Searching for cancer-related information online: Unintended retrieval of complementary and alternative medicine information

Purpose: The Web is an important source of health information for consumers. Use of complementary and alternative medicine (CAM) is also increasing. Therefore, we studied the likelihood that consumers will incidentally encounter CAM information while searching the Web and the factors that influence retrieval of CAM information. Methods: We evaluated results retrieved by 10 cancer-related searches on six common search engines. Results: Of 1121 search results, 16.2% displayed CAM information. Sponsored (i.e., paid) results were more likely to display CAM information than non-sponsored results (38% versus 7.5%, p < 0.001). In Overture and Google, sponsored results accounted for 51% and 39% of results on the first page. These search engines also retrieved more CAM web pages. Search engines distinguished sponsored and non-sponsored results, but disclosure statements describing the differences were confusing. Cancer type used as the search keyword did not influence the number of CAM web pages retrieved. However, synonyms of cancer differed in their retrieval of CAM web pages (p < 0.001). Consistent with prior studies of Web search engine overlap, we found that 28% of CAM results were retrieved by two or more search engines. Conclusions: Clinicians should help consumers recognize sponsored results and encourage search engines to clearly explain sponsored results.