RESUMEN
The effectiveness of osteopathic manipulative treatment (OMT) in the modification of various hormones has been studied; however, there is still a need for quantitative measurements to determine how large of an influence exists. The goal of this meta-analysis is to investigate the implications OMT has on cortisol levels. A systematic literature search restricted to English was performed from October 2022 to November 2022 using Google Scholar, OSTMED.DR, and PubMed and included articles from 2000 onward. Articles were excluded if they did not include a measurement for the control group in their study. We identified 4120 studies for potential inclusion. Of these, a total of four studies met the inclusion criteria, with a total of 135 participants (N= 68 OMT, N= 67 control). Out of the 135 participants, 126 participants (N= 62 OMT, N= 64 control) made up the salivary cortisol studies, and the remaining nine participants made up the serum cortisol studies (OMT N= 6, control N= 3). The National Institutes of Health (NIH) bias assessment tool was utilized to measure the risk of bias. Standard mean differences were calculated for effect size. A mean difference in cortisol of 0.10µg/dl (-10µg/dl, 95%CI -0.15, -0.04) was found when comparing all pre- versus post-cortisol levels with OMT versus sham control groups. OMT demonstrated a 0.10µg/dl larger decrease in cortisol than sham control treatments. The standard mean difference was found to be -0.46 (95%CI -1.40, 0.48) making this finding a medium effect size without significance. Heterogeneity for the salivary analysis measured by I2 was 0% indicating no significant heterogeneity across studies. When serum cortisol was included, heterogeneity stayed at 0%. A larger number of high-quality studies, especially those specific to serum cortisol, are recommended, to elucidate the relationship between OMT and cortisol. This research suggests OMT reduces cortisol more than sham treatment before versus after OMT treatment, and though the change is small when comparing after one treatment, it may have clinical usage if multiple OMT sessions are performed.