With time, there has been acknowledgement of the importance of mental health. It is now regarded as important as other physical ailments. Rather, other physical ailments are also studied on the basis of psychological aspect. A similar and very significant one of these psychological issues is anxiety. 
Anxiety can be loosely defined as emotions of fear or worry regarding a future event, most often accompanied by other systemic physiological signs and symptoms.
Anxiety is a normal emotional response towards unwelcoming situations. Anxiety is not synonymous with fear in more specific psychological terms. Fear is a response to a real future event. However, anxiety is more often associated with an irrational fear of something or an event.
Anxiety can also take a pathological course. It can be diagnosed as an anxiety disorder in some patients. This diagnosis is established on lines that are still not very clear. Constant state of worrying or fear, marked with an inability to cope with the normal day to day activities because of uncontrollable associated symptoms of anxiety is a diagnostic criterion for a generalized anxiety disorder. 
There are multiple types of anxiety disorders, and the symptomatology varies with each type. Recognizing the type is important in mapping out a coping mechanism as treatment or therapy.
1Anxiety and Age Relationship
Anxiety as a normal emotional response is common to all age groups. Yes, it is often wrongly perceived as a concern only in the adult population. A number of anxiety disorders have a preference of occurrence in different age groups, depending upon the developmental psychology of human nature. The phobic and separation-anxiety types have a predisposition for young children. Teens and adults suffer more with panic attacks and social anxiety etc. Elderly people may be more concerned with the health-related anxiety.