We also know that environmental stress will bring on the symptoms...but once the syndrome is seen, it will respond to drugs.
And again, some children will come out of absolutely dismal environments relatively unscathed, whereas other kids brought up with every convenience and ease will be thieves, killers or rapists.
But there is no reason to believe that severe anxiety disorders brought about by environmental stressors will not respond to medication. The brain chemistry is affected by experience and by its genetic potential. The best explanation I've seen says that our genes give us a range--and our environment puts us at a specific point within that range.
We consistently see that in a clinical setting psychotropics work wonders while released patients left to their own self-medication cause grievous failures.