Although breast cancer patients' depression changes over time, most longitudinal studies have assessed the influence of only baseline depression on quality of life (QoL). Therefore, this study investigated the influence of changes in depression status on QoL in the year after surgery.

Participants were interviewed at 2–5days and at 1year after surgery. Depression was diagnosed at both time points, and participants were classified into four groups: no, recovered, incident, and persistent depression. QoL-related functioning and symptoms were evaluated with the EORTC QLQ-C30 questionnaire and the interaction of depression and QoL was analyzed using a repeated-measures analysis of covariance (RMANCOVA).

Of the 306 participants, 247 were evaluated at 1year after surgery; 165 had no depression, 40 had recovered from depression, 24 had incident depression, and 18 had persistent depression. The RMANCOVA revealed significant time-by-group interactions; the no-depression group exhibited better recovery in general QoL and functioning, whereas the persistent-depression group showed the worst recovery. QoL and functioning improved in the recovered depression group, but worsened in the group with incident depression.

The different impacts of changes in depression status on QoL highlight the importance of periodic screening for depression.