Only on Invitation? How the Recruitment Strategy Determines Who Is Treated Online

Abstract

Background: Participants for efficacy studies on Internet-based interventions (IBI) are recruited through self-selected convenience sampling or targeted external invitations. Comparisons are necessary to determine how recruitment strategies influence sample composition. Such comparisons consequently yield potential for evaluating which conditions are more probable to fulfill IBI's promise to be an effective treatment option for underserved populations. Methods: A comparison of sociodemographic and clinical characteristics of differently recruited participants in an IBI for mild to moderate depression was made: (1) individuals on sick leave due to an affective disorder who were informed about the IBI by their health insurance (n= 308) and (2) individuals who self-selected to participate (e.g., after seeing information on the IBI in print media; n= 699). Results: Compared to the self-selected group, the externally selected group was older, less educated, spent less time on the Internet, had a less positive attitude towards IBI, and comprised more men. Groups did not differ in initial symptom severity, in-treatment symptom change, or previous psychotherapeutic experiences. Conclusions: The results indicate that larger shares of underserved subpopulations (e.g., less educated, older, male, less internet-savvy) begin an IBI treatment when the insurer informs them about the IBI. Recruitment source does not influence efficacy.