I know most people will reject this, but there is a physiological reason for anxiety,depression and the like just as you suspect, and it's because your brain isn't producing enough neurotransmitters from the food you eat. Now I'm not a doctor by any means, but I have successfully treated my bipolar 2 disorder using amino acids and the mineral supplement lithium orotate for the last 9+ years. I was on meds for 13+ years, and am doing much, much better now than I ever did on meds.

The thing that I believe happens is that those of us with a genetic predisposition to these types of issues don't or can't produce adequate neurotransmitters to keep our moods and emotions stable so we're depressed, anxious, hyper and the like. I view it like a person with diabetes needing insulin to keep their blood sugar stable. No one blames them for that, or thinks it's weird. Neither is it weird to realize that we need specific nutrients to keep our moods and emotions stable.

Amino acids are the building blocks of life, and what the brain makes neurotransmitters out of. I take 3 different ones--two to control depression and one to control hypomania and anxiety. There are a lot of different ones along with a lot of wonderful herbs that are very helpful in controlling anxiety.

Here are some resources to get you started in your research:

This is the largest non-drug mental health site with lots of great articles and links to resources:

Alternative Mental Health

This is a brain function questionnaire showing what neurotransmitters are related to what emotion/feeling. I found this especially helpful when I began treating myself:

http://drjolee.com/Brain-Function-Questionnaire.pdf

This is a good site that has a lot of great books and DVDs on treating anxiety, depression and other mental health issues with amino acids and other nutrients. I have her book on healing with amino acids, and it's very helpful. Put 'books' into the search box and it will bring them up. She also has a good book on treating anxiety and panic with amino acids that is very good.

Pain and Stress Center: Alternative Health Products