Supplementary Material 2. Description of Conditions with Ess Identified As Outliers

Supplementary material 2. Description of conditions with ESs identified as outliers

Before the calculation of the combined effect sizes (ES), two studies were excluded because of their unusually large ESs. One prevention study(Berkowitz, Stover, & Marans, 2011) used a child-caregiver intervention to prevent the development of PTSD within a 30-day range after exposure to a PTE (potentially traumatic event). The intervention group (n = 53) received four Child and Family Traumatic Stress Intervention (CFTSI) sessions, while the control group (n = 53) received the same amount of supportive therapy. Both programs were conducted in child-only sessions, parent-only sessions and parent-child sessions. Throughout the sessions, behavioral and cognitive techniques were applied, and in the parent sessions, the importance of daily routines and PTSD symptoms that might occur were explained. The children were 7 to 17 years old and were recruited from a pediatric emergency department. The participants needed to have shown a new symptom since the occurrence of a PTE. The PTEs experienced by the participants included motor vehicle accidents (24%), sexual abuse (18%), the witnessing of violence (19%), physical assaults (21%), injuries (e.g., sports, cycling) (8%), animal bites (5%), and threats of violence (e.g., mugging) (5%). The authors of the paper offered no explanation for the extremely large ES, but such a result may have been obtained because it was a pilot study with an extremely high dropout rate (n = 20). The authors did not report the dropout rates separately for each group, and they reported their post-treatment results based on the total sample; therefore, the ES may have been overestimated. Furthermore, the study included participants who were not severely traumatized and it had a prevention character. Thus, the study is not comparable to the other studies included in the present meta-analysis that aimed to reduce existing PTSD symptoms. The study also did not provide information about blinding for the clinicians who recorded the measures or information about the therapist’s experience.

The second study that was excluded examined the efficacy of an adjunctive trauma-focused art therapy in an inpatient psychiatric facility(Lyshak-Stelzer, Singer, St. John, & Chemtob, 2007), comparing the intervention group with a treatment as usual (TAU) art intervention. Both interventions were conducted in 1-hour sessions over 16 weeks. The intervention group conducted trauma-specific art activities. The crafts and drawings seemed to constitute a type of trauma narrative at the end of therapy. By contrast, the TAU group made non-trauma-related drawings, bags, ceramic coil bowls, and so forth. The participants in both conditions were 13- to 17-year-old adolescents, most of whom had experienced multiple instances of traumatization. The authors did not provide any information about blinding for the clinicians who recorded the measures or explanations for the large ES observed.

Berkowitz, S. J., Stover, C. S., & Marans, S. R. (2011). The Child and Family Traumatic Stress Intervention: Secondary prevention for youth at risk of developing PTSD. Journal of Child Psychology and Psychiatry, 52(6), 676-685.

Lyshak-Stelzer, F., Singer, P., St. John, P., & Chemtob, C. M. (2007). Art therapy for adolescents with posttraumatic stress disorder symptoms: A pilot study. Art Therapy, 24(4), 163-169.

Psychological Treatments for Symptoms of Posttraumatic Stress Disorder in Children and Adolescents: A Meta-Analysis, Clinical Child and Family Psychology Review, Gutermann, J., Schreiber, F., Matulis, S., Schwartzkopff, L., Deppe, J., Steil, R., Department of Clinical Psychology and Psychotherapy, Goethe University, Frankfurt am Main, Germany,