I believe your question may have been posted before you completed it. You can edit your post and resubmit it, or feel free to reply with the full question you want to have answered.
I am sorry for the confusion, now I see your whole question.
The symptoms that you describe your son having sounds as though it very likely may be either depression or bipolar disorder with a strong anxiety component. Because of his "overreaction" to the antidepressant he tried, this very well may be bipolar disorder since this often happens if bipolar disorder patients are treated too aggressively with antidepressants not balanced with a mood stablizing medication to prevent the extreme "highs". I understand that this must be very difficult to deal with since your son sounds like a very intelligent young man.
This is probably bipolar II disorder rather than bipolar I since it does not sound as though your son has had full blown manic episodes (except perhaps with the use of the antidepressant). Bipolar II is usually characterized by primarily depressed mood with occasional hypomanic episodes (elevated mood, enegery, perhaps some racing thoughts but not to the extreme of severe manic episodes). The best treatment for this is usually a low dose antidepressant along with a mood stabilizing medication such as valproic acid, lamotrigine or lithium. Counselling and sometimes anxiety medications such as clonazepam or antipsychotic medications like seroquel may also be needed.
Though I cannot recommend a specific doctor in California for you personally, I suspect that his university would have on-staff counsellors or psychologists who would be able to refer him to a local psychiatrist to confirm his diagnosis and begin treatment. If he goes to a university affiliated with a medical school (there are many in California), he also could contact the Psychiatry department there and set up an appointment.
The following link may be helpful, though since you have a background in Psychiatry you may not need this! Please let me know if you have further questions.
Yes I agree that your son likely has bipolar II disorder. The issue that may occur when bipolar patients are only on an antidepressant is that they may begin to have more severe and more frequent manic episodes. Their depression certainly may improve but if they are also not on a mood stabilizing medication at the same time, they can "swing" too far toward the manic end of the spectrum. Therefore, if a low-dose antidepressant is prescribed on its own, your son should certainly be followed closely by a psychiatrist to monitor for worsening of his hypomanic episodes. My suspicion is that after examining your son, a psychiatrist would recommend both a mood stabilizer and an antidepressant.
Again, if your son can make an appointment with his university's counsellors or psychologist, I suspect they would be able to refer him to a local Psychiatrist to begin treatment.