Hyperbaric oxygen therapy for treatment of children with autism: a systematic review of randomized trials

Hyperbaric oxygen therapy (HBO) is suggested for treating some medical problems, such as air or gas embolism, carbon monoxide poisoning, intracranial abscess, and radiation injury; however, its mechanism of action is not clear [1]. It is suggested that HBO increases the production of reactive oxygen species [2]. Moreover, HBO is a safe intervention [1] and middle ear barotraumas is one of its common adverse effect [3].Autism is a complex neuro-developmental disorder with an increasing prevalence which is characterized by three main symptoms, including impairments in socialization and communication, restricted interests, and repeated behaviors. Meanwhile, there is no curative treatment for autism. Moreover, there are only two Food and Drug Administration (FDA) approved medications, including risperidone and aripiprazole for managing its symptoms [4]. Therefore, there is an urgent need to provide alternative therapeutic approaches for autism. In recent years, HBO is investigated as an alternative treatment for autism. Early uncontrolled studies reported the efficacy of HBO therapy. However, the results of later controlled-studies are controversial.There are many reports about the possible role of neuro-inflammation in autism [5-9]. This neur-inflammation can be a possible target for the treatment of some cases with autism [10,11]. Besides, the regional cerebral blood flow is decreased in the bilateral frontal lobe, temporal, limbic system, and basal ganglias in autism spectrum disorders [12]. Moreover, it is proposed that HBO may improve the cerebral hypoperfusion and decrease brain inflammation as well as oxidative stress in autism [13,14]. On the contrary to some expectations, HBO therapy does not exacerbate the increased oxidative stress in autism [6,15]. Moreover, it does not affect plasma oxidized glutathione level. However, HBO therapy decreased C-reactive protein (CRP) level in a fasting blood sample [15]. Also, plasma concentration of some interleukins (IL), s