Objective: Seligman, Steen, Park, and Peterson (2005) suggested that positive psychology interventions (PPIs) contain specific, powerful, therapeutic ingredients that effect greater increases in happiness and reductions in depression than a placebo control. This study reexamined the three PPIs that Seligman et al. found to be most effective when delivered over the internet.

Method: Three PPIs and a placebo control, identical with the interventions used by Seligman et al., were examined in a web-based, randomized assignment design.

Results: Mixed-design analysis of variance and multilevel modeling showed that all interventions, including the placebo, led to significant increases in happiness and reductions in depression. The effects of PPIs were indistinguishable from those of the placebo control.

Conclusion: Using web-based delivery, both PPIs and theoretically neutral placebos can increase happiness and reduce depression in self-selected populations. Possible explanations include that non-specific factors common to most therapeutic treatments are responsible for the observed changes, or that cultural or other context-related variables operate to account for the divergent findings.