Participants in both conditions showed statistically significant improvement on indices of psychological well-being , including overall quality of life ( Functional Assessment of Cancer Therapy-Breast ) , intrusive thoughts ( Impact of Event Scale-Revised ) , depressive symptoms ( Center for Epidemiologic Studies-Depression ) , and stress levels ( Perceived Stress Scale ) over the 6-month postintervention follow-up ( all repeated measures analysis of variance within-subjects time effects : P < .05 , except for overall mood ; Profile of Mood States-Short Version ) .