Anxiety (cf. the Latin word anxietas, i.e., anxiety, trouble of the mind, and the verb angere, meaning to choke or oppress) is characterised by a variety of generally unpleasant sensations including fear, nervousness, apprehension, worry, the sensation that things may get out of hand, the need to find an immediate solution and, in the case of prolonged exposure to stress, also frustration and desperation.Anxiety is in any case a natural, universally-experienced emotional state. It is generated by a psychological mechanism of response to stress (see: "Stress"), which has the function of ensuring timely and early perceptions of possible danger. Through this mechanism, specific physiological responses are triggered, which on the one hand drive the individual to explore the environment in order to identify danger and cope with it in an adequate manner and on the other hand prepares the organism for avoidance or possible flight. The mechanism of avoidance and attention to possible dangers, which is found only in human beings and primates, facilitates the development of knowledge of the surrounding world and improves our level of adaptation.For this simple reason we have all experienced anxiety and are always subject to occasionally experiencing the condition. We are thus also capable of easily comprehending anxiety in others and identifying with their state. Generally speaking, anxiety is a basic and entirely spontaneous human emotional state, which has the function of protecting us against external threats. It prepares us for action and simultaneously provides us with a form of motivation to interact with the world surrounding us.