Content analysis
After collecting all of the citing sources, we conducted a relational content analysis15that explored the relationship between Portenoy and Foley’s 1986 article and each of the citing works. While similar studies have focused on whether citations were affirmative or negative,16we expanded the scope of our study to construct a more detailed analysis of the citation patterns in the scientific literature. We identified five relevant outcomes: sign (affirmational, negational, or neutral reference), accuracy of index study citation, attribution of the index citation to driving the opioid crisis, agenda-setting, and article type (Table 1).