Working mechanisms of a web-based self-management intervention for cancer survivors: a randomised controlled trial.

OBJECTIVE: The aim of this study was to investigate whether problem-solving skills and perceived personal control over cancer recovery mediated the intervention effects on depression and fatigue of a web-based computer-tailored intervention for cancer survivors - the Kanker Nazorg Wijzer (Cancer Aftercare Guide).

DESIGN: Patients were recruited through 21 Dutch hospitals (November 2013-June 2014). The mediation model was tested in a randomised controlled trial with an intervention group (n = 231) and a waiting list control group (n = 231).

MAIN OUTCOME MEASURES: Hypothesised mediators problem-solving skills (SPSI-R) and personal control (IPQ-R) were measured at baseline and 3 months from baseline. Outcomes depression (HADS) and fatigue (CIS) were measured at baseline and 6 months from baseline.

RESULTS: The intervention effects in decreasing depression and fatigue were mediated by personal control. Problem-solving skills did not mediate the intervention effects on depression and fatigue.

CONCLUSION: While personal control in the control group decreased in the first three months after baseline, levels of personal control within the intervention group were maintained. This effect partially explained the intervention effects on depression and fatigue. The results provide evidence for the relevance of addressing personal control in web-based interventions in order to improve psychosocial well-being in early cancer survivors.