Randomized Trial of Hyperbaric Oxygen Therapy for Children with Autism
Granpeesheh, D., Tarbox, J., Dixon, D.D., Wilke, A.E., Allen, M.S., & Bradstreet, J.J. (2010). Randomized trial of hyperbaric oxygen therapy for children with autism. Research in Autism Spectrum Disorders, 4, 268-275.
Reviewed by ToniAnne Giunta
Why study this topic?
Because the cause of autism spectrum disorders (ASD) is unknown, numerous treatments exist. Only few, however, have been deemed effective via controlled, scientific research. A common, yet scientifically unproven, treatment for ASD is hyperbaric oxygen therapy (HBOT). HBOT involves delivering a mixture of gases from 21% oxygen (room air) to 100% oxygen at atmospheric pressures above ambient pressure, usually via a chamber or gas mask. Although HBOT is an evidence-based treatment for decompression sickness, studies have yet to demonstrate it as one that improves ASD symptoms. The goal is to reduce inflammation in the brain, but it remains unclear whether or not individuals with ASD have such inflammation. The few studies that have analyzed the effects of HBOT in individuals with ASD have done so in 40 sessions and have (a) been uncontrolled, (b) found inconsistent responses to treatment, or (c) found only minimal (not clinically or statistically significant) differences between experimental and placebo groups. The findings thus far show that HBOT does not produce meaningful treatment effects for individuals with ASD. Other questions, however, have yet to be answered. The present study attempted to analyze the effects of HBOT on ASD symptoms using the most commonly prescribed dose (24% oxygen at 1.3 atm) over a relatively longer duration (80 sessions).
What did the researchers do?
The researchers randomly assigned individuals with ASD, ages 2-14, to either a treatment group (receives HBOT) or control group (does not receive HBOT). The researchers then compared these groups in regards to (a) performance on a variety of standardized assessments (Aberrant Behavior Checklist, Autism Diagnostic Observation Schedule (ADOS), Behavior Rating Inventory of Executive Functioning, Clinical Global Impression Scale, Parent Stress Index, Peabody Picture Vocabulary Test, Repetitive Behavior Scale, Social Responsiveness Scale (SRS), Vineland Adaptive Behavior Scales, Beery-Buktenica Developmental Test of Visual-Motor Integration) and (b) behaviors observed during direct observation of toy play (hyperactivity, appropriate vocalizations, vocal stereotypy, physical stereotypy, aggression, self-injury, property destruction, toy play). Both groups received 80, 1-h sessions in an HBOT chamber. The 18 participants in the experimental (HBOT) group received compression to 1.3 times normal atmospheric pressure with 24-28% oxygen. The 16 participants in the control group received free airflow at ambient pressure.
What did the researchers find?
In regards to outcome measures that are symptomatic of ASD (i.e., social reciprocity, communicative approach, repetitive behaviors), improvements occurred in both groups as per results of two standardized assessments (ADOS and SRS), with differences not reaching high enough levels to be called significant. Performance between the groups on the remaining standardized assessments also did not yield significant differences. Furthermore, data obtained during direct observations failed to yield significant differences between the groups. In summary, although improvements were found in both groups, performance was not superior in one group versus the other.
What were the strengths and limitations of the study? What do the results mean?
Compared to previous studies analyzing the therapeutic effects of HBOT on ASD symptoms, the present experimental design was of a higher rigor and the outcome measures were more comprehensive. Therefore, it is unlikely that an effect was present but not detected. That is, one can interpret the findings with confidence. The present study adds to the limited body of scientific research on this topic. Some clinicians prescribe biomedical treatments with trial-and-error systems that pose high costs and unknown risks, and base their recommendations on unvalidated anecdotal evidence. Although the study failed to show evidence for treatment efficacy, more such studies on biomedical approaches to ASD treatment are needed to determine whether or not these approaches are safe and effective. Several limitations, however, are pointed out. The sample size (34 individuals) was relatively small. Also, both groups were receiving intensive applied behavior analysis (ABA) interventions throughout the study, making it unclear whether HBOT produced additive effects to the ABA effects. Nonetheless, minimal differences were observed between the groups, and the study indicates that HBOT should continue not being recommended for addressing ASD symptoms.