A meta-analysis combines the results of many independent studies on the same question. Pooling the data gives a more reliable estimate of how well an intervention works than any single study can.
The results are usually reported as an effect size, which shows how much difference the intervention made compared with children who did not receive it. Researchers commonly interpret effect sizes as follows:
Small (0.2): the average child who received the intervention did better than about 58% of children who did not.
Medium (0.5): better than about 69%.
Large (0.8): better than about 79%.
In psychological treatment research, an effect size of 0.5 or above is generally regarded as a meaningful result.
Child-Centred Play Therapy (CCPT) and Child-Parent Relationship Therapy (CPRT) have been studied with many groups of children and for a range of outcomes.
Much of this research has focused on internalising difficulties. Researchers have looked at anxiety and depression separately, and at broader groupings that also include withdrawal.
The research has also included children from diverse backgrounds and with a wide range of presenting concerns, including:
Adverse childhood experiences
Chronic illness
Academic difficulties
Disruptive behaviour
These studies give a picture of how play-based and parent-involved approaches may support children across different circumstances and needs.
Several meta-analyses of play therapy have been published (LeBlanc & Ritchie, 2001; Bratton et al., 2005; Lin & Bratton, 2015; Ray et al., 2015; Taylor, 2024), and some have looked specifically at internalising difficulties.
One of the earliest, by LeBlanc and Ritchie (2001), combined the results of controlled play therapy studies and found an overall mean effect size of 0.66, a moderate-to-large effect. It also found that parental involvement and the number of sessions were significant predictors of outcomes. Children tended to benefit more when parents took part and when therapy continued over enough sessions.
One of the largest meta-analyses of play therapy, by Bratton, Ray, Rhine and Jones (2005), combined the results of 93 controlled outcome studies published between 1953 and 2000. Its main finding was that children who received play therapy did better than those who did not, with an overall effect size of 0.80, which counts as a large effect. Humanistic, non-directive approaches such as child-centred play therapy had a larger effect (0.92) than non-humanistic approaches (0.71). While both were effective, the authors noted that far more humanistic studies were included, which may partly explain the difference.
Consistent with LeBlanc and Ritchie (2001), Bratton et al. (2005) reported larger effects in studies where parents were trained and supervised by a therapist to deliver play therapy (filial therapy; effect size 1.15) than in studies where play therapy was delivered by a professional alone (0.72).
References
Bratton, S., Ray, D., Rhine, T., & Jones, L. (2005). The efficacy of play therapy with children: A meta-analytic review of treatment outcomes. Professional Psychology: Research and Practice, 36(4), 367-390. https://doi.org/10.1037/0735-7028.36.4.376
LeBlanc, M., & Ritchie, M. (2001). A meta-analysis of play therapy outcomes. Counselling Psychology Quarterly, 14(2), 149-163. https://doi.org/10.1080/09515070110059142
Lin, Y. W., & Bratton, S. C. (2015). A meta-analytic review of child-centered play therapy approaches. Journal of Counseling and Development, 93(1), 45-58. https://doi.org/10.1002/j.1556-6676.2015.00180.x
Ray, D. C., Armstrong, S. A., Balkin, R. S., & Jayne, K. M. (2015). Child-centered play therapy in the schools: Review and meta-analysis. Psychology in the Schools, 52(2), 107-123. https://doi.org/10.1002/pits.21798
Taylor, J. L. (2024). Impact of child-centered play therapy and child-parent relationship therapy on internalizing behaviors in children: A meta-analysis (Order No. 31520137). Available from Psychology Collection. (3078152337). Retrieved from https://www.proquest.com/dissertations-theses/impact-child-centered-play-therapy-parent/docview/3078152337/se-2