I know someone who suffers from agoraphobia.
Really? What is agoraphobia? Is that one of the anxiety disorders?
It's the fear of wide open spaces. It can also be fear of crowds, which would cause social anxiety and even traveling short distances.
That sounds really difficult. Can it be treated with cognitive behavioral therapy?
Yes it can be treated with cognitive behavorial counseling.. I know it's considered an anxiety disorder.
I think agoraphobia doesn't usually resolve on its own, so therapy must be pretty important. 
Yes therapy is extremely important to help recovery. I was surprised to find out that it could also be inherited.
leave their homes.
Agoraphobia is believed to be due to a combination of genetic and environmental factors. The condition often runs in families, and stressful or traumatic events such as the death of a parent or being attacked may be a trigger. In the DSM-5 agoraphobia is classified as a phobia along with specific phobias and social phobia. Other conditions that can produce similar symptoms include separation anxiety, posttraumatic stress disorder, and major depressive disorder. Those affected are at higher risk of depression and substance use disorder.
Without treatment
meaning "fear".
Signs and symptoms.
Agoraphobia is a condition where sufferers become anxious in unfamiliar environments or where they perceive that they have little control. Triggers for this anxiety may include wide-open spaces, crowds (social anxiety), or traveling (even short distances). Agoraphobia is often, but not always, compounded by a fear of social embarrassment, as the agoraphobic fears the onset of a panic attack and appearing distraught in public. Most of the time they avoid these areas and stay in