The 1947 judgment against Nazi doctors is recognized as the cornerstone of modern research ethics [2]. The 10-statement Nuremberg Code (Table 1) emphasizes the importance of sound scientific research protocols and informed consent [3]. Despite this, several reports of unethical medical studies conducted without informed consent on vulnerable research participants have been published since the early 1960s [4,5]. Such unethical events have emphasized the need for informed consent of the research participants and required the researcher to take responsibility for the potential risks of the research [6]. Among several declarations related to research ethics [7-9], the Declaration of Helsinki published by the World Medical Association in 1964 has undergone revision and is now accepted as an ethical principle in medical research involving humans [10-12]. The major changes in the latest revision published in 2013 are compensation for clinical trial-related injuries, approval for use of placeboes in clinical trials, protection of vulnerable populations, and post-trial provisions [13].

Clinical research is essential for the advancement of medicine, but there should be no greater priority than the safety and interests of the research participants. Even when sufficient informed consent has been obtained, it is entirely the responsibility of the physician or research team conducting the study to protect the study participants [1]. Clinical research should be conducted within the ethical and legal regulations of each respective country or the international guidelines. Researchers must be educated, trained, and qualified in scientific research methods as well as research ethics, and the research process must be supervised by an accredited expert or center [1].

Prior to initiation of the study, the study protocol must be submitted to a qualified research ethics committee for review and approval. The committee should be neutral and transparent, and there should be no conflict of interest with the researchers or institutions sponsoring the research [1]. The committee should be able to monitor the research process, and the researcher should provide necessary information when requested by the committee. If protocol violations or adverse events occur during the study, they must be reported to the committee according to the established regulations [6,14]. The committee should resolve or refer the issues for resolution and may terminate or suspend the research when deemed to have significant ethical violations or higher-than-expected risks [14].

Editors of journals should state the editorial policy to let the authors disclose sources of funding for research or publication [1]. The submitted manuscript should state that the study was approved by the research ethics committee or institutional review board, and that it was undertaken with informed consent from the research participants [1,6].

Authorship has significant academic, social, and financial implications as well as responsibility for published work. The International Committee of Medical Journal Editors (ICMJE) [20] recommends that authorship be based on the following four criteria: (1) substantial contributions to the conception or design of the work or the acquisition, analysis, and interpretation of data for the work; (2) drafting the work or revising it critically for important intellectual content; (3) final approval of the version to be published; or (4) agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

In other words, only when all four criteria are met should the researcher be listed as an author and their contribution described [1,20]. Contributors who do not meet the criteria must be described in the acknowledgment section. Since these criteria are intended to allow authorship to those with qualifications and responsibilities as authors, researchers who meet the first criterion should be given an opportunity to participate in the other three criteria [20].

Fabrication is inventing data or results, while falsification is an act of omission or alteration of research materials, process, and data [1]. Such misconduct is considered the most serious violation in clinical research, as it seriously impairs trust in the research as a whole.

The word “plagiarism” stems from Latin word, “plagiarius” (an abductor) and “plagiare” (to steal) [1,19]. The World Association of Medical Editors defines plagiarism as the use of published or unpublished ideas or words (or other intellectual property) from others without attribution or permission and presenting them as new and original rather than derived from an existing source [21]. This definition applies regardless of whether the idea or word is taken from an abstract, a research grant application, an institutional review board application, or an unpublished or published manuscript [21]. Plagiarism can be categorized as direct (plagiarism of the text), mosaic (borrowing ideas and opinions from the original source and a few verbatim words or phrases without crediting the author), and self‑plagiarism [1,22]. In particular, self-plagiarism is using a part of the authors’ previously published work without mentioning the original article [19,23]. The degree of similarity to be judged as plagiarism varies from 10% to 30% and is ultimately decided by the editor of the journal [19,24]. Therefore, when citing text or ideas from other sources, the authors should describe them in their own words, cite them appropriately, and mention the references [1,19,22].

Duplicate submission of the same manuscript simultaneously to more than one journal is prohibited. Duplicate publication of a prior publication with substantial overlap without reference or related statement is another misconduct in clinical research [20]. Journals may decide to accept re-publication of previously published studies with accurate translations in other languages [1]. In such cases, the authors should describe the original article or source of the material and ensure that the manuscript has been translated and re-published [1]. When the submitted manuscript contains a substantial portion of previously published articles, the authors should clearly state it in a letter to the editor and provide the relevant data or copies so that the journal can decide whether or not to accept it. When the submitted manuscript is published on the preprint server, the authors must notify the journal and provide a link to the preprint. If different research teams submit manuscripts from the same database (such as a public database), the studies should be considered independently for publication [20].