The explosion in happiness studies of the last 20 years did has not improved effect sizes of happiness interventions; the supposed epistemological superiority of positive psychologists has not produced more effective happiness advice

Diminishing Effectiveness of Happiness Interventions: Positive Psychology Stumbles on the Dodo Verdict. Ad Bergsma. Journal of Psychology & Psychotherapy, Sep 6 2020. https://www.longdom.org/abstract/diminishing-effectiveness-of-happiness-interventions-positive-psychology-stumbles-on-the-dodo-verdict-58408.html

Rolf Degen's take: https://twitter.com/DegenRolf/status/1340924363856556033

Abstract: Some positive psychologists claim that quantitative research leads to the most effective interventions for the intentional pursuit of happiness. A similar claim made in psychotherapy research resulted in failure; fifty years of experimental research has not improved psychotherapy outcomes. In this essay it is argued that the explosion in happiness studies of the last twenty years did has not improved effect sizes of happiness interventions. The supposed epistemological superiority of positive psychologists has not produced more effective happiness advice. This should not be taken as an encouragement to throw the baby out with the bathwater. If we follow current reasoning in psychotherapy research, we can conclude that positive psychological research can correct misguided or counterproductive happiness advice, but will not offer definitive answers. The individuals making his their own choices on the basis of a personal life philosophy count. A further conclusion is that happiness interventions should not just be about acquiring skills to correct the affective system in our brains, so that we are able to overcome our negativity bias or hedonic adaptation. Intervention should also be about following our emotional action tendencies; promoting doing to do more of what feels right to us and avoiding what causes pain.