Editorial: Treatment resistant depression: epidemiology, clinic, burden and treatment, volume II.

Cultivating a high-quality nursing workforce is one of the key measures to achieve the goals of optimizing health services and building a healthy environment in the Healthy China 2030 Blueprint (). It is also a common challenge for nursing educators worldwide, and workforce development should prioritize the cultivation of core competence (). Core competence in undergraduate nursing students integrates knowledge, skills, attitudes, values, and personal traits (). Nursing students are required to possess core qualities including interpersonal relationships, decision-making ability, ethical values, critical thinking, and problem-solving skills (). As a primmary objective of nursing education, it significantly associated with students' future professional performance (). Studies have shown that nursing colleges should attach great importance to the cultivation of nursing students' core competencies, and undergraduate teaching reform should highlight the advantages of undergraduate nursing education to systematically improve nursing students' core competencies (). This emphasis aligns with the current international consensus on nursing education, which calls for strengthening the systematic training of core competencies to ensure that graduates can adapt to evolving healthcare needs (), and is reflected in the broader movement toward competency-based frameworks adopted across Europe and other regions in recent years (). However, current evidence indicates that nursing undergraduates generally exhibit only a moderate level of core competence, with notable deficiencies in critical thinking and research capabilities (). These gaps hinder their transition into competent clinical practitioners and may lead to inadequate preparedness of newly recruited nurses in clinical decision-making, teamwork, and patient safety. Self-directed learning ability allows nursing students-driven by intrinsic motivation and positive attitudes—to actively seek and utilize resources to master requisite professional knowledge and skills (). Evidence indicates that undergraduates with strong self-directed learning skills often perform better in their subsequent nursing careers (). A recent multi-country study has also identified self-directed learning readiness as a significant correlate of self-assessed competence among graduating nursing students across Europe (). However, the specific mechanisms underlying the relationship between self-directed learning and sustainable core competence, and whether an essential psychological transitional pathway mediates this relationship, warrant deeper exploration. Professional self-concept refers to students' evolving perceptions of the nursing profession as they transition from undergraduates to registered nurses. As a foundational professional attitude, it encompasses an individual's cognitive understanding, self-esteem, and behavioral orientation toward nursing (). A positive professional self-concept is associated with students' career commitment and their resilience against negative public perceptions (). Bandura's Triadic Reciprocal Determinism theory posits a dynamic and continuous interaction among personal factors (cognition, motivation, and emotion), behavior, and the environment (). Grounded in this framework, our study conceptualizes self-directed learning as the cognitive and behavioral foundation for nursing undergraduates, professional self-concept as their professional cognition and emotion, and core competence as the ultimate behavioral outcome. In this conceptualization, professional self-concept is positioned as the personal cognitive factor that translates active learning behaviors into professional competence, making it a conceptually appropriate mediator. However, a cross-sectional design cannot statistically rule out alternative directional paths. Alternative model specifications—such as reversing the direction of mediation—would be less consistent with the theoretical and temporal ordering of these constructs, as self-directed learning represents a foundational capacity that develops early, whereas professional self-concept emerges through ongoing learning and socialization. Consequently, a strong intrinsic correlation among these three constructs is hypothesized. Although one study suggests positive correlations between professional self-concept, self-directed learning, and core competence (), this study predominantly focused on nursing interns—defined as fourth-year nursing students undertaking full-time clinical rotations in hospitals—rather than pre-internship undergraduates. Furthermore, the specific mediating role of professional self-concept in linking self-directed learning to core competence remains largely unexplored.