[The neurobiology of burnout: the hypothalamus-pituitary-adrenal gland axis and other findings].

OBJECTIVE This review aimed to present an overview of neurobiological research on the etiology of burnout and to evaluate the proposed arguments. METHOD A retrospective literature review of the relevant studies conducted within the last 17 years. For this purpose a literature search was conducted via internet-based search engines, including PubMed, Science-Direct, Medline, GoogleScholar, ULAKBIM Turkish Medicine Index, and Turkish Psychiatry Index, using the key words, burnout, cortisol, the hypothalamus-pituitary-adrenal gland (HPA)-axis, stress, neurobiology, neurogenesis, BDNF, immunology, and etiology, in different combinations. RESULTS The pioneering studies that focused on the relationship between burnout and dysregulation of the HPA-axis have yielded inconsistent results. Data from subsequent studies with improved designs suggest there is no HPA-axis dysregulation in burnout, but the results do not lead to more concrete interpretations. There is some evidence of impaired immunity function in burnout as compared with controls. Although there is strong evidence of a relationship between stress and impairment in hippocampal neurogenesis, there is no study of burnout in the field. Data about monoaminergic involvement in burnout, which is one of the probable pathways, is scarce. CONCLUSION In future research the essential guidelines for evaluating HPA-axis functioning (i.e. timing of collecting samples from saliva or blood and controlling for possible influencing factors on HPA-axis functioning) in patients clinically diagnosed with burnout should be taken into account, and in addition to the HPA-axis, evaluation of hippocampal neurogenesis, neurotrophins, immunity functioning, and the monoaminergic system will provide more data on the neurobiology of burnout.