Biological and clinical markers to differentiate the type of anxiety disorders.

The present chapter is an overview of possible biomarkers which distinguish anxiety disorders as classified by the DSM-5. Structural or activity changes in the brain regions, changes in N-acetylaspartate/creatine, dopamine, serotonin, oxytocin, hearth rate variability, hypothalamic–pituitary–adrenal axis activity, error related negativity, respiratory regulation and genetic variants are proposed. However, their clinical utility is questionable due to low specificity and sensitivity: the majority do not distinguish subjects with different anxiety disorders and they might be influenced by stress, comorbidity, physical activity, psychotropic medications. In this framework, the staging model, a clinimetric tool which allows to define the degree of progression of a disease at a point in time and where the patient is located on the continuum of the course of the disease, is proposed since several DSM anxiety disorders take place at different stages of the same syndrome according to the staging model. Thus, a stage-specific biomarker model for anxiety disorders is hypothesised and illustrated.