There are some organic and physiological causes of depression we need to be aware of because all the dietary and behavioral changes we make cannot have an impact on these things:
- Food Allergies
- Heavy metal poisining
- Pre-exisiting physical conditions such as cancer, inflammation, diabetes, heart disease, liver disease, lung disease
I hesitate to put thyroid conditions on here because depression can be an early manifestation of thyroid disease. Even subtle decreases in available thyroid hormone are suspected of producing depression or depression-like symptoms. The link between low thyroid production and depression is well known in medical sources but its one of those chicken or egg things, the link is there, but no one is sure which comes first.
Suffice it to say that we should have our doctors check our hormone levels and for metal poisoning to rule out any of these other causes of depression.
The encyclopedia of Natural Medicine, Third ed.