In health research publications, the number of authors is strongly associated with collective self-citations but less so with citations by others.

Objective:. This study investigated the associations between the number of authors and collective self-citations versus citations by others. Study design and setting:. We analyzed 88,594 health science articles published in 2015 and citations they received until 2020. The main variables were the number of authors, the number of citations by co-authors (collective self-citations), and the number of citations by others. Results:. The number of authors correlated more strongly with the number of citations by co-authors than with citations by others (Spearman r 0.31 vs. 0.23; mutually adjusted r 0.26 vs. 0.12). The percentage of self-citations among all citations was 10.6% for single-authored articles, and increased gradually with the number of authors to 34.8% for ≥ 50 authors. Collective self-citations increased the proportion of articles reaching or exceeding 30 total citations by 0.7% for single-authored articles, but by 11.6% for articles written by ≥ 50 authors. Conclusions:. If citations by others reflect scientific utility, then another mechanism must explain the excess of collective self-citations observed for multi-authored articles. The results support the hypothesis that the authors' own motivations explain this excess. The evaluation of scientific utility should also be based on citations by others, excluding collective self-citations. [ABSTRACT FROM AUTHOR]