Breathomics for depressive disorders

 

Introduction Especially for psychiatric disorders, there are no in vivo and easy-to-use biomarkers that could help in diagnosis or therapy. In severe depressive disorders (MDD), there is strong evidence that stress, particularly through the action of glucocorticoids, induces an increase in excitatory (glutamatergic) neurotransmission, leading to dendritic remodelling in some brain regions associated with behavioural changes. This hypothesis is called the stress-toxicity hypothesis of MDD. Since the lung acts as a gas exchanger between the internal and external environment, the effects of MDD could easily be assessed by analysing the exhaled breath. The aim of the study was to identify non-invasive markers that could indicate MDD in comparison to healthy subjects.

Methods 20 patients with severe depressive disorder according to DSM-V, as well as 20 healthy controls from the general population were initially used. Exclusion criteria are all other psychiatric, internal or neurological diseases that influence the functions of the central nervous system. Breathing air analysis is carried out using proton transfer reaction mass spectrometry (PTR-MS), whereby molecules (VOCs) of 1 – 500 amu can be detected with corresponding concentrations. From these data individual molecule patterns result, from which general rules can be derived, analogous to omics databases. The clinical applicability of respiratory gas analysis has already been demonstrated at our university using the example of diabetes mellitus using volatile organic compounds (VOC).

Results There are significant differences for the time-diagnosis effect between the two samples with respect to MDD. The pathological order of the molecular pattern known to us suggests that the biomarkers might be cyclic or aromatic hydrocarbons, and NO derivatives might also play a role.

Conclusion The exact classification of the VOCs and the pathophysiological mechanism is still pending. However, the current data situation is promising.