In healthcare environments, healthcare professionals (HCPs) often encounter situations that require them to voice patient safety threats, such as failure to follow standardized protocols, missed diagnoses, inadequate hand hygiene, or insufficient handoff (Martinez et al., 2017; Okuyama et al., 2014; Schwappach & Richard, 2018). HCPs should speak up when there are concerns about patient safety, as this provides an opportunity for organizations to nurture a safety culture and improve healthcare quality (Etchegaray et al., 2020). Speaking up behavior related to safety, which is one of the assertive communication strategies (Morrow et al., 2016; Schwappach & Richard, 2018), can be conceptualized as “safety voice” or “voice behavior.” There are two types of safety voice in employees: speaking up and withholding voice, and these concepts have been used mainly in patient safety research, commonly considered as opposite poles. Speaking up is defined as stating concerns rather than remaining silent (Morrow et al., 2016), while withholding voice can be defined as an intentional behavior not to verbalize ideas, information, or opinions (Schwappach & Richard, 2018).

Speaking up can contribute to individuals' behavioral changes and organizational improvements in patient safety (Okuyama et al., 2014). In particular, speaking up about patient safety concerns is closely associated with important patient safety outcomes, such as the prevention of medication errors and the reduction of infection rates (Aydon et al., 2016; Kuo et al., 2020; Robbins & McAlearney, 2016). Furthermore, it is expected to have a preventive effect on human errors and to improve system deficiencies that may lead to patient safety incidents (Okuyama et al., 2014). For example, previous studies have shown that interventions such as assertive communication training can effectively improve nurses' speaking-up behavior and communication skills, thereby increasing the reporting of safety concerns and fostering a positive safety culture that helps prevent medical errors in healthcare settings (Chen et al., 2023; Omura et al., 2017). However, despite its crucial role in patient safety, the factors influencing ‘safety voices’ can differ in each clinical situation, making it challenging to speak up, and withholding voice remains common among HCPs (Schwappach & Richard, 2018).

Although nurses recognize the importance of speaking up, they frequently experience discomfort or hesitation when voicing concerns (Lee, Choi, Dahinten, et al., 2023; Morrow et al., 2016). In a vignette study of anticipated behaviors in hypothetical safety-related situations (e.g., infection), nurses compared to doctors showed greater awareness of patient harm risks but felt more discomfort with speaking up and reported a lower likelihood of speaking up (Schwappach, 2018). Previous studies have indicated that personal (e.g., job attitude, personality, hospital tenure), organizational (e.g., hierarchy, power dynamics), contextual (e.g., organizational culture, safety climate), and sociocultural factors can all affect HCPs' voice behaviors regarding safety issues (Ahn & Kim, 2024; Lee, Dahinten, Seo, et al., 2023; Morrow et al., 2016; Okuyama et al., 2014; Schwappach & Richard, 2018). In an organizational culture where unsafe behaviors are considered routine, HCPs may not recognize such issues as needing attention, or may be reluctant to speak up even if they perceive a safety concern (Edwards et al., 2009; Schwappach & Richard, 2018).

Safety culture encompasses various dimensions relevant to safety voices, such as open communication, leadership commitment to safety, organizational learning, teamwork, a non-punitive approach to adverse event reporting and analysis, and a shared belief in the importance of safety (Halligan & Zecevic, 2011), and it is one of the crucial factors shown to be associated with HCPs' speaking up behavior (Etchegaray et al., 2020). Organizations with a positive safety culture are characterized by communication based on mutual trust, shared perceptions of the importance of safety, and confidence in the efficacy of preventive measures (Halligan & Zecevic, 2011), with shared norms and values influencing safety practices (Noort et al., 2016). In a previous study, HCPs who reported that they would always speak up had higher safety culture scores than those who gave reasons for not speaking up (Etchegaray et al., 2020). While previous literature has tried to identify the relationship between HCPs' patient safety culture and speaking up (Etchegaray et al., 2020; Lee, Dahinten, Seo, et al., 2023), little is known about the linkage between nurses' patient safety culture and both safety voices—speaking up and withholding voice—simultaneously.

Systems thinking has emerged as a key element in enhancing nurses' patient safety competency and in strengthening the quality of healthcare systems (Dolansky et al., 2020). Systems thinking involves the ability to view a system as a whole, rather than partially, and is a holistic approach to problem-solving (Dolansky & Moore, 2013; Moazez et al., 2020). In nursing care, incorporating systems thinking into nursing practice is considered a key component of quality and safety, as it enables nurses to understand and evaluate the impact of complex healthcare system components on individual patient care (Dolansky & Moore, 2013; Phillips & Stalter, 2016). Systems thinking plays a significant role in safety-enhancing behaviors, as nurses with higher levels of systems thinking are less likely to be involved in the occurrence of adverse events (Dolansky & Moore, 2013; Kakemam et al., 2022). However, there has been little research directly linking systems thinking to nurses' safety voices. Identifying this relationship is needed in order to develop effective interventions to enhance assertive communication and promote patient safety among hospital nurses.

As the largest portion of HCPs, nurses are expected to speak up to promote safe clinical practice and provide optimal care, acting as patient advocates (Nsiah et al., 2019). Therefore, it is crucial to identify factors that increase nurses' willingness to speak up for patient safety. The aim of this study was (a) to examine factors affecting safety voices (i.e., speaking up and withholding voice) and (b) to determine the mediating effects of patient safety culture on the relationship between perceived concerns about patient safety and safety voices.