Authors: Elin Skotta, Liu L. Yanga, Miranda Stiernborga, Åsa Söderströmc , Joëlle Rȕeggb, Martin Schallinga, Yvonne Forselle , MaiBritt Giacobinia,Catharina Lavebratt.
Published: Brain, Behaviour and Immunity 89 (2020).
The study was conducted in vivo, involving human participants.
Design: Randomized double-blind parallel placebo-controlled trial. Participants were randomly assigned to receive either the synbiotic (Synbiotic2000) or a placebo. The study had a double-blind parallel group RCT. The Synbiotic 2000 or placebo, allocation ratio 1:1, were allocated via computerized randomization by the independent Karolinska Trial Alliance, not involved in the study.
Treatment: 9 weeks of Synbiotic 2000.
Where and when: Karolinska Institutet, Stockholm. January 2016 to June 2018.
Sample size: 182 people (both children and adults) completed the study. (s.10).
Sample criteria: Eligibility criteria for participation were: a confirmed ADHD-diagnosis, age 5–55 years, stable pharmacological treatment (no change during the last four weeks). Exclusion criteria were: autism diagnosis, GIdisorder diagnosis other than irritable bowel syndrome (IBS), antibiotic treatment during the last six weeks, diabetes and celiac disease.
Analysed material: Emotion regulation, measured using the questionnaires SNAP-IV, ASRS, WFIRS, SCQ, AQ and DERS-16. Levels at baseline of plasma C-reactive protein and soluble vascular cell adhesion molecule-1 (sVCAM-1), central to leukocyte-endothelial cell adhesion facilitating inflammatory responses in tissues, were measured using Meso Scale Discovery.
This is the first randomized placebo-controlled trial exploring the effects of a probiotic or synbiotic on symptoms and functioning in individuals with ADHD (s.15).
The total sample size was large and treatment time long for being a probiotic intervention trial in neuropsychiatry. The baseline clinical characteristics were similar in completers and drop-outs, suggesting that drop-out did not add important bias (s.17).
Results
The study detected no definite Synbiotic 2000-specific effect on ADHD symptoms, functionality or comorbid autistic symptoms.
However, the results of those with elevated sVCAM-1 levels at start of intervention suggest a Synbiotic 2000-specific reduction of autism symptoms in children and an improvement of emotion regulation in adults with ADHD. Also, an improvement of autism traits in children by Synbiotic 2000 was driven by those without ADHD medication.
On group level, the study showed that Synbiotic 2000 and placebo interventions improved the ADHD symptoms, inattention and hyperactivity/impulsivity. However, there was no difference in ADHD symptom improvement between the two arms (s.16)
The child cohort with ADHD showed a tendency towards greater reduction in autistic symptoms after treatment with Synbiotic 2000 compared to placebo and a statistically significant reduction was found for the autistic symptom subscale restricted, repetitive and stereotyped behavior. In accordance with that the Synbiotic 2000 has known anti-inflammatory properties, an effect on total autism symptoms and on the restricted, repetitive and stereotyped behaviors was seen in children with elevated baseline sVCAM-1 levels, and not in the children with sVCAM-1 levels below median levels of the study cohort. This putative effect of Synbiotic 2000 on autism symptoms is supported by the previously suggested positive effects of prebiotics, probiotics and clinical fecal transplantation on autistic symptoms, and the extensive animal model studies demonstrating a role of the gut-brain axis on rodent repetitive, stereotyped and antisocial behavior (s.16).
The secondary outcome emotion regulation is a measure of functioning in an emotionally upset state and was assessed only in adults. The study found that Synbiotic 2000 improved difficulties in engaging in goal directed behavior. Moreover, among those with elevated sVCAM-1 levels at baseline, there was a Synbiotic 2000-specific improvement in emotion regulation (s17).
Previous studies have suggested that prebiotics and probiotics may have positive effects on autism symptoms. Although most studies have been non-blinded. In this study, no study participant had an autism diagnosis at recruitment, but as expected, autistic traits were common.
There are only a few treatments specific for autism symptoms. If synbiotic dietary supplements could ameliorate symptoms and improve functioning in persons with ADHD that would potentially benefit many
patients. However, the findings are preliminary and need replication in larger samples to explore also possible sex and age influences. (s.17).
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