Recent demonstration that probiotics administration has positive effects on depressive feelings in healthy populations suggests its possible role as an adjuvant therapy for depression in clinical populations and as a non-invasive strategy to prevent depressive feelings in healthy individuals. The present study extends current knowledge on the beneficial effects of probiotics on psychological well-being, as measured by changes in mood (e.g., depression, anxiety, cognitive reactivity to sad mood), personality dimensions, and quality of sleep, which have been considered as related to mood. For this double-blind, placebo-controlled study healthy volunteers pseudo-randomly assigned to an experimental or control group assumed a daily dose of probiotic or placebo, respectively, for 6 weeks. Mood, personality dimensions, and sleep quality were assessed four times (before the beginning of the study, at 3 and 6 weeks, and at 3 weeks of washout).

A. THEORETICAL BACKGROUND The intestine and the brain are intimately connected with each other through the gut-brain axis, which involves bidirectional communication between the nervous, endocrine and immune systems. In the last years, it has become increasingly evident that this communication implies also interactions with the intestinal bacterial flora, which releases immune activation and other signalling molecules that may play a major role in the regulation of the brain and human behaviour. For instance, the microbiota produces neuroactive substances and their precursors (e.g. tryptophan) that may reach the brain through the endocrine and autonomous nervous system. Recently, the interest has been focused also on the cognitive field. Indeed, there is experimental evidence that bacterial products may positively influence cognitive functions, such as spatial memory and problem-solving abilities. Moreover, probiotics seem to exercise influence on mood, anxiety and depression, opening new therapeutic prospects. A recent trial showed that four weeks of taking probiotics (Bifidobacterium bifidum W23, Bifidobacterium lactis W52, Lactobacillus acidophilus W37, Lactobacillus brevis W63, Lactobacillus casei W56, Lactobacillus salivarius W24, Lactococcus lactis W19 e W58) led to an improvement in mood, fostering reduction in negative thoughts.

B. THE PURPOSE OF THE RESEARCH PROJECT The primary goal of the trial is to investigate the effect of probiotics on depression. Moreover, it will assess also effects on anxiety and other personality traits in healthy young students. The trial intends also to investigate whether probiotics may influence the quality of sleep and bowel habits. The trial will be placebo-controlled, randomized, pre- and post-intervention, double-blind designed (investigator and participants). In the light of the several end-points examined, the statistical analysis will be of explorative type.

The collection of faecal samples will allow, in case of finding any effects of the administered product on mood, to go back to any microbial components that have changed in individuals following the treatment. Monitoring (see below) the normal feed and physical habits of the individuals will allow to check the possible effect of these confounding factors on the parameters measured in the trial.

Inclusion Criteria:

• Male and Famale subjects.
• Aged between 18 and 35.
• Already owing a smartphone with Android or iOS system.

Exclusion Criteria:

• Drug taking, smoking, coeliac disease, lactose intolerance.
• Disorders such as IBS (Irritable Bowel Syndrome), IBD (Irritable Bowel Disease), UC (Ulcerative Colitis) and other serious diseases, e.g. MS (Multiple Sclerosis) and diabetes (type 1/type 2).
• Oral intake of antibiotics and other medicines on a continuative basis.

Study Protocol

from April 2018

Plos One