Determination of endocannabinoids and N-acylethanolamines in human hair with LC-MS/MS and their relation to symptoms of depression, burnout, and anxiety.

The endocannabinoid system has been implicated in the dynamic regulation of the stress response, fear memory formation, and inflammatory processes. Endocannabinoids (eCBs) and N-acylethanolamines (NAEs) are primarily quantified from serum or cerebrospinal fluid representing acute measures, while no validated method for the quantification of long-term integrated eCBs and NAEs concentrations exists. We here present an online solid phase extraction-liquid chromatography-mass spectrometry method (LC-MS/MS) for quantification of long-term integrated eCBs and NAEs in human hair and examine their association with burnout, depression, and anxiety symptoms. Hair samples were washed with isopropanol and endocannabinoids were extracted from 7.5 mg hair by methanol incubation. A column switching strategy for online solid phase extraction (SPE) was applied, followed by mass spectrometer detection. eCBs and NAEs levels were determined in 207 hair samples from an ongoing longitudinal study and related to individual burnout, depression and anxiety symptoms. The limits of detection were between 0.06 and 6.0 pg mg-1, the recoveries of this method were between 87.2% and 114.2%. Hair AEA levels showed a negative correlation with burnout and anxiety symptoms. Participants with clinically relevant burnout and anxiety symptomatology exhibited lower hair AEA levels compared to those participants with low burnout and anxiety symptomatology, while for depressive symptomatology no association was identified. The presented LC-MS/MS method provides a highly specific analytical strategy for the detection of eCBs and NAEs concentrations in human hair and is thus likely to further shed light on the temporal dynamics of eCBs and NAEs secretion. The analysis of eCBs and NAEs in hair emerges as useful strategy in biopsychological research and as a valid and easily implementable method for the retrospective assessment of cumulative long-term eCBs and NAEs secretion.