Epigenetic correlates of the psychological interventions outcomes: A systematic review and meta-analysis

Background: In the last years, there was a growing interest in exploring the potential epigenetic effects of psychotherapeutic approaches, but no clear directions have been identified. This article aimed to test and summarize the epigenetic correlates of the different psychological treatments’ outcomes. Methods: We considered only studies, published from inception to July 2021, that provided an epigenetic outcome assessed pre-and post- psychological treatment in either clinical or non-clinical populations. The article adhered to PRISMA, STROBE, Cochrane, and New Castle Ottawa bias scales, and it has been registered on PROSPERO. Results: A systematic review of 14 studies and a meta-analysis on 2 observative prospective cohort studies were processed. The findings of the systematic review showed that, in the majority of the studies, subjects responding to therapy were associated with a specific decrease or increase in the methylation status, that in subjects not responding to therapy was associated in the opposite way. The meta-analysis showed a significant increase in the methylation status of the MAOA gene after a symptom-vocalization CBT only in the respondent participants with anxiety. Limitations: The design of the majority of the studies included in the systematic review was observational, which is more prone to confounders and selection bias. There were few eligible studies for the meta-analyses, making the findings to be considered as preliminary. Conclusions: The findings suggest dynamic changes in epigenetic mechanisms after a psychological treatment that are related to clinical outcomes with an inverse association between remitters and not-remitters.