Functional Behavioral Assessment-based interventions on adults' delusions, hallucinations and disorganized speech: A single case meta-analysis.

The Functional Behavioral Assessment (FBA) approach involves the use of single-case designs (SCD) to study the problem behavior-environment contingencies and conduct interventions that consider this functional relationship. Although this approach has been considered an evidence-based practice (EBP) for the treatment of several psychological problems, no meta-analytic studies of FBA-based interventions on delusions, hallucinations and disorganized speech -commonly operationalized as "atypical vocalizations"- have been carried out. Therefore, the purpose of this study was to review and synthesize the results of FBA-based interventions on adults' atypical vocalizations. We conducted a systematic review and a multi-level meta-analysis of these interventions, using a recently developed effect size estimator for SCD studies (i.e., log response ratio). All the studies that met our eligibility criteria provided evidence supporting the effectiveness of FBA-based interventions on atypical vocalizations, with an overall average effect size of a 72% reduction. Both the publication year and the methodological quality were found to be significant moderators. Despite some methodological limitations, we can conclude that FBA-based interventions are effective to reduce atypical vocalizations. The implications of these results could be of interest for the mental health community.