My folic acid ended up being 4.88 ng/ml (range - 4.6 - 18.7). could this have potentially played a role in my depressive/anxious nature?

My opinion: Some of the studies suggest micro-nutrient deficiency may play a role in depression, but may not be the main cause in most adults. However, Deplin, which contains biologically active folate, (folic acid) is used to treat depression by many psychiatrists. Suggest you take tetra-hydro-folate to boost your levels, unlikely to hurt and may well help.