Application of Probiotics in the Treatment of Autism Spectrum Disorder

Autism Spectrum Disorder (ASD), commonly known as autism, is a developmental neurological disorder. Individuals with ASD may exhibit behaviors, interactions, and learning patterns that differ from those of others [1]. They may encounter challenges in social interactions, interpretation, and the use of non-verbal and verbal communication. Researchers consider ASD as a lifelong disorder, but individuals with ASD vary in the severity of their symptoms. A child with autism can have an impact on the entire family, leading to stress, time consumption, and economic burdens. Globally, estimated rates of ASD range from 0.1% to 1.8%  [2]. Patients with ASD also develop various comorbidities, from mental issues like anxiety to an increasing prevalence of gastrointestinal (GI) disorders. These GI disorders can be challenging to treat with conventional methods, presenting a challenge for appropriate intervention, such as using probiotics as a psychobiotic therapy to improve ASD symptoms.

Causes and Symptoms of Autism Spectrum Disorder

Research identifies genetic and environmental factors as potential causes of autism [3, 4]. Scientists believe that multiple factors may contribute to ASD and act together to alter human development. There is still much to learn about the causes and how they impact individuals with ASD.

ASD often leads to symptoms such as difficulty interacting with others, challenges in using and understanding non-verbal communication, delayed or absent language development, and difficulties in forming and understanding relationships. Additionally, repetitive behaviors, such as hand-flapping and body rocking, are common [5].

Treatment Approaches for Autism Spectrum Disorder

Treatment approaches focusing on support have been discussed in global research [6, 7], including methods such as:

Behavioral and communication therapy: Various methods address social, language, and behavior difficulties associated with autism spectrum disorder, often involving teaching new skills.

Educational therapy: Children with autism spectrum disorder often respond well to highly structured and specific educational programs.

Family therapy: Parents and other family members can learn how to play and interact with their children in ways that promote daily social interaction and communication skills.

Other therapies: No medication can improve the core symptoms of autism spectrum disorder, but specific medications can help manage symptoms. For example, medications like aripiprazole and risperidone may reduce irritability associated with autism.

Mechanisms and Applications of Probiotics in Autism Spectrum Disorder Support

Studies suggest that the levels of Bifidobacteria in the feces of autistic children are significantly lower compared to healthy control groups [8, 9]. Probiotics aim to restore the normal balance of the human gut microbiota and researchers have proven their effectiveness in treating other gastrointestinal (GI) disorders such as diarrhea and irritable bowel syndrome. Recent studies have indicated the potential benefits of prebiotics or probiotics in children with ASD [9-11]. Concerning probiotic supplementation based on a systematic evaluation of current evidence, there is substantial proof demonstrating the effectiveness of probiotics in reducing digestive symptoms or common behaviors in children with ASD.

Probiotics may influence certain nervous system metabolites, such as gamma-aminobutyric acid (GABA) and serotonin. Serotonin has been shown to be influenced by gut bacteria, especially in individuals with ASD, where there is an over-activation of a gene encoding serotonin reuptake transporter [12, 13]. Simultaneously, probiotics help restore the gut microbiota to normal levels. Probiotics have been demonstrated to prevent the invasion of Candida in the gut, and one study found reduced levels of D-arabinitol, a Candida metabolite, in the urine of children with autism after probiotic supplementation. Another examined study reported a decrease in Clostridium species in the fecal samples of children using probiotics.

Several clinical trials have been conducted, such as evaluating the gastrointestinal (GI) bacterial community in fecal samples from 30 autistic children aged 5 to 9 before and after 3 months of probiotic supplementation (each gram containing 100×106 Colony Forming Units of three beneficial strains; Lactobacillus acidophilus, Lactobacillus rhamnosus, and Bifidobacteria longum) [14]. After probiotic supplementation, the feces of autistic children showed an increased quantity of Bifidobacteria and Lactobacilli, along with a significant reduction in body weight (autistic children often have associated overweight or obesity).

Moreover, there was a substantial improvement in the severity of autism and gastrointestinal symptoms compared to the beginning of the study. Another study, conducted on 62 autistic patients supplemented with probiotics (Lactobacillus plantarum) for 12 weeks, reported results of reduced disruptive behavior and social opposition in the probiotic-treated autistic group [15]. Additionally, recent evaluations have concluded that researchers should study biological formulations in children with ASD. Oral biological formulations may produce positive effects in supporting ASD patients. [16-18].

In summary, digestive symptoms in autistic children are prevalent and often associated with abnormal behaviors and social interactions. Researchers hypothesize that probiotics can have a positive impact on the gut bacterial community and change the levels of specific metabolites that might be harmful in children with ASD. Whether probiotics improve behavior and these symptoms is yet to be determined. Although research papers present promising results, researchers still need to conduct further studies and confirm the benefits of probiotics in ASD patients. Nevertheless, it provides a solid foundation for designing larger prospective trials.

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