Elevated fingernail cortisol levels in major depressive episodes

Background The extent to which cortisol levels are elevated in major depressive episodes (MDE), and hence could act as a biomarker of illness, remains unclear. Although patient characteristics may explain some of this variation – for example elevated cortisol being more often found in patients with severe, psychotic or melancholic depression – problems with the methods used to measure cortisol may also have contributed to the inconsistent findings. Fingernails are a novel sample that can be used to assess aggregate cortisol concentrations over a 15-day period, and may provide a more accurate reflection of longer term cortisol level changes in MDE and help clarify this issue. This methodology has not yet been utilised in MDE. Methods Cortisol levels reflecting a period of 15 days were measured using fingernails in a group of 26 subjects experiencing a major depressive episode (MDE) and in an age and gender matched group of 45 healthy controls. Results Depressed subjects showed significantly higher mean cortisol levels measured in fingernails when compared with control subjects. Higher levels of cortisol were associated with higher depression severity scores, a diagnosis of non-reactive depression, and more prominent melancholic symptoms. Conversely, fatigue was negatively correlated with cortisol levels. Conclusion There is elevated cortisol in MDE when assessed using an aggregate measure over two weeks.Alterations in fingernail cortisol correlate with key clinical symptoms and subtypes of depression.