You said:
The average age of onset of the first panic attack is consistent with these events : about 23 years for agoraphobia, about 16 years for social phobia and about 16 years for obsessive-compulsive.

BOB:
Your right about the ages, however the DSM etal are wrong about separating the diseases into sub classes. For instance- I am bi-polar and have been for 33 years, although a good definition was not provided until 1992. My first attacks appeared as panic disorder. Many years later in a unique group of bi-polar people, virtually 100% of the groups said thier illness started with panic and/or anxiety attacks. Most of the group- many yeears later- still had some symptoms of both panic and anxiety, however they haad learned to structure thier lives in such as way as to avoid conditions which precipitated the attacks.
There are MANY mitigating circumstances. I am aware of several, as in my 7 children, 4 have OCD with significant symptoms. 2 have severe panic attacks. 2 have bi-polar. Only 2 of the children, now adults are without symptoms.
We have had over dozens of years starting with Walter Reed Army Medical Center and beyond, of experience with these problems. Now---as to agoraphobia....It is very common for someone with panic attacks to become phobic of the attack itself....in otherwords "fear of the fear", which readily leads to agoraphobia. A can be treated with heavy doses of medication and continuing therapy by a QUALIFIED MD.
Believe me---If you EVER have a question about mental health, feel free to ask....I am a walking dictionary.....

Bob