. 2022 Feb 28;7:23969415211073118. doi: 10.1177/23969415211073118

Table 2.

Included Studies and Study Characteristics

Study ID	Study reference, publication, and country	Sample characteristics	Research design	Play intervention	Outcome variable	Summary of results
S01	Corbett et al. (2017) Publication: Journal of Autism Country: USA	Sample size: N = 30 Sample: Children with ASD Age: 8-14 years old Girls: N = 6 (20%) Boys: N = 24 (80%) INV: N = 17 CON: N = 13	Design: RCT Type of control: Randomly allocated, waitlist control Control group treatment: SENSE Theatre® Outcome Measure: The STAI-C (Spielberger et al., 1983) Measure standardised: Yes	Name of intervention: SENSE Theatre® Intervention valid: Yes Type of play: Role play Place: Outside of school Provider: Not reported Duration: 40 hours	Reported outcome:Trait anxiety Category: Negative mental health	Test of between-subject effects revealed a significant group effect on post-STAI-C Trait, with pre-STAI-C Trait included as a covariate (F(1, 27) = 9.16, p = 0.005). Changes in play did not show a significant mediational effect on changes in trait-anxiety (B = −0.32; CI = −3.35 to 2.11). Conversely, the direct effect of the intervention on changes in trait-anxiety remained significant (B = −6.97, CI = −12.62 to −1.31).
S01					Reported outcome: State anxiety Category: Negative mental health	No group effect was observed for STAI-C State (F(1, 27) = 0.03, p = 0.86)).
S02	Doernberg et al. (2021) Publication: Journal of Autism and Developmental Disorders Country: USA	Sample size: N = 25 Sample: Children with HF ASD Age: 6-9 years old Girls: N = 3 (12%) Boys: N = 22 (88%) INV: N = 18 CON: N = 7	Design: RCT Type of control: Randomly allocated, waitlist control Control group treatment: Treatment as usual Outcome Measure: The APS (Fehr & Russ (2014)) Measure standardised: Yes	Name of intervention: Pretend Play Intervention valid: Yes Type of play: Pretend play Place: School Provider: The researchers Duration: 100 minutes	Reported outcome: Total positive affect Category: Positive mental health	Results did not indicate any significant effects for children’s abilities to generate a list of positive feelings, nor define complex emotions appropriately.
S02					Reported outcome: Total negative affect Category: Negative mental health	Results did not indicate any significant effects for children’s abilities to generate a list of negative feelings, nor define complex emotions appropriately.
S03	Ioannou et al. (2020). Publication: Frontiers in Psychology Country: USA	Sample size: N = 77 Sample: Children with HF ASD Age: 8-16 years old Girls: N = 18 (24%) Boys: N = 59 (76%) INV: N = 44 CON: N = 33	Design: RCT Type of control: Randomly allocated, waitlist control Control group treatment: SENSE Theatre® Outcome Measure: The STAI-C (Spielberger et al., 1983) Measure standardised: Yes	Name of intervention: SENSE Theatre® Intervention valid: Yes Type of play: Role play Place: Outside of school Provider: Not reported Duration: 40 hours	Reported outcome: State anxiety Category: Negative mental health	There was no difference in State anxiety between EXP and WCL groups [F(2,71) = 0.07, p = 0.935].
S03					Reported outcome: Trait anxiety Category: Negative mental health	Children in the EXP group reported significantly less Trait anxiety than children in the WLC group following intervention [F(2,71) = 6.87, p = 0.01].
S04	Pajareya & Nopmaneejumruslers (2011) Publication: Journal of Autism Country: Thailand	Sample size: N = 32 Sample: Children with ASC Age: 2-6 years old Girls: N = 5 (15%) Boys: N = 28 (85%) INV: N = 16 CON: N = 16	Design: RCT Type of control: Randomly allocated control group Control group treatment: Treatment as usual Outcome Measure: (1) The FEAS (Greenspan, DeGangi & Wieder, (2001). (2) The FEDQ (Pajareya, Sutchritpongsa & Sanprasath, 2014). Measures standardised: Yes	Name of intervention: DIR/Floortime Intervention valid: Yes Type of play: Parent and child interaction play Place: Home Provider: The first author Duration: 240 hours	Reported outcome: Functional Emotional Assessment Score (FEAS) Category: Positive mental health	The change of the FEAS score for the control group reflects the overall developmental progression of only 1.9 (SD = 6.1), compared to the increment of 7.0 (SD = 6.3) for the intervention group. The Student t test shows that the difference is statistically significant (p = .031).
S04					Reported outcome: Functional Emotional Developmental Score (FEDQ) Category: Positive mental health	Developmental rating of the children was estimated by the parent using the Thai version of the Functional Emotional Questionnaires at baseline and follow-up. The change in data for the intervention group shows that there was a more statistically significant gain in it than in the data of the control group.
S05	Rezaei et al. (2018) Publication: Journal of Children Country: Iran	Sample size: N = 34 Sample: Children with ASD Age: Mean = 12.36 Girls: N = 12 (35%) Boys: N = 22 (65%) INV: N = 17 CON: N = 17	Design: RCT Type of control: Randomly allocated, waitlist control Control group treatment: PRT + Risperidone Measures: The ABC (Akhondzadeh et al., 2010) Measures standardised: Yes	Name of intervention: Pivotal response treatment (PRT) (Koegel, 2011) + Risperidone Intervention valid: Yes Type of play: Parent and child interaction play Place: School Provider: Speech/language therapist Duration: 27 hours	Reported outcome: Irritability Category: Negative mental health	There was no significant difference between the INV and Control groups in Irritability subscale.
S05					Reported outcome: Hyperactivity Category: Negative mental health	There was no significant difference between the INV and Control groups in Hyperactivity subscale.
S06	Schottelkorb et al.. (2020) Publication: Journal of Counseling & Development Country: USA	Sample size: N = 23 Sample: Children with ASD Age: 4-10 years old Girls: N = 4 (17%) Boys: N = 19 (83%) INV: N = 12 CON: N = 11	Design: RCT Type of control: Randomly allocated, waitlist control Control group treatment: Treatment as usual Measure: CBCL (Achenbach & Rescorla, 2001). Measures standardised: Yes	Name of intervention: Child-centred play (Axline, 1947) Intervention valid: Yes Type of play: Non-directive play Place: Not reported Provider: Graduate-level counselling students and two licensed counsellors Duration: 12 hours	Reported outcome: Externalising problems Category: Negative mental health	Following the same trend as previous analyses, participants in the play therapy treatment group were reported to have decreased externalising symptoms from pre- to post-testing (M = 68.67, SD = 9.35; M = 63.08, SD = 7.90), whereas control group scores increased (M = 65.36, SD = 9.54; M = 67.27, SD = 8.72).
S07	Siller et al. (2014) Publication: Journal of Autism and Developmental Disorders Country: USA	Sample size: N = 70 Sample: Children with ASD Age: 2-6 years old Girls: N = 6 (9%) Boys: N = 64 (91%) INV: N = 36 CON: N = 34	Design: RCT Type of control: Randomly allocated control group Control group treatment: Parent Advocacy Coaching (PAC) Measures: (1) PCSB (Ainsworth, 1978) (2)AB (Ainsworth, 1978) (3) MPCA (Hoppes & Harris, 1990) Measures standardised: Yes	Name of intervention: Focused Playtime Intervention (Siller et al.,2013) Intervention valid: Yes Type of play: Parent and child interaction play Place: Research lab + participants’ home Provider: Trained graduate and postdoctoral students in developmental psychology and counselling. Duration: 18 hours	Reported outcome: Maternal Perceptions of Child Attachment (MPCA) Category: Positive mental health)	A significant main effect of treatment group allocation on gains in parent reported attachment behaviours (MPCA scores), t(48) = 3.0, p < .01.
					Reported outcome: Proximity/ Contact Seeking Behavior Scale (PCSB) Category: Positive mental health)	Proximity and Contact Seeking Behaviors was only marginally significant, t(54) = 1.8, p\.08.
					Reported outcome: Avoidant Behavior Scale (AB) Category: Positive mental health)	For children’s Avoidant Behaviors, results revealed a significant main effect of treatment group allocation on improvements in Avoidant Behaviors from Time 1 to Time 2, t(54) = 2.2, p\.05.
S08	Solomon et al. (2014) Publication: Journal of Developmental and Behavioral Pediatrics Country: USA	Sample size: N = 128 Sample: Children with ASD Age: 2-5 years old Girls: N = 20 (16%) Boys: N = 108 (84%) INV: N = 64 CON: N = 64	Design: RCT Type of control: Randomly allocated control group Control group received treatment: Treatment as usual Measure: The FEAS (Greenspan et al., (2001). Measures standardised: Yes	Name of intervention: PLAY Project home consultation programme (Solomon et al., 2007) Intervention valid: Yes Type of play: Parent and child interaction play Place: Home Provider: 6 PLAY consultants (1 occupational therapist, 2 speech and language therapists, and 3 special educators) Duration: 36 hours	Reported outcome: Functional Emotional Assessment Score (FEAS) Category: Positive mental health	The FEAS video ratings showed a significant moderate time 3 group effect with the PLAY group showing improvement in observed socioemotional behaviour, whereas the CS group remained stable.
S09	Duifhuis et al. (2017) Publication:Journal of Autism and Developmental Disorders Country: Netherlands	Sample size: N = 24 Sample: Children with ASD Age: 3-8 years old Girls: N = 4 (16%) Boys: N = 20 (84%) INV: N = 11 CON: N = 13	Design: QE Type of control: Non-randomly allocated control group Control group received treatment: Yes, treatment as usual Measure: Child Behavior Checklist (CBCL; Achenbach & Rescorla, 2001). Measures standardised: Yes	Name of intervention: Pivotal response treatment (PRT) (Koegel, 2011) Intervention valid: Yes Type of play: Parent and child interaction play Place: School Provider: Therapist Duration: 15 hours	Reported outcome: Internalizing score Category: Negative mental health	The analysis did not show any treatment effects on internalising score of the INV group on CBCL.
S09					Reported outcome: Externalizing score Category: Negative mental health	The analysis did not show any treatment effects on externalising score of the INV group on CBCL.
S10	Pilarz (2009) Publication: PhD Dissertation Country: USA	Sample size: N = 26 Sample: Children with ASD Age: 3-12 years old Girls: N = 5 (19%) Boys: N = 21 (81%) INV: N = 13 CON: N = 13	Design: QE Type of control: Non-randomly allocated control group Control group received treatment: No treatment Measure: The Functional Emotional Assessment Scale (FEAS) (Greenspan, DeGangi & Wieder, (2001). Measures standardised: Yes	Name of intervention: DIR/Floortime Intervention valid: Yes Type of play: Parent and child interaction play Place: Not reported Provider: Certified school psychologist Duration: 16 hours	Reported outcome: Functional Emotional Assessment Score (FEAS) Category: Positive mental health	The slopes of the pretest scores for the total scale score did not significantly vary across conditions; p-values ranged from .092 to .549.