Mar 16 2009

Hyperbaric Oxygen for Autism

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A new study looks at the effectiveness of hyperbaric oxygen therapy in autism. The study is the first double-blind placebo controlled study of such therapy in autism and found a significant improvement in those children in the treatment group.

However, the treatment is very controversial and remains so, even after this study.

Hyperbaric oxygen therapy involves placing patients in a chamber with pressure increased above atmospheric pressure with an enriched oxygen content.  It has many legitimate medical applications, such as treating certain kinds of infection, but also has become popular among some as an unscientific treatment. It is offered by practitioners and chambers are even sometimes purchased by private individuals for their own family’s use.

The problem, of course, is that some claims for hyperbaric oxygen go way past the evidence, or exist in the utter absence of evidence. This includes autism – there are no compelling studies showing any benefit from hyperbaric oxygen therapy in autism. The few studies that do exist are uncontrolled, which means they are mostly worthless.

This current study is at least a double-blind controlled trial. But it still has significant weaknesses. The primary weakness, in my opinion, is that the parents of the children being studied were allowed in the chamber with their children. The two groups in the study either received 24% oxygen in 1.3 atmospheres, or 21% oxygen in 1.03 atmospheres. It’s probable that many of the parents knew if they were getting increased pressure or not, and this therefore could have unblinded the study.

Tight blinding is critical for these type of studies because the assessment of the effect on the autistic children is highly subjective. For example, the assessment includes how much eye contact the children make.

The study is also on the small side, with 62 children total. However, the clinical effects were very robust.

Some have pointed out that the study leader, Daniel Rossignol, has a potential conflict of interest in that he offers hyperbaric oxygen therapy in his practice. He therefore stands to gain personally if its effectiveness is proven. While such conflicts are important to expose, I think they are trumped by a well-enough controlled study. The whole point of a well-designed study is to eliminate the effects of bias. But given that this study was poorly blinded, and bias was present, it certainly diminishes its impact.

Everyone agrees, even Rossignol, that this study will not end the controversy over hyperbaric oxygen in autism. It needs to be replicated. This is generically true of any new treatment – the first few smallish studies are never enough to establish its effectiveness. The strength of clinical trials rests primarily in replication. Only when various researchers with different biases come to the same conclusion from well-designed studies can we confidently come to a conclusion. The history of medicine is littered with treatments that initially seemed promising but just did not pan out.

Another weakness of the study is that it was short term, only four weeks. It therefore did not test if the effect of hyperbaric treatment survives much beyond the treatment itself. Even if the effect in this study is real, it may represent only a temporary symptomatic benefit – not altering the course of autism itself. Therefore longer followup studies are needed as well.

It is not impossible that hyperbaric oxygen may have some benefit in some children with autism. Although there is no established mechanism at this time, and proposed mechanisms (like the notion that hyperbaric O2 decreases inflammation) are largely speculative. But a physiological effect is not implausible. The treatment is also fairly safe. Therefore it is reasonable to study it further.

The biggest risk of the treatment now is that it is expensive – costing 150-900 dollars per treatment or 14-17 thousand dollars for a chamber. It also diverts energy and emotions away from possibly more productive treatments.

Because of this, this is one treatment where I think high quality research may have an actual impact. If it works, of course, than more people can benefit from it. If high quality studies show it does not work I think there are families who will save themselves from the expense of an ineffective treatment. It will likely not go away completely, but would be significantly marginalized.

But one thing is clear – any future studies should be very tightly controlled, or they will be counterproductive.

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