Principles of Personnel and Human Resource Management

Is there any empirical data to show the support of stress interventions?  If so, can you discuss the methoodolgy and the effect sizes?  Some studies rely on self-report measures.  Why are self-report measures potentially problematic?

I need some literature support and outcome-based research to show that psychologically healthy workplace practices actually work.  There have been recent studies showing that wellness programs do not demonstrate a significant impact.  Please see if you can locate a study or two.