Table 3.

Summary of findings from the 67 articles included in the scoping review

Domain	Summary of findings
Readmission time interval	Wide variation from 7 days to 60 months  Most prevalent were 1 and 12 months, reported by 32.8% and 43.3% of the included articles, respectively
Unnecessary readmission definition	Only one article made explicit the criterion that was applied to designating a readmission as unnecessary (ie, preventable/avoidable)
Case-mix adjustment approach	73.1% of the articles did not specify risk adjustments that were made  Most prevalently adjusted variables were clinical (including diagnosis; 17.9%), service use (19.4%) and sociodemographic (20.9%)
Study setting	71.6% of the articles reported on studies conducted in the setting of one or more psychiatric hospitals  14.9% reported on studies conducted at general hospitals/systems
Target population	25.4% of the articles reported on studies considering their population’s substance use diagnoses  9.0% reported on studies of military veterans
Sample size and comparisons conducted	Wide variation among studies reporting (23–60 254 participants)  40.3% and 29.9% of the articles reported on studies examining comparisons to usual care and having no comparisons, respectively
Voluntariness of readmissions	73.1% of the articles did not state whether they were differentiating between voluntary and involuntary readmissions  17.9% stated including both voluntary and involuntary readmissions
Care transition processes	65.7% and 35.8% of the articles were on care transition processes involving outpatient follow-up and patient education, respectively  (these and other process categories are defined in the main text)