:
Further elaborate on the need and importance of conducting a systematic review. For example, please describe the characteristics of mental health nursing care that led the researchers to use action research. Please clarify the problems, confusions, etc. of the researchers in using action research in the field of mental health nursing.

THE REVIEW:
The inclusion criteria did not include literature quality requirements, and the quality of the existing included articles varies, so please discuss whether there is any impact on the reliability of the results.

RESULTS:
1. When presenting the results, several sections only show the categories, topics, etc. Please briefly and visually describe the specifics of one or several typical high-quality studies under each category to facilitate the reader's understanding.
2. Please revise Figure 2 to be more self-explanatory. I doubt that the top half could improve nursing practice and the bottom half could improve team practice.

DISCUSSION:
Please discuss what are the key points of an effective and high-quality action research on mental health nursing care after going through your systematic review, summarize the process and characteristics, how it differs from others, and what are the considerations. I think that could inform and advise the other researchers.

Thank you for the opportunity to review your manuscript. After the first revision, the paper is better presented, but I have the following additional suggestions to further the understanding of the paper.
RESULTS:
1. Pages 15 to 16: Please describe more clearly the section “Topics of interest for improving mental health nursing care through action research”. What is the logical relationship between "topics" and "categories"? For example, the paper shows that “topics were classified into two categories” and “the category included those topics”. Using a table or figure may make it easier to understand. And please standardize which words are in single quotes.
2. Page 17, line 7 to 8: The sentence “the category ‘improving the adoption of a person-centered approach to care’ included studies aimed at improving person-centered care” does not serve as an explanation.
3. Please continue to refine the language and make the paper concise. Check and correct grammatical errors throughout the text. For example, “In most cases, the needs and priorities that existed for the participants were identified and the difficulties and barriers they encountered in practice” (Page 18, line 10 to 13).

Thank you for the opportunity to review your manuscript. Please make minor changes to Figure 2. Delete the apostrophe from "Lived experience of service users'" and please align the top and bottom order of topics in the figure with the order in which they appear in the text.