India, Oct. 13 -- Anxiety disorder can be a mental illness. Anxiety is a normal reaction to stress, but when a person experiences a lot of anxiety and irrational fear which remains all the time, it can be very disturbing and even affect a person's day-to-day functioning. People can stop doing things that they enjoy, stop doing their work and be emotionally distressed. And if left untreated, this kind of anxiety will keep getting worse and interpersonal relationships can also be adversely affected. Such anxiety disorders are the most common form of emotional disorder and can affect anyone at any age....