The physical and mental health benefits of touch interventions: A comparative systematic review and multivariate meta-analysis

Introduction: Receiving touch is of critical importance for human well-being. A number of studies have shown that touch promotes mental and physical health. However, effect sizes differ considerably across studies and potential moderators of touch interventions remain unknown to this day. Methods We conducted a preregistered (CRD42022304281) systematic review and a large-scale multivariate multilevel meta-analysis encompassing 137 studies in healthy participants and patients (166 cohorts, 9617 participants and 643 effect sizes) in the meta-analysis and 75 additional studies as part of the systematic review to identify critical factors moderating touch intervention efficacy. Included studies always featured a touch vs. no touch control intervention with health outcomes as dependent variables. Results We found comparable and medium-sized (Hedges’ g ∼ 0.5) effects of touch on both mental and physical health. Touch interventions were especially effective in regulating cortisol levels (0.78 [0.24;1.31]) and increasing weight (0.65 [0.37;0.94]) in newborns, as well as in reducing pain (0.69 [0.48;0.89]), feelings of depression (0.59 [0.40;0.78]) and state (0.64 [0.44;0.84]) or trait anxiety (0.59 [0.40;0.77]) for adults and children. Comparing touch interventions involving objects or robots with humans resulted in similar physical (0.56 [0.24;0.88] vs. 0.51 [0.38;0.64]) but lower mental health benefits (0.34 [0.19;0.49] vs. 0.58 [0.43;0.73]). Adult clinical cohorts profited stronger in mental health domains compared to healthy individuals (0.63 [0.46;0.80] vs. 0.37 [0.20;0.55]) but showed comparable physical health benefits (0.53 [0.38;0.69] vs. 0.47 [0.29;0.65]). We found no difference in children and adults comparing touch applied by a familiar person or a health professional (0.51 [0.29;0.73] vs. 0.50 [0.38;0.61]) but parental touch was more beneficial in newborns (0.69 [0.50;0.88] vs. 0.39 [0.18;0.61]). Intervention frequency positively correlated with increased health benefits in adults and children while session duration did not show significant effects. Discussion Leveraging those factors that influence touch intervention efficacy will help maximize the benefits of future touch interventions and focus research in this field. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Protocols ### Funding Statement JP was supported by the German National Academy of Sciences Leopoldina (LPDS 2021-05). HH was supported by the Marietta-Blau scholarship of the Austrian Agency for Education and Internationalisation (OeAD) and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation - Project-ID 422744262 - TRR 289). CK received funding from OCENW.XL21.XL21.069, VG from the European Research Council (ERC) under European Union Horizon 2020 research and innovation program, grant HelpUS (758703), and from the Dutch Research Council (NWO) grant OCENW.XL21.XL21.069. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study is a meta-analysis and made use of publicly available data only through published articles. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data are available under the following link: https://osf.io/c8rvw/?view_only=6298307ead2e423eb20f9675f843de0d