A systematic review and meta-analysis of the effect of whole body cryotherapy on mental health problems

ObjectiveTo give an overview of the nature and methodological quality of studies on whole body cryotherapy (WBC) as add-on intervention for mental health problems.MethodsA meta-analysis according to PRISMA guidelines was conducted (Prospero registration: CRD42020167443). Databases MEDLINE, PsycINFO and the Cochrane Library were searched. Risk of bias was scored according to the Cochrane ROBINS-I-tool to which an extra bias-dimension of allegiance bias was added. Within and between Hedges’ g pooled effect sizes were calculated for the main aspect of mental health measured. Treatment efficacy was examined using a random effects model. Heterogeneity was examined through identification of visual outliers and by I² statistics.ResultsOut of 196 articles coming up from the search, ten studies met all inclusion criteria, six of which were (randomized) controlled trials. Together these studies report on a total of 294 participants receiving WBC. The within-group pooled effect size for mental health problems is large (Hedges’ g = 1.63, CI: 1.05-2.21), with high heterogeneity (I² = 93%). Subgroup analyses on depressive symptoms and quality of life (QOL) showed a diminution of heterogeneity to moderate. Effect sizes for depressive symptoms are very large (Hedges’ g = 2.95, CI: 2.44-3.45) and for QOL medium (Hedges’ g = 0.70, CI: 0.15-1.24). The between-group pooled effect size is medium (Hedges’ g = 0.76, CI: 0.17-1.36).ConclusionsResults indicate preliminary evidence for WBC as efficacious add-on intervention for mental health problems, especially depressive symptoms. Further research in the form of RCTs with larger numbers of participants is needed.