Anxiety is a normal psychological and physiological reaction to stress that serves as a coping mechanism. But when anxiety becomes excessive, overwhelming and irrational, or when it interferes with everyday activities and behaviors, it can become a disabling mental disorder. Anxiety sometimes occurs without an identifiable stimulus, often arising not from an observable threat but during daily activities, or due to a perceived or anticipated threat. Anxiety disorders come in various forms and extremes, and can even occur simultaneously with other anxiety disorders, depending on the level of the disorder’s progression. Each disorder has a distinct method of treatment that has effectively improved with modern research and therapeutic studies, which have continually refined the taxonomy of symptoms and these disorders over the last century.