The researchers were interested in populations with subclinical psychological symptoms, such as low mood and mild stress, that may impair quality of life, but are below the thresholds for medical treatment.
Probiotics and postbiotics can work through the gut-brain axis to modulate psychological symptoms, but human evidence in participants with sub-clinical symptoms is limited.
“These findings highlight modest improvements in mood and anxiety; specifically, psychophysiological domains—including vitality, stress and social functioning—may benefit more from targeted biotic interventions,” researchers from ADM Health & Wellness, Parc Científic Universitat de València, and Atlantia Food Clinical Trials wrote in Brain Sciences.
Subthreshold symptoms
Previous research has suggested that subthreshold generalized anxiety disorder (GAD) is twice as prevalent as clinically diagnosed cases.
While individuals who meet medical criteria may receive pharmaceutical treatments or cognitive behavioral therapy, those with less severe or emerging symptoms may experience suffering or impairment at work and in their everyday lives.
As well as the risk of untreated subthreshold symptoms leading to clinically diagnosed anxiety, individuals may also develop other conditions, such as depression and sleep disorders.
Additionally, traditional management strategies for mental health conditions may not be effective in everyone, underscoring the need for safe and accessible approaches. Bacterial strains such as Lactobacilli and Bifidobacterium have demonstrated positive effects on the brain, influencing serotonin signaling and hyperactivity of the Hypothalamus–Pituitary–Adrenal (HPA) axis.
Postbiotics are a newer, inactivated addition to the psychobiotics arena that have shown advantages over probiotics due to better safety and stability. Early studies suggest that postbiotics may exert anxiolytic effects in animals, but human evaluation is lacking.
Study details
The research aimed to assess the effects of live and heat-treated probiotics on anxiety, mood, perceived stress, and quality of life in healthy adults experiencing mild stress.
The study was conducted in two parts. In the first part, researchers randomly assigned 100 participants with mild-to-moderate self-reported anxiety to receive either a blend of live microorganisms (Bifidobacterium longum CECT 7347 and Lactobacillus rhamnosus CECT 8361) or a placebo daily for 12 weeks.
The second part was a pilot feasibility study involving a subset of eight placebo non-responders from Part I. These participants received a heat-inactivated preparation of the same bacterial strains in a six-week trial extension phase.
The researchers used the Hamilton Anxiety Rating Scale (HAM-A), the Beck Depression Inventory (BDI), and other appropriate scales to measure symptoms and quality of life.
In part one, they found no significant effects of the live blend on the HAM-A, “indicating that the primary endpoint was not met.” Similarly, there were no effects on the stress scales. They noted, however, a trend towards reduced scores on the Patient Health Questionnaire and suggestions of improvements in anhedonia (inability to feel pleasure or interest in activities).
Microbiome analysis suggested that the live blend was associated with preservation of butyrate-producing bacteria, and that perceived stress scores were inversely associated with the abundance of Bifidobacterium longum.
The results of part two suggested that the inactivated probiotic improved vitality and social functioning scores on the short form survey, as well as perceived stress scores, compared to baseline.
“Our findings identify a potential role for B. longum CECT 7347 in modulating the HPA axis, supporting further research in exploring its effects on mental health and wellbeing,” the researchers wrote, calling for further studies to explore mechanisms.
Source: Brain Sciences; doi: 10.3390/brainsci16040419, “A Randomised, Double-Blind, Placebo-Controlled Trial of Probiotic and Postbiotic Strains in Healthy Adults with Self-Reported Anxiety: Effects on Mood, Vitality, Quality of Life and Perceived Stress.” Authors: R. Day et al.
