Objective: Anxiety is partly driven by changes in neuroendocrine signaling, which continues to be an area of study. Birds are a useful model to study anxiety disorders due to their unique behaviors and social makeup, leading to several observable behaviors indicative of anxiety.

Methods: Using PRISMA guidelines, a systematic review of studies published from January 2000 to August 2022 in PubMed, PsycINFO and MedLine was conducted. Inclusion criteria included animal studies utilizing an avian model, examining the relationship between a neuroendocrine biomarker and behavioral displays of anxiety. Exclusion criteria included review articles, editorials, studies where anxiolytic drugs were used and studies where anxiety was not the primary studied behavior.

Results: 376 articles were screened. 10 papers met the review criteria. Dopamine, serotonin and glycogen synthase kinase 3β (GSK-3β) were found to be inversely related to anxiety levels. Ghrelin and γ-Aminobutyric acid type A (GABAa) were directly correlated with anxiety levels. Corticosterone correlated in a bidirectional manner depending on when a stress was applied, however, lower levels at baseline were more predictive of less anxious birds. Pituitary adenylate cyclase was shown to increase anxiety but was also time-dependent. Arginine vaso-peptide was found to reduce anxiety, but was also context-dependent. Vasointestinal Peptide had no relation to anxiety.

Conclusion: Birds display similar chemical responses to humans when anxious, and due to anxiety-related behaviors unique to birds, allow for an additional approach to the investigation of different neuroendocrine markers that are not always strongly considered when studying the neurobiology of anxiety in humans.