PubMed (www.ncbi.nlm.nih.gov/pubmed) could help you examine your hypothesis. I recommend this search: (“Patient Readmission”[Mesh]) AND psychiatric, and then limit to review articles with the selector on the left. There seem to be several recent reviews (most recently 2017) about pre- or post-discharge predictors for readmission to psychiatric hospitals that you may find informative. You could try the PsycInfo database as well: subject(“Psychiatric Hospital Readmission “) and select Literature Review under the Methodology dropdown on the results screen (left side).