Multispecies probiotic administration reduces emotional salience and improves mood in subjects with moderate depression: a randomised, double-blind, placebo-controlled study

Abstract

Background The potential antidepressant properties of probiotics have been suggested, but their influence on the emotional processes that may underlie this effect is unclear. Methods Depressed volunteers (n = 71) were recruited into a randomised double-blind, placebo-controlled study to explore the effects of a daily, 4-week intake of a multispecies probiotic or placebo on emotional processing and cognition. Mood, anxiety, positive and negative affect, sleep, salivary cortisol and serum C-reactive peptide (CRP) were assessed before and after supplementation. Results Compared with placebo, probiotic intake increased accuracy at identifying faces expressing all emotions (+12%, p < 0.05, total n = 51) and vigilance to neutral faces (mean difference between groups = 12.28 ms ± 6.1, p < 0.05, total n = 51). Probiotic supplementation also reduced reward learning (−9%, p < 0.05, total n = 51), and interference word recall on the auditory verbal learning task (−18%, p < 0.05, total n = 50), but did not affect other aspects of cognitive performance. Although actigraphy revealed a significant group × night-time activity interaction, follow up analysis was not significant (p = 0.094). Supplementation did not alter salivary cortisol or circulating CRP concentrations. Probiotic intake significantly reduced (−50% from baseline, p < 0.05, n = 35) depression scores on the Patient Health Questionnaire-9, but these did not correlate with the changes in emotional processing. Conclusions The impartiality to positive and negative emotional stimuli or reward after probiotic supplementation have not been observed with conventional antidepressant therapies. Further studies are required to elucidate the significance of these changes with regard to the mood-improving action of the current probiotic.

The Role of Probiotics and Their Metabolites in the Treatment of Depression

“…Some strains, e.g., Bifidobacterium infantis , B. longum , and L. acidophilus , may improve mental conditions via regulating the expression of endocannabinoids or by producing and secreting neurotransmitters such as 5-hydroxytryptamine (serotonin, 5 HT), ACh, catecholamines, dopamine, histamine, GABA, glutamate (Glu), glycine, and norepinephrine in a species-dependent manner [ 56 , 108 ]. These neurotransmitters modulate signaling pathways of the local enteric nervous system and then the gut–brain axis [ 226 ]. Moreover, some probiotic strains and their metabolites reverse depressive diseases via immunomodulation.…”

Effect of probiotic supplementation on cognition and depressive symptoms in patients with depression: A systematic review and meta-analysis

“…Additionally, research involving animal subjects was not within the scope of this review and was thus excluded from consideration (n = 94). The final selection process resulted in the inclusion of 4 studies [18][19][20][21] in the review.…”

“…Table 2 presents a comprehensive overview of the key characteristics and assessments of the selected studies, [18][19][20][21] which collectively investigate the impact of probiotic supplementation on cognitive and related brain functions in patients with depression. Table 3 provides a comprehensive summary of the technical characteristics and key findings from the selected studies.…”

“…Baião et al [18] 2022 RCT (double-blind) United Kingdom 71 28.80 ± 8.93 45 females 1 Chahwan et al [19] 2019 RCT (double-blind) Australia 71 36.65 ± 11.75 49 females 2 Rudzki et al [20] 2019 RCT (double-blind) Poland 79 38.90 ± 12 43 females 2 Schneider et al [21] 2023 RCT (double-blind) Switzerland 60 38.03 ± 11.32 36 females 1 RCT = randomized controlled trials. Medicine Table 3 Technical characteristics pertaining to the correlation between probiotics and cognition in patients with depression as observed in the included studies.…”

Recognizing the role of the vagus nerve in depression from microbiota-gut brain axis

“…Indeed, clinical and animal studies have shown that probiotics supplementation could alleviate depression symptoms. In randomized, double-blind, placebo-controlled studies, probiotics significantly improved depression symptoms of depressive patients, though inconsistent results were reported concerning improvement of anxiety symptoms and serum inflammation markers ( 117 – 119 , 193 ). Animal studies indicated that the anti-depressive effect of probiotics may attribute to mitigating gut microbial dysbiosis ( 120 – 122 , 195 ), and this effect may not require the bacteria to be alive ( 112 ), suggesting a vital role of bacteria components in the effect.…”