Probiotic and Oxytocin Combination Therapy in Patients with Autism Spectrum Disorder: A Randomized, Double-Blinded, Placebo-Controlled Pilot Trial

Abstract

Autism spectrum disorder (ASD) is a rapidly growing neurodevelopmental disorder. Both probiotics and oxytocin were reported to have therapeutic potential; however, the combination therapy has not yet been studied. We conducted a randomized, double-blinded, placebo-controlled, 2-stage pilot trial in 35 individuals with ASD aged 3-20 years (median = 10.30 years). Subjects were randomly assigned to receive daily Lactobacillus plantarum PS128 probiotic (6 × 10¹⁰ CFUs) or a placebo for 28 weeks; starting on week 16, both groups received oxytocin. The primary outcomes measure socio-behavioral severity using the Social Responsiveness Scale (SRS) and Aberrant Behavior Checklist (ABC). The secondary outcomes include measures of the Clinical Global Impression (CGI) scale, fecal microbiome, blood serum inflammatory markers, and oxytocin. All outcomes were compared between the two groups at baseline, 16 weeks, and 28 weeks into treatment. We observed improvements in ABC and SRS scores and significant improvements in CGI-improvement between those receiving probiotics and oxytocin combination therapy compared to those receiving placebo (p < 0.05). A significant number of favorable gut microbiome network hubs were also identified after combination therapy (p < 0.05). The favorable social cognition response of the combination regimen is highly correlated with the abundance of the Eubacterium hallii group. Our findings suggest synergic effects between probiotics PS128 and oxytocin in ASD patients, although further investigation is warranted.

Keywords: autism spectrum disorder (ASD); inflammation markers; microbiome; oxytocin; probiotics.

Figure 1

Flowchart of overall study design and conduct.

Figure 2

Proportion of subjects displaying improvement in CGI-I overtime among all subjects within a treatment condition. The z-test for equality of proportions is applied and the number of subjects displaying at least minimal improvement (CGI-I ≤ 3) in the control condition and the probiotic + OXT condition is significantly different (p < 0.05), while the changes of probiotic and OXT alone groups are non-significant, though a trend of improvement is seen in both intervention groups.

Figure 3

SparCC network associations between genus-level gut microbiota between subjects receiving placebo and those receiving the active probiotic overtime, using a SparCC cutoff of 0.7. Placebo group V1 is baseline, V2 is after placebo, V3 is after placebo added OXT; probiotics group V1 is baseline, V2 is after probiotics, V3 is after probiotics added OXT. (A) SparCC co-occurrence network. Articulation points are marked as halos around the node. Hub score is indicated by the size of the node. (B) The number of lines or edges is significantly enriched in both the OXT alone and combination groups at visit 3 (Pearson’s χ²-test with Yates’ continuity correction, p < 0.005). (C) The number of articulation points is only significantly increased in the combination group at V3 compared to baseline number of articulation points (Pearson’s χ²-test with Yates’ continuity correction, p < 0.05).

Figure 4

Heatmap of mean change in predicted functional profile based on gut microbiota abundance across four study groups. Shown changes in functional profiling indices demonstrated more changes in the combination group, although these changes are not significantly different when compared to the control group (p > 0.05).

Figure 5

Summary of longitudinal serum marker changes and associated correlations. Absolute changes in serum OXT (A), S100B (B), and IL-1β (C) levels, comparing each treatment group against controls. Baseline serum S100B is positively correlated with ABC irritability T (D) and ABC hyperactivity/noncompliance T-scores (D’).