Prebiotics and Mental Health: Behavioural

Research suggests that modifying microbial ecology therapeutically via the intake of so-called 'psychobiotics' could help reduce stress responses and symptoms of anxiety and depression (Burnet & Cowen, 2013; Dinan, Stanton, & Cryan, 2013; Tang, Reddy, & Saier, 2014). The term psychobiotics refers to both, beneficial gut bacteria (probiotics), as well as prebiotics, which enhance the growth of beneficial gut bacteria (Sarkar et al., 2016). In a recent study, Schmidt and colleagues explored the effects of prebiotics on the secretion of the stress hormone cortisol and emotional processing in healthy volunteers (Schmidt et al., 2015). They found that cortical awakening response was significantly lower after BimunoÒ-galacto-oligosaccharides (Bimuno) intake over 4 weeks compared with placebo. Moreover, participants exhibited decreased attentional vigilance to negative information in a dot-probe task. Given that anxious people show increased biases towards negative information (Bar-Haim, Lamy, Pergamin, Bakermans-Kranenburg, & van, 2007), this suggests that prebiotic intake may be useful in modifying anxiety-related cognitive mechanisms.

These findings will be extended to a sample of late adolescents in order to investigate how prebiotic intake for 4 weeks affects cognitive functioning, psychological well-being and gut microbiota a sample of 60 undergraduate students (aged 18-25 years).

At time 1 (pre-assessment), participants in both groups will undergo comprehensive behavioural and psychological testing to establish baseline measures of cognitive functioning and psychological well-being (such as anxiety levels) and asked to collect a stool sample at home for 16s rRNA sequencing of the microbiome. Group 1 will then receive a daily dosage of a galactooligosaccharide (GOS) prebiotic over 4 weeks, whereas group 2 will receive a placebo over the same period. At time 2 (post-assessment), both groups will again undergo cognitive and psychological testing and stool sampling.

Hypothesis: It is predicted that the treatment group (GOS) will show improvements in behavioural indices of emotion regulation (e.g. dot probe task) and in self reported psychological measures related to emotion regulation (e.g. anxiety) in comparison to the placebo group. Changes/differences in gut microbiome samples will be explored.

Inclusion criteria

• Females
• Aged between 18-25

Exclusion criteria

• Clinical levels of anxiety and/ or co-morbid diagnoses (e.g. depression)
• Current or previous neurological disorders
• Current or previous psychiatric disorders
• Current or previous gastrointestinal disorders
• Current or previous endocrine disorders
• Antibiotic use 3 months prior to the study
• Regular use of pre- and probiotics, including 3 months prior to the study
• Vegan diets
• BMI >30