Table 2.

Summary of questionnaire measures included in the Bugs and Brains Study

Category	Questionnaire	Phase 1 (screening questionnaire)	Phase 2 (SCID-5-RV interview)	Phase 4 (during sample collection)
Demographic information	Phase 1 Health Questionnaire*	✓
	Phase 4 Demographics, Health and Exercise Questionnaire*			✓
Emotional functioning	Difficulties in Emotion Regulation Scale56			✓
Mental health and behaviour	Psychiatric Diagnostic Screening Questionnaire‡36	✓
	Global Assessment of Functioning†37		✓
	Social and Occupational Functioning Assessment Scale†37		✓
	Beck Depression Inventory57			✓
	Beck Anxiety Inventory58			✓
	Adult Self Report59			✓
Diet	Dietary Questionnaire for Epidemiological Studies (DQES)60			✓
	Phase 1 Health Questionnaire* Specific diet information (past 4 weeks; eg, gluten-free, specific carbohydrates, FODMAPs, vegetarian).	✓
Exercise	Phase 4 Demographics, Health and Exercise Questionnaire*			✓
Quality of life/well-being	The WHO quality of life assessment- abbreviated version (WHOQOL-BREF)61			✓
Oral health	The WHO Oral Health Questionnaire for Adults62			✓
Physical health /medical history	The Physical Health Questionnaire63			✓
	Phase 1 Health Questionnaire* Current bacterial, fungal or viral infection Obesity, hypertension, cardiovascular disease, respiratory disease, diabetes mellitus, liver cirrhosis, fatty liver disease, coeliac disease, other autoimmune disease (eg, rheumatoid arthritis, lupus, etc), and polycystic ovary syndrome Current pregnancy/lactation Mode of birth Medication (past month): antidepressants/anxiolytics, antibiotics, psychotropics, oral or injected steroids, probiotics, prebiotics, synbiotics, dietary supplements including laxatives; other medication (past 2 weeks): NSAIDs, antifungals	✓
Gastrointestinal health/history	Rome IV Diagnostic Questionnaire34	✓
	Phase 1 Health Questionnaire* Non-surgical procedures related to the digestive system (past 6 months): enema, colonoscopy, gastroscopy, inflammatory bowel disease (eg, ulcerative colitis, Crohn’s disease), short bowel syndrome, and lifetime history of abdominal surgery (eg, appendectomy, ileostomy, bowel surgery, caesarean section, etc)	✓
	Phase 4 Demographics, Health and Exercise Questionnaire* Lifetime history of gastric infections: Salmonella, Shigella, Campylobacter, Giardiasis, viruses, other			✓
Stressful life events	The Lifetime Incidence of Traumatic Events64			✓
	Childhood Trauma Questionnaire65			✓
Substance use	Phase 1 Health Questionnaire* Alcohol (past month) Smoking (past month): tobacco cigarettes, vape, e-cigarettes containing nicotine Illicit drug use (past month)	✓
	DQES (alcohol consumption in the past year)60			✓

*Designed specifically for the Bugs and Brains Study.

†Measure completed by researchers, rather than participants.

‡Modified version used, see online supplemental material.

DQES, Dietary Questionnaire for Epidemiological Studies; FODMAPs, fermentable oligosaccharides, disaccharides, monosaccharides, and polyols; NSAIDS, non-steroidal anti-inflammatory drugs; SCID-5-RV, Structured Clinical Interview for the Diagnostic and Statistical Manual fifth edition, research version; WHO, World Health Organization.