Background: The Delphi technique has become established in public health research, yet there is a lack of methodological standards in questionnaire development. We here demonstrate how the Delphi technique can be used in an interdisciplinary public health topic for framework development, and we highlight methodological challenges and possible solutions. Methods: We developed the questionnaire through a comprehensive literature review and the generation of an item pool based on the rules of item construction. We used cognitive interviews, Delphi experts' assessment and group discussions to refine the questionnaire and to ensure content validity. Finally, we pre-tested the online questionnaire on LimeSurvey. Results: The questionnaire consists of three main sections, namely gender (norms), the social environment and the mental health of adolescents, and another section on the expert's characteristics. The questionnaire comprises a total of 32 questions and includes rating and ranking questions, content-related and comment questions, open and closed questions as well as questions on personal characteristics and evaluation questions. Conclusion: Interdisciplinary researchers need to be involved in the development process of the questionnaire to address challenges related to interdisciplinarity. They should consider certain aspects of the development process, such as comprehensively preprocessing the content, disentangling the theoretical concepts, reducing the complexity, providing more structure and clarity and extensively shortening the length of the questionnaire. Future research should focus on developing methodological guidelines and testing their applicability for different objectives of the Delphi technique (e.g. framework development).

The authors have declared no competing interest.

This paper is part of a PhD and was thereby funded within the scope of the junior research group project GendEpi (Gender Epidemiology) within the Department of Epidemiology & International Public Health, School of Public Health, Bielefeld University.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethical approval was obtained from the ethics board at Bielefeld University, Germany, in May 2023 (application number: 2023-111 of 2023/05/22)

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.