Because there is limited research on participants under the age of 18, participants must be at least 18 years of age. Participants must also live within driving distance of Wolfville, Nova Scotia, be able to come to Wolfville for appointments with the researchers, and have a valid email address. Exclusionary criteria for participation include having an academic-related occupation, including University/College professor or student (to avoid cohort effects related to specific fluctuations in conditions associated with high stress during the academic term); having HIV/AIDS; currently undergoing chemotherapy; having a diagnosed serious metabolic, immune, or digestive problem, including cancer, Crone's disease or ulcerative colitis, multiple sclerosis, lupus, Addison's disease or other form of adrenal insufficiency; currently using medication for anxiety; taking probiotic capsules; taking antibiotics; or having any other serious medical illness.