Open Science and Meta-Analyses in Clinical Psychology: Lessons Learned

We have learned several lessons from our meta-analytic work in the past decades, and we discuss a few important ones. (a) Publication bias is still a major issue, seriously affecting outcomes of meta-analyses. (b) Preregistration of trials can still be improved because only 50% of trials comparing psychotherapy for depression with control conditions was prospective registered since 2021. (c) A considerable number of trials (at least 28% in published “individual participant data” meta-analyses of psychological interventions for mental-health problems) do not provide their primary data for such meta-analyses. (d) Manuals of treatments are often not open at all. (e) Open access of meta-analytic data sets will considerably increase efficiency, reduce waste of resources, and speed up clinical research.