Mechanisms for the testing effect on patient-reported outcomes

The testing effect is when patient-reported outcomes (PRO) improve with repeated administration without intervention. The testing effect can confound interpretation of clinical trials using PROs as endpoints. This study investigated potential mechanisms. The parent study (n = 302) investigated a self-management intervention for depression. We qualitatively analyzed exit interview feedback from the 89 control group participants completing the last assessment. Participants reported several perceived benefits from control group participation including novel mechanisms (study participation was meaningful, emotional support, appreciating outreach), a possible negative testing effect and mechanisms previously identified (behavioral change).