Ironic that you mention “puzzle”; I write about that metaphor at length.
Here’s a new piece, absent missing content from your comment:
Depression is caused by hormonal imbalance (my own theory, particularly-given my health recovery and its positive effects, including reversing all symptoms of depression et al). Systemic hormonal imbalance, when unchecked, is like cocking the gun at the temple. The problem is that the shot never comes; it’s a slow, painful demise in many cases.
I don’t agree with the B12 shots for depression. Your comment on “symptom of a greater undiagnosed problem” is very prescient.
The problem is that waiting until cancer expresses is too late, but humans respond better to crises than evidence...
There are many types of depression, or causes, both biochemically and psychologically.
For example for women with severe PMS and/or post partum there is a copper toxicity depression that only happens when certain hormones are out of balance.
This is why genotyping is such a fabulous medical screening diagnostic tool as it determines which type of depression a person is more likely to have and which treatment and dose would most likely be best/ This all from looking at DNA.
I’ve pulled the referenced research article and will read it, as I do many. While the Science Daily articles are good, they are just a quick summary.
Too many variables are left unconsidered in most research and the normal research trick is to create sample bias in specific attributes of the general population and then try to extrapolate it back over the entire population.