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.