Scoping review of the relationship between salivary cortisol and depression

Anxiety and depression are some of the most common mental disorders associated with a dysregulation of the hypothalamic-pituitary-adrenal axis (HPA) and elevated cortisol levels in the saliva. The aim of this scoping review was to synthesize all of the current information about the relationship between salivary cortisol and depression as well as address some of the shortcomings in prior research to explore its potential applications in diagnosing depression. In late July 2022, records from 2012-2022 were identified using Web of Science, PubMed, and Scopus. Unique abstracts were screened using the following criteria: (1) depression and saliva; (2) anxiety and saliva; (3) age and salivary cortisol and depression; (4) sex and salivary cortisol and depression. 4,869 records were identified across all three databases; resulting in 90 unique abstracts. 11 articles met all inclusion criteria. On balance, most studies associated the dysregulation of the HPA with depression and anxiety disorders, with a cofactor being the cortisol awakening response. Several studies also presented sex and age-related differences in salivary cortisol measures. However, there were several inconsistencies with some studies showing no age and/or sex-related differences. Furthermore, several studies also emphasized the importance of testing morning salivary cortisol as an effective method to diagnose depression and anxiety disorders. The oral microbiome may play a role in mental health disorders through changes in inflammation and cortisol levels in saliva. Our review contributes to the existing literature on the topic, highlighting gaps and strategizing the next steps.