Probiotics may improve symptoms in children with autism

What may seem questionable at first glance has a perfectly plausible explanation: the gut-brain axis as an important mediator between the enteric and central nervous systems.

Autism and gastrointestinal symptoms:

Many children with autism spectrum disorder (ASD) suffer from gastrointestinal complaints such as abdominal pain, flatulence, diarrhoea and constipation, suggesting a link between abnormal gut microbiota and autism.
In addition, gastrointestinal symptoms in children with ASD have been observed to be associated with challenging behaviour, self-harm, aggression and sleep disturbances.
Via the so-called gut-brain axis, the gut microbiome and enteric nervous system communicate with the central nervous system (CNS), thereby influencing cognitive, behavioural, neurological and psychological functions.
In ASD, this axis is often disrupted due to dysbiosis, leading to increased intestinal permeability to exogenous food proteins and neurotoxic bacterial peptides.

Probiotics reduce the severity of behavioural symptoms

The randomised, placebo-controlled study involved 180 children with ASD (90 in each of the probiotic and placebo groups) aged between 2 and 9 years. Over a period of three months, they received a daily sachet containing a probiotic preparation (9 billion colony-forming units of 12 probiotic strains) or a placebo. At the beginning and end of the study, parents completed a questionnaire using validated instruments to assess behavioural symptoms and gastrointestinal complaints.

While there was no significant difference in behavioural symptoms between the two groups at the start of the study, clear differences emerged after three months. In the probiotic group, the overall severity of symptoms was reduced more significantly than in the placebo group (47.77% compared to 23.33%). Severe symptoms in particular, such as social withdrawal, lethargy, stereotypical behaviour and hyperactivity, decreased significantly more in children treated with probiotics after the intervention. Only irritability did not show a significant change in either group.

Less constipation and diarrhoea with probiotics

In terms of gastrointestinal complaints, children in the probiotic group showed a significant improvement in constipation and diarrhoea compared to those in the placebo group. The average stool consistency of children treated with probiotics improved significantly compared to baseline (6.66% less watery stool and 18.88% more formed stool). No side effects were reported.

Finally, the researchers found a statistically significant correlation between gastrointestinal and behavioural symptoms in both groups.

The study authors explain the dual effect of probiotics in children with ASD by the fact that the live microorganisms they contain stabilise existing microbial communities, improve the integrity of the gut-brain axis and reduce inflammatory cytokines. Probiotic supplementation could therefore be a useful addition to conventional ASD therapy. However, it is first important to consider the connection between the two symptom complexes and to specifically ask children with ASD about gastrointestinal complaints.

Sources

Khanna HN et al. Impact of probiotic supplements on behavioural and gastrointestinal symptoms in children with autism spectrum disorder: A randomised controlled trial. BMJ Paediatrics Open 2025; 9: e003045.