Anxiety disorders are considered among the most common psychiatric disorders in general population. They may be characterized by prominent subjective suffering, frequent chronic courses of illness, increased rates of comorbid other psychiatric disorders and somatic diseases, a distressing amount of psychosocial disabilities, in all, a challenging high burden of disease. Anxiety disorders have principally to be conceptualized within a multifactorial biopsychosocial model. Various psychological and psychosocial approaches have contributed to a multi-layered understanding of various major predisposing, eliciting, and maintaining factors in the course of illness. Modern neurobiological research has significantly broadened and deepened the aetiopathogenetic complexity of anxiety disorders. The main focus of this short review is on neural fear- and anxiety circuits, neurotransmitter systems, neuroendocrine and inflammatory stress systems, genetics and epigenetics that characterize the general basis of fear and anxiety regulation and their dysregulation in anxiety disorders. Anxiety disorders may be effectively treated both by psychotherapeutic and pharmacological approaches. Basic principles and general guidelines in the treatment of anxiety disorders are being presented.