Fermented foods, neuroticism, and social anxiety: An interaction model
Introduction
Social anxiety disorder (also known as social phobia) is the third most prevalent psychiatric disorder with lifetime prevalence estimates as high as 10.7% (Wittchen et al., 1999, Veale, 2003, Kessler et al., 2012). This disorder is defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as the experience of significant distress or impairment that interferes with ordinary routine in social settings, at work or school, or during other everyday activities (American Psychiatric Association, 2013). As a result, social anxiety disorder can negatively affect many areas of life including dating, school, work, and family relations, with subthreshold social anxiety showing almost the same level of impairments in daily life (Wittchen et al., 2000).
Phobias have been shown to run in families (Hettema et al., 2001). Although it is not clear exactly what is inherited, vulnerability to social phobia is associated with fundamental personality traits such as neuroticism, defined as the general tendency to experience negative emotions such as nervousness, anger, envy, guilt, and depressed mood (Matthews and Deary, 1998). In fact, according to a recent large-scale twin study, genetic factors that influence individual variation in neuroticism appear to account almost entirely for the genetic vulnerability to social anxiety disorder (Bienvenu et al., 2007).
Although treatment for social anxiety disorder typically consists of cognitive-behavioral therapy or pharmacotherapy with selective serotonin reuptake inhibitors (Veale, 2003), more recently there has been increased interest in understanding how nutritional factors, such as probiotic intake, influence psychiatric disorders (Logan and Katzman, 2005, Forsythe et al., 2010, Dinan and Quigley, 2011, Bested et al., 2013a, Bested et al., 2013b, Bested et al., 2013c; Foster and Neufeld, 2013; Wall et al., 2014). Probiotics are defined as “live micro organisms, which, when administered in adequate amounts, confer a health benefit on the host” (FAO/WHO, 2001). Preclinical studies have demonstrated potential gut-brain pathways that allow gut microbiota to exert anxiolytic effects (see Mayer et al., 2014). For example, using mouse models Bravo et al. (2011) demonstrated that ingestion of the lactic acid bacteria Lactobacillus rhamnosus resulted in vagus nerve dependent anxiolytic behavioral effects and modulation of GABA receptor expression. Similarly, Bercik et al., 2010, Bercik et al., 2011 have shown that probiotic treatment can minimize anxiety induced by gut inflammation and these anxiolytic effects were associated with changes in brain derived neurotrophic factor and dependent on the vagus nerve.
A recent study in humans has shown that consumption of a fermented milk product containing a combination of probiotics (Bifidobacterium animalis, Streptococcus thermophiles, Lactobacillus bulgaricus, and Lactococcus lactis) can modulate brain activity (Tillisch et al., 2013). After four weeks of consuming the fermented milk product, there was a reduction in brain activity in a network of areas, including sensory, prefrontal, and limbic regions, while processing negative emotional faces. Importantly, a control group that ingested a non-fermented milk product showed no such changes in brain activity, suggesting that the probiotics in the fermented milk were responsible for the modulation in brain activity. This study demonstrates that fermented foods containing probiotics can alter how the human brain processes negative social stimuli.
Clinical trials have also demonstrated anxiolytic effects of probiotics in humans, but not specifically in those with social anxiety. In a study of patients with chronic fatigue syndrome, ingestion of Lactobacillus casei was associated with decreased scores on the Beck Anxiety Inventory (Rao et al., 2009). Similarly, adminstration of the prebiotic trans-galactooligosaccharide, which promotes the growth of indigenous beneficial gut bacteria such as Lactobacilli, resulted in decreased scores on the anxiety subscale of the Hospital Depression and Anxiety Scale (HADS-A) in patients with irritable bowel syndrome (Silk et al., 2009). Improvement in HADS-A scores has also been shown in healthy participants from the general population following ingestion of a probiotic formulation consisting of both Lactobacillus helveticus and Bifidobacterium longum (Messaoudi et al., 2011).
The current study sought to address several open questions regarding the anxiolytic effects of fermented foods that likely contain probiotics. No previous studies have examined the specific relationship between fermented food consumption and social anxiety. Furthermore, it is unclear how natural patterns of fermented food consumption relate to anxiety in humans because all existing studies are clinical trials in which consumption of probiotics was controlled. In addition, no studies have investigated whether consumption of fermented foods that likely contain probiotics can moderate the relationship between neuroticism, a known genetic risk factor for certain anxiety disorders, and anxiety symptoms. Thus, in the current study, a cross-sectional approach was undertaken to examine whether consumption of fermented foods that likely contain probiotics was related to social anxiety in a population of young adults, and if so, to explore whether consumption of fermented foods interacts with neuroticism to predict social phobia symptoms. If this in fact the case, we hypothsize that young adults who are high in neuroticism will demonstrate lower levels of social anxiety if their fermented food intake is high when compared to those with low intake.
Section snippets
Participants
Data were collected as part of mass testing for introductory psychology classes at a medium-size public liberal arts university in Virginia which counted for partial fulfillment of a course requirement. Surveys were completed electronically using Qualtrics software by 732 students. All participants provided informed electronic consent. The study protocol was approved by the Protections of Human Subjects Committee, and the investigation was carried out in accordance with the Declaration of
Results
Of the 732 participants who completed the questionnaire, 22 were excluded due to missing data on key variables of interest, leaving a final sample size of 710 (445 female). These participants were between the ages of 18 and 38 years (M=19.1 years, S.D.=1.5). The sample was ethnically diverse (45% reported their race as Caucasian, 31% non-Caucasian, and 23% as multiracial).
The means and distributions of the variables of interest are presented in Table 1. Skewness and kurtosis are presented to
Discussion
Consistent with previous research on other types of anxiety (Rao et al., 2009, Silk et al., 2009, Messaoudi et al., 2011), the current results demonstrate that consumption of fermented foods likely to contain probiotics is negatively associated with symptoms of social anxiety in a sample of young adults. Moreover, the current paper is the first to demonstrate that consumption of fermented foods interacts with neuroticism to predict social anxiety symptoms. That is, those at higher genetic risk
Acknowledgments
We thank Dr. Cheryl Dickter and Gandalf Nicolas for assistance with data collection.
References (42)
- et al.
Regular exercise, anxiety, depression and personality: a population-based study
Preventive Medicine
(2006) - et al.
Probiotic food supplement reduces stress-induced gastrointestinal symptoms in volunteers: a double-blind, placebo-controlled, randomized trial
Nutrition Research
(2008) - et al.
Mood and gut feelings
Brain, Behavior and Immunity
(2010) - et al.
Gut-brain axis: How the microbiome influences anxiety and depression
Trends in Neuroscience
(2013) - et al.
Treatment of functional gastrointestinal disorders with antidepressant medications: a meta-analysis
The American Journal of Medicine
(2000) - et al.
Major depressive disorder: probiotics may be an adjuvant therapy
Medical Hypotheses
(2005) - et al.
Disability and quality of life in pure and comorbid social phobia: Findings from a controlled study
European Psychiatry
(2000) Diagnostic and Statistical Manual of Mental Disorders
(2013)- et al.
Let׳s get physical: a contemporary review of the anxiolytic effects of exercise for anxiety and its disorders
Depression and Anxiety
(2013) - et al.
Consensus statement on social anxiety disorder from the international consensus group on depression and anxiety
Journal of Clinical Psychiatry
(1998)
Chronic gastrointestinal inflammation induces anxiety-like behavior and alters central nervous system biochemistry in mice
Gastroenterology
The anxiolytic effect of Bififobacterium longum NCC3001 involves vagal pathways for gut-brain communication
Neurogastroenterology & Motility
Intestinal microbiota, probiotics, and mental health: from Metchnikoff to modern advances: Part I - autointoxication revisited
Gut Pathogens
Intestinal microbiota, probiotics, and mental health: from Metchnikoff to modern advances: Part II - contemporary contextual research
Gut. Pathogens
Intestinal microbiota, probiotics, and mental health: from Metchnikoff to modern advances: Part III - convergence toward clinical trials
Gut. Pathogens
Low extraversion and high neuroticism as indices of genetic and environmental risk for social phobia, agoraphobia, and animal phobia
American Journal of Psychiatry
Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve
Proceedings of the National Academy of Sciences
Alternative transformations to handle extreme values of the dependent variable
Journal of the American Statistical Association
Moderation in management research: What, why, when, and how
Journal of Business Psychology
Probiotics in the treatment of depression: science or science fiction?
Australian New Zealand Journal of Psychiatry
A functional MRI study of amygdala responses to angry schematic faces in social anxiety disorder
Depression and Anxiety
Cited by (64)
Fermented foods: Harnessing their potential to modulate the microbiota-gut-brain axis for mental health
2024, Neuroscience and Biobehavioral ReviewsBrain-gut microbiome profile of neuroticism predicts food addiction in obesity: A transdiagnostic approach
2023, Progress in Neuro-Psychopharmacology and Biological Psychiatry2.33 - Microbiota-Gut-Brain Axis
2022, Comprehensive Gut MicrobiotaEvidence-Based Nutrition and Clinical Evidence of Bioactive Foods in Human Health and Disease
2021, Evidence-Based Nutrition and Clinical Evidence of Bioactive Foods in Human Health and DiseaseDevelopment of the gut microbiota in the first 14 years of life and its relations to internalizing and externalizing difficulties and social anxiety during puberty
2024, European Child and Adolescent Psychiatry