2-AG	2-arachidonoylglycerol
5-HT	5-hydroxytryptamine (serotonin)
5-HTTLPR	serotonin-transporter-linked polymorphic region
AEA	anandamide (N-arachidonoylethanolamine)
CABS	Companion Animal Bonding Scale
CBT	cognitive behavioral therapy
CEBM	Centre for Evidence-Based Medicine
CGT	complicated grief treatment
CRP	C-reactive protein
DSM-5	Diagnostic and Statistical Manual of Mental Disorders, 5th Edition
ECS	endocannabinoid system
FSPI	First-Study Priority Index
GAD-7	Generalized Anxiety Disorder 7-item scale
HHI	Herfindahl-Hirschman Index
HPA	hypothalamic–pituitary–adrenal (axis)
HRV	heart rate variability
ICD-11	International Classification of Diseases, 11th Revision
ICG	Inventory of Complicated Grief
ICG-K	Inventory of Complicated Grief, Korean version
IDO	indoleamine 2,3-dioxygenase
IL-6	interleukin-6
OT	oxytocin
OXTR	oxytocin receptor gene
PAS	Pet Attitude Scale
PBQ	Pet Bereavement Questionnaire
PGD	prolonged grief disorder
PHQ-9	Patient Health Questionnaire-9
PRISMA	Preferred Reporting Items for Systematic Reviews and Meta-Analyses
RCT	randomized controlled trial
SANRA	Scale for the Assessment of Narrative Review Articles
TNF	tumor necrosis factor
TRI	Translational Readiness Index