Hair brain-derived neurotrophic factor (BDNF) as predictor of developing psychopathological symptoms in childhood

Background: Dysregulation in the expression of neurotrophins is implicated in the pathophysiology of several mental disorders. Peripheral brain-derived neurotrophic factor (BDNF) can be measured in hair and might represent a marker of adequate neuroplasticity regulation. In early developmental periods, neuroplasticity regulation might be particularly important, but BDNF markers have not yet been analyzed in this regard. We used the hair-BDNF concentration (HBC) to investigate the prediction of emerging symptoms of anxiety/ depressive and attention-deficit hyperactivity disorder (ADHD) in the developmentally crucial period from preschool to school age.Methods: 117 children (58 girls, 59 boys) participated in a longitudinal study at the ages of 4-5 (T1) and 8 (T2) years. At T1, HBC was measured in a 3 cm hair segment. At T1 and T2, symptom domains were assessed using a multi-method (clinical interview, questionnaire) and multi-informant approach.Results: T1 HBC was significantly negatively associated with T1 anxiety/depressive symptoms (r =-0.27) and predicted T2 anxiety disorder symptoms (r =-0.34) after controlling for the T1 symptoms. T1 HBC also pre-dicted T2 depressive disorder symptoms (r =-0.18) but was not associated with ADHD symptom development. Limitations: BDNF hair analysis is a new method with a not yet large number of studies on methodological issues. Our study adds evidence to the validity of the method.Conclusions: Prediction of anxiety/depressive symptom development by HBC was shown. As this study was the first to use HBC in this context, cross-validation is necessary and worthwhile. HBC might prove to constitute a useful, non-invasive early marker of risk for anxiety/depressive disorders in childhood.