Falling between the cracks: The effect of using different levels of suicide risk exclusion criteria on sample characteristics when recruiting for an online intervention for depression

Background
Despite a strong link between suicide risk and depression, a recent literature review found that many effectiveness studies for online depression interventions exclude individuals at risk of suicide. This study scrutinizes how different suicide risk exclusion criteria impact recruitment rates and final sample characteristics.
Materials and Methods
Two recruitment periods for an online depression intervention trial utilized different suicide risk cutoff exclusion criteria, a one-point difference on the last item of the Personal Health Questionnaire (i.e., more than 0 (Not at all) vs. more than 1 (Several Days)). Bivariate statistics were used to assess differences in recruitment rates and sample characteristics between these two recruitment periods, while all other eligibility criteria and recruitment strategies remained consistent.
Results
The recruitment period using the least restrictive suicide risk exclusion criteria yielded twice as many participants; however, recruited sample characteristics did not significantly differ among demographic or clinical characteristics, despite observable trends.
Discussion
Researchers should carefully select suicide risk exclusion criteria that balance recruitment rates, study budgets, and sample selection biases, while minimizing participant harm. Moreover, researchers are urged to report suicide risk exclusion rates and consider these exclusions when interpreting results. Limitations of the results are also discussed.