Self-citation in nursing research: Patterns, outliers, and empirical thresholds

Self-citation plays a dual role in scientific communication: it may reflect legitimate scholarly continuity, but excessive self-referencing can distort citation-based metrics used in research evaluation. As citation indicators increasingly influence faculty promotion, institutional benchmarking, and the global visibility of nursing schools, understanding typical self-citation patterns within nursing has become important.

To examine the distribution of self-citation among highly cited nursing researchers and to establish empirical thresholds for identifying unusually high self-citation patterns.

This bibliometric analysis used the publicly available Scopus-based standardized author-level citation database developed by Ioannidis (2024). The sample included 1,375 career-long (1996-2024) and 1,403 single-year (2024) highly cited nursing researchers. Self-citation rates were computed following Scopus definitions, encompassing citations from both authors and coauthors. Thresholds for excessive self-citation were identified using an interquartile range (IQR)-based outlier approach (strict = Q3 + 1.5 × IQR; liberal = Q3 + 3 × IQR).

The mean self-citation rate was 9.27% (median = 8.65%) in the career-long dataset and 7.88% (median = 6.41%) in the 2024 dataset, with both distributions showing right-skewed patterns. Using strict and liberal IQR-based thresholds, 2.1% and 0.2% of career-long nursing researchers, respectively, and 3.2% and 0.4% of single-year researchers exceeded the thresholds for unusually high self-citation.

Self-citation among highly cited nursing researchers is generally concentrated at relatively low levels, with higher values confined to a small minority of authors. The empirical benchmarks derived in this study provide a discipline-specific reference for interpreting self-citation patterns in nursing research. These thresholds should be viewed as analytical reference points that may help contextualize citation-based evaluation rather than as indicators of unethical citation behavior.