Biomarkers in burnout: a systematic review.

Background: Burnout is a stress state characterized by symptoms of mental exhaustion and physical fatigue, detachment from work, and feelings of diminished competence. Several biomarkers have been tested for association with burnout, but the results are conflicting.

Aim: The objective of this review was to identify potential biomarkers for burnout.

Methods: We carried out a systematic review of studies comparing biomarkers in individuals with burnout and healthy controls, or individuals with low scores and those with high scores on burnout questionnaires. Literature searches in MEDLINE and EMBASE were performed. We describe biomarkers on which at least three studies were available. Where appropriate, a meta-analysis was carried out.

Results: We identified 31 studies on 38 biomarkers involved in the hypothalamus-pituitary-adrenal axis, autonomic nervous system, immune system, metabolic processes, antioxidant defense, hormones, and sleep. At least 3 studies were available for cortisol in saliva and blood, blood pressure, heart rate, cholesterol, dehydroepiandrosterone sulfate, (numbers or activity of) natural killer cells, C-reactive protein, and prolactin. The comparability of studies was limited, due to differences in the methods used to characterize patients and controls, to assess biomarkers, and to control for confounders. Furthermore, burnout was operationalized in different ways. Meta-analyses showed no differences for cortisol awakening response and cortisol awakening response after administration of dexamethasone, cortisol in blood, and blood pressure.

Conclusions: No potential biomarkers for burnout were found, largely due to the incomparability of studies. We emphasize the need for a dimensional and longitudinal approach in future research to account for the heterogeneity of burnout.