Author Year Type and duration of study Sample size Type of intervention Comparators Dose Outcome measure Findings Comments Granpeesheh et al. [45 ] 2010 Randomized, double blind, placebo controlled, parallel group Duration: maximum 15 weeks (gender not reported) Age: 2–14 years Drop-out Patients controlled for medication and educational therapyHBOT (1.3 atm and supplemental oxygen approximately 24–28% FiO2 ) Completers ( ) Placebo Completers ( ) 80 1-h sessions ABC, ADOS, CGI, Vineland, SRS, BRIEF, PSI, PPVT-III, VMI No significant difference High attrition rate Rossignol et al. [46 ] 2007 Open label Duration: 4 weeks (M 14; F 4) Age: 3–16 years HBOT (1.5 atm and supplemental oxygen (100% FiO2 ), HBOT (1.3 atm and supplemental oxygen (24% FiO2 ), Drop-out None 40 1-h sessions ATEC, ABC-community, SRS Significant improvement in both groups in ATEC and SRS Open label Small sample size Rossignol et al. [47 ] 2009 Randomized, double blind, parallel group Duration: 4 weeks (M 52; F 10) Age: 2–7 yearsHBOT (1.3 atm and supplemental oxygen (approximately 24% FiO2 ), “active group,” Drop-out HBOT (1.03 atm and supplemental oxygen (approximately 21% FiO2 ), “control group,” Drop-out 40 1-h sessions ATEC, CGI, ABC Significant improvement in the active group in CGI receptive language, social interaction, and eye contact. Improvement in ATEC sensory/cognitive awareness No placebo Sampanthavivat et al. [48 ] 2012 Randomized, double blind, parallel group Duration: unclear Age: 3–9 yearsHBOT (1.5 atm and supplemental oxygen 24% FiO2 ), Drop-out Sham air (1.15 atm), Drop-out 20 1-h sessions ATEC, CGI-change, and CGI-severity No differences between the two groups No placebo