In March 2019 researchers from China published their review of the medical scientific literature to assess the effect of laughter and humour on depression, anxiety and sleep quality. A total of 10 studies involving 814 individuals were included in the review. Results showed that both laughter and humour appeared to significantly reduce levels of depression and anxiety as well as improving sleep quality.
Zhao J et al. A meta-analysis of randomized controlled trials of laughter and humor interventions on depression, anxiety and sleep quality in adults. J Adv Nurs. 2019 Mar 18. [Epub ahead of print]