Objectives: We review outcome studies regarding the effectiveness of hyperbaric oxygen therapy (HBOT) for Autism Spectrum Disorders (ASD). Method: Studies were identified through electronic bibliographic databases and manual searches of article reference lists. Results: A total of 8 studies met eligibility criteria, consisting of three randomized controlled trials (RCTs), one quasi-experimental study involving a comparison group, two pre-experimental one-group pretest–posttest studies, and two single-system designs. Studies reviewed did not offer credible evidence to suggest that HBOT is an effective treatment for autism. Conclusion: It is premature to call HBOT an effective treatment for Autism and ASD. Individuals clinically treated with HBOT outside the context of a RCT should have the effects of the therapy evaluated using rigorous single-subject designs
