<qa>  What is the main focus of the intervention?Participants are randomly assigned to receive either an active intervention or treatment as usual for 6 weeks. The active intervention is followed by 4 weeks of maintenance. The intervention is implemented primarily by existing nursing facility staff and focuses on increasing opportunities for residents to experience pleasant events through increased levels of activity and positive affect. The maintenance treatment involves incorporation of protocol-based activities into patient care plans. Patients have a follow-up visit 12 weeks after the study. Psychiatric evaluations, depression and mood rating scales, observed affect and activity participation, behavior problems, and staff burden are assessed. 