Human trafficking leaves victims with long-term social, psychological, and health effects. Research in this area is still nascent, and there are limited studies that show the effectiveness of existing services for survivors. This study fills the gaps in knowledge of the effectiveness of existing programs through a comprehensive systematic review and meta-analysis. Inclusion and exclusion criteria retained 15 studies using the preferred reporting items for systematic reviews and meta-analyses method, containing 16 populations. Included studies examined programs and/or interventions providing direct services to human trafficking survivors using quantitative pre- and post-intervention measurements published from January 2010 to June 2022. Outcomes among survivors were grouped into five categories: (a) mental health, (b) physical health, (c) social support or social behavior, (d) personal development, and (e) other. Roughly half (n = 31, 51.66%) of the outcomes across the 15 studies were statistically significant. Most measured constructs showed a moderate effect size (E.S.; n = 31, 51.67%). In all, 21 constructs (27.91%) met high E.S. levels, and eight (13.33%) met the criteria for a low-level effect. Analyzing different intervention types, physical-based interventions represented the smallest subset and the largest mean effect size (n = 5, g = 1.632, 95% CI [0.608, 2.655]) followed by standardized therapy (n = 23, g = 1.111, 95% CI [0.624, 1.599]), wrap-around services (n = 14, g = 0.594, 95% CI [0.241, 0.947]), and peer and support group modalities (n = 18, g = 0.440, 95% CI [0.310, 0.571]). A meta-regression showed that non-U.S.-based interventions were significantly more effective than U.S.-based interventions (z = -2.25, p = 0.025). While only 15 studies contributed to this analysis, the current study ushered in new avenues regarding future research, policies, and practice in services for survivors of human trafficking.
Keywords: human trafficking; meta-analysis; survivors; systematic review.