Efficacy of a synbiotic in the management of adults with Attention-Deficit and Hyperactivity Disorder and/or Borderline Personality Disorder and high levels of irritability: Results from a multicenter, randomized, placebo-controlled, "basket" trial.

Irritability worsens prognosis and increases mortality in individuals with Attention-Deficit and Hyperactivity Disorder (ADHD) and/or Borderline Personality Disorder (BPD). However, treatment options are still insufficient. The aim of this randomized, double blind, placebo-controlled study was to investigate the superiority of a synbiotic over placebo in the management of adults with ADHD and/or BPD and high levels of irritability. The study was conducted between February 2019 and October 2020 at three European clinical centers located in Hungary, Spain and Germany. Included were patients aged 18-65 years old diagnosed with ADHD and/or BPD and high levels of irritability (i.e., an Affectivity Reactivity Index (ARI-S) ≥ 5, plus a Clinical Global Impression-Severity Scale (CGI-S) score ≥ 4). Subjects were randomized 1(synbiotic):1(placebo); the agent was administered each day, for 10 consecutive weeks. The primary outcome measure was end-of-treatment response (i.e., a reduction ≥ 30 % in the ARI-S total score compared to baseline, plus a Clinical Global Impression-Improvement (CGI-I) total score of < 3 (very much, or much improved) at week 10). Between-treatment differences in secondary outcomes, as well as safety were also investigated. Of the 231 included participants, 180 (90:90) were randomized and included in the intention-to-treat-analyses. Of these, 117 (65 %) were females, the mean age was 38 years, ADHD was diagnosed in 113 (63 %), BPD in 44 (24 %), both in 23 (13 %). The synbiotic was well tolerated. At week 10, patients allocated to the synbiotic experienced a significantly higher response rate compared to those allocated to placebo (OR: 0.2, 95 % CI:0.1 to 0.7; P = 0.01). These findings suggest that that (add-on) treatment with a synbiotic may be associated with a clinically meaningful improvement in irritability in, at least, a subgroup of adults with ADHD and/or BPD. A superiority of the synbiotic over placebo in the management of emotional dysregulation (-3.6, 95 % CI:-6.8 to -0.3; P = 0.03), emotional symptoms (-0.6, 95 % CI:-1.2 to -0.05; P = 0.03), inattention (-1.8, 95 % CI: -3.2 to -0.4; P = 0.01), functioning (-2.7, 95 % CI: -5.2 to -0.2; P = 0.03) and perceived stress levels (-0.6, 95 % CI: -1.2 to -0.05; P = 0.03) was also suggested. Higher baseline RANK-L protein levels were associated with a significantly lower response rate, but only in the synbiotic group (OR: 0.1, 95 % CI: -4.3 to - 0.3, P = 0.02). In the placebo group, higher IL-17A levels at baseline were significantly associated with a higher improvement in in particular, emotional dysregulation (P = 0.04), opening a door for new (targeted) drug intervention. However, larger prospective studies are warranted to confirm the findings. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03495375.