Everyone knows what it is like to feel anxious - your heart pounds, you feel flush and tense.
For some, this emotion is triggered by a traumatic event such as a car accident.
For others, small things like being late for a meeting trigger this emotion.
But at what point does a general anxious emotion become an anxiety disorder? Anxiety disorders aren't just a case of "nerves".
They are illnesses often related to the biological makeup and life experiences of an individual.
There are several types of anxiety disorders, each with its own distinct features.
Generalized anxiety disorder is more than the normal day-to-day anxiety people experience.
It is chronic, constant and exaggerated worry and tension over minor things that occur in daily life.
According to the National Institute of Mental Health (NIMH), "having this disorder means always anticipating disaster, often worrying excessively about health, money, family or work".
A person with generalized anxiety disorder usually demonstrates symptoms of poor sleeping patterns and the inability to relax.
Panic disorder is another type of anxiety disorder.
People with panic disorder have feelings of terror that can occur suddenly.
Because these attacks occur without warning, the individual spends time consumed with worry that another attack could happen at any minute.
When a panic attack strikes, a person might feel faint, dizzy, weak or sweaty.
During these attacks individuals can experience chest pain or believe they are going to die.
Studies from the NIMH indicate that panic disorder affects between three and six million Americans.
Like other anxiety disorders, it is twice as common in women as in men and most often begins in young adulthood.
The NIMH also points to studies that show that cognitive-behavioral therapy, medication or a combination of the two can help between 70 to 90 percent of people with panic disorder.
Phobias are also a type of anxiety disorder.
While there are several different categories of phobias, each involve an intense irrational fear of some sort.
Characteristics might include fear of people, heights or closed-in-places.
Again, with the right combination of medication and/or therapy, phobias are treatable.
Obsessive-compulsive disorder (OCD) also falls under the category of anxiety disorders.
This illness involves a pressing need to do everything in a ritualistic manner.
People with OCD might be obsessed with germs or dirt and wash their hands a lot.
Many healthy people can identify with having some symptom of OCD, such as checking the stove several times before leaving the house, but the disorder is diagnosed only when such activities consume at least an hour a day, are distracting and interfere with daily life.
Post-traumatic stress disorder (PTSD) is a debilitating condition that follows a terrifying event.
Often people with PTSD relive a traumatic event over and over causing them to feel emotionally numb.
Recollections of the event consume their thoughts and can cause repeated nightmares.
Once believed to effect war veterans exclusively, PTSD (formally referred to as shell shock or battle fatigue) is now the diagnosis for individuals experiencing similar symptoms after a traumatic event, rape, kidnapping or car accident.
The important thing to remember about anxiety disorders, no matter what type, is that they are treatable.
How the disorder is treated varies with each individual.