Synbiotic supplement fails to show significant effects in ADHD trial

The trial was published recently in the journal Brain, Behavior, and Immunity​. It was conducted by researchers in Sweden using a commercial product supplied by Swedish firm Super Synbiotics, AB.

The research material, dubbed Synbiotic 2000, is a complicated mixture of four probiotic species: Pediococcus pentosaceus​ 16:1 (LMG P-20608), Lactobacillus casei ssp paracasei ​(LMG P-17806), Lactobacillus plantarum​ 2592 (LMG P-20606), Leuconostoc mesenteroides​ (LMG P-20607).  These are combined with prebiotics in the form of Inulin, resistant starch, pectin and beta glucan from oats.

Gut-brain connection

The gut-brain connection is a research field that has received increasing attention in recent years.  Results such as showing that transplanting the microbiome of a anxious mouse into a placid one would make the second mouse act anxious, too (and vice versa) have been strongly suggestive that targeted microbiome modification might be one way to help people deal with unwanted psychological symptoms​​.  Another mouse study found that mice fed Lactobacillus rhamnosus ​JB-1 showed fewer behavioral markers of depression​​ than did mice fed on broth. But scaling up these results to humans, so to speak, has proven difficult.

The trial was structured as a double blind, placebo controlled trial using 114 adults and 68 children with ADHD (attention deficit hyperactivity disorder) symptoms.  The groups took the synbiotic supplement or a placebo daily for nine weeks.

The primary measures were a score of ADHD symptoms using various validated questionnaires. Secondary outcomes were the effects on various manifestations of autism, which often accompany a diagnosis of ADHD.

Confounding factors could account for similar results for placebo and intervention

The population recruited for this study points to the difficulty of translating focused animal results into the human realm, especially where cognitive measures are concerned.  Both study groups and those receiving the placebo improved in the ADHD measures.  A huge confounding factor, one that the researchers could not really control for, was that a significant number of the participants (34% of the children and 49% of the adults) were receiving melatonin and/or antipsychotic or antidepressant medications to manage their symptoms.  

For obvious ethical reasons the participants could not be required to stop these as a condition of being included in the study. And trying to find a large enough cohort that was not receiving treatment within a realistic time frame would probably have proven to be unworkable. In addition, 42% of the children and 72% of the adults were using dietary supplements of one sort or another, which the authors said might have obscured an effect for the synbiotic intervention.

The researchers did find a trend toward improvement in lessened autism symptoms and improved emotional regulation for those subjects that showed elevated plasma sVCAM-1, a marker of vascular inflammation that may be associated with cognitive effects​​. But the number of subjects that fell into this subgroup was too small to draw statistically valid conclusions, the authors said, and they were not specifically measuring changes in inflammation markers, such as CRP or sVCAM-1.

Potential benefit warrants more research

The researchers noted that this is the first study of its type.  Because there are few effective treatments for ADHD the potential for benefit of a synbiotic intervention in these cases warrants further research, they said, even if the results of the current study were inconclusive.

“Our exploratory 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. . . .If synbiotic dietary supplements could ameliorate symptoms and improve functioning in persons with ADHD that would potentially benefit many patients. However, our findings are preliminary and need replication in larger samples to explore also possible sex and age influences,”​ they concluded.

Source:​ Brain, Behavior and Immunity​
https://doi.org/10.1016/j.bbi.2020.05.056​
Effects of a synbiotic on symptoms, and daily functioning in attention deficit hyperactivity disorder – A double-blind randomized controlled trial​
Authors: Skott E, et al.